Limestone cleaning & sealing tips

What is the best sealer for Limestone exterior walling?

When applying a penetrating sealer to Limestone exterior walling, you are first and foremost requiring water repellency. There are good options for this in both water and solvent-based options. The 4 best products for this application are:

1. Defender CSD 50 – Provides water repellency and surface consolidation (strengthening)
2. Defender Gold WB – Provides premium water repellency as well as a high degree of oil repellency
3. Defender SV – Water repellent and rising damp cure (solvent-based)
4. Defender WB – Water repellent. (water-based)

What coverage would I expect to get from a penetrating sealer on a Limestone exterior wall?

Limestone is typically very porous. However vertical surfaces tend to accept less sealer. Probably around 1Lt per 4m2 / application. If the area to be treated is large it would be wise to do a trial few square metres to better assess coverage.

How many applications should I do of the sealer?

Two applications is standard, but three may be required if the surface is very porous.

How do I clean the surface of the stone before applying the sealer?

Best results will be obtained using Tile & Grout Power (dilute 1:60). Use Chlorosan for any mould or discoloured areas which remain. Ensure that the surface is rinsed very well after cleaning. Walls should be left for 24 – 48 hours between cleaning and sealing.