I have a 24m X 0.5m electric underfloor heating mat(ThermoLam) and I need to reduce the length by several meters. How should the ends of the heating element wires be joined. A qualified electrician will be testing and doing the final connection.
Thanks for your help. Harryw

I note that they don't list a 24 meter x 0,5 meter mat in the instructions. Are you sure it's not a 20m long mat?

More on the reason why you can't cut it down... Suppose you have a 20m mat athen the resistance is 38 ohms. If you were to (incorrectly) cut say 5 meters off the end the resistance would reduce to 15/20 x 38 = 28.5 Ohms. The power would go up from around 1400W to 1900W. However because the area is also reduced from 10sqm to 7.5sqm the power density goes up from 140W/m^2 to 253W/m^2. That's an 80% increase. The mat isn't designned for that and the might overheat itself or the floor covering.

There are a few of us about. We've traced our Watters line back to 1810 ish. They were in India for about 100 years.