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  • Reinforcing & site supplies

Building Plastic and Damp-Proof Membrane: Free Quotes from Local Suppliers

Need building plastic or 250 micron DPM under a concrete slab? Tell us what you need and independent South African suppliers will quote free. No obligation.

  • Quotes frombuilding plastic and DPM suppliers
  • Areaall nine provinces
  • Cost to youfree

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A worker unrolling black building plastic over compacted ground inside edge shuttering before a floor slab is poured
A worker unrolling black building plastic over compacted ground inside edge shuttering before a floor slab is poured

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Tell us what you need and where. A contractor or supplier who works in your area quotes you directly. Free, no obligation.

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Length and width in metres, thickness in millimetres. Add a row for each slab, footing or path. The totals go into your request.

#Length mWidth mThick mmQty
1×××
2×××
3×××
0m² area
0m³ concrete
06 m³ trucks

Order about 5–10% more than the net volume to allow for waste and uneven ground.

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Building plastic under a concrete floor stops moisture rising from the ground into the slab and the house above. It is called a damp-proof membrane, or DPM, and it is a small cost on a floor that you cannot fix once the concrete is down. ConcreteSlab.co.za is a free quote service. You fill in one form and we pass your request to independent suppliers and merchants in your area, who quote you directly. We do not sell or lay plastic ourselves. There is no fee and no obligation.

What a damp-proof membrane does

Ground is rarely dry. Water vapour rises through a concrete slab by capillary action and can damp the floor, lift tiles, peel paint and rot timber floor coverings. A damp-proof membrane is a sheet of polyethylene laid under the slab to block that moisture.

SANS 10400-J (floors) and SANS 10400-H (foundations) set out the need for damp-proofing in houses. Under floors, the usual product is polyolefin film that complies with SANS 952, laid under the concrete.

Do not confuse the DPM with the DPC. A damp-proof course is a strip built into the walls, higher up.

Thickness: why 250 micron is common

Building plastic comes in different thicknesses, measured in microns. Thin plastic tears easily when stone is walked on or concrete is dropped onto it.

  • 250 micron: the usual choice for house floors and garage slabs.
  • Thinner film: often fails on rough ground and is a false saving.
  • Heavier or reinforced sheets: used for industrial floors, damp sites and gas barriers.

Rolls are sold in wide widths so you can cover a house floor with few joins. Check the width and roll length with the supplier, and buy enough to allow for laps.

Laying it properly

The best membrane fails if it is torn or badly joined. Take a few minutes to get it right before the concrete arrives.

  • Base: compact the ground or sand blinding and remove sharp stones.
  • Laps: overlap joins by at least 150 mm and seal them with tape.
  • Edges: turn the plastic up at the walls and trim it later.
  • Protect it: avoid dragging mesh across it, and patch any holes.
  • Termite treatment: where required, treat the soil before the plastic goes down.

On wet sites or sloping ground, ask your builder or engineer about extra drainage.

What affects your quote

People often search for the building plastic price per roll, but we never give prices here. Suppliers will look at:

  • The thickness and the total area of floor to cover, with laps.
  • Roll width and length.
  • Jointing tape and any sand blinding.
  • Delivery to site, and minimum order sizes.
  • Supply only, or supply and laying with the slab.

Give the floor length and width, and suppliers can work out the number of rolls.

Comparing damp-proof membrane quotes

Concrete products are priced on the detail, so compare like with like. When quotes arrive, check:

  • Exact product: the strength class, size, grade or reference number, and that it meets the relevant SANS standard.
  • Quantity and minimums: the unit (m³, m², sheets, bags or panels), any minimum order and part-load charges.
  • Delivery: the delivery fee, the truck size, offloading and whether the site can take the truck.
  • VAT and validity: whether VAT is included, how long the price holds and the lead time.

What to include in your request

  • Give the floor length and width.
  • State the thickness, such as 250 micron.
  • Say whether you need jointing tape.
  • Mention if sand blinding is needed under the plastic.
  • Give your town and whether you want it laid for you.

Frequently asked questions

Does ConcreteSlab.co.za sell building plastic?
No. ConcreteSlab.co.za is a free quote service. You send one request and we pass it to independent suppliers, builders' merchants and contractors near you. They contact you directly with a quote. We do not sell, deliver or lay plastic, and there is no obligation.
Do I need plastic under a concrete slab?
Yes, for most house floors. It stops damp rising into the floor and the walls. SANS 10400-J covers floors in houses, and your plans or inspector may ask for it. A garage or shed floor that stays dry may be treated differently, so ask your builder.
What thickness should I use?
A 250 micron membrane is the usual choice under house floors. Thin plastic tears easily on site. For industrial floors, damp ground or sites with a gas risk, an engineer may ask for a heavier product. Check the rating on the roll.
What is the difference between DPM and DPC?
A DPM is the plastic sheet under the floor slab. A DPC is a damp-proof course, a strip laid in the brickwork above ground to stop damp rising into the walls. A house normally needs both, working together.

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