Internal walls are a critical component of any new build home, providing structural support, privacy, fire protection and sound insulation. The NHBC (National House Building Council) has established comprehensive standards that builders must follow when constructing internal walls. Understanding these standards can help you appreciate what to expect in your new home and what our snagging inspections assess during property evaluations.

This guide explains the key NHBC standards for internal walls, covering everything from basic compliance requirements to the specifics of masonry and timber wall construction. Whilst a professional snagging inspection focuses on identifying defects and finish issues rather than conducting a full structural survey, awareness of these standards helps you understand the quality benchmarks your new home should meet.

6.3.1 – Compliance with Technical Requirements

All internal walls in new build homes must comply with NHBC Technical Requirements, and this forms the foundation of acceptable construction practice. Internal walls include separating walls (those between different properties), compartment walls (which provide fire separation within a building) and standard partition walls that divide spaces within your home.

When builders follow the guidance set out in Chapter 6.3 of the NHBC Standards, their work will generally be considered acceptable. These standards represent industry best practice and are designed to ensure that internal walls are structurally sound, safe and fit for purpose. During a snagging inspection, whilst we cannot verify full structural compliance (which would require invasive testing), we can identify visible defects that may indicate departures from these standards, such as walls that are not plumb, poor finishes or inadequate fire stopping.

6.3.2 – Provision of Design and Specification Information

Proper construction of internal walls begins long before any bricks are laid or timber studs erected. The NHBC standards require that designs and specifications must be produced in a clearly understandable format, include all relevant information and be distributed to all appropriate personnel on site.

This documentation should be issued to site supervisors, specialist subcontractors and suppliers, providing comprehensive details including wall layouts with dimensions, the position and size of openings and lintels, details of junctions with fire-stopping where applicable, specifications for wall constructions and materials including ties and restraints, details of junctions between separating or compartment walls and roofs, information about pipes and cables penetrating walls, and manufacturers’ recommendations for proprietary components.

When this information is clear and properly communicated, it significantly reduces the likelihood of construction errors. However, communication failures or misinterpretation of specifications can lead to defects that become apparent during occupation. A professional snagging inspection can identify issues that may have resulted from poor implementation of the design, such as incorrectly positioned walls, missing fire-stopping or inadequate junctions between different building elements.

6.3.3 – Supporting Load-Bearing Internal Walls

Load-bearing internal walls carry significant weight from floors and roofs above, and therefore must be adequately supported by foundations or other structural elements capable of transferring these loads safely. The NHBC standards specify that load-bearing internal walls should either have their own foundation or be supported by a means that transfers loads safely to a foundation, such as a concrete floor slab or steel beam.

The foundations for internal load-bearing walls must comply with Part 4 of the NHBC Standards, which covers strip and trench fill foundations as well as raft, pile, pier and beam foundations. The choice of foundation type depends on ground conditions, the loads to be carried and the overall building design.

Whilst the adequacy of foundations cannot be assessed during a snagging inspection (as they are buried underground), we can identify signs that might indicate foundation issues, such as cracking in internal walls, doors that bind or won’t close properly due to movement, or gaps appearing between walls and ceilings. These visible symptoms may warrant further investigation by a structural engineer, particularly if they appear shortly after completion.

6.3.4 – Masonry Walls

Internal masonry walls, constructed from bricks or blocks, are common in new build homes and must be designed to support and transfer loads to foundations safely and without undue movement. The NHBC standards address multiple aspects of masonry wall construction, including structural elements, mortar mix and jointing, workmanship, bonding and tying, lateral restraint, masonry separating walls, and lintels and beams.

6.3.4.1 – Structural Elements and Materials

The structural design of masonry walls should comply with BS EN 1996-1-1, the European standard for masonry structures. For buildings up to three storeys high, the NHBC provides guidance on minimum compressive strengths for blocks and bricks. In one or two storey buildings, blocks should have a minimum compressive strength of 2.9 N/mm², whilst bricks should meet 9.0 N/mm². The lowest storey of a three-storey building, or where individual storeys exceed 2.7m in height, requires stronger materials, with blocks needing 7.3 N/mm² and bricks requiring 13.0 N/mm² compressive strength.

Concrete blocks must comply with BS EN 771, and the maximum load-bearing capacity should not exceed the manufacturer’s recommendations. When masonry is used in separating walls between properties, it must meet structural, fire and acoustic requirements as specified in relevant Building Regulations. The use of appropriate materials is fundamental to wall performance, and using substandard or incorrect materials can lead to structural issues over time.

6.3.4.2 – Mortar Mix and Jointing

The quality of mortar and jointing significantly affects the strength and durability of masonry walls. Mortar should be the correct mix and used within two hours unless it is retarded mortar, which has additives that slow the setting process. Once mortar has started to set, it must not be re-tempered (have water added to make it workable again), as this compromises its strength. Sulfate-resisting cement should be used where required to prevent chemical attack in certain ground conditions.

