Waterproof Render Interior & Exterior
A protective shield for your walls against damp, rain and cold!
Render is much more than a finish. It forms a protective layer that shields your walls from cold and from moisture working its way into the masonry. No render is 100% waterproof on its own, but a properly specified and applied waterproof render protects most of the wall structure beneath it, preventing frost damage, cracking, mould and damp patches. At Crystal Damp Proofing & Basements Ltd, we apply waterproof renders to interior and exterior walls, using the right system for each building.
Why Is Waterproof Render So Important!!
Waterproof render protects your property against:
- Driving rain and splashback: water hitting the walls and bouncing up from the ground.
- Rising and penetrating damp: moisture soaking into the masonry from the ground or through the walls.
- Frost damage: water trapped in the wall freezes, expands and cracks the masonry and render.
- Cold and heat loss: dry walls insulate far better than wet ones.
- Mould, algae and moss: damp surfaces quickly become a breeding ground for growth, inside and out.
How Do We Make Render Waterproof?
We achieve waterproof render by adding specialist waterproofing additives to the mix. These chemicals penetrate the pores of the material, bond together and form a protective coating within the render, greatly reducing how much water it can absorb. Depending on the location and conditions, we use:
- Cement renders with waterproofing additives: the strongest and most watertight option, highly resistant to impact, ideal for areas most exposed to moisture and for interior basement walls.
- Silicone renders: highly water-repellent, so rain runs off and carries dirt with it. Flexible and resistant to moss and algae.
- Acrylic renders: low water absorption, flexible and weather-resistant, though less breathable than mineral or silicone renders.
- Mosaic (resin) renders: very resistant to water and impact, most often used on plinths and ground-floor areas where rain splashes up from the ground.
- Renovation renders: highly breathable, salt-resistant renders for restoring old, damp walls.
Where and When Should Waterproof Render Be Used?
- Plinths and lower walls (the bottom 30–50 cm of the facade): exposed to splashback from rain and lying snow.
- Foundation and basement areas: where there is no full vertical waterproofing, or as extra protection for walls in contact with the ground.
- Exposed walls: walls facing the prevailing wind and rain, and walls that dry slowly and attract algae.
- Around terraces, balconies and entrances: where water from flat surfaces splashes or runs onto the render.
- Near water and trees: buildings close to rivers, lakes or woodland, where the air is constantly humid.
- Old, damp walls: when restoring buildings damaged by moisture.
- Interior walls: in basements, cellars and other rooms exposed to damp.
Should the Mortar Be Repaired Before Rendering?
Yes, and it is essential. Render is only as good as the wall underneath it. If the existing masonry mortar is crumbling or loose, it must be replaced without delay, raked out and repointed to a depth of at least 20 mm. This gives the render a sound base and is key to achieving proper waterproofing.
How We Carry Out the Work
- Survey: we assess the walls, the source of any damp and the right render system for your property.
- Removing old render: we strip damaged or blown render back to sound masonry.
- Repairing the mortar: we rake out crumbling joints and repoint to a depth of at least 20 mm.
- First coat: we apply the first coat of render with waterproofing additives, at a minimum thickness of 10 mm.
- Further coats and finish: we build up the following coats and apply the chosen finish, whether mineral, silicone, acrylic or mosaic.
We only render in suitable weather, between +5°C and +25°C, with no rain or strong wind, and onto a sound, properly prepared wall that is not saturated with water. Rendering over a soaking wet wall traps moisture inside, which causes the finish to blister and come away.
We Take Full Responsibility for Our Work
We take responsibility for every render we apply. If a defect appears in our work, we put it right. Every project is carried out by our own qualified team, so you always know who did the job and who stands behind it.
Trusted Manufacturers & High-Quality Materials
We use proven products from well-known manufacturers such as Wykamol, Delta, Biokil and Mapei. Together, they form one complete system that keeps your walls protected for years to come.
Qualified Specialists & a 10-Year Guarantee
Our family-run team holds CSSW qualifications, with a minimum of 10 years’ experience each. We back our work with a 10-year guarantee covering workmanship, plus a QANW Insurance Backed Guarantee that transfers to the new owner if you sell your property. Based in Croydon, we work on domestic and commercial properties across London and the South East.
See What Our Clients Say
We are proud of our 5-star Google rating: see our reviews. If your basement is damp or takes in water, book a survey in our Booking Survey section, or call or message our fully qualified advisors.
