Types of Waterproofing: A Full Comparison and the Right Choice for Every Location

Anyone who has looked into waterproofing a roof or a tank has heard many names: rolls, foam, polyurea, acrylic, cementitious, crystalline, epoxy. The problem is that these names do not belong to one list from which you simply pick «the best». They belong to different families that work by different mechanisms, each with places where it excels and places where it fails. This guide arranges the types of waterproofing on a single map, compares them in one table, and then routes you to the right type for each location in a Saudi building: the roof, the bathroom, the tank, the basement, the pool, the septic tank, the balcony and the planter.

Types of waterproofing: six main families and how each works

The simplest way to understand the types of waterproofing is to ask how the barrier is formed. Does it arrive on site as factory-made rolls of fixed thickness, is it applied as a liquid that cures in place, or does it become part of the concrete itself? The answer defines strengths and weaknesses: rolls have factory-controlled thickness but their laps are the weak point; liquids have no seams but their thickness depends on the applicator; cementitious systems tolerate damp and pressure but do not stretch with moving cracks.

1) Sheet membranes

These are factory-made rolls that are laid out and bonded, torched or fixed, with overlapping edges forming a continuous barrier. The most common in Saudi Arabia are polymer-modified bituminous membranes. US specifications separate them by modifier and reinforcement: ASTM D6222 (external source via the Consumer Safety Center) covers polyester-reinforced APP sheets and ASTM D6164 (external source via the Consumer Safety Center) covers polyester-reinforced SBS sheets.

• APP rolls: bitumen modified with a plastomeric polymer, more tolerant of heat and therefore common in hot regions. Torch-applied.
• SBS rolls: bitumen modified with an elastomeric polymer that stays flexible in the cold and accommodates more movement, suited to relatively cool highlands such as Abha and Taif.
• Thermoplastic membranes (PVC and TPO): plastic sheets whose seams are hot-air welded so the seam becomes part of the membrane. Common on large commercial and metal roofs, less so on villas.
• EPDM membranes: a very flexible synthetic rubber whose seams are joined with special tapes or adhesives. Suits large, simple roofs and some planters and ponds, and needs an applicator experienced in seam detailing.

What they share: thickness is guaranteed by the factory, and the weakness lies in seams, laps and penetrations. Sheet systems are therefore judged on their details more than on the roll itself.

2) Liquid-applied membranes

Applied by roller, brush or spray, they cure in place into a continuous, seamless membrane. Their main advantage is that they wrap easily around pipes, corners and complex shapes; their drawback is that final thickness depends on how much material was actually applied, so it has to be measured.

• Liquid polyurethane: a flexible rubbery membrane usually rolled on in two or more coats. Many products need a UV-resistant top coat when left exposed, while some are designed for direct exposure; the datasheet decides.
• Polyurea: sprayed with heated high-pressure equipment and set within seconds. A tough membrane resistant to abrasion and traffic, but very sensitive to substrate moisture and preparation, and it requires equipment and a trained operator. The Sikalastic-8800 (external source via the Consumer Safety Center) datasheet specifies a minimum of 2 mm on UV-exposed or immersed surfaces.
• Elastomeric acrylic: a white, reflective water-based coating whose specification ASTM D6083 (external source via the Consumer Safety Center) requires an elongation of at least 100%. Excellent for lowering roof temperature and renewing roofs, but not to be left under permanent ponding unless the product datasheet allows it.
• Bitumen-rubber emulsions: such as cold, rubber-modified bitumen coatings, widely used on footings, ground beams and buried walls. The Sika Igolflex AE (external source via the Consumer Safety Center) datasheet states explicitly that it is not suitable for waterproofing against hydrostatic pressure, an important caution when choosing it for basements.

3) Cementitious systems: flexible and crystalline

Flexible cementitious waterproofing is a cement-based powder mixed with a polymer liquid and applied by brush or trowel in two coats. It bonds well to slightly damp concrete and accepts tile adhesive and mortar directly, which makes it a common choice under bathroom, kitchen and balcony tiles and inside some tanks and pools. Its flexibility is far lower than that of rubbery membranes, so it is not relied on alone over moving cracks.

Crystalline waterproofing works in a completely different way: its active chemicals react with water and cement constituents to form crystals that block the pores and hairline cracks of the concrete. Xypex and Penetron datasheets state that it seals static hairline cracks up to about 0.5 mm and can be applied from either side, which makes it the practical solution for existing basements and tanks whose outer face cannot be reached. It does not treat moving cracks or expansion joints.

