Lift pit waterproofing. Lined before the pour.
·1 min read·FORSPEC Technical Team
The short version
- A lift pit is the lowest point of a building and the hardest to fix later. This one was lined before the concrete was poured.
- PREFLEX 3000 sheet covers the pit floor and runs up the formwork walls.
- Every pile head was sealed where the starter bars come through.
Once a lift pit is poured, its outside face is gone for good. A pre-applied membrane is laid first, and the wet concrete bonds to it as it cures. Water that finds a way in cannot track between the sheet and the slab.
What was built
- PREFLEX 3000 sheet over the pit floor.
- Sheet taken up the formwork walls, so the wall concrete is poured against it.
- Each pile head detailed where the starter bars come through the sheet.
- The junction between wall and floor closed all the way round.
The parts that decide it
The flat sheet is the easy part. A lift pit leaks at the pile heads, the corners and the construction joints. Pile heads are treated with ACTFLEX HBR epoxy mortar at 3 mm, and the sheet laps onto it by at least 50 mm.
Those are the details to draw before anyone is in the pit. FORSPEC has standard drawings for the lift pit base joint and for the negative side of a pit that is already built.
FORSPEC on Instagram · 10 Nov 2026A lift pit lined blindside with PREFLEX 3000Loads when you tapWhere this comes from
- PREFLEX 3000 Technical Data Sheet
- FORSPEC on Instagram, 10 November 2026
- Job facts: the FORSPEC site photo folder for this job (what the photos show; no place, dates or quantities on file)
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