Air-entraining agents can help reduce frost damage but cannot be used as anti-freeze, and they must be carefully measured for each batch to ensure consistency. Bricks and blocks should be laid on a full bed of mortar with perpend joints (vertical joints) solidly filled. Where walls are to receive wet plaster, joints should be raked out to a shallow depth to provide a key, unless the masonry units have a suitable texture or metal lathing is used. For walls that will be dry lined, mortar joints should be struck off flush.

During a snagging inspection, we can identify poor mortar work, such as unfilled joints, excessive mortar smearing on block faces (which can affect plaster adhesion), inconsistent joint thickness or mortar that appears to be weak or crumbly. These defects not only affect appearance but can also compromise the structural integrity and acoustic performance of walls.

6.3.4.3 – Workmanship Standards

The NHBC standards place considerable emphasis on workmanship quality. Internal masonry walls should be constructed in lifts or stages to prevent distortion during construction, accurately set out, reasonably plane and true, and plumb with courses level. Walls that are out of plumb, have bowing or show significant deviation from vertical or horizontal alignment represent clear departures from acceptable standards.

These workmanship issues are readily identifiable during a snagging inspection. We check walls for plumbness and straightness, and can identify where poor workmanship has resulted in walls that are noticeably out of alignment. Such defects can cause problems with fitting kitchens, wardrobes and other fixtures, and in severe cases may indicate more serious structural concerns.

6.3.4.4 – Bonding and Tying

Internal masonry walls must maintain a regular bonding pattern to ensure structural integrity. The standards prohibit mixing bricks or blocks of different types in the same wall, as differential movement characteristics can lead to cracking. Where walls meet, they should be fully bonded or tied, either with a tooth (alternate courses interlocking) or with expanded metal strips or wall ties at maximum 300mm vertical spacing.

Joist filling, where floor joists bear into masonry walls, should use brick or blockwork without excessive mortar joints. Poor bonding or tying can lead to cracks appearing at wall junctions, and during snagging inspections we frequently identify inadequate junctions where walls meet, particularly at returns and where partition walls meet external walls.

6.3.4.5 – Lateral Restraint

Load-bearing masonry walls, including separating walls between properties, require lateral restraint at each floor level and at ceiling level below a roof to prevent them from bowing or collapsing outwards. For timber floors, adequate restraint can be provided where joists have a minimum 90mm bearing on the wall. Alternatively, restraint can be achieved using restraint straps with a minimum 30mm x 5mm cross-section, restraint type joist hangers complying with BS EN 845-1, or proprietary straps.

For concrete floors, adequate restraint requires a minimum 90mm bearing on the wall, or restraint straps that are at least 450mm long with the end turned down between joints in the concrete floor or suitably fixed with screws. Restraint straps should be provided to separating walls on each level at a maximum of 2m centres when the floor is not on the same level or does not provide adequate restraint.

Whilst restraint straps are typically concealed once walls are finished, inadequate lateral restraint can manifest as cracks, bulging or movement in walls. During snagging inspections, we look for signs that might indicate restraint issues, though confirming proper installation would require opening up walls, which is beyond the scope of a standard snagging inspection.

6.3.4.6 – Masonry Separating Walls

Both leaves of a masonry cavity separating wall (the wall between two properties in semi-detached or terraced houses) must be tied together to provide structural stability. The type of tie and spacing should be carefully selected to limit sound transmission across the cavity whilst maintaining structural integrity, in accordance with relevant Building Regulations.

6.3.4.7 – Lintels and Beams

Lintels and beams above openings in masonry walls must be specified according to loads and spans, either in accordance with manufacturers’ recommendations or designed by an engineer. For masonry construction, concrete and steel lintels are suitable, but timber lintels should not be used. Lintels must extend beyond the end of each opening in accordance with minimum bearing requirements, typically 100mm for spans up to 1.2m and 150mm for spans over 1.2m, though manufacturer’s recommendations may specify different requirements.

Lintels and beams should have padstones where required to spread loads, be installed the correct way up (particularly important for reinforced concrete lintels), bear on a full masonry unit and be level and bedded on a solid bed of suitable mortar. Soft or non-durable packing should not be used, and lintels must have appropriate fire resistance where required by Building Regulations.

During snagging inspections, we can identify visible issues with lintels, such as incorrect installation, inadequate bearing, cracking around openings that might indicate lintel problems, or lintels that are visibly sagging. We also check that lintels over windows and doors are properly positioned and that any exposed lintels are appropriately finished.

6.3.5 – Load-Bearing Timber Walls

Internal load-bearing timber walls, whilst less common than masonry, are used in many modern new build homes, particularly in timber frame construction or for upper floor partition walls in traditional builds. These walls must be designed to support and transfer loads to foundations safely and without undue movement, addressing structural elements, timber separating walls and timber quality.

6.3.5.1 – Structural Elements

The structural design of load-bearing timber walls should comply with BS EN 1995-1-1, the European standard for timber structures. When constructing these walls, several key requirements must be met. The underside of the lowest sole plate (the timber member at the base of the wall) should be positioned at or above internal finished floor level to prevent moisture damage. Individual studs (vertical members), rails and head binders should be a minimum of 38mm x 75mm, though larger sizes may be required to achieve adequate fire resistance.

