Bitumen Coating for Foundations: Hot, Cold and Rubberised

What is bitumen and how does it work?

Bitumen (tar or asphalt) is a black, sticky hydrocarbon material produced by refining crude oil. It does not dissolve in water and bonds well to concrete. A bitumen coating forms a continuous film that seals the pores of the concrete surface and cuts off moisture rising by capillary action from the soil into the concrete and reinforcement. It is therefore classed mainly as dampproofing for buried elements.

Types of bitumen coating

• Hot oxidized (blown): air is blown through the bitumen during manufacture, raising its softening point and reducing flow. Grades are named by two numbers such as 85/25: the first refers to the softening point (80–90 °C) and the second to penetration (20–30 in tenths of a millimetre). It is melted in a kettle and brushed over a primer; ASTM D312 classifies roofing asphalt into four types by its properties.
• Cold solvent-based (cutback): bitumen dissolved in a solvent that evaporates after application. Its best-known use is the bitumen primer covered by ASTM D41 for concrete and metal surfaces before waterproofing.
• Cold water-based (emulsion): bitumen droplets suspended in water, solvent-free, curing as the water evaporates. Easier and safer in narrow excavations.
• Rubberised (elastomeric): a rubber-modified emulsion that gives a thicker, more flexible film, such as the «high-build rubberised bitumen emulsion» products that Sika data sheets describe for foundations and retaining walls.

A complete system consists of a primer, two or more coats, mesh reinforcement at corners and joints as the manufacturer recommends, and a protection board before backfilling.

Recommended uses

The main use of bitumen in Saudi Arabia is protecting concrete in contact with soil: isolated and strip footings, ground beams, column necks up to ground-slab level, and the outer face of retaining and basement walls. Service details are on the foundation insulation page.

Advantages and technical properties

• Low cost compared with membranes and crystalline systems.
• Good adhesion to concrete and continuous coverage of complex shapes such as column necks and corners.
• Chemical compatibility with bituminous rolls, so it works as their primer and complementary system.
• Water-based emulsions are solvent-free and better suited to narrow, poorly ventilated excavations.

Disadvantages and cautions

• Not a barrier against water pressure: the Sika Igolflex AE data sheet explicitly states it is not suitable as waterproofing against hydrostatic pressure.
• Does not tolerate sun: it must not be left exposed and should be backfilled or covered as soon as possible after curing.
• Vulnerable to mechanical damage: stones and compaction equipment scratch the film during backfilling, which is why a protection board is needed.
• Temperature limits: the rubberised emulsion in the example above is not applied above 35 °C, which means working early in the morning or in shade during summer.
• Rain: emulsion is not applied during rain and must be protected until dry.
• Safety: hot bitumen causes burns and kettle fire risk, and solvent-based products are flammable and need ventilation.

Standard application steps

1. 1

   Concrete preparation

   Remove formwork remnants, tie wires, oil and dust, repair honeycombing and exposed bars, and form rounded fillets where the footing meets the column neck.

2. 2

   Primer

   Apply a bitumen primer that penetrates the pores and improves adhesion, and let it dry as the data sheet specifies.

3. 3

   First coat

   Apply the first coat by brush or roller at the specified consumption, concentrating on corners and footing edges and reinforcing them with mesh where needed.

4. 4

   Second coat

   Once touch dry (1–6 hours for the rubberised emulsion in the example), apply the second coat in a perpendicular direction to close pinholes.

5. 5

   Inspection and testing

   Measure wet film thickness with a comb gauge, check actual consumption against area, and visually confirm the film is free of pinholes, blisters and uncovered spots.

6. 6

   Protection board

   After curing, fix bitumen-impregnated protection boards to vertical faces to shield the film from stones and compaction equipment.

7. 7

   Backfilling

   Backfill in layers and compact carefully without dumping stones onto the film, and document the work with photos before backfilling.

Climate suitability by Saudi region

For local work: foundation insulation in Riyadh, foundation insulation in Jeddah, foundation insulation in Dammam and waterproofing in Khamis Mushait.

Estimated cost

Foundation insulation typically costs SAR 15–35 per square metre, depending on coating type, number of coats and whether a protection board is included. The range is indicative, excludes VAT and is confirmed after a site inspection. Cost drivers: the actual buried surface area, access inside the excavation, concrete condition and the soil report findings.

Before casting ground beams or backfilling, request an inspection to choose the right system.