Domakihub Lay Underfloor Heating Pipes in Screed the Right Way
Get the insulation, pipe routing, and pressure test right before the screed goes down — or pay for it later.
Reviewed by Domakihub home & decor pros · 2026-06-23 · 5 min read
Wet underfloor heating is one of the best investments you can make in a Greek property — whether it is a family home, a holiday villa, or a boutique hotel. The video above walks through the complete installation process from start to finish. This article breaks down the five stages where precision matters most, because mistakes made before the screed is poured are sealed in permanently and can cost thousands to put right.
Why the Pre-Screed Stage Makes or Breaks the Whole System
Underfloor heating efficiency is determined almost entirely by what happens beneath the screed, not above it. If heat can escape downward into the slab or the ground, your boiler runs longer, your bills rise, and the floor never reaches the target temperature — a problem that is especially punishing in older Greek stone or concrete buildings that were never designed for radiant heat.
The three elements that must be right before a single litre of screed is poured are: a continuous insulation layer that meets minimum thickness requirements, a vapour barrier that protects the insulation from screed moisture, and pipes that are spaced and fixed correctly so the heat distributes evenly across the entire surface.
Choosing the Right Pipe Spacing for Greek Climates
A common mistake on Greek renovation projects is copying Northern European pipe spacing without adjusting for local conditions. Coastal properties and island villas often have milder winters and different floor coverings — ceramic and natural stone tile are standard here, and both conduct heat well. For a main living zone in Greece, 200 mm centre-to-centre spacing is a reasonable starting point, while bathrooms and entrance halls with higher heat loss may need 150 mm.
Perimeter zones — the metre of floor closest to external walls and glazing — always need tighter spacing regardless of climate, because that is where the most cold air infiltrates. Plan your manifold position and pipe circuits before you cut a single clip, because changing the layout once pipes are laid and clipped is slow and risks kinking the tubing.
How to Lay UFH Pipes in a Screed Floor: 5 Critical Steps
- 1
Lay and Join the Rigid Insulation Boards
Start with a clean, level subfloor — any high spots will cause the insulation boards to rock and crack under foot traffic before the screed is poured. Use tongue-and-groove EPS or PIR boards rated at a minimum of 75 mm for ground floors (100 mm is better on an uninsulated Greek slab). Butt all joints tightly and tape them with aluminium foil tape. Do not leave gaps at the perimeter: cold bridges at the wall-floor junction account for a disproportionate share of standing heat loss in practice.
- 2
Fit the Perimeter Edge Strip and Vapour Barrier
Run a compressible edge strip around every wall before the vapour barrier goes down. This strip absorbs the thermal expansion of the screed and prevents cracking at the perimeter — a failure point that is endemic in Greek projects where the strip is skipped to save cost. Once the edge strip is in place, roll out a heavy-duty polythene membrane (minimum 500-gauge, ideally 1000-gauge) over the insulation and lap it 150 mm up every wall. Tape all overlapping joints so moisture from the wet screed cannot migrate down into the insulation.
- 3
Fix the Pipe Rail or Clip Mat
Clip mats stapled to the insulation or snap-in pipe rail systems both work well — choose based on your pipe spacing and budget. Lay the rail or mat according to your circuit plan, keeping rows parallel and at your target centre-to-centre distance. The most common error at this stage is inconsistent spacing mid-circuit; mark your insulation with chalk lines at the correct intervals before you clip a single metre of pipe, and check against the marks as you go. Consistent spacing is what gives you an even floor temperature rather than a patchwork of warm and cool zones.
- 4
Route the Pipes in the Correct Pattern and Fix Them Down
Feed pipe from the manifold in a single continuous loop per circuit — never join pipe within the screed, because any joint buried in concrete is a permanent leak risk. Use a double-spiral (snail) layout where possible: this routes the hot outflow pipe next to the cooler return pipe on every pass, which averages out surface temperature far more evenly than a simple serpentine. Keep bends gentle and well above the minimum bend radius printed on the pipe, and fix down every clip before moving on — loose pipe floats when wet screed is poured and ruins your spacing.
- 5
Pressure-Test the Circuits Before Calling the Screed Team
Fill every circuit with water, bleed all air, and test at 1.5 times the working pressure (typically 6 bar) for a minimum of one hour — many installers hold pressure overnight. Walk the full circuit while it is under pressure and check every manifold connection and any fitting used at the manifold tails. The screed crew must arrive to find the system still pressurised: this is the only way to catch a pipe damaged by foot traffic or a screed rake before it is buried. Leave the system pressurised throughout the screed pour and for the full curing period.
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FAQ
- How thick does the screed need to be over underfloor heating pipes in Greece?
- A minimum of 65 mm of sand-cement screed is standard over 16 mm or 20 mm pipe in residential builds. Flowing anhydrite screed can go thinner — around 45 mm — and has better thermal conductivity, but it requires a sealing coat before any adhesive is applied. Thinner is faster to heat up; thicker holds heat longer after the boiler cycles off. For holiday rentals that need rapid warm-up between guest changeovers, thinner flowing screed is worth the extra cost.
- What pipe spacing should I use for ceramic tile floors in a Greek villa?
- For a main living area with ceramic or stone tile, 200 mm centre-to-centre is a solid default. Perimeter zones and rooms with large glazed doors or high ceilings should drop to 150 mm. Tile is an excellent conductor of radiant heat, so you generally do not need to over-specify spacing — but do run a proper heat-loss calculation for each room rather than applying one spacing to the whole floor, especially in older buildings with uninsulated external walls.
- Can I walk on the insulation boards and pipes before the screed is poured?
- Yes, but carefully and always on boards laid flat across the pipes — never directly on the pipe itself. Use scaffold planks or sheets of OSB to distribute your weight and move them as you work across the floor. Pipe kinks and crushed clips from foot traffic are the single most common cause of failed pressure tests, and finding the damage after the screed has gone down means breaking up the floor. Keep the number of people walking the zone to a minimum on pour day and ensure the screed crew are briefed before they start.