A consistent approach to finishes

9.1
Also See:
6.11

9.1.2External walls

External walls shall be built to appropriate tolerances and have an acceptable finished appearance. Issues to be taken into account include:

  1. fairfaced masonry
  2. render
  3. curtain walling
  4. rainscreen cladding
  5. brick slip cladding
  6. timber cladding
  7. tile hanging
  8. cast stone sills.

Tolerances and appearance should be considered:

  • for the entire wall (e.g. panels and interfaces), and not for the individual elements of the construction, such as bricks, or design features and details (e.g. quoins, soldier courses and plinths)
  • in daylight, and from a minimum distance of 10m.

Fairfaced masonry

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
  • be within a maximum deviation of 4mm over 1m at external reveals.

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 be:

  • 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 (approx. 2.5m)
  • a maximum of 8mm from plumb in any storey height (2.5m storey height)
  • a maximum of 8mm from plumb in total for walls up to 5m high
  • a maximum of 12mm from plumb in total for walls over 5m high.

Bed joints should:

  • not have frequent variations in level
  • have a maximum deviation of ±8mm, in walls 5m long (a pro rata tolerance is applicable for walls less than 5m long),
  • have a maximum deviation of ±12mm in walls more than 5m long.

The thickness of an individual bed joint should not vary from the average of any eight successive joints by a maximum of 5mm.

The vertical alignment of perpend joints should not deviate significantly from the perpendicular. As bricks can vary in length, not all perpend joints will align; however, there should not be a cumulative displacement of the perpend joints in a wall.

Render

Render should:

  • be reasonably consistent in texture, finish and colour
  • be flat, within a maximum ±8mm vertical and horizontal deviation in 5m, though this may increase where render is in close proximity to features
  • not have crazing 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 hairline cracking and crazing is likely to occur in both traditional render and proprietary render systems. Such cracking and crazing should not impair the performance of the render.
  • 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 on plan 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 be within:

  • reasonable tolerances and appearance for the materials
  • ±8mm maximum vertical and horizontal deviation from flatness in 5m
  • a tolerance of ±8mm maximum deviation for each 5m section of wall for bed joints (a pro rata tolerance is applicable for walls less than 5m long).

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, and may vary in colour and size depending on the manufacturing process.

Cast stone sills

Surface abrasions and chips which occur on site should be removed in accordance with the manufacturer’s recommendations, which may include filling, polishing out, respraying or painting as appropriate.

Also note:

  • Cast stone is manufactured with natural products and colour variations are inevitable.
  • Efflorescence, fungicidal growth and colour variation may occur due to orientation, shading and pollution.