Now we’re getting to the really interesting part, the point of no return with the floor! Putting in the underfloor heating is a job involving three different teams from Stan’s building firm, and slowly (well, quite quickly really!) the inside of the house takes on another guise.
The story so far: you may recall when we put the foundations in, we dug out the shape of the house and poured a concrete slab into the space. That slab has been the floor ever since. But now we’re ready to get a bit closer to the finished floor height.
So on top of the 150mm of compressed hard core and 150mm of reinforced concrete, we’re now about to add 140mm of floor grade foam insulation, more than half a kilometre of underfloor heating pipes topped off with another 60mm or so of concrete screed.
The idea with underfloor heating is to pass warm water through the pipes covered in the screed and warm the rooms like that rather than with a radiator. Although it takes longer to heat a room up from cold, it does mean you don’t have to have the water quite so hot (45 degrees instead of 70) which is just perfect for our ground source heat pump. It takes a bit of tuning though, but with thermostats in each room controlling a different loop of pipework, we will eventually get it all under control.
Here you can see the 8×4 sheets of insulation laid down and taped together. These went down everywhere on the ground floor except under the hearth in the living room for the wood burning stove. (This means we can have a hearth the same level as the wood flooring rather than a raised hearth.)
Then Brian and Nicky paid a flying visit and installed the underfloor heating manifold and all the pipework. Brian said he wasn’t looking forward to pushing in all the plastic staples by hand but much to his delight the supplier (Myson) had included a dedicated staple gun that could dispense the staples while the operator just walked along the pipe. No kneeling down and the job done in 5 hours.
The manifold will eventually be hidden in a cupboard under the stairs.
So, now with all the pipework in place, we’re ready for the concrete screeding. Some builders use a very liquid self levelling screed and pump the mix into the house. From experience, Stan prefers to use a very dry mix, mixed on site and trowelled over the pipes. If required, a thin level of self levelling mix can be applied at the end where it’s needed.
The resulting floor is remarkably level (although I wouldn’t expect anything less from Brian who is a bit of a perfectionist in these things). Examining it the day after, the conclusion is that there’s no need for any screed adjustments – ready for flooring, just as soon as it’s dried off enough.