10 · CHAPTER 10 · SUBSTRATE Chapter 10 · Substrate
How is the substrate tested?
A load-bearing, clean and sufficiently dry substrate is a prerequisite for the adhesion of the system. This chapter describes suitable substrates, testing steps and exclusions.
Which substrates are suitable?
Load-bearing, mineral and other porous substrates such as concrete, cement, masonry, stone, render, unglazed ceramics, plasterboard, fibre cement, concrete tiles, wood or tar paper — including old, load-bearing stock (e.g. listed buildings).
What condition must the substrate be in?
Dry, firm and load-bearing, and free of loose parts, oil, grease, dust, mould, salt and old, loose coatings. Loose or non-load-bearing old coatings must be removed.
How is moisture tested?
The substrate moisture must be below 4 % (below 2.5 % for concrete). Measurement is carried out with a suitable moisture meter; if in doubt, wait until the substrate is ready to be coated.
How is load-bearing capacity assessed?
By visual and wipe test (dust, sanding), scratch/tap test (voids) and — if in doubt — an adhesive pull-off or cross-cut test on the intended primer.
Testing checklist before priming
| Test point | Requirement |
|---|---|
| Strength / load-bearing capacity | firm, load-bearing, no voids or sanding |
| Cleanliness | free of dust, oil, grease, mould, salt, loose parts |
| Old coatings | retain only load-bearing coatings, remove loose ones |
| Substrate moisture | < 4 % (concrete < 2.5 %) |
| Substrate temperature | +5 °C to +30 °C, not in direct sun above +30 °C |