Studs should be spaced at a maximum of 600mm centres to provide adequate support for loads and wall finishes. Mid-height noggings (horizontal members between studs) should be installed when required for additional stiffness. Lintels and cripple studs (shortened studs) must be provided to each opening, except when the stud spacing is unaffected. Multiple studs should be included to support multiple joists, beams, girder trusses and other point loads unless otherwise specified by the designer. Where a head binder is not provided, joists, roof trusses and similar loads should bear directly over studs to avoid overloading the wall.

Framing joints should be secured with a minimum of two nails per joint, and where internal walls are made up from panels, structural continuity must be maintained, typically through the use of a continuous head binder. During a snagging inspection, whilst we cannot see the internal framing once walls are finished, we can identify issues that might indicate structural problems, such as deflection in walls, cracks around openings, doors that don’t close properly or floors that feel springy or uneven.

6.3.5.2 – Twin Leaf Timber Separating Walls

Where timber construction is used for separating walls between properties, special consideration must be given to sound insulation. Twin leaf construction consists of two independent timber frames with a cavity between them. The type and spacing of wall straps connecting these frames must limit sound transmission across the cavity in accordance with relevant Building Regulations.

Wall straps should be specified according to the system designer’s recommendations, have a maximum cross-section of 40mm x 3mm to minimise sound transmission, be fixed below ceiling level, and be spaced a minimum of 1.2m horizontally. The straps provide necessary structural connection whilst minimising the acoustic bridge between the two leaves.

6.3.5.3 – Timber Quality

The quality of timber used in load-bearing walls is critical to their performance. Timber should be of the appropriate grade, moisture content and size to support imposed loads. Structural timber components must be of a suitable strength class as specified by the designer to BS EN 338. Solid structural timber should be machine graded to BS EN 14081 or visually graded to BS 4978 for softwoods or BS 5756 for hardwoods. When visually graded, timber should be assigned a strength class based on BS EN 1912, must be dry graded and marked in accordance with BS EN 14081.

Engineered wood products such as I-section or metal-web studs should be assessed in accordance with NHBC Technical Requirement R3, which covers the assessment of new products and systems. Crucially, timber should have a maximum moisture content of 20% at the time of dry lining to minimise shrinkage, which can cause cracks in plasterboard finishes, gaps at skirting boards and other defects.

During snagging inspections, we cannot verify timber grades or moisture content without invasive testing, but we can identify problems that may result from poor quality or excessively wet timber, such as significant cracking in plasterboard, gaps appearing at wall junctions, nail pops (where nails push through the plasterboard surface as timber shrinks), or twisted or bowed walls.

6.3.6 – Fire Resistance

Fire safety is a critical aspect of building construction, and internal walls play a vital role in preventing the spread of fire and smoke throughout a property. The NHBC standards require that internal walls have adequate resistance to the spread of fire, addressing fire resistance ratings, cavity barriers and fire-stopping, services penetrating walls, and the materials used.

6.3.6.1 – Fire Resistance Requirements

Internal walls, including those where a garage is attached to or forms an integral part of a dwelling, must provide fire resistance in accordance with relevant Building Regulations. The level of fire resistance required varies depending on the wall’s purpose and location. Separating walls between different properties require the highest level of protection, typically 60 minutes of fire resistance. Compartment walls, which divide a building into separate fire compartments, also require specific periods of fire resistance. Even some internal walls within a dwelling may require fire protection, particularly those enclosing protected escape routes or separating habitable accommodation from attached garages.

The fire resistance of a wall is measured by its ability to maintain its load-bearing function, prevent the spread of flames and hot gases (integrity), and limit the temperature rise on the unexposed face (insulation). During a snagging inspection, whilst we cannot test the fire resistance of walls, we can identify defects that would compromise fire protection, such as gaps in plasterboard, missing fire-stopping materials, or penetrations through fire-resisting walls that have not been properly sealed.

6.3.6.2 – Cavity Barriers and Fire-Stopping

Cavity barriers and fire-stopping are essential components of fire protection, preventing fire and smoke from spreading through concealed spaces within the building structure. The NHBC standards require that these elements be provided in accordance with relevant Building Regulations, with careful attention to sizing, fitting and fixing.

Cavity barriers should be sized appropriately for the cavity they’re protecting, tightly fitted to rigid construction to prevent gaps that could allow fire spread, mechanically fixed in position rather than just friction fitted, and installed according to manufacturers’ recommendations. Particular attention must be paid to junctions between compartment or separating walls and pitched or flat roofs, including any boxed eaves where the roof overhangs the wall.

At these junctions, compartment or separating walls should stop approximately 25mm below the top of adjacent roof framing, with soft fire-stopping material installed above and below the roofing underlay. This allows for movement in roof timbers whilst preventing fire spread, avoiding a problem known as ‘hogging’ where tiles can lift if the wall pushes up against them. Any fire-stopping should be installed to seal imperfections of fit or design tolerances and must be fixed according to manufacturers’ recommendations.

