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Good brickwork : a snaggers guide

There are many resources on the net on what good brickwork looks like , but little on what bad brickwork is and perhaps how it’s come about

One useful resource is the NHBC guide to good brickwork which now out of print is available to view and download

So what to look for in terms of appearance only and how to look …well the nhbc state that brickwork should be viewed from a minimum distance of 10 metres

Problems to avoid:
„ Low strength
„ Variations in mix
„ Poor durability
What to do:
„ keep mixers and plant clean
„ store materials correctly
„ ensure that the mix is correct for:

  • bricks/blocks being used
  • location in building
  • exposure of area
    (see table on page 10)
    „ do not use masonry cement as if it is OPC. More
    masonry cement is needed – refer to manufacturer’s
    recommendations
    „ keep mix proportions consistent

Problem to avoid:


„ Excessive cracking
What to do:
„ provide movement joints in the outer leaf to
minimise cracking:
Material Joint width(mm) Normal spacing
Clay brick 16 12m (15m maximum)
Calcium silicate brick 10 7.5 to 9m
Concrete block and brick 10 6m
Any masonry in a parpet wall 10 half the above spacings
and 1.5m from corners
(double the frequency)
The spacing of the first movement joint from a return should not be more
than half of the above dimension
„ install ties to each side of movement joints:
Vertically – 300mm or each block course

Ok so there’s a lot more to this brick laying game and lots more to learn

The nhbc guide a Consistant approach to finishes is the snaggers Bible and a constant companion

Fairfaced masonry should:

  • be reasonably uniform in texture, finish and colour, including mortar
  • not have excessive colour banding
  • not have significant cracks in the facing bricks or other damage, such as chips and marks greater than 15mm in diameter.

Where a fairfaced finish can only be achieved on one side (such as half brick walls), the other faces should be left neat and tidy.

Also note:

  • some mortar blemishes will occur on individual masonry units.
  • some variation will occur in the texture, finish and colour of mortar, in individual masonry units and generally over the wall.
  • efflorescence occurs naturally in some types of masonry. it is not harmful and generally disappears over time.
  • some brick products have features or marks which may be in excess of 15mm in diameter.
  • some minor shrinkage cracking may occur between masonry units (bricks and blocks) and mortar joints.

Fairfaced masonry should meet the following tolerances:

  • adequately straight on plan, with a ±8mm maximum deviation in any length of wall up to 5m
  • adequately straight in section, with a tolerance of ±8mm per storey height (up to 3m)
  • a maximum of 8mm from plumb in any storey up to 3m. Taller walls should be a maximum of 8mm from plumb per storey and 12mm in total
  • a maximum deviation of 4mm over 1m at external reveals.

Bed joints should be reasonably straight, measured along the top of a given row of bricks, with:

  • a maximum deviation from straightness of ±8mm in any 5m section of wall.

The thickness of an individual bed joint should not vary from the average of the next eight successive joints by a maximum of ±1.5mm.

Example of how to determine if bed joint thickness is acceptable

Measure and add 8 successive bed joints and divide by 8 to determine the average size:

11+10+12+10+11+9+11+10 = 84
Divide by 8 = 10.5mm

Therefore, the acceptable range of the bed joint below the 8 measured bed joints is 9-12mm.

Perpend joints should not cumulatively displace in the same direction for more than 5 joints. The centre line of any perpend joint should generally be within ±15mm of the centre line of the next 5 successive perpend joints.

Also note:

  • to achieve setting out, perp joints in masonry panels between openings may be offset with the perp joints in the panels above and below. The joints within the panel should not cumulatively displace.

Render

Render should:

  • be reasonably consistent in texture, finish and colour
  • be flat, within a maximum ±4mm vertical and horizontal deviation in 5m
  • be free from crazing (a set of hairline cracks, generally less than 1mm in depth and no more than 0.2mm wide).

Also note:

  • there may be some colour variation in appearance due to differences in suction of the background and orientation of the wall.
  • daywork joints, patching and other repairs may be visible but should not be unduly obtrusive.
  • some localised hairline cracking is likely to occur in both traditional render and proprietary render systems. such cracking and crazing should not impair the performance of the home.
  • areas of render in close proximity to features (e.g. bell casts) are excluded from the tolerance.
  • flatness is measured in a similar way to straightness and plumb of masonry.

Curtain walling

Curtain walling should be within:

  • reasonable tolerances and appearance for the materials
  • a maximum deviation of ±2mm in any storey height or structural bay width, and ±5mm overall, unless otherwise specified in the design.

Rainscreen cladding

Rainscreen cladding should be within:

  • reasonable tolerances and appearance for the materials
  • a maximum deviation of ±3mm in any storey height or structural bay width, unless otherwise specified in the design.

Brick slip cladding

Brick slip cladding should meet the same tolerances as fairfaced masonry.

Timber cladding

Variation in colour may occur in uncoated timber exposed to the weather, and the rate and extent may vary.

Also note:

  • the effects of normal weathering may cause certain uncoated timber, over time, to develop a silver/grey colour.

Tile hanging

Panels should be reasonably uniform in appearance, particularly at abutments. Tiles should not have significant variations in texture, finish and colour. See Clause 9.1.13.

Cast stone elements

Cast stone should be reasonably uniform in both colour and texture.

Also note:

  • efflorescence, fungicidal growth and colour variation may occur due to orientation, shading and pollution.
  • surface abrasions and chips should be repaired in accordance with the manufacturer’s recommendations.

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