Who do you share your space with? Tumblr blog post.
One of the many processes we’re going through in the Westacre renovation project is making rafter extensions. It involves a lot of careful measuring and sawing.
We’re installing external wall insulation, hoping to get our 1930s semi to near passive house standard. It is making our walls 16cm thicker. And that means the roof needs to be extended on all sides to cover that thickness.
Where the rafters come down to the wall, we have to make them longer. We’re also kicking them out slightly so that making the roof wider doesn’t also mean making the eaves lower, which would cover the tops of some of the upstairs windows.
Because this is a renovation, we have to work with the existing building. Working on some of the earlier rafter extensions, we noticed that just making identical pieces of wood does not make for a straight roof edge. Evidently, the angle of the roof isn’t uniform.
So in the section we are currently working on, we have had to make some extra measurements.
We measured the horizontal and vertical along the joists, so that we could calculate the angle of the roof at each of those points. The angles varied from 31.2 to 32.5 degrees. Over the length of the joist extension (132 cm), that makes quite a difference.
Alex fed the numbers into his computer. It calculated the equations and told us the exact angle of the birds mouths in the rafter extensions, and the height of the blocks that they will rest on. We meticulously measured those out on the wood and tried to cut them as precisely as possible.
The next step was to paint the rafter extensions black. We’ll have to protect the wood somehow, and we’ve decided that black wood against the black roofing felt will probably look better than very blonde pine. It’ll also hide a multitude of sins going on under the eaves.
We hung the rafter extensions from a wire in the garage for easy access and painted them with bitumen paint. That was a sticky couple of hours for Hilde and Roger, Alex’s dad. Sometimes we’re very grateful for small mercies like rubber gloves.
When we get back from Belgium, we’ll be nailing the blocks and rafter extensions into place. And then we can finish insulating that long wall. That’ll complete roughly 2/3 of the external wall insulation. We’ll be waiting for more clement weather to do the remaining third.
It is a truth universally acknowledged that big projects never go the way you expect. Ours is no different. But we have done some great stuff in 2014.
Installing external wall insulation doesn’t start where you expect it to, though. Why you would make a substantial raised vegetable bed in order to insulate a house isn’t exactly obvious.
It’s because of the earth works. You need to insulate right into the foundations to below the level of the insulation under the floor. So we had to dig out all the foundations. The spoils of the digging works were transferred into the raised vegetable bed. Which is as huge as we could make it, but still nowhere large enough for all the soil we dug out.
And of course, once you’re digging, you may as well dig the path we are going to have all around the house, with the help of a posse of friends. It was a good idea to have the paths ready, so the scaffolding we’d need for installing the insulation would have something level to stand on. And while you’re doing that, you may as well dig the trenches for the drain pipes around the house. No use filling in the path and then having to dig it up again another time.
Consequently, the first half of the year was taken up with earth works of various kinds. We finished the raised vegetable bed with sturdy timbers and
- dug out the foundations.
- spray-insulated the foundations.
- uncovered drain pipes.
- dug out pathways around the house.
- created new trenches for new pipes.
- laid the pipes and connected them up with the existing ones.
- made foundations for the balcony we’ll eventually build.
- filled all the trenches in again.
- covered over the new pipes complying with the building regulations.
- created brick edges for the paths.
- filled the paths with gravel.
And only after that were we ready to start putting insulation on the house. Which requires a lot of measuring and cutting of polystyrene. And a lot of drilling holes and hammering in fastenings. And because we’re particular, we are also filling any gaps with expanding builders’ foam.
Of course, the polystyrene makes the walls 16 cm thicker, so we also have to extend the roof in all directions. We extended verges by adding an extra rafter, and eves by lengthening the rafters. A lot of meticulous measuring and cutting.
The insulation is not just polystyrene, though. Far more is going on underneath.
- A vapour barrier, custom tailored for the house.
- The wall around each window carefully smoothed out with crack-free render.
- Then the gap between render and window frame filled with a fibrous filler.
- An airtight membrane with a rubber gasket pushed into the window frame.
- Membrane glued to the wall.
- Vapour barrier glued to the membrane.
Hopefully, all of that will make the result pretty air tight.
By now, a few days after Christmas, we have covered just over half the walls with external wall insulation. And some of that has been covered with render by our plasterer. At least we have some idea of what the place is going to look like.
A few other jobs got done as well:
- Steel I-beam installed to replace the partition that was holding up the roof.
- Floor in the old kitchen and dining room taken out.
- Floor boards used to make a new wood store.
- Ceiling joists in the big room upstairs replaced with bigger, better ones.
It feels quite satisfying looking at it all like that. We have worked hard and achieved an awful lot.
Not according to plan, of course. If all had gone the way we imagined it, we wouldn’t have done most of this year’s work ourselves – or even at all. For one reason and another, these jobs added themselves to our list. That has slowed us down quite a lot, but we have learned so much in the process.
We’re having a rest now. And who knows what adventures we will have in the year to come…
Joists are those bits of wood that span your room from wall to wall. The ceiling plasterboards are attached to them.
In our big bedroom, the joists were sagging quite significantly. They were not thick enough to span across the whole extension and hold up their own weight. They were sagging in the middle of the span by about 7.5 cm, or their own thickness.
That would be bad enough, but those same flimsy joists were also supporting a beam going in the other direction. And that beam had two posts resting on it that were supporting the whole roof of the extension. And that was rather worrying.
So we are now in the process of replacing the flimsy joists with much bigger ones, 20 cm thick. Plus two steel I-beams that will definitely be man enough to hold up the roof.
Back in July, we manoeuvred the I-beams up into the loft. Hilde was sitting up there manning the winch, while Alex and his dad made sure the beams didn’t hit anything on the way up through the balcony door and the big bedroom.
They’ve been sitting there patiently, waiting for us to open up the edge of the roof on that side of the house. We need to extend the rafters there, and at the same time we can position the joists and get at the ends to nail them into the wall plate.
It takes a bit of doing to move the joists from the floor up into the loft. We each manage an end. One of them goes out through the balcony door (a very handy thing to have) and then we point the other end up into the loft. When enough of it is up there, Alex gets up into the loft and pulls it past the cross beam.
Moving the steel I-beams is another story. That involved a trestle plank, some plastic tubing to function as rollers, and some rope to catch all of the above should it fall in mid span. With a bit of shoving and pulling, we did get it across the room.
We have replaced about half the joists now. They are also holding up the post that is holding up the roof. And it all looks a lot straighter and more secure. It feels like quite an achievement.