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I ordered my EPDM in a single hefty 40kg piece as the width I needed for the warm room roof was very close to the length I needed for the roll-off roof, so the first (slightly scary) job for today was to unpack the EPDM, lay it out and cut the right size piece off the end for the warm room.

I’m surprised by how bright it looks in that photo. It’s really quite a dark grey. Anyhow, I took far longer than strictly necessary to measure up, making sure the remainder would definitely fit the rolling roof and then checking again, mistakes at this point being rather costly 🙂

I still needed to put the lip on the top edge of the roof to help stop rain or snow being blown underneath, so I got that done, fixed a few other bits and pieces that couldn’t be done after the roof was on and then broke out the adhesives and worked on each side of the roof separately, using the roof rails to keep the EPDM taught. Thanks to the lower temperatures at this time of year I didn’t have to rush too much with the contact adhesive either, and in fact where there will be spare rubber to trim off I’ve temporarily stapled it to the woodwork to keep the EPDM in place whilst the adhesive dries. The negative side of the lower temperatures was that the creases didn’t want to drop out of the sheet so easily. I’ll have to see how that goes when it comes to doing the rolling roof.

Unfortunately I didn’t quite have time to finish off at the top and bottom edges, so I’ve clamped those in place for the time being and hopefully I’ll get to them during the week as it looks like we’re forecast a few more warm days.

Too late I realised that the spare bit of 3×2 that I used for holding the top edge in place was just too wide to allow the rolling roof to pass it so I wasn’t able to run the roof off and make sure the rails are aligned before screwing them down, hence the clamps holding the rails down at this end 🙂

What a gorgeous day! It was definitely shorts and t-shirt weather by the time I went out to start work on the observatory. The insects were clearly making the most of things too. I think I saw more wasps today than I have done all year, and when l looked back towards the house when the Sun was over the roof at around 3pm I could see huge clouds of small insects caught in the sunlight.

First job today was to slip some DPC material under the roof rails and then start fixing the rails down. I used some zinc-coated “self-tapping” hex head coach screws for the rails, which meant I could put them in using the drill and a socket. With the first rail on each wall fully fixed down and the second loosely fixed I could work out how much more I needed to allow the roof to open fully — just another 20 to 30 cm as it turns out, so I’ll cut a couple of pieces long enough to have a set of fixing holes at each end. I’ve left the second rails loosely fixed for the time being as I’ll need to lift them when the EPDM goes on the warm room roof.

Although the OSB I ordered wasn’t delivered this week I found two and a half sheets plus some smaller offcuts in one of the sheds, probably left over from building the beer shack — nowhere near enough to do the rolling roof, but plenty to cover the warm room. So for the rest of the afternoon that was what I did. One sheet did most of the job and then the cutting took more time than anything else. I still have a little more woodwork to do before I put the EPDM on, but I’m hoping I can get all of that done tomorrow.

Not a good weekend weather-wise here thanks to “Storm Callum”, but nowhere near as bad as it seems to have been a few tens of miles north on the other side of the Severn Estuary, so I shan’t be complaining too loudly.

I overrode the objections of #1 offspring that “he wasn’t strong enough” and made him help me lift the roof frame into position. In the end it really wasn’t hard. I propped one end of the frame up on the end wall, then he “wiggled” the frame into position whilst I supported the other end. Once the first set of wheels reached the wall it was just a question of lifting them onto the rails and then rolling it along until the second set of wheels were in position.

Standing inside it looks enormous. The total wall height (including the sides of the roof) is now 2.08m which should be plenty large enough to allow the roof to be closed without needing to move telescopes out of the way.

I’d always planned to clad the roof with OSB and cover that with EPDM, but it was suggested in the last couple of days that I should consider PVC-coated box section steel sheeting. My main objection to that was the potential for condensation to form on the underside of the roof when it cools at night, but in fact it’s now possible to get anti-condensation coatings on the underside of the sheets. The idea was finally spiked however by the fact that delivery charges are very high considering the small number of sheets I need (if in fact the manufacturer will deliver small orders at all) and lack of guarantees over delivery times (because small orders have to be tacked onto the end of larger orders for manufacturing). Unfortunately it doesn’t appear there is anywhere selling these sheets locally either. So it looks like the OSB and EPDM solution will be the way I go.