Still Slating

We are still slating the roof, as the weather permits. We are solidly into Autumn, so it is cooler and the weather is wetter, but we have not lost many days so far. We would not want it to get much colder, so it is a bit of a race against time. We probably have another 8 days work left on the north-facing roof, plus the time we will ned to flash the solar panels on the south side and to fit the ridge tiles.

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We are working much more quickly now and have a good system going where one of us can pass slates up to the other one up until 9 courses from the top, then use the short roof ladder to get those upper courses done. It is much quicker to move the short ladders than one long one and so far we have not cracked any slates through resting ladders on slated roof.

We installed a second roof slate, this time for our stove flue-pipe. The latter will be 6” inside, 8” outside diameter, so we got one with a 219mm tube. It arrived well folded up and-battered looking, we got it straightened out and waited until we got the slates up to where we wanted the bottom of the lead slate to line up. We used the jigsaw to cut out the sarking to the diameter of the tube +75mm all round. So a comparatively enormous hole. Fitting the slate turned out to be simple because it lined up nicely and I was able to use full sized slates and slate-and-halves without any cutting. The top edge was just below the ridge so we fitted the top-most course of slates above, directly onto the lead. The ridge tiles will cover the top edge, all very simple and neat. The areas we have slated have been fully tested and we have not seen any leakage at all, so we have the whole east wing and chunks of the north wing properly weathertight. I also understand why we had so many leaks through the membrane – rain was ponding up above the battens we used to hold the membrane down, the water was running through nail holes to the sarking and wicking down the underside of the membrane. When the water got down to the rooflights, there was no membrane left and the water dripped off the sarking immediately above.

Preparing for PV panels

Our building warrant expects us to put a row of PV panels across our south-facing roof overlooking the courtyard. Now was the time to do something because we cannot finish the roof without the panels. We slated along the lower half of the roof, along the entire 23m+ length, taking in the five rooflights and getting the slates to the tops, so we could completely install the flashing kits. We worked right to the bottom corner of the west end of the roof and left the slates on the diagonal, to just cover the 5^th rooflight. We will probably nail OSB up over the edge of the slates over the winter, to preserve the breather membrane until we get the west wing roof on.

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We contacted 6 companies, some very local and others around Edinburgh, saying we wanted a 4kWp array with microinverters, mounted directly on the sarking boards/breather membrane. We explained that longer term, we wanted an integrated system with the ASHP, woodburner and thermal store.

Five responded. One, Install Solar from Livingston, were the first to visit us on site. The person was surprisingly helpful and appeared to live, breathe and eat solar panels. He persuaded us to go for as many panels as would fit, he thought 20 at 310Wp each – around 6kWp – because the panels are relatively cheap i.e half as much capacity again for around £1,000. He also suggested 4.7kWh-worth of batteries because it makes it easier to make full use of all the electricity generated. We would still divert unused electricity to heat water, but should be able to cover evening use of electricity – lighting etc.. He thought we did not need microinverters because the shading of panels at each end would be gradual and regular and should be covered by bypass diodes in the panels. These prevent a panel that is shaded from stopping the other panels from working fully. Finally he said that they did not do heat pumps etc., but thought it was a good plan. He suggested a phase-change thermal store rather than just hot water. It was a very useful visit and we even had in the back of our minds putting extra panels on the west wing, to get earlier morning and later evening sun. Two days later, Aberdeen Solar visited us. They suggested a set-up that was exactly what we asked for, but they seemed resistant to going from 16 to 20 panels. Novus Elements were interested in quoting but did not visit. They were flexible and were happy to quote for 20 panels. Two companies did respond but did not react in time. So we ended up with three sensible quotes. After only a day or two, we went for the Install Solar quote, including the batteries. They said they could install the system on the following Wednesday. It was all a bit cheaper than we were expecting, I expect the recent demise of FIT meant the industry is mostly below capacity.

Finishing the first roof

Slating up to the lower corner of the roof
We started the roof against the extension of the gable wall. This originally allowed large doors to open back over the opening that is becoming our big window. All the other corners end above our runs of facia boards, which project outside the building line – a consequence of lifting the roof by 45cm without building the stonework with it. So whilst most of the edges of the roof will be against coping stone, the bottom edges come past the padstones into open space. We handled this by projecting slates on the corners 50mm outwards as well as downwards. This involved quite a bit of cutting, plus we fixed the slates using A2 stainless screws to avoid stressing the fascia support by whacking roof nails in. The end-result was pretty good because it was neat, solid, but also unobtrusive.

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Slating round a soil vent pipe
We have three openings to make in the roof (two more if we install the MVHR). We have soil vent pipes above the east and west upstairs en-suites and a stovepipe in the north wing. The east wing soil pipe follows a circuitous route into the family bathroom from the inspection chamber outside, diagonally across the adjacent bedroom, up to the en-suite in what will be the wardrobe for the ground-floor bedroom, across the gable wall of the en-suite, then a dogs leg across until it is directly above where it entered the building, in what be another wardrobe (for the upstairs bedroom) and finally upwards and through the roof. The soil pipe in the west wing en-suite is handled similarly, our other soil pipe is all downstairs and we can get away with air-admittance valves to vent them.

