Category: Structure & materials
Prepared by Eng. Ahmed Fathy, Projects Manager ·
Definition
A hollow block (ribbed) slab replaces part of the concrete with hollow blocks or foam between concrete ribs, making it lighter and suitable for longer spans.
Why it matters on a project
Common in Saudi villas because it saves concrete and steel, gives a flat soffit and the blocks help with thermal insulation.
Measurement and pricing
Blocks in square metres, concrete in cubic metres net of blocks, rebar in tonnes.
Worked example
With ribs at 50 cm and 40 × 20 cm blocks, each square metre takes about 10 blocks, so a 100 m² slab needs about 1,000 blocks before waste.
Common mistake
Fixing heavy hanging loads into the blocks instead of the concrete ribs.
Frequently asked questions
Are blocks or foam used in ribbed slabs?
Both are common: foam is lighter and insulates better, blocks are usually cheaper and easier to fix into from below.
How do I hang a heavy chandelier from a ribbed slab?
Fix it into a concrete rib or a designed hanger, never into the block itself.
Related terms
- Solid slabA concrete slab of uniform thickness without voids, common for small and medium spans.
- Reinforced concreteConcrete containing steel reinforcement to resist the tensile forces concrete alone cannot carry.
- Thermal insulationMaterials reducing heat transfer through walls and roofs, required by the Saudi Building Code.
- CantileverA structural element fixed at one end and free at the other, such as balconies and canopies.
Does your project need structural design and reinforcement drawings? Send the drawings or a short description and we reply within one working day.
Service detailsRequest a quote