Water tank waterproofing for duplexes in Alzulfi

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

Water tank waterproofing in Alzulfi: the local context

Team note on Alzulfi: 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.. The centre of Alzulfi sits about 615 m above sea level (SRTM open elevation data).

Main roads in or near Alzulfi: King Fahd Road, Sheikh Ibn Baz Square, King Salman Road.

An owner of a duplex in Alzulfi often lives on one floor and rents out the other, and the rooftop water tank is easy to forget until a stain appears on the ceiling below. Water tanks on these buildings sit exposed to the sun and to repeated filling and draining, so their concrete walls and joints wear over time. By the time a leak is visible, water has usually been seeping into the structure for a while, which is why a planned inspection and waterproofing job is far cheaper than emergency repairs.

Alzulfi sits at high ground, with its centre about 615 m above sea level. For a duplex owner this matters because elevated towns can see sharp temperature swings between day and night, and that expansion and contraction stresses the surface of a tank and the roof slab beneath it. The practical lesson is that the tank and the roof around it should be treated as one system. The internal tank coating, the external roof membrane and any crack repairs need to be planned together, so that a fix on one surface does not push water into another.

Start by emptying the tank and cleaning it fully, then inspect the inside walls, floor and corners for cracks, flaking or soft spots. Repair any cracks with crack injection, which is priced at SAR 40–120 per metre, before applying anything else. Next, coat the inside of the tank, which typically runs SAR 25–60 per m², and choose a finish suitable for drinking water if the tank supplies the household. For the roof slab around the tank, decide between liquid roof waterproofing at SAR 8–25 per m² or a bitumen membrane at SAR 15–35 per m², depending on how much movement the roof shows. Finally, check the overflow pipe, the inlet valve and the outlet fittings, since poor sealing around them is a common cause of leaks, and fill the tank once to confirm everything holds before you close the job.

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

When do you need water tank waterproofing?

The following signs are worth checking before they grow:

• Unusual colour or taste in the water
• A tank that leaks after testing
• Deposits and flaking inside the tank

Causes we see in the field

• Construction joints — we check this before anything else.
• Damaged old coating.
• Cracks in the walls or floor — we check this before anything else.

Tools we use in Alzulfi

The steps in order

1. Emptying and ventilation: The tank is emptied and ventilated before entry.
2. Cleaning and preparation: Loose material is removed down to a sound surface.
3. Crack treatment: Active cracks are treated first.
4. Coating layers: A material intended for drinking-water tanks is applied.
5. Disinfection and fill test: The tank is disinfected and the level is monitored after filling.

Facts and costs — Alzulfi

Questions from Alzulfi

Common mistakes we see

• Using a material that is not intended for drinking water

The written outputs

The written output: the material name, its batch number and the fill-test result. The report is numbered and can be checked with its verification code.