During snagging inspections, we can identify visible fire-stopping defects, such as gaps where walls meet ceilings or roofs, missing fire-stopping materials around penetrations, or inadequate sealing at junctions. However, cavity barriers concealed within wall or floor construction cannot be inspected without invasive investigation.

6.3.6.3 – Services Penetrating Fire-Resisting Walls

Where services such as pipes, cables and ducting pass through fire-resisting walls, the penetrations create potential routes for fire spread and must be properly sealed. The NHBC standards require that these penetrations be fire-stopped in accordance with relevant Building Regulations and design information, with the work completed neatly.

Common penetrations include waste pipes, heating pipes, electrical cables and ventilation ducts. Each penetration should be sealed with an appropriate fire-stopping product that maintains the fire resistance of the wall. The type of fire-stopping system depends on the service passing through, the size of the penetration, and the required fire resistance period.

During snagging inspections, we regularly identify inadequately sealed penetrations, which represent one of the most common fire safety defects in new build homes. These can include pipes passing through walls with large gaps left around them, cables bundled through holes without proper fire-stopping, or the use of inappropriate materials such as ordinary expanding foam where fire-rated products should be used.

6.3.6.4 – Materials for Fire Protection

The materials selected for cavity barriers and fire-stopping must be appropriate for the application and meet the performance requirements of relevant Building Regulations. Products should have appropriate certification demonstrating their fire resistance performance and must be used in accordance with their certification and manufacturers’ instructions.

Common fire-stopping materials include intumescent products (which expand when exposed to heat to seal gaps), fire-rated boards, mineral wool cavity barriers, and specialist collars for plastic pipes. Using incorrect or substandard materials, or installing approved materials incorrectly, can significantly compromise the fire protection of the building.

6.3.7 – Sound Insulation

Adequate sound insulation between properties and between different rooms within a home is essential for comfort and privacy. The NHBC standards require that walls be insulated with materials of suitable thickness and density to provide adequate resistance to the transmission of sound, with particular attention to sound-resisting construction and rooms containing WCs.

6.3.7.1 – Sound-Resisting Construction

The requirements for sound insulation are most stringent for separating walls between different properties in semi-detached and terraced houses, or between flats in apartment buildings. In England, Scotland, Wales and Northern Ireland, separating walls may be registered and built in accordance with Robust Details as an alternative to pre-completion sound testing. Robust Details are pre-designed construction specifications that, when correctly implemented, should achieve the required sound insulation performance without the need for testing.

Masonry Separating Walls

For masonry separating walls, maintaining sound insulation requires careful attention throughout construction. The correct density and type of blocks must be used as specified in the design, with particular attention to using dense blocks for the separating wall itself whilst lightweight blocks may be used for the inner leaf of external walls. All mortar beds and perpend joints must be fully filled, as even small gaps can significantly reduce sound insulation. Only approved wall ties should be used, spaced at 900mm minimum horizontally and 450mm minimum vertically to limit sound transmission across cavity walls.

Any reduction in the thickness of masonry should be avoided, as thinner sections provide less sound insulation. Spaces around floor joists where they bear into separating walls must be fully filled with masonry and pointed with sealant around the joist to prevent flanking sound transmission. The junction between separating and external cavity walls should be closed with flexible cavity stops to prevent sound travelling through the cavity. In solid separating walls that pass through the inner leaf of external cavity walls, proper bonding or tying must be provided in accordance with Building Regulations or Robust Details guidance.

Care must be taken when specifying dry lining, as the thickness of plasterboard layers and the methods of sealing and fixing can significantly affect sound transmission. All holes, voids and even hairline cracks should be avoided or made good, as they can dramatically reduce the effectiveness of sound insulation.

Chases cut into walls for electrical cables or pipes can reduce sound insulation value and require careful control. They should only be cut where specified in the design and not using impact power tools where there’s a risk of damage that could create cracks. Horizontal chases must not exceed one-sixth of the single leaf thickness, whilst vertical chases must not exceed one-third of the thickness. Chases should not be cut in hollow blocks unless specifically permitted by the manufacturer, must be fully filled with mortar after cables or pipes are installed, and should be staggered on each side of the wall to avoid being back-to-back, which would create a weak point for sound transmission.

During snagging inspections, we can identify various defects affecting sound insulation in masonry walls, such as unfilled joints, damaged blocks exposing holes or cracks, inadequate sealing around services, or visible gaps at wall junctions. However, we cannot verify the density of blocks or the condition of concealed elements without invasive testing.

Separating Walls of Framed Construction

Timber frame or steel frame separating walls require equally careful construction to achieve adequate sound insulation. These walls should not have any gaps in the mineral wool quilt filling the cavity, the plasterboard layers, or the fire-stopping. Even small gaps can create acoustic paths that significantly compromise performance.

