A Little Window Progress

An Eccentric Anomaly: Ed Davies's Blog

It's a wet and breezy Sunday morning nearly three months after I last posted so time for an update even though there's not a huge amount of interest to report. tl;dr I'm ready to put some more windows in but haven't actually done any yet.

In the last post I'd got the first window in the east gable of the main bedroom in. The house will have a total of seven windows, that one and six in the south roof, one in each room. The two end windows in the south roof will be double-glazed top-hung windows forming a “means of escape” from the main and small bedrooms. The others will be triple-glazed centre-pivot windows.

They'll all be the same height but as originally planned the four middle windows (on, west to east, the bathroom, kitchen, living room and study) were going to be the next width up in the Velux range (PK08 rather than MK08). Having seen them in place I've decided that the bathroom window would actually be better as a narrower MK08. That'll need a non-material amendment to the planning application (and a note to the BCO) but shouldn't be a problem, I think.

The first batch of windows I bought consisted of the centre-pivot one which has been fitted to the east gable and the two top-hung ones to go on the south sides of the bedrooms so they were the next to do.

Somebody more experienced than me would have constructed the window frames for the remaining windows while making up the south roof but I wasn't confident enough that I understood how the framing would work. Actually it's quite simple, just a rectangular opening of the required dimensions, but I wasn't sure. Consequently I need to cut the rafters, fit the framing then cut out the sarking to form the opening.

What with the weather and things it was the end of March before I really started on all this. First mark up the rafters where the middle one needs cutting and the side ones need blocking.

Then decide to sand off the purlin above the window before fitting the window to avoid dropping dust on it unnecessarily so have a trip to Inverness to get a better dust mask and some Celotex insulation to embed in the JJI beams forming the window frame to keep the cold bridges to a minimum.

On JJI rafters you're supposed to leave a gap of about 5 mm between blocking and the flange in the direction the force is going hence the blocking being split into different parts here. After doing this header I decided that just putting continuous blocking across the whole of the footers and header would be more sensible, with the gap oriented for the main force which would be the support onto the side rafters.

Add blocking to the rafters and cut through the middle rafter.

…and the trimmer up the side which did have room for a useful amount of Celotex.

Get it all nailed in place and add 9 mm OSB round the edges to trim it all out (held in place by a clamp where the remains of the rafter in the middle makes using the nailgun impossible).

Getting the trimmer “vertical” was an interesting exercise as, with the 60° slope of the roof, just casually shining a laser level at it wasn't sufficient as quite a small variation in the position of the laser makes a big difference to the line on the roof. Luckily mine's a 90° cross laser; it has a side beam which comes out sideways, at right-angles to the horizontal and vertical beams coming out the front, so I used that to orient the laser perpendicular to the joists running along the length of the house. That's the first time I've found a practical use for the side beam.

What I should have done at the same time was check the vertical on the rafter on the left which would form the other side trimmer for the window. It turns out that was too far off vertical to be used so I had to rip this lot out again and use C24 trimmers on both sides of the opening.

Then cut out the sarking boards with my multitool. Here, still hanging on the membrane via the nailing on the battens over the rafters.

What I didn't think about when I decided to leave making up the window openings until after the sarking was on was that the tops of the brackets holding the headers and footers would need to be nailed through to the rafters from above. Consequently, I had to cut holes in the sarking to gain access:

Then fill the holes with squirty foam (and add battens round the edge of the opening):

View looking out.

Insulating collar and frame in place with sash standing by (upside down as needed for fitting):

The opening's now got a temporary cover which keeps most of the rain out. Most of the rain which gets in runs down the roof to the top of the frame then through/under the insulating collar. This will be sealed up with a bib that goes round the frame but I can't fit that until the sash is in and the frame has been squared up.

Unfortunately, that sash is too heavy for me to lift other than for short movements around on a relatively flat surface. I tried various schemes such as putting up a temporary deck to get it almost to the right height:

but a combination of the weight, the awkwardness of feeding it under the top edge of the opening then up at an angle and the need to be absolutely sure of not having it tip outside defeated me.

I asked a local builder (who'd done some work on the house I'm renting) if he and his lad could come round and do the job. He was busy that week and hasn't got back to me since and I really don't feel like chasing as he didn't sound all that enthusiastic to start with.

In the mean time I've sanded a few more purlins (just the one in the study left to do on the south side) and made up the frames for the other window in the main bedroom and the one in the bathroom. I got most of the one for the kitchen finished yesterday afternoon - just the trimmers to fit.

I now have a cunning plan for lifting these windows. It mightn't work but I don't think it's likely to fail too spectacularly if it doesn't. We'll see. What it does need, though, is a calm and reasonably dry day so it might be a while. Meanwhile I don't want to get too far ahead doing the frames for the other windows in case I learn something interesting while doing this one.

With the light coming through the window opening the loft area was nicely illuminated when I put a spare sheet of Celotex up there.