In short: a 500ml can of Tuskbond FD170 covers up to about 2.5m². Divide the area you are bonding by 2.5, add a spare can for edges and joints, and round up. If you spray both surfaces, the area doubles.
What you need
Parts list
How the calculator works
Cans = area to bond x surfaces sprayed x (1 + extra) / coverage per can, rounded up. The default coverage is the "up to 2.5m² per can" figure that UK suppliers give for the 500ml Tuskbond FD170. Rough, porous or dusty surfaces take more, so lower the coverage if you are unsure.
Where spray adhesive is useful on UFH jobs
- Bonding EPS and XPS panels where you want a quick tack instead of a trowelled adhesive.
- Holding foil insulation and membranes in place while you work.
- Keeping insulation from moving before the pipe and screed go down.
For tile backer boards on timber, use flexible tile adhesive with screws and washers instead. See the fixings calculator.
Frequently asked questions
How much does a can of Tuskbond FD170 cover?
Up to about 2.5m² per 500ml can, sprayed on one surface. Spraying both surfaces halves that.
How many cans do I need for 10m² of insulation boards?
About 5 cans at 2.5m² per can with 10% extra, sprayed on one surface.
Can I use spray adhesive under tiles?
No. Use it to hold insulation and panels in place. Tiles and backer boards need a proper tile adhesive.