4) Potable-water tank coatings

Inside a drinking-water tank it is not enough for a material to be waterproof; it must also be safe for the water. Potable-grade epoxy or polyurea linings are used here, provided the specific product holds drinking-water contact certification such as NSF/ANSI/CAN 61 (external source via the Consumer Safety Center), which covers protective materials such as coatings, and is applied at the thickness and cure time stated in the certification. Hempel's technical guideline on potable water tank linings (external source via the Consumer Safety Center) explains the importance of preparation, full cure and washing before service.

5) Bentonite (in brief)

Sheets or panels containing bentonite clay, which swells on contact with water to form a dense barrier. They are used on foundations and buried walls from the outside, and they need confining soil pressure to work. Always confirm from the product datasheet that it suits saline groundwater, an important consideration in the sabkha areas of the Eastern Province. Bentonite is used far less in Saudi homes than bituminous rolls and coatings.

6) Injection systems (in brief)

Not a surface waterproofing but a local cure for an existing leak through a crack, a construction joint or around a pipe. A polyurethane resin that reacts with water is injected to stop the leak, or epoxy to rebond a dormant crack when the engineer requires it. The SealBoss comparison (external source via the Consumer Safety Center) explains that hydrophilic polyurethane may shrink if its surroundings dry out, while hydrophobic grades are more dimensionally stable, and the De Neef TB-0055 bulletin (external source via the Consumer Safety Center) describes procedures for injecting leaking cracks and joints. Injection complements waterproofing; it does not replace it.

Master comparison table of waterproofing types

The table below places the families side by side on eight criteria. The expected-life column deliberately contains no numbers: actual life depends on the specific product, its thickness, its protection and the quality of workmanship, and no single published figure can fairly be applied to a whole family. The reference is the product datasheet and the written warranty terms.

Which waterproofing type suits each location in the building?

The location raises three questions before any material: is the waterproofing exposed to the sun or protected? Does the water press on it from the same face (positive side) or from the opposite face (negative side)? Does the surface move thermally or structurally? The answers below shortlist suitable options; the final decision follows an inspection.

Roofs: exposed, tiled, green and inverted

• Exposed roof: faces the harshest radiation and heat, so choose a system designed for exposure: mineral-surfaced bituminous rolls, polyurethane or polyurea with a UV-resistant top coat, or reflective acrylic over sound waterproofing. The deciding detail: a light reflective colour and renewing the top coat before it wears through.
• Tiled roof: the traditional build-up in Saudi Arabia is waterproofing (rolls or a liquid membrane), then protection, then screed to falls, then tiles. The deciding detail: a flood test before tiling, because tracing a leak under tiles later is very costly.
• Inverted roof: the waterproofing is laid directly on the concrete, followed by moisture-resistant thermal insulation boards and then ballast or tiles. The thermal insulation thus shields the membrane from sun and temperature swings. Details are in roof insulation and the thermal insulation types guide.
• Green or planted roof: needs a membrane certified by its manufacturer as root-resistant, with protection, drainage and filter layers. An ordinary coating under permanently wet soil is not enough.

For large concrete roofs using rolls, see the membrane insulation service; if you need waterproofing and thermal insulation together, the systems are compared on the roof insulation page.

Bathrooms and kitchens

Here the waterproofing is hidden under tiles and never sees the sun, but it faces frequent water, cleaning chemicals and many penetrations: floor drains, supply pipes, the toilet base and the bathtub. Suitable options: flexible cementitious, liquid polyurethane, or sometimes a thin bituminous roll on larger floors. More important than the material: turning the waterproofing up the walls around the floor and higher inside the shower zone as specified, reinforcing corners with tape, sealing around the drain with a purpose-made piece, and flood testing before tiling. Practical details are in bathroom waterproofing.

Water tanks

Tank waterproofing has two faces. The outer face of a below-ground tank meets soil moisture and is protected with bitumen, rolls or crystalline systems. The inner face touches drinking water and only accepts a product certified for potable-water contact: a certified epoxy or polyurea lining, a certified crystalline slurry, or a certified flexible cementitious coating. The deciding detail: never use an ordinary bitumen coating or roof acrylic inside a drinking-water tank, and ask for the certificate of the product itself, not of the company. See tank insulation.

Foundations and basements: positive side vs negative side

The positive side is the face in direct contact with water, i.e. the outer face of a buried wall. Waterproofing there stops water from entering the concrete at all and is the preferred position, but it can only be done during construction or after excavating fully around the building. The negative side is the inner face of a basement or tank; waterproofing there resists water pushing from behind, so it must bond very strongly to the concrete or work from within it.

In the Eastern Province and coastal areas, with saline groundwater and sabkha soils, foundation waterproofing becomes a matter of structural durability rather than just keeping damp out. Details are in foundation insulation.

