The National House Building Council (NHBC) sets specific standards for steelwork in new build homes to ensure structural integrity and safety. Chapter 6.5 of the NHBC Standards provides detailed guidance on steelwork that supports masonry partitions and timber floors, including requirements for installation and protection.

Why This Matters to Homeowners

Understanding NHBC steelwork standards is important because structural steel plays a vital role in the integrity and safety of your new home. These standards ensure that all steelwork is properly specified, installed, and protected against corrosion and fire.

These standards are particularly relevant if your home includes:

• Steel beams supporting internal walls – These beams need to be correctly sized for the weight they carry, properly supported at each end, and protected against corrosion. The standards specify exact requirements based on the wall type (dense, medium, or lightweight masonry) and height.
• Steel supports for timber floors – These require careful consideration of beam sizes based on the floor area supported, proper connections between beams, and adequate support where the beams rest on walls. The standards also ensure proper allowance for natural timber shrinkage to prevent future issues.
• Steel structures around staircases or floor openings – These need special attention as they often support additional loads from the staircase itself. The standards specify how these areas should be reinforced and supported to ensure long-term stability.
• Steel lintels over doors or windows – While these might seem simple, they need proper sizing and support to prevent any settlement or movement that could lead to cracking in the walls above. The standards ensure these crucial support elements are correctly specified.

Key Requirements for Steelwork

Support Requirements

The way steel beams are supported is crucial for the structural integrity of your home. The NHBC standards set out clear requirements for beam support to ensure safe load distribution and prevent any future structural issues.

Steel beams in your home must:

• Have proper support on both ends, with a minimum 100mm bearing length – This means each end of the beam needs to rest on at least 100mm of solid wall or support. This requirement ensures the beam’s weight and the loads it carries are properly distributed to the supporting structure. Inadequate bearing length could lead to structural problems over time.
• Not be supported above window or door openings – Beams must rest on solid masonry, not above openings where the support might be compromised. This is because the area above windows and doors is already under stress from the lintel supporting the opening itself, and adding additional load could cause problems.
• Rest on clean, dry, and level surfaces – This ensures the beam sits properly and evenly on its supports. Any debris, moisture, or uneven surfaces could lead to uneven load distribution or corrosion of the steel over time.
• Include padstones where necessary to distribute loads safely – Padstones are special supporting blocks that help spread the concentrated load from steel beams over a wider area of the wall. They are required when:
  • The wall supporting the beam isn’t strong enough to take the concentrated load directly
  • The flange of the beam is narrower than the required bearing area
  • The beam needs to be raised to the correct height to support floor joists or wall plates

The size and specification of padstones varies depending on factors such as:

• The load being carried by the beam
• The thickness of the supporting wall
• The type of masonry used in the wall construction
• Whether the beam runs parallel or perpendicular to the wall

Proper beam support is essential for preventing structural movement and ensuring your home remains stable throughout its lifetime. If you notice any cracks near beam supports or movement in supported walls or floors, these should be investigated promptly by a qualified professional.

Protection Standards

The protection of structural steelwork is vital for ensuring its longevity and maintaining the structural integrity of your home. The NHBC standards specify different levels of protection depending on where and how the steel is used.

All steelwork in your home should:

• Have appropriate protective coatings applied before installation – All structural steel must arrive on site with factory-applied protective coatings. These initial coatings form the primary defence against corrosion and must be applied in controlled conditions. If any damage occurs to these coatings during installation, they must be properly repaired on site before the steelwork is built into the structure.
• Be protected against corrosion based on its location and exposure conditions – Different environments require different levels of protection:
  • External steelwork above ground needs high-level protection (C4 or C5 category)
  • Steel within splash zones (up to 150mm above ground) requires very high protection (C5 category)
  • Steel in ventilated sub-floor spaces needs medium protection (C2 category)
  • Steel in kitchen and bathroom areas needs specific protection against moisture (C2 category)
  • Steel embedded in external walls requires special consideration and protection (C5 category)
• Meet fire resistance requirements as specified by Building Regulations – This might involve:
  • Intumescent coatings that expand when heated to protect the steel
  • Encasement in fire-resistant materials
  • Specific minimum coating thicknesses for fire protection
  • Regular inspections to ensure fire protection remains intact
• Have compatible decorative finishes if visible – Where steelwork is exposed and requires decorative finishing:
  • Any decorative paints must be compatible with the protective coatings
  • The original protective system must not be compromised
  • Manufacturer recommendations must be followed for any additional coatings
  • Regular maintenance may be required to maintain both protection and appearance

The level of protection required depends on factors such as:

• The location of the steel within your home
• The environmental conditions it’s exposed to
• Whether it’s internal or external
• Its proximity to moisture sources
• The structural importance of the element

If you notice any rust, flaking paint, or damage to protective coatings on visible steelwork, you should have this assessed by a qualified professional, as it could indicate a need for maintenance or repair to maintain the steel’s protective systems.

Connection Standards

The way steel beams connect to other structural elements is crucial for your home’s stability and safety. The NHBC standards provide detailed requirements for these connections to ensure they can safely transfer loads between different parts of the structure.

