Floors and skirtings: acrylic on top, not underneath

Two joints, two products

A skirting on a PVC floor (or any floor you mop) does not want the same sealant top and bottom. Below there is rub, floor movement, often plasticisers from the PVC, and mop water. Above there is plaster or paint: you want a joint you can paint with the wall.

One cartridge for both lines is the usual mistake. Acrylic sealant underneath drinks water, goes soft, picks dirt and cracks. It also does not have the elasticity of a floor joint.

PVC carries plasticisers to stay flexible. Some silicones react: the bead stays tacky or discolours. Underneath I want a plasticiser-resistant neutral or an elastic hybrid. No aggressive acetic chemistry against PVC.

When to seal — and when not

Yes, below: neutral silicone or elastic hybrid that takes mopping.

Yes, above: paintable elastic acrylic, to finish with the wall.

No acrylic below. First mop, water in; black edges follow.

Do not lock a floating floor that is hard against the wall. Without an expansion gap the floor humps. That is not “fixed” with paste: free the perimeter first, then an elastic bead that does not block the float.

How I do it

1. Degrease floor, skirting and wall. Factory PVC often has a film; without a clean, adhesion is weak.
2. If the gap is deep, closed-cell PE backer rod. Without it, three-sided adhesion: floor, skirting and the wall or slab behind. The bead tears.
3. Even bead below; tool with a suitable finisher and a spatula.
4. Above, acrylic between skirting and wall. Tool it and let it cure before painting. Depending on temperature and humidity, from a few hours to a day; the product decides, not a universal clock.

Common mistakes

Acrylic on the floor edge. Skipping the degrease on PVC. Filling a wide slot without backer rod. A hybrid or silicone that is too stiff below: the floor still wants to move.

Exceptions

Solid timber skirting on a stone floor has different chemistry and movement; the principle (wet and elastic below, paintable above) usually still holds. A floor that already humps is a perimeter problem, not a cartridge colour.