Domakihub How to Lay a Concrete Slab: A Step-by-Step Guide
Everything you need to know before mixing your first batch or calling a pro.
Reviewed by Domakihub home & decor pros · 2026-06-23 · 5 min read
A solid concrete slab is the foundation for terraces, storage rooms, garden sheds, and utility areas — all common upgrades in Greek homes, holiday rentals, and small hotels. The video above walks through the full pouring process from marking out to finishing; this guide breaks it into clear steps and flags where Greek building regulations or structural demands mean a licensed professional should take over. Whether you are doing the job yourself or supervising a contractor, understanding each phase helps you get the result right the first time.
When You Can DIY — and When You Cannot
A simple ground-level slab for a terrace, pathway, or non-structural outbuilding base is within reach of a careful DIYer in Greece. You do not need a permit for most slabs that are not part of the building's structural envelope, but local municipality rules vary — always check with your local planning office (Poleodomia) before you break ground, especially in a listed area or near a property boundary.
Any slab that forms a structural floor, supports a load-bearing wall, sits over damp or unstable ground, or requires waterproofing against a rising water table must be designed by a licensed civil engineer (Politikos Michanikos) and built under certified supervision. Getting this wrong is expensive to fix and can affect the safety certificate of your property.
Materials and Tools You Will Need
For a typical non-structural garden or terrace slab you will need: timber formwork boards (or steel edge forms), compacted hardcore or gravel sub-base material (coarse gravel 5-20 mm is standard in Greece), ready-mixed concrete or bags of C20/25 mix, steel reinforcement mesh (B500C welded mesh is widely sold at Greek builders' merchants), a tamping bar or plate compactor, a screed board, a bull float or magnesium float, a steel finishing trowel, a spirit level, and expansion joint strip.
For a slab larger than about 15 m² or deeper than 10 cm, ordering ready-mix concrete (etoimoskyrodeama) from a local batching plant is far more practical than mixing by hand. Specify the strength class and workability (slump) when you order — for a standard terrace slab, C20/25 with a slump of S3 (100-150 mm) is appropriate for most Greek climates.
How to Lay a Concrete Slab: 5 Steps
- 1
Excavate and Prepare the Sub-base
Mark the slab area with stakes and string lines, keeping it square using the 3-4-5 triangle method. Excavate to a total depth of at least 20 cm below finished surface level — 10 cm for the sub-base and 10 cm for the slab itself (increase slab thickness to 15 cm if vehicles will use it). Fill the excavation with compacted coarse gravel in two 5 cm layers, compacting each layer firmly with a plate compactor. The sub-base must be level, well-drained, and have no organic material; poor compaction is the number-one cause of cracking later on.
- 2
Build and Level the Formwork
Cut timber boards or set steel edge forms to the exact perimeter of the slab, fixing them firmly with wooden stakes driven into the ground every 60-80 cm. Use a spirit level and string line to set the top edge of the formwork at your intended finished surface height. Allow a slight drainage fall of 1-2 cm per metre away from buildings. Double-check that the formwork is square, will not flex when concrete is poured against it, and that the internal face is lightly oiled or lined with plastic sheet so it releases cleanly once the concrete sets.
- 3
Lay the Reinforcement Mesh
Cut B500C welded steel mesh to fit inside the formwork, leaving a 40 mm cover gap at all edges. Support the mesh on plastic spacer chairs so it sits at mid-depth in the slab, not resting on the sub-base. Overlap adjacent sheets by at least one full mesh square and tie the overlap with wire. For larger slabs, place expansion joint strip at intervals of roughly 4-5 m in both directions to control where shrinkage cracks form — this keeps the slab looking clean and structurally sound over time.
- 4
Pour, Screed, and Compact the Concrete
If using ready-mix, arrange site access for the truck and have enough helpers ready — you have roughly 90 minutes from the time of batching before the concrete stiffens. Pour the concrete in a continuous operation if possible, working away from the truck chute. Use a tamping bar to consolidate the mix around the edges and against the formwork, eliminating air pockets. Pull a straight screed board across the top of the formwork using a sawing motion to bring the surface to a uniform level. Follow immediately with a bull float to embed aggregate and close the surface without overworking it.
- 5
Finish, Cure, and Protect the Surface
Once the bleed water has evaporated from the surface (typically 1-4 hours depending on temperature and humidity), work the surface with a steel trowel for a smooth finish, or drag a stiff brush across it for a slip-resistant texture — the brushed finish is preferred for outdoor terraces. As soon as finishing is complete, begin curing: cover the slab with wet hessian or a plastic sheet and keep it moist for at least seven days. In the Greek summer, cure in the early morning and late evening to avoid rapid drying; high temperatures above 32 °C can cause surface crazing if the slab dries too fast. Do not walk on the slab for 24 hours and do not apply full loads for at least 28 days.
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FAQ
- Do I need a building permit for a concrete slab in Greece?
- For a detached, ground-level slab used as a terrace or shed base, many municipalities do not require a permit, but rules differ by area, zone, and slab size. You should always check with your local Poleodomia office before starting work. A slab that is part of a building's structure, increases the footprint of a property, or is built in a listed or coastal zone almost certainly requires a permit and a licensed engineer.
- How thick should a concrete slab be for a garden terrace or patio?
- For pedestrian use — a terrace, pathway, or garden area — a slab of 10 cm with reinforcement mesh is sufficient on stable, well-compacted ground. For areas where light vehicles (cars, small trucks) will park or drive, increase the thickness to 15 cm and use heavier reinforcement. For structural applications such as ground floors of buildings, an engineer must specify the thickness based on soil bearing capacity.
- How long does it take for a concrete slab to cure fully?
- Concrete reaches approximately 70% of its design strength after 7 days and its full rated strength at 28 days. You can walk on the slab after 24-48 hours and place light furniture after 7 days, but you should wait the full 28 days before applying heavy loads or building on top of it. In hot Greek summers, active curing — keeping the surface wet or covered — for at least 7 days is essential to prevent surface cracking.