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Dimpled membrane basement lining is not the system

Updated: 21 October 2026

You want a UK cellar dry enough to use, and a dimpled membrane basement search makes a studded roll look like the whole answer. It is not. For a room you will live in, the sheet is the drained lining inside a system you can maintain, not the guarantee. The structure still provides the primary resistance. The cavity takes controlled seepage. Water has to leave, and someone has to service the arrangement. None of the four listings in the [dimpled membrane comparison](/hub/flooring/dimpled-membrane) includes a pump or names a certificate. A purchase through our links can earn a commission at no extra cost to you.

You want a UK cellar dry enough to use, and a dimpled membrane basement search makes a studded roll look like the whole answer. It is not.

Our top picks

Einside Einside embossed HDPE membrane, 2 m × 20 m

Best overall

Einside Einside embossed HDPE membrane, 2 m × 20 m
8.8/10about £69.50
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Einside Einside embossed HDPE membrane, 1 m × 20 m

Alternative

Einside Einside embossed HDPE membrane, 1 m × 20 m
8.0/10about £50.00
View offer
Generic Generic holed dimpled drainage panel, £106.99

Rank 3

Generic Generic holed dimpled drainage panel, £106.99
4.0/10about £106.99
View offer
On this page
  1. 1.What the sheet does in a cellar
  2. 2.Grades and who the room is for
  3. 3.Channels, pumps and the first service
  4. 4.When to stop and appoint a specialist

What the sheet does in a cellar

On an internal wall or floor the studs hold a void. Moisture that passes the structure can move in that gap instead of wetting the plaster. That is a lining, not a dam. PCA’s Type C guidance from June 2022 says the structure provides the primary resistance, the cavity deals with minor seepage, and the installed membrane is not a hydrostatic barrier. Newton’s BBA wording on CDM 508 says the same about water pressure. Roll an 8 mm, 400 g/m² Einside sheet across a wet wall and stop, and you have covered the damp without a way out. Type C is the cavity, the channels and a discharge, designed and then maintained. The Einside pages mention basement walls. They do not supply the pump or the service. The French reviews on the wider roll describe backfill, not a lived-in cellar.

Grades and who the room is for

BS 8102:2022, as Newton’s technical paper sets out Table 2, uses grades 1a, 1b, 2 and 3. Grade 3 is the habitable grade: no water ingress and no damp areas, with ventilation or dehumidification. Storage can sit in a lower grade. Grade 4 is not the current table. The grade is a performance of the space, not a stamp on the plastic. The 2 m roll at £69.50 and the 1 m roll at £50.00 do not deliver Grade 3. The generic panels do not settle a width, so they do not either. If you only need boxes off a damp floor, say so before you design for a bedroom. A room you will sleep or work in is Grade 3, and the roll is not what achieves it.
Einside Einside embossed HDPE membrane, 2 m × 20 m

Testsieger

Einside Einside embossed HDPE membrane, 2 m × 20 m
8.8/10about £69.50
View offer

Channels, pumps and the first service

Water in the cavity has to reach a channel and then leave. Sometimes that is a pump in a sump. Sometimes a designer can use gravity. Radon and the site drainage can rule a free outfall out. This page will not pick a pump. A Type C system of the kind Newton describes adds channels, sumps, a backup and a way to know the pump has failed. None of the four products is that kit. The cost sits in that equipment and in the visits, not in the £69.50 roll. PCA’s line is a first service within three months, then at least yearly, and sooner if lime or silt builds up. In a power cut an unattended pump stops. If you cannot describe the discharge, do not hang the sheet. Plugs and laps, once that route exists, are the fitting guide.

When to stop and appoint a specialist

Stop when water is already running, when you want a warranty, or when the room must be habitable. Cuts and holes on an Einside roll are a reason to reject the parcel, not the hardest problem in the cellar. Running water, a party wall, a floor below the sewer, or a neighbour’s ground above your slab are design problems. Newton CDM 508, at 500 g/m² or 700 g/m² under BBA 22/6357, is the kind of sheet a specialist specifies. These rolls are 400 g/m² where a weight is trustworthy, and they name no certificate. The generic panels add no stud height, no stars, and a 1 kg parcel line that fights the 700 g/m² bullet. Appoint someone who designs to BS 8102 for Grade 3. Which listing this comparison can support for a foundation job is on best dimpled membrane.

Common questions

Will this roll waterproof a cellar on its own?
No. PCA describes Type C as drained protection for seepage, not as a barrier to water pressure. The Einside rolls are 8 mm foundation sheets at 400 g/m², with no pump and no certificate in the listing. Covering a wall with one of them leaves the water with nowhere designed to go.
What is Type C in plain words?
It is a cavity that collects moisture which gets past the structure, then leads that moisture to a discharge you can maintain. The membrane forms the void. Channels, a sump or an outfall, and a service plan do the rest. The sheet without those parts is only a lining.
What is Grade 3?
In the BS 8102:2022 table Newton reprints, Grade 3 is a habitable space: no ingress and no damp areas, with ventilation or dehumidification. Lower grades can suit storage. The grade belongs to the room’s performance. It is not printed on these amazon.co.uk rolls, and buying a roll does not award it.
Do you need a sump?
You need a way for water to leave. A sump and pump are the usual answer where gravity is not acceptable. Radon and the site drainage can rule out a simple outfall, so the choice is a design decision. These four listings do not include a sump, a pump or a channel.
How often is the system serviced?
PCA’s June 2022 guidance says the first service should fall within three months, then at least every year, and earlier if lime or silt is collecting. A cavity you cannot inspect or flush is a cavity that will block. The service is part of the buy, not an optional extra after the roll is hidden.
Can you use the same sheet outside the foundation?
The Einside listings are sold as foundation sheathing, and the French reviews describe backfill, not a cellar room. An external drainage sheet is still not the internal Type C lining, and it does not replace a primary membrane. Keep that outside job separate from the habitable-room design on this page.

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Cavity drain membrane buying guide: stud and weight

How to fit cavity drain membrane on an internal wall

Sources

Public UK sources used for this comparison. Listing prices, stars and review counts are the amazon.co.uk lines kept with these four products.

  1. PCA Type C guidance, June 2022 (retrieved October 2026)
  2. Newton BS 8102:2022 technical paper (retrieved October 2026)
  3. Approved Document C, GOV.UK (retrieved October 2026)
  4. Newton CDM 508 and BBA 22/6357 (retrieved October 2026)
  5. Wykamol CM20 BBA sheet (retrieved October 2026)
  6. Newton on a DPM versus waterproofing (retrieved October 2026)
  7. Newton HydroBond 410 GeoDrain (retrieved October 2026)
  8. ABG Roofdrain (retrieved October 2026)