Bitumen membrane for duplexes in Allith

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

What is specific about Allith for bitumen membrane

Main roads in or near Allith: Al Laith Road, Amr Bin Al Aas Street. The centre of Allith sits about 5 m above sea level (SRTM open elevation data).

Allith is about 1.2 km from the sea coast (OpenStreetMap).

Bitumen membrane on a duplex roof most often fails at the upstands, the points where the membrane rises against parapets, walls and roof hatches, and at the drainage outlets. Water finds its way in at these joints long before the main roof field shows any sign of wear, so the first thing to check on any duplex is whether these edges have been sealed and lapped properly. Ponding on flat sections is the second common issue, because standing water speeds up ageing of the membrane and hides small splits that would otherwise be easy to spot.

Allith sits about 5 m above sea level, and its centre is roughly 1.2 km from the sea coast. Those two facts shape the approach. A site this close to the coast is exposed to salt-laden air, which can accelerate the breakdown of exposed bitumen and the fixings that hold it down, so flashings and terminations need extra attention. The modest elevation means rainwater does not run off as quickly as it might on higher ground, so falls and outlets should be checked carefully to avoid standing water. In practice, a contractor working on a duplex here should inspect the upstands, outlets and fixings first, and plan the membrane detailing around those edges rather than treating the flat field as the main task.

Before the visit, ask the provider to confirm which parts of the roof they will inspect, whether they will check the upstands and drainage outlets as well as the general surface, and how they will handle any cracks found in adjoining areas. Ask whether they quote per square metre for the bitumen membrane and what that rate covers, as typical bitumen membrane work is priced in the range of SAR 15–35 per m². It also helps to ask whether liquid roof waterproofing or spray foam might be considered for particular sections, since those options are priced differently. Finally, ask how the site will be left once work is complete, including protection of the membrane edges and a clear note of any areas that need checking later.

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

When do you need bitumen membrane?

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

• A flat concrete roof that needs waterproofing
• Old rolls that are cracking

Where the problem usually comes from

• No protection layer.
• Seams that were not welded properly — we check this before anything else.

Tools and methods, and when we use them

The steps in order

1. Preparation: Cleaning, priming and repairs.
2. Torch welding: Overlaps are welded and checked.
3. Details: Upstands, drains and bases.
4. Protection and flood test: Protection is laid after a successful flood test.

Facts and costs — Allith

Questions from Allith

Common mistakes we see

• Leaving the membrane exposed without protection

The written outputs

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