Replastering After Installing a Damp Proof Course

Installing a damp proof course (DPC) is one of the most effective ways to treat incidences of rising damp, an issue which can be seriously damaging. After installation, the masonry walls often require replastering. This should be done to an extremely high standard so that the new plaster is protected and so the DPC continues to perform optimally. 

Wykamol, a leading manufacturer of a wide range of superlative products, has created RenderProof to help in this important regard. Twistfix is a proud supplier of RenderProof, along with many other items from Wykamol's exceptional collection of products. 

RenderProof is a unique formula that has been expressly designed to add to sand-and-cement renders. As well as improving the workability of the render, the plasticising additive reduces the size of pores in masonry, which dramatically minimises the ability of water to pass through its structure and thus prevents the damage that this can cause. After a DPC has been installed as a treatment for rising damp, RenderProof helps to hold back naturally-evaporating water, preventing efflorescent salts from being transferred to the new plaster.  

When cured, RenderProof retains its vapour-permeability, allowing the walls to breathe. It can be used with equal success on all masonry types and allows for large areas to be quickly and effectively plastered. Here is a quick guide for using RenderProof though you should of course read all of the provided instructions thoroughly and follow them to the letter. 

• Before commencing application, make sure that the surface of the masonry wall is dry. The surface should also be clear of any organic matter, plaster, dust and any other loose materials. All masonry joints should be raked out.
• If the surface is particularly porous or has a high level of suction, it should be primed before plastering. For this purpose, we can highly recommend using SBR Latex Bonding Agent, which is also manufactured by Wykamol. It is available to purchase from the Twistfix website.
• Backing coats require that one part of cement be mixed with three parts of washed sharp sand; ensure that these materials meet the BS EN 197-1:2011 and BS EN 13139:2002 standards respectively. Four parts of sand should be used to create a float coat. 
• Add one part of RenderProof to 24 parts of clean water. Combine this mixture with the sand and cement and mix thoroughly. 
• The backing coat can now be applied, with the thickness being between 10mm and 12mm. The coat should end at a height of at least 50mm above the floor. Make sure that the DPC is not bridged.
• As the coat of render begins to set, scratch its surface to create a mechanical key for a subsequent coat.
• You can then proceed to apply a float coat that reaches a thickness between 8mm and 10mm. It is important to note that you should not apply more than two plaster coats in a single working process. 

If you need advice about using RenderProof, our technical team can help so please do not hesitate to reach out to us. If you'd like to stay in touch with all of the latest news from Twistfix, please subscribe to our email newsletter.