Swimming pools

A pool is an open tank exposed to chemically treated water, sun and changing water levels. Common options: crystalline or flexible cementitious waterproofing under tiles or mosaic, or polyurea or polyurethane rated for immersion. The deciding detail: sealing around suction fittings, lights and overflow lines before finishing, and a full fill test before tiling. Details are in pool waterproofing.

Septic tanks and sewage chambers

A septic tank faces sewage and gases that attack the concrete from inside, and soil moisture from outside. The outer face is waterproofed like a foundation; the inner face needs a chemically resistant coating such as epoxy or polyurea formulated for that environment. The deciding detail: nobody enters a septic tank or any tank before it has been ventilated and the atmosphere confirmed free of gases, with protective equipment; read the health and safety page before any confined-space work.

Balconies and planters

• Balconies: a small roof, often over an occupied room, with a low door threshold. Suitable: flexible cementitious or polyurethane under tiles. The deciding detail: taking the waterproofing under the door threshold, not stopping in front of it, and falls towards a drain rather than towards the door.
• Planters: permanent moisture, roots and fertilisers. Suitable: a root-resistant membrane, or polyurea or polyurethane rated for immersion, with a drainage layer and an outlet. The deciding detail: a drain outlet that soil cannot block, and a protection board between membrane and soil.

The details that decide success whatever the waterproofing type

Most leaks do not come from the middle of the roof where the membrane is laid evenly, but from edges, corners, pipes, drains and joints. The best material on the market fails if these points are neglected, and the simplest material performs for years if the details around it are done well.

1. 1

   Substrate preparation

   Remove dust, oil, weak layers and any detached old waterproofing; repair honeycombing and cracks; and confirm the surface is as dry as the datasheet requires. Liquid membranes in particular will not bond to a friable or wet surface. For damaged concrete, see the restoration guide.

2. 2

   Falls and drains

   Ponding water accelerates the ageing of any waterproofing and exposes every defect. Falls must lead to drains that are adequate in number and unblocked, and the waterproofing must be sealed into the drain outlet, not just around it.

3. 3

   Upstands

   The waterproofing is turned up parapets, walls and thresholds, its top edge is fixed and covered with protection or render, and the floor-to-wall corner is rounded with a fillet so the membrane does not crack there.

4. 4

   Penetrations

   Every pipe, equipment base or post passing through the roof needs a detail piece or an extra reinforcing layer. These are the most frequent leak points, especially air-conditioner bases and rooftop tank supports.

5. 5

   Joints and cracks

   Expansion joints are never covered with a rigid system; they need a flexible detail that allows movement. Dormant cracks are treated and reinforced with tape before waterproofing, while active cracks must be diagnosed before any coat is applied.

6. 6

   Flood test

   The standard guide ASTM D5957 (external source via the Consumer Safety Center) describes flooding a horizontal installation with water to a depth of at least 25 mm and no more than 100 mm at the lowest point, for between 24 and 72 hours, with drains temporarily plugged and the ceilings below monitored. It is carried out before protection layers and tiles.

7. 7

   Protection layer

   A membrane that will be backfilled, tiled or walked on needs protection from gravel, workers' tools and the sun: a protection board, a mortar screed or thermal insulation boards depending on the system. Fosroc's Protection Board (external source via the Consumer Safety Center) page explains the role of protection boards over membranes before backfilling.

Five questions that shortcut the choice of waterproofing

1. Will the waterproofing stay exposed to the sun? If yes, choose a system designed for exposure or add a UV-resistant top coat.
2. From which side does the water come? From the same side (positive) all options are open; from behind (negative) the choice narrows to crystalline and purpose-made cementitious systems.
3. Will it touch drinking water? If yes, the first requirement is the product's certificate, not its price.
4. Does the surface move? Sun-exposed roofs and active cracks need a flexible membrane; rigid cementitious systems alone do not suit them.
5. Can the surface be reached later? Waterproofing under tiles or behind backfill must be done and tested properly the first time, because repairing it means demolition or excavation.

If the project also needs thermal insulation, start with the thermal insulation types guide, because some systems combine both functions and others require a specific layer order. For detailed articles on specific cases, browse the waterproofing category of the blog.

Common mistakes in choosing and applying waterproofing

From comparison to execution

The table narrows the options, but the final choice needs a site visit: the condition of the concrete, the falls, the drains, any old waterproofing and the cause of any leak. If you already have a leak, identify its source before choosing a material, because new waterproofing over an untreated source brings the problem back. For an overview of the services available for each location, see the waterproofing page.

If you would like a technical opinion on your case, you can request an inspection so the Azl team can identify the location, the suitable type and the scope of work after the visit, and explain the proposed product and its datasheet before work begins.