Where steel beams connect to other structural elements, they must:

• Use appropriate connection methods specified by the standards – Acceptable methods include:
  • Black bolts (standard structural bolts) for most typical connections
  • Welded connections where specified by the design
  • Special connections designed by structural engineers for complex situations
  • High-strength friction grip bolts where required by specific designs
• Have properly sized and installed bolts or welds – For typical floor beam connections:
  • Bolt sizes and types must match the specifications (usually M20 bolts)
  • Cleats (connection plates) must be the correct size (typically 70x70x6mm rolled steel angle)
  • Welding must achieve specified strength (typically 6mm fillet welds where allowed)
  • All bolts must include appropriate washers
  • Connections must be properly tightened to the required torque
• Meet specific requirements for different beam sizes and configurations:
  • For beams between 170mm and 230mm deep, connections need six bolts or equivalent welding
  • For beams less than 170mm deep, three bolts may be sufficient
  • The difference in depth between connected beams must not exceed 40mm
  • Beams must only be cut, drilled, or welded where specifically required by the design

Important considerations for homeowners:

• Only certified welders should carry out any welding work
• Modifications to existing connections should never be made without professional advice
• Signs of movement or rust around connections should be investigated promptly
• Any loose or rattling connections should be reported to your builder during the warranty period

If your home requires steel beam connections that fall outside these standard specifications, they must be specially designed by a qualified engineer in accordance with NHBC Technical Requirement R5.

Common Applications in New Homes

Supporting Internal Walls

Many new build homes use steel beams to support internal masonry walls, particularly where open-plan layouts are desired below. The NHBC standards specify strict requirements for this arrangement to ensure long-term stability. Steel beams must be carefully sized based on both the wall’s thickness and the type of blocks used (dense, medium, or lightweight). These beams can only support walls up to 2.7m in height and must be positioned exactly in the centre under the wall to ensure even load distribution. In most cases, special support blocks called padstones are required at the ends of the beam to help spread the load into the supporting walls. Getting these details right is crucial – if the support isn’t adequate, it could lead to cracking or movement in the walls above.

When steel beams support masonry partitions, they must:

• Be sized appropriately for the wall thickness and density
• Support walls no higher than 2.7m
• Be centrally positioned under the wall
• Have appropriate padstones where required

Floor Support

Steel beams are commonly used to support timber floors in new build homes, especially around staircases or in areas where long spans are needed. The NHBC standards require careful consideration of several factors to ensure these beams perform correctly. The design must account for natural timber shrinkage to prevent gaps developing over time, and beams must be correctly sized based on the exact floor area they’re supporting. Special attention is needed around openings such as stairwells, where additional trimming beams provide support for cut joists. All connections between steel beams must meet specific NHBC requirements to ensure they can safely transfer loads. These requirements help prevent issues like squeaky floors, excessive movement, or sagging that could develop if the support isn’t adequate.

For timber floor support, steel beams must:

• Account for timber shrinkage in the design
• Be properly sized for the floor area they support
• Include appropriate trimming around openings
• Have connections that meet NHBC specifications

What to Look For

While structural steelwork in new homes is designed to be reliable and long-lasting, it’s helpful to be aware of potential warning signs that might indicate issues. Keep an eye out for any rust or corrosion on visible steel elements, as this could suggest problems with protective coatings. If you notice any beams that appear to be sagging or deflecting, this should be investigated promptly. Watch for cracks developing in walls either above or below where steel beams provide support, and be alert to any unusual movement in floors or walls that are supported by steelwork. While these signs don’t necessarily mean there’s a serious problem, they should be reported to your builder during the warranty period so they can be properly assessed.

As a homeowner, while you’re not expected to be a structural engineer, you can look out for:

• Signs of rust or corrosion on visible steelwork
• Any visible deflection or sagging in beams
• Cracks in walls above or below steel supports
• Any movement in supported floors or walls

Maintenance Considerations

Structural steelwork in new homes is designed to be low-maintenance, but some basic care will help ensure its longevity. Any exposed steelwork should be kept clean and checked periodically for signs of damage or deterioration. If you spot any rust or damage to visible steel elements, report this to your builder while under warranty or consult a structural engineer if the warranty has expired. Good ventilation throughout your home is important to prevent condensation building up around steelwork, particularly in areas like kitchens and bathrooms. Where steelwork is visible and has a decorative finish, maintain this coating to ensure the underlying protective system isn’t compromised. These simple maintenance steps can help preserve both the appearance and structural integrity of the steelwork in your home.

While structural steelwork generally requires minimal maintenance, you should:

• Keep visible steelwork clean and well-maintained
• Report any signs of rust or damage to visible steel elements
• Maintain proper ventilation to prevent condensation around steelwork
• Ensure any decorative finishes remain intact where steelwork is exposed

Warranty Coverage

The structural steelwork in your new home is protected under the NHBC Buildmark warranty for 10 years from your completion date. This coverage includes any defects in the design, workmanship, or materials used in the structural steel elements of your home. If you notice any concerns with steelwork during this period, it’s important to report them promptly to both your builder and NHBC. During the first two years, your builder is responsible for rectifying any issues, while NHBC handles claims for years 3-10. Keep in mind that normal settlement of the building isn’t covered, but any significant structural movement or defects should be investigated.

Under NHBC Buildmark warranty:

• Structural steelwork is covered for 10 years from the completion date
• The warranty covers defects in design, workmanship, or materials
• Any issues should be reported promptly to your builder and NHBC

Further Information

Understanding the technical aspects of steelwork in your home can be challenging, but there are several resources available to help. Your home’s NHBC documentation contains important information about the structural elements used in your property, and your builder can answer specific questions about how these were implemented during construction. For any technical concerns or if you’re planning alterations that might affect structural steelwork, it’s best to consult a qualified structural engineer. The NHBC is also available to help with warranty-related questions and can provide guidance on whether any issues you’ve noticed are covered. While the NHBC standards are comprehensive in protecting homeowners, they’re technically complex, so always seek professional advice when dealing with structural concerns rather than trying to interpret them yourself.

For detailed technical specifications or concerns about steelwork in your home:

• Consult your home’s NHBC documentation
• Contact your builder directly for specific queries
• Seek advice from a qualified structural engineer
• Contact NHBC for warranty-related questions

Remember that while these standards provide crucial protection for homeowners, they are complex technical documents. Always seek professional advice for specific concerns about structural elements in your home.