Knowledge base

DO YOU NEED TO PRIME WALLS BEFORE TILING?

Before tiling or levelling, certain wall and floor substrates must be primed for a number of reasons including:

• to reduce the porosity (absorbency) of substrates or bases to prevent the formation of air bubbles or pinholes
• to minimise the risk of a chemical reaction with cement-based adhesives
• to add surface strength to weak (or powdery) surfaces
• to help prepare surfaces prior to waterproofing

Here’s our step-by-step guide to priming a wall before tiling as well as adequate floor preparation.

Step 1 

Before priming, make sure you know what type of surface you are priming and what adhesive you are going to use. This is because the BAL Primer can be used diluted or undiluted, depending on what substrate you’re tiling on to, or whether you’re using a cement-based or ready-mixed adhesive.

Step 2

Check the dilution and number of coats required. We recommend priming the following substrates with two-coats of undiluted BAL Primer:

• Gypsum plaster (when using a cementitious adhesive)
• Tongue and groove floor boards

Prime the following with BAL Primer diluted 1:1 with clean water:

• Plaster (when using a BAL ready-mixed adhesive)
• Cement Sand Render and Cement Sand Screeds (if the surface is friable)
• Concrete (if the surface is friable)

One to two coats of BAL Primer should be used for lightweight blockwork, and two coats (first coat diluted 1:1, second coat undiluted) for calcium sulphate or anhydrite screeds.

Other primers can be used before tiling including BAL Bond SBR and BAL Prime APD – always check the packaging and Technical Data Sheets for dilution ratios.

Step 3

Shake the container well before use and ensure the surfaces are free from dirt, grease and other loose materials. Brush down highly polished surfaces with a stiff bristled brush before priming.

Step 4

Apply evenly one coat of primer (for mix ratio see step 2.) Apply with a clean brush, sponge or roller and then leave to dry.

Step 5

Apply a second coat evenly (if required).

• If another coat is needed, apply at right angles to the first coat
• If using on a floor do NOT allow the primer to form puddles

Step 6

Allow the second coat to dry. Depending on the atmospheric conditions, most applications are thoroughly dry after 30 minutes. Make sure the primer is completely dry before applying adhesive.