Roof waterproofing for duplexes in Alrass

Prepared by the technical team · editorial review · last updated 13 November 2026 · Sources

Before we start: what we know about Alrass

Team note on Alrass: Kashf teams serve this city and its nearby districts with the same documented inspection standard: device-based leak detection without demolition, a written report, and a clear scope before any work begins.. Main roads in or near Alrass: King Abdulaziz Road, King Fahd Road, King Salman Road.

The centre of Alrass sits about 695 m above sea level (SRTM open elevation data).

Roof waterproofing for duplexes in Alrass most often fails at the joints and penetrations rather than across open roof areas. Where the roof slab meets parapets, drainage outlets, water tank bases and the stair-head, small cracks and lifted edges let rainwater run into the upper floor ceiling. Because a duplex shares a roof structure with one neighbouring unit, a leak on one side often shows up in the other household's rooms, which makes early repair a matter of shared interest between the owners.

The local setting changes how the work should be approached. The centre of Alrass sits about 695 m above sea level, so the area is well above the coast and sees strong sun on exposed roofs, which accelerates the drying and cracking of older coatings. A liquid roof waterproofing system, priced in the range of SAR 8–25 per m², is typically applied after the surface is cleaned and any cracks are opened and sealed. For the larger upper-level roof areas, a bitumen membrane at SAR 15–35 per m² can be used where a heavier, sheet-type layer is preferred. Spray foam at SAR 20–45 per m² and XPS boards at SAR 12–30 per m² may also be discussed when insulation is part of the goal, since reducing heat through the roof also helps the waterproofing layer last longer under the sun.

Before the visit, ask the provider which system they propose for your roof and why it suits your specific slab, and request a per-square-metre quotation that lists the roof area measured on site. Ask how they will treat the drainage outlets, parapet edges and tank base, and whether crack injection, billed per metre at SAR 40–120 per m, is included or separate. Confirm who will pay for work on the shared roof section, and ask for the written scope before any work begins. Keeping these points clear helps both households agree on the work before the first bucket of material is opened.

In a duplex, the two floors often share lines, so tests are done floor by floor.

When do you need roof waterproofing?

If you notice one of these signs in Alrass, it is a good moment to talk to the team:

• The old waterproofing is cracking
• Water pooling on the roof
• Stains on the top-floor ceiling after rain

Causes we see in the field

• Cracks in the roof slab — we check this before anything else.
• A common cause: wrong falls towards the drains.
• A common cause: damaged waterproofing around tank and AC bases.

Tools we use in Alrass

How the work is done, step by step

1. Survey: Falls, drains and the condition of the old layer are recorded.
2. Preparation: Cleaning and repairs before any new layer.
3. Primer: The base coat that the system needs.
4. Waterproofing layers and details: Corners, upstands and bases get their own detail.
5. Flood test: The roof is flooded and checked before it is covered.

Alrass in facts and sources

Common questions about roof waterproofing in Alrass

What we advise against

• Ignoring the tank bases
• Covering the waterproofing before the flood test

What you get after the work

The written output: a quality record with photos and the flood-test result. The report is numbered and can be checked with its verification code.