Astrokev

Hmm, that gives me something to think about ?. Thanks Tony for the suggestion. Certainly like the idea of sealing the walls prior to cladding to remove impact of shrinkage leaving gaps between the boards. It would also make the walls more secure. Must think on that.

Hmm ?. Starting to make the catchment structure on the gable ends. It seems that I've gotten a few measurements wrong somewhere along the way and the gap between the track-rails and the timber that will form the capture rails is too big. Not sure how that happened. I could probably make do and fudge it, but that's not my way and it would only bug me. If I moved the capture structure in to where I want it, this would leave the roof beams sticking out by a few centimetres, which would look unsightly and expose them to the elements. My design is to have the ends of the beams covered by the cladding on the gable ends, which will give them more protection. So, have decided to remove the rafters at the gable ends, trim the ridge and N & S beams back by around 17mm, and then re-attach the rafters. A lot of faffing to do this, but I'll be happier when it's done and, well, I guess I've got the time....

Thanks very much Ray. I'll check them out ?

My current plan is to paint with preservative and then paint with a pale colour to match the cabin to try and reflect the heat as much as possible.

That sounds like the holy grail there Ray! Yes, if you have any details, that would be great ?

Thanks for the replies everyone - very helpful. So far I've compared a mainstream supplier, Jewson, with a local timber merchant. Jewson only seem to supply 19x125 (finished size around 15x120). Baffles me why they bother to quote the unfinished size as this is of no use to man nor beast as far as I can see! Local timber merchant has 25x150 (unfinished size. Actual thickness is nearer 19) which is better I think. I'd prefer something a bit thicker than the Jewson stuff, which seems too flimsy to me. PVC is an option as suggested, but my personal preference is to stick with timber.

My concern with what I've seen so far is that cladding is prone to warping and may not lay flat against the studding frame. For the price you pay for this stuff you expect it to be fit for purpose. Not sure what you can do about this as its part of the drying process I guess. More expensive timber is an option I suppose, but this is really outside my budget. I noticed the other day that the tongue and groove timber used on my "cabin" has also warped badly in the recent heat and there's now a sizeable gap between a few of the timbers. This has been up for 5 years without previous problem. Any thoughts on how this can be minimised or is it just a risk one has to take?

I'm currently planning to use shiplap, which seems to be the standard cladding material, but is feather-edge boarding worth considering? The cost of shiplap is currently coming in at over £400 ?

Thanks for the suggestion. Will look into this ?

So, what d'you do when it's too hot to work on the observatory? Why, work out how much cladding I need and start to price it up of course! Could be pricey ?

Yes take care! I've developed what I think might be tennis elbow over my build. Ought to see the GP I suppose but he'd only say rest it. How can I do that - I've got an observatory to finish!

Yes, although my garden is fairly big, I certainly don't have the space you have! I've left enough room for general maintenance work on the west side of the obsy, but I've decided to have a fairly big overhang over the gable end which will make it difficult to extend a step ladder up the fence/hedge without it being more or less vertical. Now that the roof is nearly complete I think I could have gotten away with a lighter structure, but it's not a problem. Rather have it too strong than not strong enough. The only downside is a few more ££ spent on a few extra pieces of timber. I used 63x38 studding for the roof (except for the ridge and north & south end beams of course which are bigger).

Partly because I think I'll have to, to be able to put the adhesive in the middle bits, and partly because it would be handy to be able to stand on the roof to keep next doors hedge in check! There isn't really enough room along the side of the obsy for a ladder to reach the top ?

11mm, but OSB isn't as rigid as ply. I want the roof to be strong enough to walk on ?

Yes it's pretty heavy I think - although I can roll the roof with one finger. Not sure that'll be the case when the OSB and EPDM are on though! Six wheels was definitely the right decision! Over-engineered, as usual ?

...and update for today... Completed the eave beams on both sides of the obsy, and added diagonal bracing timbers across the rafters. Although the roof appears really solid without them, these will ensure the roof stays square. Probably not required, but that's just me ? . Just need to sort out the ridge support now, and add a bit more structure to the gable ends, and then I can lay the OSB.

Today's progress - Completed the noggins on the north side of the roof, and attached the edge timber along the eaves on the south side. Due to the width of the roof, I need 2 lengths to edge the eaves - a long and a short length. The short length still needs to be fitted. Will complete the eave timbers tomorrow and then probably faff around, wondering which bit to do next - either the gable ends and the capture mechanism, or the ridge support once I decide how to approach this. Either way, getting close to being able to get the OSB out and try it for size, which is exciting ? . Ubiquitous pictures below and, to mix it up a bit, also posted an image of the NLC's I was watching at midnight last night.

Yeah, I need to think through the options! im sitting in a field at the moment just watching some NLC's develop. Gives me something to think about while I wait ?

I just used clout nails. Seemed to go ok.

I considered that but I'm not that confident in my skills using my plane for precision work! I could give it a go I suppose and see how I get on. This would undoubtedly be a more satisfying solution! If I do need to resort to gap-filling adhesive, I note that you can get solvent-based and solvent free. Would solvent-based stuff give any issues with OSB d'you think?

Yes that was my worry. Once the EPDM is down, there's no way of rectifying future problems. I may add supporting timber as close to the ridge line as I can, but this will still leave a small "V" gap which I could fill with adhesive. Just looking up Evo-Stick Gripfill which seems good stuff.

Thanks Dave. I've never heard of expanding acrylic glue so must look this up. Sounds a good suggestion though ?

Well, I managed to find an hour this evening, so completed adding noggins to the south side of the roof to support the edges of my patchwork OSB layout ? . Should hopefully get the north side of the roof done tomorrow. I'm now wondering whether I need to add more support right along the ridge line. As it is, the OSB boards on both sides of the roof will meet along the ridge, but there is nothing to support the edges between the rafters. The rafters are only ~360mm apart, so not sure if I need more support or not. Will ponder on this.... Also posting a full side elevation pic, since I haven't uploaded one since I completed the main part of the roof. I think this angle nicely shows the relative dimensions and balance between roof and main structure. The site looks a bit of a bomb-site ?

Great progress James ?

Forgot to give an update from today - probably because there's not been much progress. Put in another load of screws to stiffen-up the ROR rafters. I'm a lot happier with them now. Next job is to add noggins between the rafters. Each side of the roof is too big to cover with a single sheet of OSB so am having to cover it with a patchwork of full sheets and smaller bits left over from the warm room roof. Doing the noggins is a drag, which is maybe why I didn't crack on with this today! The next few days are busy with other stuff so time on the obsy is more limited, but hopefully I can make a start.