October and November

An Eccentric Anomaly: Ed Davies's Blog

After getting the roof membrane put on early in October I was fairly busy for the rest of the month running around with minor things. November has been distinctly quieter.

A couple of days after that last blog post I put the sash in the living room window (the last sash). Over a few days I also taped round the windows to connect them better to the membrane. Most of the rest of October was spent on working out more details of how the roof covering should work.

The flashings for Velux windows are really designed for use with tiles or slates so it's a bit of a puzzle how to make them work properly with profile steel; I found this BuildHub discussion very helpful. In particular, looking at @Cpd's pictures pushes me in the direction of wiggly tin rather than box/trapezoidal shape for the profile of the steel sheets partly from an aesthetic point of view and partly because there are more closely spaced “low points” making it easier to get them lined up on the flashings to the sides of the Velux windows.

I bought the Velux flashings needed and tried them out on that window I dropped. I also got the cavity firestop battens needed to stop fire spreading in the walls and between the walls and the roof. I wasn't sure where they'd be needed exactly (a day spent reading the regulations didn't clarify things for me) and how to fit them without compromising the ventilation of the cavity between the roof membrane and the profile steel, important for getting rid of any water that leaks or condenses there.

At the end of October my building control officer suggested a meeting on site to discuss the implications of changing the version of building regulations my house would be required to meet. In general, once you start on a building project you freeze to the version of the regulations in force at that time but if the build takes long enough they can bump you up to the regulations current later though they won't generally require you to undo anything already done or make changes which are impractical given what's already been built.

For my project the only changes of relevance were the need for a CO₂ monitor (which I already have and which I'll want in the house for controlling the MVHR) and the need to provide reinforcement in the bathroom walls so handrails can be retrofitted relatively easily which I'd also had in mind as the result of various Buildhub discussions of the matter.

In principle, they could also ask for a new SAP (energy assessment) calculation but they'd decided that my house was sufficiently clear of the requirements that that wouldn't be necessary.

While he was there I also took the opportunity to ask about the cavity firestops. He wasn't sure about the need for them in the roof (do the wall or roof rules apply to an A-frame?) and went away to check. I don't, it seems, as they're required in walls which are defined as being steeper than 70° and my roof's at 60°.

We also discussed my ideas for the entrance ramp and the insulation in the main house floor. Nothing amazingly controversial but useful to be able to run them past him and not get any objections.

I went away for a family visit to England for the first weekend of November as it was forecast to be very wet and windy in the north. Straight after I got back I did my back in and didn't really go out much for a well over a week which was a pity as there were a couple of reasonable days.

On the 13th I put the “bib” on the living room window. I'd already done the bibs for the narrow windows (3 bedroom windows and the bathroom) so I had the 3 wide windows (kitchen, living room and study) to do.

The difference being, of course, that the wide ones would be going on top of the membrane whereas the narrow ones were already installed when the membrane was fitted. This made installing the metal drainage gutter across the top a bit more awkward as it goes across the top of the counterbattens running up and down the roof.

The way this gutter is intended to be used is to wrap the bib into it with a slice cut out from the membrane so any water trickling down the roof is guided into it then off to one side. I haven't been doing that partly because I wasn't convinced that I'd get a good seal with the butyl tape supplied but mostly because I didn't think the poor state of the then existing roof membrane justified the effort.

For these last three windows the problem is slightly different. I didn't want to cut the counterbattens to lay put the gutter directly on the sarking because that'd mean cutting the membrane as well. At the same time, sealing to the membrane draped between the counterbattens would be awkward and unreliable.

What I did instead was to cut an approximately 250mm wide strip of membrane feeding the top edge under the bottom edge of the next sheet of the roof membrane above (which was conveniently close and accessible below the next batten above the window).

The white bit is the underside of the bib folded over the gutter ready to be pushed and clipped into the gutter. A few staples in the overlap between the new sliver of membrane and the sheet above gave a good seal without compromising the ventilation under the batten.

The rest of the month was wet, windy or a few days just cold when I wasn't feeling particularly well so the only other work I did on the house was stapling a join between membrane sheets high up on the south roof where the few staples the builders had put in had pulled out.

Yesterday I put the bib on the kitchen window, which was a fairly quick job given that I'd already worked out how to do the membrane/gutter connection shown above. I didn't tape it up as by the time I finished it was beginning to cool down a bit and the Tyvek tape I've been using works really well but it does need to go on dry. As it was forecast to be dry until this evening I left it until today but actually it started raining just as I was about to go out this morning so that'll have to wait until it's had a chance to dry out again.