A concrete floor slab in a house, and the alternatives
A concrete floor slab in a house ties the frame columns into a rigid diaphragm, which is why in masonry houses in Adjara we choose it more often than anything else. Formwork on props, two layers of reinforcement to the calculation, sleeves for soil stacks, concrete in one shift. For light houses and extra storeys we build floors on steel or timber beams. A cast-in-place slab costs from 305 ₾ per m².
from 305 ₾/m²200 mm slab with formwork, reinforcement, concrete and sleeves; screed extra. The final price is confirmed once agreed.
- Timeline: a cast-in-place slab for a 70–100 m² storey usually takes 2–3 weeks from formwork to striking
- Warranty: Our work on floor slabs and concrete has a 2-year warranty
Who it’s for
You are building a house on a concrete frame with a cantilevered balcony
You are adding a storey and need a light floor structure
You are comparing a cast-in-place slab and hollow-core planks on price
You want a usable flat roof over the second storey
A timber-frame house where you need a quiet floor between storeys
What’s included
- review of the slab and opening design with the engineer
- formwork on telescopic props, set out with a level
- two reinforcement meshes with extra bars over the columns
- trimming of openings for the staircase and shafts
- sleeves for soil stacks, ventilation and cables
- photos of the reinforcement before the pour
- pour in one shift with vibration and curing
- striking the formwork once strength is reached
Which floor structures we build in private houses
| Type | Where it fits | Limitations |
|---|---|---|
| Cast-in-place slab | A masonry house on a frame, a complex plan, cantilevers and balconies | Needs formwork, props and time to gain strength |
| Hollow-core precast planks | A simple rectangular plan with load-bearing walls | Needs a crane, fixed sizes, plank connections designed for seismic loads |
| Steel beams with a slab on metal decking | An extra storey, large spans, a light frame | Protecting steel by the sea, fire protection to the design |
| Timber joists | A timber-frame or log house, an attic storey | Sound between floors, protection from damp and insects |
In a masonry house on a concrete frame we almost always choose a cast-in-place slab: it ties the columns into a rigid diaphragm, which matters most for seismic loads, and allows cantilevers, openings and balconies of any shape. For cast-in-place concrete as a method, see the page about cast-in-place concrete construction.
A concrete floor slab in a house: how it is built
First the formwork: plywood on beams and telescopic props, spaced to carry the weight of wet concrete. It is set out with a level, otherwise the ceiling and floor end up uneven. Then two layers of reinforcement mesh, the bottom on spacers and the top on support chairs, with extra bars over the columns and round openings. The engineer sets the slab thickness and reinforcement from the span and the load. For a house it is often a slab of about 200 mm, but we only take the figure from the calculation.
Concrete is pumped and the whole slab poured in one shift, compacted with a vibrator. Over the following days it is watered and shaded from the sun. The props under the slab stay until the concrete reaches the strength set in the design: if they are struck too early the slab deflects and cracks appear in it.
Openings, sleeves and cantilevers
Openings for the staircase, ventilation shafts, the flue and soil stacks are trimmed with reinforcement to the drawing and formed before the concrete. A finished slab next to a column must not be cut through without the engineer's consent: that is where the stresses are highest. The plumber and electrician walk the formwork with the site foreman before the pour.
A balcony or terrace on a cantilever continues the slab outwards, and heat escapes through it. The cantilever is either insulated underneath and at the edge or, if the seismic calculation allows, the thermal bridge is broken with a special connector. For a flat roof house the top slab is designed with an allowance for waterproofing, insulation and, if needed, a usable roof terrace.
Sound between floors
A concrete slab holds voices back reasonably well, but carries footsteps and knocks. So a floating screed goes on top over an acoustic layer, with a perimeter strip at the walls. That is already rough work, but the thickness of the floor build-up is allowed for in the storey height from the start, otherwise there will not be enough ceiling height later. In a timber floor, mineral wool goes between the joists and separate linings are fixed above and below.
