WBS ROUGHCAST ONTO NEW / EXISTING BLOCKWORK
For Refurbishment Only Applications
If applying directly to existing brickwork /blockwork / render surface, the substrate must be brushed down to remove any friable material, algae or lichen and fungicidal wash should then be applied. Any ridges or protrusions should be removed and hollows filled to provide a smooth surface.
For Refurbishment & New Build Applications
Stabilising solution may be applied if required to help improve adhesion and offer uniform suction.
- Install all beads and trims using approved WBS fixings at a maximum of 300mm centres (depending on the substrate – please consult WBS technical department for assistance).
- Mix basecoat to a pliable consistency using approximately 4-5 litres of clean water per 25kg bag of basecoat and dash receiver, Use approximately 5-7 litres of clean water per 25kg bag of Roughcast Render. A suitable measuring bucket ensures the correct quantity and accuracy each time.
- Ensure that the basecoat is mixed thoroughly – it takes at least 10 minutes to dissolve the powder additives. Note how the dryish mix becomes creamy after several minutes. Mix will normally be slightly sticky.
- Note: Renders with a high polymer content should be left to stand for 10-15 minutes and be remixed to break the initial set.
- Do not add anything to the mix other than clean water.
- First Coat – Basecoat
- Trowel apply basecoat to substrate, dubbing out to a minimum of 8mm (or to architect’s specification) until a level surface is achieved.
- Bed in alkali resistant reinforcing mesh into top third of basecoat (if required), ensuring that an overlap of a minimum of 75mm is achieved.
- When basecoat is dry, apply additional stress patches and corner reinforcements across all window and door openings at a 45° angle.
- Tidy up base rails and profiles with a damp paint brush or similar to ensure a professional finish.
- Lightly scratch basecoat surface with a scratch comb to provide a key for finishing coat.
- Allow 24 hours curing time before further application, unless advised otherwise.
- Second Coat – Coloured Dash Receiver
- Trowel apply coloured dash receiver to first layer of basecoat, in a single coat 4-6mm thick (or to architect’s specification).
- Allow to firm but not set. A 16mm overall finish will avoid ghosting.
- Dashing Coat – Coloured Roughcast
- Always turn a sufficient quantity of the final coat for a gable or large panel into a bath or box to ensure that regularity of colour is achieved.
- Do not add any further water to the mix in the gauging box on the scaffold.
- Throw the Roughcast on to the surface of the Dash Receiver while the Dash Receiver is still green, using a hand scoop or alternatively, an adjustable Tyrolean gun may be used.
- Do not go over semi-cured areas to fill in misses, as this can lead to inconsistency of colour. Do not apply water during set.
Provided strictly for guidance purposes only. For technical support please call 0800 107 32 99.