In short: for a tacker system, allow one clip every 500mm of pipe plus three on each bend. Clip rail goes down about every metre across the pipe runs. Grid membrane covers 60m² per 50m roll, foil covers 50m² per roll before laps, and edge insulation runs round every wall. Choose your fixing system below to get the full list.
What you need
Parts list
How much of each fixing do you need?
| Fixing | Rule of thumb |
|---|---|
| Tacker clips | One about every 500mm of straight pipe, three on each bend with one at the apex. Clip closer under flowing screed. Packs of 300. |
| Grid membrane | 1.2m wide. A 50m roll covers 60m² and a 100m roll covers 120m². |
| Clip rail | Rails about 1m apart across the pipe runs, so roughly 1m of rail per m² of floor. Sold by the metre. |
| Foil insulation roll | 50m² per roll. Lap the joints by 50 to 100mm and tape them, so allow about 10% extra. |
| Edge insulation | The perimeter of every room, plus round any columns. 25m and 50m rolls. |
| Overlay panel washers | One under each screw head. Tile backer board on timber: 6 per 1200 x 600mm board. |
| Pipe support bends | Two per loop, where the flow and return rise to the manifold. |
| Pipe conduit | Wherever the pipe passes through a wall, doorway or expansion joint. At expansion joints, sleeve about 300mm each side. |
Which clip length?
Pick the longest clip that is still shorter than the insulation is thick. It then grips the board without piercing through to the slab or damp proof membrane. The calculator suggests 60mm clips for insulation of 65mm or more and 40mm clips below that.
Frequently asked questions
How many tacker clips per m² of underfloor heating?
At 150mm centres there is about 6.7m of pipe per m², so allow about 15 to 18 clips per m² once the bends are included, depending on the room shape.
How far apart should UFH pipe clips be?
About every 500mm on straight runs, with three clips on each bend. Clip closer if the screed is a flowing type, as it can lift the pipe.
How much edge insulation do I need?
The perimeter of each room plus any columns. Fit it after the floor insulation and before screeding, and trim it flush once the screed is down.
Do I need foil and grid membrane?
Use the grid membrane with tacker clips, as it sets out the pipe centres and gives the clips something to grip. Use foil with clip rail, where it reflects heat up and acts as a vapour barrier.