Tile Adhesive Guide: Walls, Floors and Underfloor Heating

Tiles come away from walls and floors for a small number of predictable reasons, and adhesive choice is near the top of the list.

When flexibility matters

A rigid adhesive is fine on a stable, dry, unheated wall. It is the wrong choice everywhere else:

• Underfloor heating. The screed expands and contracts every time the heating cycles. A flexible adhesive absorbs that movement; a rigid one transfers it into the tile bed and the grout lines crack.
• Timber floors. Any deflection at all needs flexibility, on top of proper board preparation.
• Tanked walls and wet rooms. A waterproofing membrane is a smooth, non-absorbent surface that moves fractionally. It needs an adhesive designed to bond to it.
• Large format tiles. The bigger the tile, the less forgiving the bed.

Our flexible tile adhesive covers all of these situations.

Grey or white?

Grey is the default and the cheaper option, and it is fine under anything opaque. Use white under natural stone, marble, glass mosaic and light porcelain: translucent and light-coloured tiles let grey adhesive show through as a dull shadow, and once it is set there is no fixing it.

How much do I need?

A 25kg bag covers roughly 5 m2 at a normal bed thickness, but the notch size moves that figure a lot:

Tile	Notch	Rough coverage per 25kg
Mosaic and small wall tiles	6 mm	6-7 m2
Standard wall and floor tiles	8-10 mm	5 m2
Large format, solid bed	12 mm plus back-buttering	3-3.5 m2

The product page has a calculator so you can work from your floor area rather than guessing.

The habits that prevent callbacks

• Comb in one direction and back-butter big tiles. You are aiming for full contact, not a pattern of ridges with voids between them.
• Check coverage as you go. Lift the first tile back off. If you cannot see adhesive across nearly the whole back, change your notch or your technique.
• Prime absorbent floors before you spread anything.
• Respect the open time. Adhesive that has skinned over has already let go, even though it looks fine.

Need a hand with your job?

Send us your measurements and we will put together a materials list with prices. Call 085 868 8459, message us on WhatsApp or email sales@all4building.ie. We deliver across Ireland from our Cork warehouse.