Substrates & Preparation
Detailing Drains, Pipe Penetrations and Thresholds Before Screed
Drains, pipework and thresholds each interrupt a floor's finished level, so their protection and detailing has to be planned before the screed goes down.
Floor got drains, pipework or awkward thresholds to work around?
We'll detail every penetration and transition properly so the finished floor performs as well as it looks.
Or call our landline on 01392 237700
Every point where something passes through or interrupts a floor — a gully, a stack pipe, a doorway threshold — is a place where the smooth logic of a self-levelling pour meets a fixed obstacle. These features need to be identified and detailed before the pour starts, both to protect them from being fouled by liquid screed and to make sure the finished floor meets them at the right level.
Floor drains in particular need special attention, since they usually sit at the low point of a fall and the screed around them has to be graded correctly rather than simply poured flat and left to find its own way to the outlet.
A short survey of every drain, pipe and threshold in the pour area, carried out well before the pump is booked, gives time to agree the detail at each one rather than discovering an unresolved junction with the pour already underway.
Falls to drainage don't come from the screed itself
A standard liquid screed levels itself to a flat horizontal plane, which is exactly the opposite of what's needed around a floor drain that requires a fall toward the outlet. Where falls are needed, they're normally formed in an underlying levelling screed or a shaped substrate build-up, with the liquid screed then poured to a consistent depth over that shaped base rather than being relied on to create the fall itself.
Confirming who is responsible for forming the fall — the groundworker, a separate levelling contractor, or the screed team as part of a wider package — avoids a gap between trades where neither party assumes the fall is their job.
Protecting penetrations during the pour
Pipes, stacks and drain outlets passing through the floor need a sleeve or collar at the point they meet the screed, both to stop liquid material running down alongside the pipe into the void below and to allow for the small amount of movement that occurs as the screed cures and the building settles. This is worth agreeing on site before the pour date, since retrofitting a sleeve after the screed has gone off is far more disruptive.
Where multiple pipes cluster together, such as at a manifold or stack, each one still needs its own individual sleeve rather than a single shared seal, since movement and settlement can affect adjacent pipes differently.
Resetting covers and gratings to the new level
Once a liquid screed has been poured, drain covers and gratings that previously sat flush with the old floor may now need adjusting to match the new finished level. Where the screed adds noticeable depth, this often means building up the surround or fitting a raising piece before the cover is refitted, so it doesn't sit proud or recessed relative to the new surface.
This step is easy to overlook if it isn't planned alongside the screed depth itself, and a cover left at the wrong height can create a trip hazard or trap water at the low point it was meant to drain.
Coordinating threshold details with adjoining trades
A doorway threshold between two areas with different finishes, screed depths or drainage requirements is often where several trades' work meets in one small area — the screed, the floor finish, the door frame and sometimes a drainage channel all converge. Agreeing the exact detail here, including any trim, upstand or fall, avoids each trade assuming a different finished arrangement.
Where a wet area such as a shower room or utility space adjoins a dry room, the threshold detail also needs to manage any risk of water crossing between the two, which is worth resolving on the drawings before the screed and floor finishes are specified.
Drains, Penetrations & Thresholds — the points that decide it
- Floor gullies and drains need protecting from being filled with liquid screed during the pour, typically by masking or temporarily plugging the outlet
- Falls to a drain generally need forming with a levelling screed or the drain surround built up before a self-levelling liquid screed is poured, since liquid screed itself finds a flat plane rather than a fall
- Pipe penetrations through the floor should be sleeved or sealed at the point they pass through the screed to allow for movement and to stop the pour tracking down alongside the pipe
- Door thresholds mark a transition point that often needs a fixed edge or trim to give the screed something to finish against cleanly
- Where a threshold sits between two different screed depths or two different rooms' finished levels, the detail either side needs agreeing before the pour
- Any temporary protection over drains or fittings should be checked and removed promptly once the screed has set enough to expose them safely
- Drain covers and gratings often need resetting to the new finished floor level once the surrounding screed has cured
- Coordinating drainage detailing with the groundworks or plumbing trade avoids conflicting assumptions about where falls and outlets actually sit
Floor got drains, pipework or awkward thresholds to work around?
We'll detail every penetration and transition properly so the finished floor performs as well as it looks.
Or call our landline on 01392 237700
Drains, Penetrations & Thresholds — your questions
In short
Drains, pipework and thresholds each interrupt a floor's finished level, so their protection and detailing has to be planned before the screed goes down.
Floor got drains, pipework or awkward thresholds to work around?
We'll detail every penetration and transition properly so the finished floor performs as well as it looks.