How much a floor slab costs
A 200 mm cast-in-place floor slab costs from 305 ₾ per m²: formwork, two layers of reinforcement, concrete and sleeves. A hollow-core plank floor with installation is from 240 ₾ per m², a floor on steel beams with a slab on metal decking from 410 ₾ per m², and a timber joist floor with insulation from 245 ₾ per m². If formwork and concrete are priced separately, formwork is from 39 ₾ per m² and placing concrete from 90 ₾ per m³. Floor insulation, screed and acoustic layers are extra. The final cost is set from the design, after agreement on the estimate. Floor slabs are also part of the house shell estimate, and the stair openings in them are tied to the staircases.
Stages and timelines
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Formwork
3–5 days
Props, beams, plywood, set out with a level, edge forms round the slab.
-
Reinforcement
3–7 days
Bottom mesh on spacers, top on chairs, extra bars and trimmers.
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Sleeves and fixings
1–2 days
Soil stacks, ventilation, cables, cast-in fixings for the staircase, photos.
-
Pour
1 day
Pump, concrete in one shift, vibrator, levelling.
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Curing and strength gain
2–4 weeks
Watering and covering; the props stay until the design strength is reached.
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Striking
1–2 days
We remove the formwork and check levels and deflection.
Local specifics in Batumi
In Batumi summer a slab in the sun dries out in hours, and the surface cracks before the concrete has gained strength. We plan the pour for early morning and cover and water the slab for several days. In the rainy season, by contrast, we wait for a window without a downpour: water on fresh concrete washes cement out of the top layer.
By the sea, balcony cantilevers and slab edges sit in the salty wind, and their reinforcement rusts first if the cover is thinner than designed. So we place spacers more densely at the edges and, after striking, check that steel has not come close to the surface anywhere. An open slab is closed over winter with a roof or at least with sheeting: a slab that spends a season under the rain then gives off moisture into the screed for a long time.
Materials and brands
Plant concrete with a batch certificate, class to the design, placed by pump. Ribbed reinforcement and plastic spacers. Formwork of laminated plywood on reusable beams and telescopic props. For steel floors we use beams with a factory primer and metal decking as permanent formwork, with heavier protection by the sea. For timber floors, joists of dry timber or glulam with fire and rot protection.
What makes up the cost
Timeline: a cast-in-place slab for a 70–100 m² storey usually takes 2–3 weeks from formwork to striking
- floor type: cast-in-place, planks, steel or timber
What raises the cost
- large spans without intermediate columns
- cantilevers, balconies and complex openings
- concrete pumped from another street
- a usable roof on top of the slab
What lowers the cost
- a simple rectangular plan with columns on a grid
- identical repeated storeys
We prepare the exact estimate from measurements and photos. It’s free and comes with no obligation.
Get an estimateGuarantees
Our work on floor slabs and concrete has a 2-year warranty. Photos of the reinforcement and sleeves before the pour go into the handover file. We advise everyone, including later crews, not to cut through a finished slab without the engineer's consent.
Questions and answers
How much does a concrete floor slab in a private house cost?
From 305 ₾ per m² for a 200 mm slab with formwork, reinforcement, concrete and sleeves. The engineer sets the thickness and reinforcement, so for large spans the price is higher. Floor insulation, screed and acoustic layers are extra. The final cost is set from the design, after agreement on the estimate.
Which is better for a house in Batumi, a cast-in-place slab or hollow-core planks?
For a framed house with a complex plan and balconies, a cast-in-place slab: it ties the columns into a rigid diaphragm and allows any openings. Hollow-core planks are cheaper on a simple rectangular house with load-bearing walls, but they need a crane, and the engineer designs the plank connections for seismic loads separately.
How many days before the formwork can come off a slab?
The edge forms can come off after a couple of days, but the props under the slab stay until the concrete reaches the design strength. That is usually several weeks, faster in heat and slower in cool weather. Striking too early causes deflection and cracks that cannot be removed later.
Can a hole be made in a finished floor slab?
A small hole for a pipe away from the columns is usually possible, but only after agreement with the engineer and after locating the reinforcement. Next to columns and in the support zones it must not be cut. That is why all soil stacks, shafts and openings are formed with sleeves before the pour.
How thick should a floor slab be in a private house?
The engineer calculates the thickness from the span, the load and seismic loads. For a house with ordinary spans it often comes to about 200 mm, more for large spans or with beams. Thickness must not be chosen without a calculation: a thin slab deflects, and extra thickness makes the house heavier and increases the seismic load.
Further reading
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