A waterproofer additive is mixed directly into mortar, render or screed during preparation, making the mix itself more resistant to water penetration. Damp proof paint is applied as a coating to an already-set surface to create a vapour-resistant barrier on top. For new render or screed work, the additive approach builds protection into the material from the start rather than relying on a surface coating afterwards.
Liquid Waterproofing Chemicals for Renders, Mortars and Surfaces
Controlling moisture at source is far cheaper than fixing the damage it leaves behind. MacBlair stocks liquid damp and waterproofing chemicals for use in renders, screeds, mortars and on exposed surfaces, giving both new builds and renovation projects a reliable barrier against water ingress. These are working-chemical solutions applied during mixing or brushed onto surfaces directly, not decorative coatings.
The range includes two distinct product types suited to different stages of a job:
- Waterproofer and plasticiser additives — concentrated liquids mixed into sand and cement to improve workability, reduce water penetration and protect external renderings and screeds long term
- Bituminous brush waterproofers — solvent-based coatings applied to roofing surfaces including felt, corrugated iron, fibre cement, slates and lead, forming a tough, fibre-reinforced barrier that cures faster than water-based alternatives
Waterproofer plasticisers are particularly useful when laying external render or screed in Northern Ireland's wet climate, where protection against rain and damp needs to be built into the mix rather than added after the fact. Bituminous coatings suit cold or damp weather conditions, making them a practical choice for roof repairs when weather windows are short. Pair either product type with concrete and mortar additives for a more complete mix specification on larger jobs.
Once surfaces are treated and sound, construction sealants can be used to seal joints and gaps where water might otherwise track through. For surface preparation before applying any waterproofing treatment, the brick and patio cleaners range covers pre-treatment cleaning of masonry and external surfaces. MacBlair also stocks primers and bonding agents where adhesion to an existing substrate needs to be established before a coating goes down.
Damp Waterproofing FAQ's
Most concentrated waterproofer plasticisers are suitable for use in standard sand and cement renders and screeds. Always follow the manufacturer's dilution instructions, as overuse can affect the set time and workability of the mix. They are particularly well suited to external renders, chimney flaunching, copings and any cement work exposed to rain.
Bituminous brush waterproofers are better suited to large surface areas such as roofing felt, corrugated iron, fibre cement sheets and flashings, where a broad, seamless coating is needed. Sealants are more appropriate for sealing specific joints, gaps or cracks. Solvent-based bituminous coatings also have the advantage of curing in cold or damp conditions when water-based alternatives may fail to form a reliable film.
Yes. Waterproofing chemicals are protective treatments, not structural repairs. Active leaks, cracked masonry or failed flashings should be addressed first. Applying a waterproofer over an unresolved damp source may slow moisture movement temporarily but will not produce a lasting result. Surface preparation, including cleaning and removal of loose material, is essential before any chemical treatment is applied.
Most manufacturers recommend two coats for a continuous, weather-resistant finish. Allow the first coat to cure fully before applying the second. Coverage rates typically run at around 1.2 to 1.5 square metres per litre per coat depending on surface porosity, so calculate the area carefully before ordering to avoid running short mid-job.