The integrity of the plasterboard layers is particularly important, as sound can travel through even hairline cracks. All joints should be properly taped and filled, and penetrations for electrical boxes, pipes or other services must be carefully sealed with acoustic sealant.

Flanking Walls

Flanking walls are walls that connect to separating walls, typically external walls or internal walls perpendicular to the party wall. Sound can travel around a separating wall through these flanking walls, so their construction and the position of openings must comply with relevant Building Regulations. Windows, doors or other openings too close to a separating wall can significantly reduce the overall sound insulation between properties.

6.3.7.2 – Rooms Containing a WC

Building Regulations require sound insulation between rooms containing a WC and adjacent living rooms, dining rooms, studies, and bedrooms (except where the WC is ensuite to a bedroom). This requirement recognises that noise from WC use and plumbing can cause significant disturbance and ensures a reasonable degree of privacy.

Studwork Partitions

To achieve the required level of sound reduction using studwork, 75mm timber studwork or 45mm steel framing should be constructed with either two layers of 12.5mm plasterboard (each sheet weighing at least 10kg/m²) on each side with joints staggered and filled, or one layer of 12.5mm plasterboard (at least 10kg/m²) on each side with 25mm of unfaced mineral wool (at least 10kg/m³ density) between the studs, with all joints well sealed.

The use of higher density plasterboard and mineral wool insulation increases the mass and absorption, both of which help reduce sound transmission. Proper sealing of all joints is essential, as gaps will allow sound to pass through. Other forms of studwork construction may be acceptable where they accord with guidance in Building Regulations supporting documents or where independent test evidence of performance is available.

Blockwork Partitions

Masonry partitions provide adequate sound insulation where blocks have a minimum density of 600kg/m³ and are finished on both sides with 13mm of plaster or 12.5mm plasterboard, and blocks are tied at every course to adjoining walls with joints fully filled. The mass of the masonry provides the sound insulation, so lightweight blocks are not suitable for this application.

Proprietary Partitions

Proprietary partition systems designed to provide acoustic separation require independent test evidence of performance in accordance with NHBC Technical Requirement R3. The system should be installed exactly as tested to achieve the certified performance.

Sound Insulation of Soil Pipes

All sections of soil and vent pipes, including those in bathrooms or ground floor stub stacks, must be fully soundproofed to prevent the noise of water discharge from causing disturbance. Where soil and vent pipes run horizontally through a floor void above or below a habitable room, they should be wrapped in at least 25mm of unfaced mineral wool (minimum 10kg/m³ density) and adequately supported to avoid contact with floor decking or ceiling.

Sound insulation should be provided to soil pipes passing through homes by encasing them in boxing using material weighing at least 15kg/m² and wrapping the pipe with a minimum 25mm of unfaced mineral wool (minimum 10kg/m³ density). The insulation should be continued through the thickness of each sound-insulating floor to prevent sound bypassing the protection.

Soil and vent pipes that hold satisfactory assessment by an appropriate independent technical approvals authority may be acceptable where they meet Building Regulations requirements without additional wrapping or boxing.

During snagging inspections, we can identify exposed soil pipes that lack proper acoustic protection, gaps in boxing or insulation, or bathroom installations where noise from plumbing is likely to cause disturbance. This is particularly important to check in homes where bathrooms are located above or adjacent to living spaces.

6.3.8 – Partitions: Internal Non Load-Bearing

Non load-bearing partitions are internal walls that divide spaces within a home but do not carry any structural loads from floors or roofs above. Despite not having a structural function, these partitions must still have adequate strength and support to remain stable and provide a suitable substrate for finishes.

The NHBC standards accept various partition constructions, including masonry partitions built from bricks or blocks, timber partitions using 63mm x 38mm studs, rails and head binders with compatible spacing and plasterboard thickness, steel partitions using studs and head and base rails from a minimum section of 43mm x 32mm x 0.45mm, and proprietary partition systems assessed in accordance with Technical Requirement R3.

All walls and partitions should be appropriately supported and used in accordance with manufacturers’ guidance. Importantly, partitions should not be supported by a floating floor that incorporates a compressible layer (such as acoustic insulation), unless the material is specifically manufactured for that purpose, as the partition weight could compress the layer unevenly causing instability.

Masonry partitions require particularly robust support and should be supported on foundations, other masonry partitions or walls, concrete floors, or steel or concrete beams which may require padstones to distribute the load. Masonry partitions must not be supported by timber joists or beams, as the concentrated load could cause excessive deflection or failure.

Where stud partitions or proprietary plasterboard partitions are supported by a timber floor, extra noggings or joists should be specified unless it can be demonstrated that the deck can transfer the load without undue movement. This typically means providing additional joists directly beneath the partition or installing strutting between joists at close centres to stiffen the floor.

During snagging inspections, we can identify partitions that appear unstable, show excessive movement when pushed, have visible deflection, or exhibit cracks suggesting inadequate support. We also check that door frames in partitions are properly fixed and that doors operate correctly, as binding or poorly fitting doors can indicate partition movement or inadequate fixing.

