Wykamol RenderProof Render Additive & Waterproofer

Wykamol RenderProof Render Additive & Waterproofer

Wykamol Group | Waterproofer Additive

RenderProof is a Render Additive & Waterproofer based on an alkaline soap mixed with fatty acids, designed for use in sand / cement, external render coats following the insertion of a chemical DPC.

Available in 5 Litre and 25 Litre Containers, Concentrated Solution.

 Renderproof is part of the Wykamol Re-Plastering Specification which is supported by BBA Certification Certificate No: 02/3961.

  Read our Guide on 'How To Identify & Treat Rising Dampness On Walls'


Renderproof Render Additive & Waterproofer

RenderProof is an additive based on an alkaline soap mixed with fatty acids, designed for use in sand / cement, external render coats following the insertion of a chemical DPC.

Efflorescent salts are often left behind in the wall after a chemical DPC, which are harmful to the plaster finish, leaving the appearance of damp patches.

A suitable re-plastering specification must therefore be used, including a salt inhibiting and waterproofing product such as RenderProof.

  Read our Guide on 'How To Identify & Treat Rising Dampness On Walls'

Product Benefits:

  • BBA Approved

  • Reduces pore size in Render to prevent passage of water

  • Covers large areas in a single application

  • Highly Concentrated: 1 part RenderProof to 24 parts water

  • Prevents passage of residual ground salts which are harmful to plaster finishes

  • Vapour permeable, allowing the walls to breathe


Surface Preparation (Masonry):

  1. Masonry joints should be raked out and all surface thoroughly cleaned to remove dust or other friable material. All traces of previous plaster must be removed. Any organic matter (including timber fixings) must be removed

  2. Where appropriate, fixing points which necessitate cutting into the background must be prepared.

  3. High suction surfaces should be thoroughly wetted or primed using an SBR Bonding Agent. SBR can also be used to provide a mechanical key on smooth, dense surfaces.

  4. Where very high levels of salt contamination are present, or suspected, further preparation with Salt Neutraliser may be necessary before application commences. Consult our Technical Department if the extent or nature of the salt contamination is unclear

Mixing - Backing Coat:

A mix of 3 parts by volume of washed, sharp sand to 1 part of cement, gauged with potable water containing 1 part of RenderProof with 24 parts of water. The constituents of mixes should conform to the following descriptions:

  1. Ordinary portland Cement (OPC) to BS EN 197-1:2011

  2. Aggregate-clean, sharp, washed sand. The coarsest, sharpest sand, suitably graded for plastering, should conform to BS EN 13139:2002

  3. Water - Fit for drinking and free from organic matter.

N.B. The amount of gauging water in the undercoats should be
the minimum consistent with reasonable application.

Mixing - Float Coat:

A mix of 4 parts volume of washed, sharp sand to 1 part by volume of Ordinary Portland Cement.

Pack Size Gauging Water
5 Litre 120 Litres of gauging water in dry sand per 250Kg of cement
25 Litre 600 Litres of gauging water in dry sand per 1250Kg of cement

Application - Backing Coat:

The plaster should be applied to a thickness of 10-12mm. The backing coat should finish at least 50mm above the solid floor and must not bridge the Damp-Proof Course.

Care should be taken to avoid dropping plaster or other debris through the gap between the wall and the edge of any suspended floor.

The surface should be scratched as it begins to set, to give a good key for subsequent coats.

Application - Float Coat:

The plaster should be applied to a thickness of 8-10mm in the same areas as the backing coat.

Application - Subsequent Coats:

No more than two plaster coats should be applied in one continuous working process. If a greater thickness is required:

  1. The first coats should be scratched and left to cure for 7-14 days

  2. Apply SBR Bonding Agent as a primer before proceeding

  3. The sand/ cement undercoats should be scrape finished and mist sprayed for the first 48 hours to reduce the risk of shrinkage and cracking.

Conditions & Limitations:

Under no circumstances should Gypsum based plaster be used for the backing or float coat, nor should it be added to the mix of either coat.

RenderProof is not suitable for use in lime-based mixes or mixes with a lower cement content than recommended.

The recommended sand and cement mix can be used to to ‘dab’ any angle beads etc. to avoid salting.


A minimum of 24 hours curing time must be allowed after application of the float coat, even under ideal curing conditions.


The finishing plaster should be applied at a thickness of 1.5mm - 3mm. Since polished surfaces are undesirable, excessive use of the trowel or brush should be avoided.


Initial decoration should be delayed as long as possible and should not be applied within 14 days of the finish plaster coat.

Temporary decoration should be limited to a vapour permeable finish such as a breathable paint. Final decorations which reduce permeability, such as papers and oil paints, should not be applied until the walls have dried out, with at least 12 months being allowed following temporary decoration (for typical 225mm brickwork walls).

Drying times for thicker walls may extend to several years and will depend, in part, on the level of winter time heating etc. If impermeable decorative finishes are to be applied, in such situations an alternative approach to reinstatement may be considered, involving the use of vapour impermeable ‘air-gap’ membranes

Data Sheets

Technical Data Sheet

Safety Data Sheet

BBA Certificate (Re-Plastering Specification)

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