We decided on old-fashioned lead slates for the SVPs, with the soil pipe projecting upwards through it by 600mm or so. We got a pair with the pipe opening at 45 degrees, near enough for our 42 degree slope. We cut away a short section of one sarking board and a sliver off the one immediately below it, to make a hole loose enough not to restrict soil pipe. We then spent a merry couple of hours cutting slates to fit around the upstand and flashing the lead slate in to be fully watertight. I added extra lead below it, fixed with double sided butyl tape, to give a good enough overlap onto the slates below. We left the upstand without pipe in it until we get round to doing our soil pipe – not far away now.

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Finishing off
We slated onwards and upwards, flashed lead over the soakers and mortared the lead in. Apart from the very top rows, which we will slate from the other side, that was the roof fully sorted and ready for guttering.

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Starting with the slating

Ric has started us working on slating. We will cover the east side of the east wing roof, since this runs between copings at each end, with no valleys.

As with most things in life, there is a lot of preparation. There has been the weeks of work sorting the slates into weight categories. Ric worked out the spacings we needed between courses, including the two starter rows that are hidden below the first visible course. The slates are around 465mm long and 230mm wide, we will have a headlap of 190mm and the bottom two courses will be ?? and ??mm long respectively. We made up a suitably large set square, attaching batten to our aluminium square. We used this to mark a vertical line up close to the coping, to find out where the coping was furthest from the line. This is where a whole width slate would be used, all others above/below would need trimming to size. The bottom-most slates needed special treatment because that is where the coping runs down onto the extension walling rather than a simple retaining stone. Ric cut a right-angled notch out of the first and third slates.

We agreed that the first five courses would use the heavy, thicker slates, then mediums for most of the roof, then a couple of courses of the light ones. The lowest course is nailed on upside down, with the second course right way up and lined up with the bottom of the first, 50mm beyond the edge of the eaves tray. The third, full length course also lined up with the bottom edge and it was then the 190mm intervals upwards with full-sized slates. We cut slates for the start of each row, to fit the space and avoiding having less than 150mm width. Cue the slate & halves that we got from the Slate Centre. The slate cutter was pretty good, though Ric reckoned it was not as good as his smaller one. I was able to cut the length of the slate & halves in two goes and across in one. We used the Hambleside Danelaw plastic soakers up against the parapet, just hidden under each slate and fixed to the sarking with a single nail. They did partly cover the slot for the flashing in the coping, Ric suggested we use the angle grinder to cut them out of the way before we fit the flashing. Where the nail holes were either too high up the slates or too low so that they were over the previous course, we found we could drill holes easily using the drill driver with a 4mm masonry bit.

I struggled early on with vertical alignment of the slates, getting successive courses exactly half a slate on from the row below. I had marked lines at 190mm across the bit of roof I was working on, I will also put vertical lines at intervals to check on the alignment. The other problem I had was that the bottom row had spacing between slates, but it ended up being squeezed out on the courses above. By the end of the first day, I had seven visible courses with the bottom row being 10 slates long. This will just about let me get up to the ridge, although we will leave the topmost ones to do from the other side, so we do not need to rest the roof ladder directly on slates. Collectively the slates looked good, even if they are a bit rough in detail (they are).

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Planning ahead – Slating & Floor Screed

The next big job is building up the gable ends of the east wing, it will take several weeks, but we have everything we need for that. We need to raise the stonework to reflect the raised wallheads and rebuild the coping stones into parapets. We also need to powder coat the fascia cladding and fit that. After that, Ric will return and we will look at slating and floor screed.

Slating
We have 430 large reclaimed slates, 24” x 14”, heading our way via Ellon Timber, from The Slate Centre in Haverfordwest. These will become our slate & halfs. It took a bit longer than expected because some of my emails did not get to them, however the phone saved the day. We have our soakers to run slates up the parapets, the lead flashing and copper nails and the slate guillotine. So this should all be ready to roll.

Screeding the floors
As with laying the floor slab, this is a job of many layers.

• The 100mm PIR foam panels are stacked in out east wing, with the aluminium tape to seal them together. We have the 25mm insulation that will be the upstands round the edges and the 6mm plywood that will hold the upstands in place against the studwork against the weight of the screed mix.
• We need to plan running heating and hot & cold water distribution pipes through the insulation (using 25mm insulation below and above) and buy it in. We will probably use copper pipe for our potable water, but WRAS-approved plastic pipe for everything else.
• We need to order two 10-port underfloor heating kits, each with 1000m of pipe, which will be fixed at 100mm spacing: We will have a heat pump that delivers water at 35c-40c, so need the closer spaced piping.  Each kit will serve up to 100 square metres of floor. The packs include manifolds, valves & pumps, but not the thermostats, wiring centres and actuators which we will source separately when we are doing first and second fits.
• We will wire the heating pipes to mesh, to even out the heat distribution. We found out about D45 wrapping mesh, which is 3mm welded wire at 100mm spacings, ideal for our purposes. We will rest it on shallow upstands and use the wire ties we used to tie the floor slab mesh together. The mesh is on order. We will order the cement and sharp sand for the screed nearer the time. We will also get a load of the quarry dust we used to blind the hardcore in the floor slabs, we will mix it 50:50 with the sand to increase the grittiness of the screed. The screeding will be a bit of a grim job, we need a bit over 11 cubic metres and will mix it by hand.

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