6.3.9 – Construction of Timber Partitions

Timber stud partitions are common in new build homes for dividing internal spaces. The NHBC standards require that construction of timber stud internal walls ensures adequate stability, addressing setting out and workmanship, size of timber members, and fixing methods.

6.3.9.1 – Setting Out and Workmanship

Timber partitions must be placed so the lowest timber is positioned at or above the internal finished floor level to prevent moisture damage from any residual dampness in the floor slab. This is particularly important on ground floors where moisture can be present in newly laid concrete for some time after construction.

Partitions should be correctly positioned, square and plumb to ensure they look right, function properly and provide a suitable base for finishes. Studwork should be spaced at centres to suit the plasterboard thickness that will be applied, typically 400mm or 600mm centres depending on whether 9.5mm or 12.5mm plasterboard is used. Extra studs should be provided at openings to support the door frame and lintel over the opening.

During snagging inspections, we can check that partitions are plumb using a spirit level and that they are correctly positioned according to floor plans. Partitions that are noticeably out of plumb, twisted or in the wrong position represent clear defects that should be rectified, as they can cause problems with fitting kitchen units, wardrobes and other fixtures.

6.3.9.2 – Size of Timber Members

The NHBC standards specify minimum sizes for timber partition components unless the design specifies otherwise. Sole plates (the bottom horizontal member), rails and head binders should be a minimum of 63mm x 38mm. Studs (vertical members) should be 63mm x 38mm at maximum 600mm centres. Blocking or nogging provided specifically for support of plasterboard should be at least 43mm x 38mm, whilst blocking or nogging for other purposes such as supporting heavy fixtures should be 63mm x 38mm.

These sizes ensure adequate strength and stiffness whilst providing sufficient depth for fixing plasterboard and adequate space for services such as electrical cables. All framing joints should be secured with two nails per joint minimum to ensure structural integrity.

Using undersized timber, excessive spacing of studs, or inadequate fixing can lead to partitions that lack stiffness, allowing plasterboard to crack, doors to bind, or the wall to feel insubstantial when touched. During snagging inspections, whilst we cannot measure concealed timber sizes without opening up the wall, we can identify symptoms of inadequate construction such as excessive deflection, hollow or unstable feeling walls, or premature cracking in finishes.

6.3.9.3 – Fixing

Proper fixing of timber partitions is essential for stability and performance. Partitions should be firmly fixed to each other and to abutting walls, with noggings or extra studs used where necessary to provide fixing points. They should be fixed to the structure where possible, typically by nailing through the sole plate into floor joists and the head binder into ceiling joists. When partitions run parallel to structural elements (such as a partition parallel to floor joists), they should be fixed to noggings installed between the joists rather than just to the ceiling finish.

A critical requirement is that partitions should not be over-wedged against floor joists or roof trusses. Where partitions are non load-bearing, allowance must be made for floors, ceilings or roofs to deflect under load without forcing the partition to become inadvertently load-bearing. This is typically achieved by leaving a small gap at the top of the partition or using a deflection head detail that allows the structure above to move independently.

The NHBC standards include detailed diagrams showing correct fixing methods for various situations. Partitions meeting at right angles to floor joists should be fixed directly to the joists. Partitions parallel to joists need noggings installed between joists to provide fixing. Where partitions meet walls, extra studs should be provided to create a fixing point. Noggings should be provided to support heavy fittings such as radiators, wall-mounted boilers, sanitary fittings and kitchen units.

During snagging inspections, we can identify partitions that are inadequately fixed by checking for movement when pressure is applied, gaps appearing between partitions and abutting walls or ceilings, or fixing points for radiators and other fittings that feel insecure. Properly constructed partitions should feel solid and show no perceptible movement during normal use.

6.3.10 – Construction of Steel Framed Partitions

Steel framed partitions offer an alternative to timber studwork and are increasingly common in new build homes. The NHBC standards require that non load-bearing steel framed walls be suitably constructed, with particular attention to preventing them from inadvertently becoming load-bearing.

Steel framed partitions should be constructed in accordance with manufacturers’ requirements and the design, correctly positioned, square and plumb. They must be supported on a structural floor, but not a floating floor that incorporates a compressible layer unless specifically designed for that purpose. Partitions should be fixed to the floor at the head, to each other and to abutting walls to ensure stability.

Extra studs should be provided at openings where required to support door frames and any lintel spanning the opening. The partition should be finished in accordance with Chapter 9.2 of the NHBC Standards covering wall and ceiling finishes, which provides guidance on plasterboard application, joint treatment and decoration.

Similar to timber partitions, non load-bearing steel framed partitions must not be wedged against floor joists, ceiling joists or roof trusses. Allowance should be made for floors, ceilings or roofs to deflect as necessary so that the partition does not inadvertently become load-bearing. This is typically achieved using a deflection head detail where a channel is fixed to the structure above the partition but is not connected to the top track of the partition framework, allowing the structure to deflect independently.

Noggings or straps should be provided as required to support fittings such as radiators, wall-mounted boilers, sanitary fittings and kitchen units. Steel partitions have the advantage of allowing special fixings designed for steel studs, which can provide secure mounting for heavy fixtures.

