The days are passing by quickly and since the last post, the ground floor is now ready for screeding.
Once we finished laying the membrane and expansion strip, Matty Beecher from MSB Heating Solutions and his team visited to install the underfloor heating. This is basically loops of plastic pipe clipped to the insulation.
The loops all make their way back to the manifold. This is a device that controls the hot water to each loop and regulates the overall temperature of each zone.
This is the final step before the screed is laid tomorrow.
Now that the roof is mostly complete, it’s time for us to move on to inside the house. Over the past few days, we’ve been preparing for a special date – the day the liquid screed is poured to provide our solid concrete floor which we’ll then finish right at the end.
The step before the first step was to make sure our block and beam floor was clean and flat enough for the next steps. We used a combination of an axe to chip away at any raised bits, and our trusty site vacuum cleaner James to clear away debris and sawdust.
Once that was done, we moved onto the first step – the radon barrier and damp-proof membrane. Since we’re in Cornwall and radon gas in the ground is a recognised issue here, all new houses need to have a radon membrane installed on the ground floor. This stops the gas rising from the ground and into the house. A damp-proof membrane is also needed to stop damp from rising through the floor. We found a two-in-one membrane that handles both and installed that – that’s the yellow sheeting in the photo. All the seams need to be overlapped, taped with double-sided tape and then sealed with duct tape. The membrane is taped to the damp-proof course running around all the walls (in black), so that any gas underneath the membrane can escape out of the building.
Of course, nothing is ever simple, so before we went ahead to the next step, we needed to make sure the steel beams were secured. They come attached to the floor with some bolts, but other than that and maybe some plastic packers, there’s a gap between the bottom of the beam and the floor. To make sure the beams are well supported, our carpenter fitted some simple formwork around them, and we filled it up with a structural grout, which looks a lot like sloppy concrete. It dries pretty quickly, however, and provides a strong support base escasing the base of the beam.
Once that was all done, we were ready for the next step – insulation! We have 150mm of rigid insulation boards across the ground floor to keep the heat in and provide a base for our underfloor heating.
These boards come in large sizes but can be cut easily with a handsaw and are relatively light.
In the middle of the photo you can see a conduit with a cable sticking out, and this is also visible in the first photo. This one is for a floor socket and so we needed those to be in place first. The bottom of the insulation board was then cut out to slot nicely over the conduit, and any gaps filled with expanding foam. The boards are staggered and nicely butted up to each other to provide a continuous base.
After this comes the last of our layers – the black membrane. This is very similar to the radon barrier/DPM, but it provides a sealed surface for the liquid screed to be poured into so it doesn’t leak and escape – therefore it’s very important that any holes are patched up. We laid it with overlaps just like the radon barrier and taped the seams and edges with duct tape, making sure there were no gaps. Finally, we laid a strip of edge foam around the perimeter, stapled to the timber frame. This foam provides space for the screed floor to expand and contract as it heats and cools.
We worked pretty hard into the night to make sure it was all ready for the next step – our underfloor heating, which I’ll write about in my next post.
Our timber frame completed a few days ago, and since then, we’ve been planning and getting materials ready for installing the first few layers of the roof. This will make it ready for the metal roofing company to arrive and install the final finish.
There are essentially four things that need to be done at this stage.
First is to install a breather membrane, which can be seen in blue in the photo above. This is similar to the familiar roofing felt which is installed under tile or slate roofs. While in that case it provides waterproofing, the breather membrane here simply provides a means of covering the roof and allowing any condensation to bead off.
The membrane comes in long rolls that we pre-cut so that each length was half of the overall length of the roof. This allowed us to install it more easily on site, which we did by stapling it to each roof truss using a heavy duty staple gun.
It’s important to layer each row of membrane on top of the row under it so that any water drips onto the next row on its way down rather than dripping underneath and into the loft space.
Next are the battens. These are long lengths of wood, 50mm × 50mm square and 4.7m long, that are attached parallel to the roof trusses running from top to bottom. This is as opposed to battens used for tiles or slates that run perpendicular to the roof trusses, from one end of the house to the other.
These battens do two jobs – they completely pin down the breather membrane and they provide a gap of 50mm between the membrane and the next layer. This gap allows air to pass and ensure any water or condensation is cleared away.
We installed these with 90mm corrosion-resistant wood screws. We chose screws that are self-drilling so that we didn’t need to pre-drill any pilot holes, and ones with Torx (star-shaped) heads to help them slip less when using a drill. 90mm ensures they go through the 50mm batten and 40mm into the roof truss for a secure attachment.
Thirdly, we have the plywood. These come in large 2.4m × 1.2m sheets that are 18mm thick and weigh about 36kg each! The plywood provides a flat deck on which the final metal roof will be installed. Since we’re using the plywood for roofing, we went with WPD structural plywood. This is a waterproof plywood that is designed for structural loading.
The detail from the roofing company specified that the first 150mm at the bottom of the roof should be 12mm plywood instead of 18mm, so we cut these strips and installed them first. Then we cut the main ply sheets so that they always start and end on a batten (this is important to make sure they’re fully supported). It’s also important to make sure each row is staggered so all the joins don’t line up – this ensures maximum structural integrity.
We installed these with a first fix nail gun. This is an invaluable tool that we hired from Jewson along with a set of 90mm nails. This made the installation much faster.
Fasicas and barge boards
Finally, we need to install the fascias and barge boards. These are narrow strips of 18mm plywood that run across the front and back of the roof as well as up and down the gable ends at each side. Guttering is attached to these boards. These will also be nailed using the nail gun.
Once all of these jobs are complete, the metal roofing company will install the aluminium standing seam roof and one job will be complete!
A few more days in and the walls of the first floor are being assembled.
Entire wall panels are delivered on trucks and then lifted into position using a crane, where they are then attached to the floor and ceiling. All the external panels are pre-insulated and battened ready for plasterboarding once the house is watertight.
At the bottom of the photo the top of the roof trusses can also be seen. These have been delivered early but will soon be lifted into place to form the roof and loft space.
It’s amazing just how quickly a timber frame gets put up once it starts!
After the soleplates and damp proof membrane were installed yesterday, it’s only taken a day to complete the frame on the ground floor.
Next up, the beams and joists will be going in, ready for the first floor to be completed, and within a couple of week we’ll have a complete timber frame ready for roofing.
We’re lucky to be able to use our next-door plot to site the telehandler that’s lifting the panels into place, and a few ground protection mats make sure it moving around doesn’t damage the levelled ground.
The last couple of weeks have seen a flurry of work on site as the groundworks are concluded. Since the last post, the block and beam floor has been laid and grouted providing a solid surface. The outline of the ground floor has also been laid with a layer of blocks on which our timber frame will sit.
Groundworks are now complete and we have a small week-long lull while we organise site visits and bring the next few trades into the schedule.
Next week, the scaffolding will go up around the perimeter, and the week after that, our timber frame build starts in earnest! As soon as that’s up, the metal roof installation will start, and this is also when we’ll get our hands dirty to do some of our own work, like insulating the loft space.
Finally, last weekend we installed our second, time-lapse camera on site. We’ve set it up but have no way of checking the result until we take it down, which we’ll do once the external block work is complete and there’s not much else to see outside.