Category: Structure & materials
Prepared by Eng. Ahmed Fathy, Projects Manager ·
Definition
Extruded polystyrene (XPS) boards are rigid closed-cell thermal insulation, commonly 30 to 35 kg/m³, that absorb almost no water and carry load. They are used on roofs, especially inverted roofs over the waterproofing, and in walls and floors.
Why it matters on a project
Thermal insulation cuts cooling energy noticeably in the Saudi climate, and the energy code sets the thickness needed for roofs and walls.
Measurement and pricing
Per square metre by thickness, with each thickness priced as its own item.
Common mistake
Using expanded polystyrene (white bead board) instead of XPS over the waterproofing, so it absorbs water and loses performance.
Frequently asked questions
What roof insulation thickness is right?
The energy code and the designer's calculation set it, usually 5 to 10 cm depending on the build-up.
What is an inverted roof?
A build-up where thermal insulation sits above the waterproofing, protecting it from heat and damage.
Related terms
- Thermal insulationMaterials reducing heat transfer through walls and roofs, required by the Saudi Building Code.
- WaterproofingLayers preventing water ingress into structural elements or spaces, such as bituminous membranes and cementitious coatings.
- Bitumen membraneModified bitumen waterproofing rolls bonded by torch.
- Saudi Building Code (SBC)The mandatory design and construction requirements in Saudi Arabia.
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