During snagging inspections, we assess steel framed partitions using similar criteria to timber partitions, checking for plumb, stability, adequate fixing and proper support for fixtures. We can also look for signs of corrosion on any exposed steel components, though this is rare in modern galvanised or coated steel framing systems. Gaps at deflection heads, inadequate fixing to adjoining elements, or partitions that deflect excessively when pressed all indicate construction defects that should be addressed.

6.3.11 – Construction of Proprietary Systems

Proprietary partition systems are pre-engineered wall systems supplied by manufacturers as complete systems, often including the framing, board products, fixings and installation methods. These systems offer advantages such as speed of installation, consistent quality and often enhanced performance characteristics. However, the NHBC standards require that proprietary partition systems be suitable for their intended purpose and erected in accordance with the manufacturer’s recommendations.

All proprietary partitions should be assessed in accordance with NHBC Technical Requirement R3, which covers the assessment and approval of innovative products and systems. This ensures that new or non-traditional partition systems have been properly tested and certified before use in homes covered by NHBC warranty.

When installing proprietary partitions, they must be constructed and specified according to the manufacturer’s recommendations, including the specified construction sequence. Many proprietary systems require components to be installed in a particular order to achieve the designed performance, and deviating from these instructions can compromise structural integrity, fire resistance or acoustic performance. Partitions should be correctly positioned, square and plumb to ensure they function as designed.

Timber or other additional fixings should be provided for radiators, electrical outlets, switches and other fixtures. Whilst many proprietary systems include provisions for fixing accessories, the specific requirements vary between systems, so manufacturers’ guidance must be followed to ensure fixtures are securely mounted without damaging the partition system.

During snagging inspections, we can identify proprietary partitions that have not been installed correctly, such as systems that are out of plumb, show gaps between components, have damaged or missing parts, or lack proper fixings for accessories. Visible manufacturer’s marks or labelling can help identify the system, allowing us to assess whether installation appears consistent with typical requirements for that type of partition. However, without access to the specific installation instructions, detailed assessment of proprietary systems can be challenging, which is why visible defects become particularly important indicators of potential installation problems.

6.3.12 – Plasterboard

Plasterboard forms the visible surface of most internal walls in modern new build homes and must be of suitable thickness for its intended use. The NHBC standards require that dry lining comply with BS 8000-8 (the code of practice for design and installation of dry lining systems), and that plasterboard meets BS EN 520 or BS EN 15283.

The thickness of plasterboard must be matched to the spacing of the supporting framework. For stud spacing up to 450mm centres, 9.5mm plasterboard is acceptable, whilst for stud spacing up to 600mm centres, 12.5mm or thicker plasterboard should be used. Using plasterboard that is too thin for the stud spacing can result in deflection between studs, leading to cracking at joints and fastener pops where nails or screws push through the surface as the board flexes.

Tapered edge boards should be used where plasterboard is to be jointed before decoration. These boards have edges that are slightly recessed, allowing joint tape and compound to be applied flush with the board surface, creating an invisible joint when properly finished. Square edge boards are suitable where joints will be covered by other materials such as coving or where the surface will receive wet plaster skim coating.

For fire and sound-resisting walls, such as separating walls between properties and walls to WCs, the correct thickness, number of layers and sealing methods must be specified in the design information. These walls often require two layers of plasterboard with staggered joints to prevent fire or sound transmission through gaps, and all joints and penetrations must be properly sealed with appropriate acoustic sealant.

The NHBC standards also reference guidance on the use of plasterboard in wet areas such as bath and shower areas, directing readers to Chapter 9.2 (Wall and ceiling finishes) for detailed requirements. Moisture-resistant plasterboard is typically required in these locations, and proper sealing and finishing is essential to prevent water penetration that could lead to deterioration.

During snagging inspections, we regularly identify plasterboard defects, which are among the most visible issues in new build homes. Common defects include poor joint finishing with visible ridges or hollows along joints, nail or screw pops where fixings are visible or pushing through, cracks at internal corners or along joints (which may indicate movement, inadequate fixing or improper jointing), damaged board surfaces from impact or rough handling, and inadequate fixing with boards that flex when pressed or fixings spaced too far apart. We also check for proper sealing around electrical boxes, switches and other penetrations, particularly in walls requiring fire or acoustic protection.

6.3.13 – Damp Proof Courses

Damp proof courses (DPCs) are essential barriers that prevent moisture from rising up through walls or transferring from wet areas such as concrete floor slabs. The NHBC standards require that DPCs be installed where required to prevent moisture entering the building, with specific requirements for different wall types and locations.

Load-bearing partition walls built on foundations should have a DPC installed at or just above ground level, similar to external walls. Where partitions that could be affected by residual damp (particularly timber or steel framed partitions) are placed on concrete floors, a DPC should be provided directly below the partition, even where there is a damp proof membrane (DPM) beneath the floor slab. This additional protection is important because concrete slabs can retain moisture for considerable periods after construction, and timber or steel in contact with damp concrete can deteriorate.

