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  • Floors & finishes
  • 25–30 MPa

Concrete Slab Waterproofing: Free Quotes from Local Contractors

Need a concrete slab or roof waterproofed? Tell us what you need and independent South African contractors will send a free quote. No fee, no obligation.

  • Quotes fromwaterproofing contractors
  • Areaall nine provinces
  • Cost to youfree

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A waterproofing crew rolling a dark membrane coating across a flat concrete roof slab on a sunny day
A waterproofing crew rolling a dark membrane coating across a flat concrete roof slab on a sunny day

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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.

Pour docketPD 572078

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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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Free and no obligation. By sending you agree that we may share your request with a suitable contractor or supplier. See our privacy policy.

Concrete is strong but it is not waterproof. Water can pass through pores and cracks, and then rust the steel or leak into the rooms below. Concrete waterproofing protects flat roof slabs, balconies, basements, water tanks and floors that sit below ground. ConcreteSlab.co.za is a free quote service. You fill in one form and we pass your request to independent waterproofing contractors in your area, who quote you directly. We do not waterproof or sell products ourselves. There is no fee and no obligation.

Why concrete leaks

Concrete is porous. Even a well-made slab absorbs water, and shrinkage or movement opens hairline cracks. Water also finds its way through poor construction joints, around pipe penetrations and at the edges where a slab meets a wall.

The damage goes beyond a damp patch. Water carries salts and, near the coast, chloride that corrodes the reinforcing steel. The steel expands as it rusts and cracks the concrete from inside, which is called spalling. Waterproofing stops this cycle before it starts.

Types of waterproofing

The right system depends on where the water is and how the slab moves.

  • Liquid membranes: bitumen-based, acrylic or polyurethane coatings, rolled or sprayed on. Common on flat roofs and balconies.
  • Cementitious coatings: a cement-based slurry brushed on, often used inside tanks and basements.
  • Sheet membranes: torch-on bituminous or other sheets laid in layers on roof slabs.
  • Crystalline admixtures: added to the mix, or applied as a slurry, to block pores inside the concrete.
  • Injection: resin or grout pumped into leaking cracks and joints.

Preparation and timing

Most waterproofing failures come from poor preparation, not poor product. The slab must be clean, sound and dry enough for the system chosen. Contractors usually grind or blast off laitance, repair cracks and cut back loose concrete first. Roof slabs also need a screed to a fall, so water runs to the outlets instead of ponding.

New concrete should cure before it is coated. Many products need about 28 days, so check the manufacturer's instructions. Rain and cold slow curing, and a coating must not be applied to a wet or very hot surface. On the Highveld, plan around afternoon storms in summer.

Under-slab protection is a different job. A damp-proof membrane (DPM) is laid under a new floor before it is poured, and is covered in its own topic.

What affects your quote

People often search for the price of waterproofing a slab per square metre. We never give prices here. Contractors will look at:

  • The area and where it is: roof, balcony, basement or tank.
  • The system chosen and the number of coats or layers.
  • Preparation work, such as crack repair, grinding and screeding to a fall.
  • Details such as upstands, drains and pipe penetrations.
  • Guarantee period, access and travel distance.

Photographs of the slab and any existing leaks help contractors quote properly.

Comparing quotes for concrete waterproofing

The lowest figure is not always the best deal. When your quotes arrive, check:

  • Specification: the thickness, the concrete strength in MPa, the steel and the membrane, so every quote is for the same work.
  • Preparation: excavation, sub-base compaction, shuttering and who removes spoil and rubble.
  • Concrete and access: ready-mix or site-mixed, whether a pump is included and any part-load or waiting charges.
  • Finish, curing and guarantee: the surface finish, how long it will be cured, where joints are cut and what guarantee covers the work.

What to include in your request

  • Say whether it is a roof, balcony, basement, tank or floor.
  • Give the area in square metres.
  • Describe where and when water gets in.
  • Mention the age of the slab and any existing coating.
  • Attach photographs of cracks, stains and drains.

Frequently asked questions

Does ConcreteSlab.co.za waterproof concrete?
No. ConcreteSlab.co.za is a free quote service. You send one request and we pass it to independent waterproofing contractors near you. They contact you directly with a quote. We do not waterproof slabs or sell products, and there is no obligation.
Can I waterproof a concrete slab roof from the inside?
It is not a good long-term fix. Water should be stopped on the outside, where it enters, so it never reaches the steel. Internal treatments can hide damp but may trap moisture. Contractors will usually inspect the roof and recommend an external system.
How long does waterproofing last?
It depends on the system, the preparation and the sun and movement the slab sees. Many contractors offer a written guarantee. Ask what it covers and for how many years, and whether the slab will need re-coating or only maintenance.
Should new concrete be waterproofed straight away?
No. New concrete must cure first, and many coatings need it dry. Follow the product maker's guidance, which is often around 28 days. Waterproofing a damp slab too early can cause blisters and peeling, so ask your contractor for the timing.

Concrete Waterproofing by province

Concrete Waterproofing by city and town

SlabSlabs & foundations
Steel & membraneReinforcing & site supplies
Saw & breakerContractors, cutting & repairs
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