Protecting a slab for polishing during the build
Between pour day and polishing day, every trade walks across the slab. Most marks they leave are permanent. What does the damage, how to protect against it, and when to grind.
By Jeremy Thomason. Updated .
A slab that will be polished is the finished floor from the day it is poured. Everything that happens to it during the build either stays in the floor or has to be ground out - and some marks go deeper than we can grind without changing the finish.
What does the damage
- Plaster, render and paint spills.
- Oil and hydraulic fluid from machinery and scissor lifts.
- Tile adhesive, glue and silicone.
- Rust from steel, reinforcement offcuts and tools left lying.
- Tannin from wet timber stacked on the slab.
- Tape stuck directly to the concrete.
- Grit ground in by foot traffic and wheels.
How to protect it
- Use a breathable floor protection product across the slab once it has cured. Plastic sheeting laid directly on concrete can trap moisture and leave marks.
- Tape protection to itself, not to the concrete.
- Stack timber, steel and materials on bearers, not straight on the slab.
- Keep drop sheets under plasterers and painters, and clean up spills straight away.
- Brief every trade that the slab is the finished floor.
Grinding early
One approach is to do the first grind at slab stage, before walls go up, then come back at the end of the build to polish and seal. The open slab is quicker to grind, the edges are easier, and the floor is already flattened before the trades arrive. It needs good protection afterwards, and a return visit in the programme. We will tell you whether it suits your job.
Who is responsible
Agree it up front. Protection should be in the builder's programme and the trades' briefing, not something discovered at handover. If a stain cannot be ground out, the options are grinding deeper - which can change the stone exposure - or living with it.