DPCs should be at least the width of the wall or partition they’re protecting to ensure moisture cannot bypass the barrier at the edges. They should be linked with any adjoining DPM to create a continuous barrier around the building envelope and should be continuous or lapped by a minimum of 100mm where joints are necessary to prevent moisture passing through gaps.

Where steps are necessary in the ground floor slab (for example, between different floor levels or where the floor steps down into a bay window area), a DPC should be incorporated as a continuous link between the upper and lower DPM. This maintains the moisture barrier across the level change. The DPC must be protected from damage during construction, as tears or punctures will compromise its effectiveness. Where steps are greater than 150mm, structural waterproofing should be provided in accordance with Chapter 5.4 (Waterproofing of basements and other below ground structures), as these deeper changes in level can create more complex moisture management challenges.

The NHBC standards specify acceptable DPC materials, including bitumen based materials to BS 6398 or BS EN 14967, polyethylene to BS 6515, thermoplastics and elastomers to BS EN 14909, and proprietary materials assessed in accordance with Technical Requirement R3. Each material type has different characteristics regarding flexibility, durability and ease of installation, but all must provide effective moisture barriers when properly installed.

During snagging inspections, we cannot directly inspect DPCs as they are concealed beneath wall finishes and floor coverings. However, we can identify symptoms that might indicate DPC problems, such as damp patches on walls near floor level, deterioration of timber sole plates or skirting boards, musty odours suggesting trapped moisture, or efflorescence (white salt deposits) on masonry near the floor. These signs are particularly important to note in new builds, as whilst some residual construction moisture is normal and will dry out over the first heating season, actual DPC defects require investigation and remediation.

6.3.14 – Components

Wall ties, joist hangers, restraint straps and other metal components used in wall construction play critical structural roles and must be of the appropriate type and strength with adequate durability. The NHBC standards require that these components have sufficient protection against corrosion to ensure they maintain their structural function throughout the life of the building.

Joist hangers support floor joists bearing into walls, restraint straps tie walls to floors to prevent outward movement, and bond ties connect different leaves of cavity walls. All these components are typically concealed within the finished construction but are essential for structural stability. If corrosion were to weaken these components, serious structural problems could develop.

The standards specify that ferrous metals (iron and steel components) must have appropriate levels of protection against corrosion. Acceptable protection includes post-galvanizing to BS EN ISO 1461, which involves dipping fabricated components in molten zinc to create a thick protective coating, or pre-galvanizing to BS EN 10143, where steel strip or sheet is galvanized before being formed into components, resulting in a thinner but still effective coating.

The choice between post-galvanizing and pre-galvanizing often depends on the component type and manufacturing process. Larger fabricated items like restraint straps and joist hangers are typically post-galvanized, whilst wall ties are often made from pre-galvanized steel. Both processes provide effective corrosion protection when properly applied.

Stainless steel components offer superior corrosion resistance and are sometimes specified in particularly aggressive environments, such as coastal locations with salt-laden air, or in situations where chemical exposure is possible. However, the additional cost means stainless steel is typically only specified where the environment justifies it.

During snagging inspections, we cannot inspect most structural components as they are concealed within walls and floors. However, we occasionally see exposed joist hangers, restraint straps or other metalwork where construction is incomplete or where access panels provide visibility. In these cases, we can verify that components appear to be properly galvanised (showing the characteristic spangled appearance of zinc coating), are free from damage that might compromise their protective coating, and are properly installed according to their intended use. Any signs of rust or corrosion on components in a new build are concerning and should be investigated, as properly protected metalwork should show no corrosion for many years.

6.3.15 – Further Information

The NHBC Standards reference BS 8000-8 (Workmanship on construction sites: Design and installation of dry lining systems, Code of practice) as the key supporting document for internal wall construction. This British Standard provides comprehensive guidance on dry lining installation, covering preparation of backgrounds, fixing methods, joint treatment, and finishing of plasterboard systems.

BS 8000-8 is particularly valuable because it bridges the gap between product standards (which specify what materials should be) and construction standards (which specify how buildings should be built). The document provides detailed practical guidance on workmanship issues such as the correct spacing and setting depth for fixings, proper joint taping and filling techniques, requirements for different moisture environments, and methods for achieving fire-resistant and acoustic constructions.

For anyone involved in assessing dry lining quality, whether as a professional inspector, site supervisor or homeowner, understanding the principles in BS 8000-8 provides valuable context for identifying good and poor workmanship. Whilst the full British Standard is a technical document requiring purchase from BSI, many of its key principles are reflected in manufacturers’ installation guides and industry guidance documents.

The reference to further information at the end of Chapter 6.3 acknowledges that the NHBC Standards, whilst comprehensive, cannot cover every detail of internal wall construction. Builders, designers and inspectors may need to consult additional sources including British and European Standards, Building Regulations and supporting documents, manufacturers’ technical literature, and specialist industry guidance for particular construction types or systems.