Before installing the wet underfloor heating and screed, we fitted the glass roof lights to make the space sufficiently weatherproof. Contractors could then continue to progress internally.
Damp proof membrane and vapour barrier
Contractors laid the damp proof course over the concrete slab, then completed internal drainage, hot and cold supplies and first fix electrics. The first property (with the kitchen island) required a sink waste, a socket and plinth light so trades positioned these under the floor. The contractor installed 75mm insulation over this, before fitting the vapour barrier (red membrane in the image below). This was now ready for the wet underfloor heating and screed.
We now had a damp proof course beneath the insulation to prevent damp penetration passing upwards; the vapour barrier above the insulation is to prevent warm, moist air passing downwards through the insulation and condensing on the cold concrete membrane below.
First fix electrics and plumbing
With the space largely weatherproof, electricians and plumbers set about first fix electrics and plumbing. They secured the wet underfloor heating pipes through the vapour barrier to the insulation beneath. Our contractors then pressure tested the system to ensure that there were no leaks.
Underfloor heating pipes
We marked the kitchen cabinet runs on the membrane to avoid heating beneath them. The plumber then fixed pipes accordingly with an approximate spacing of 200mm. The contractors decided to clip the UFH pipes in place, rather than use preformed, castellated sheets. They laid the pipes around the walkways of the kitchen all over the dining space, and in the utility. In one property, we would fit the pump and manifold in a kitchen cabinet; in the other, the utility will house these items. We will position the thermostats adjacent to the bi-fold doors, judged to be the coolest part of the space.
Wet underfloor heating and screed
The following day, the sand cement screed was delivered. Ready mixed and retarded for 12 hours (allowing a day to work the material) the team finished both properties in about 5 hours. They levelled it at a thickness of 75mm; slightly thicker in some areas where the concrete floor was not quite level. It was important that the screed itself should be precisely level ready for the floor finish. We marked the finished floor level at the very start of the project as the datum for everything that followed. This week’s work illustrated clear cost savings of the joint project. The trades could work on both properties simultaneously, preparing both floors and laying pipes in one visit and with one delivery of screed.
The plan for the next two weeks is to install the door frames with large window above, finalise changes to the existing drainage, erect the studs and start plastering. In the next instalment of this story we will be fitting bifold aluminium doors.
If you are planning your own extension or home improvements in Bath or Bristol, we produce concepts, designs, manage planning issues and oversee contractors. We also provide all furnishings and fittings, delivering the complete project. If you’d like to know more about house refurbishment we invite you to read our guide to home renovation.
