(02) 8021 3517 Send your job →
● On site

Membrane under screed. Upstairs or on the slab.

1 min readFORSPEC Technical Team

The short version

  • One job, bathrooms upstairs and on the slab, and the same build-up in each.
  • ACTFLEX 900R sheet goes down below the screed on every floor.
  • ACTFLEX 906 WPU runs down the walls and onto the sheet.
FORSPEC drawing of a bathroom floor with the sheet membrane under the screed and the wall membrane brought down over the sheet
The membrane under the screed, with the wall membrane lapped onto it.

Inside a building the wet-area standard allows the membrane above the screed or below it. With the membrane below, the screed can be laid to falls over a floor that is already watertight.

FORSPEC on Instagram · 9 Nov 2026Bathrooms in ACTFLEX 900R, under the screedLoads when you tap

Why under the screed

Drawing B100 shows a bathroom on concrete with the membrane under the screed.

Where this comes from

Standards are summarised in FORSPEC's own words as a guide. Read the standard itself and your project documents before you build.

Email thisNewsletter

Systems, products and drawings

SystemInternal Wet Area WaterproofingThe full build-up, layer by layerSystemScreeds & Self-LevellingThe full build-up, layer by layerProductACTFLEX 900RDual-fabric butyl rubber sheet membrane for showers, bathrooms and laundries, with a consistent factory-controlled 0.9 mm gauge.ProductACTFLEX 906 WPUSingle-component water-based polyurethane membrane for wet areas and protected external areas beneath tiles and screeds.DrawingB100 · Bathroom Concrete UnderscreedCAD detail: PDF and DXFRangeAll FORSPEC productsBy system, with data sheets and calculators
● Your job next

Got a job this applies to?

Send the drawings or a few photos. FORSPEC comes back with the system, the details and the products for your job, within 6 business hours.

Send us your job →Call (02) 8021 3517

On site with FORSPEC

A lift pit lined before the pour, from FORSPEC on InstagramA lift pit lined before the pourThe membrane under the screed, from FORSPEC on InstagramThe membrane under the screedA pool detailed the right way, from FORSPEC on InstagramA pool detailed the right wayPipe details welded into the sheet, from FORSPEC on Instagram▶ 3.2KPipe details welded into the sheet
@forspec.pc on Instagram →

More news

Two concrete tanks wrapped in blue ACTFLEX 5000 self-adhesive sheet membrane, starter bars above the walls and a crane behindTwo concrete tanks wrapped in ACTFLEX 5000On site1 min readLift pit lined in grey PREFLEX 3000 pre-applied sheet membrane, with sealed pile heads and starter bars standing up through the sheetA lift pit lined with PREFLEX 3000 before the pourOn site1 min readFORSPEC drawing of a pool wall to floor junction: 35 by 35 mm cove, bandage bedded in the first coat, three coats of membraneA pool detailed the right way in ACTFLEX 988 CWPOn site1 min read
All news →
● The FORSPEC Brief · monthly

The month in waterproofing. In one email.

Code and standards changes, new products, new test reports and jobs from site. Once a month. No sales emails.

One email a month. Unsubscribe in one click. We never share your address.

Send us your job →☎