Astrokev

So, I've now realised my first major design flaw of the build..... I say major as I'm sure I've made loads of minor ones! I originally didn't intend to put sheet material on the outside of the walls, just cladding. Therefore, I intentionally designed the wall studding to be less than the more conventional 400mm centres to give it more strength. This is fine except that the studs now don't fall conveniently to allow me to use full sheets, without adding more stud work. I'll have to cut the sheets to suit, which will be more wasteful and time consuming. Oh well, lets hope this is the only significant design flaw! The other thing I would have done differently is to inset the wall studding from the edges of the floor to allow room for the OSB sheets. This isn't a major problem, I just would have done it differently had I considered this approach when I designed the obsy! Onwards and upwards ?

Yes, the FH Brundle wheels and track are amazing!

Not much progress on the build today. For one thing I was at a family BBQ enjoying some social time. The other reason was it was just too hot. Electronic temp sensor was reading 33.9'C in the shade this afternoon, and it felt it! Phew! This evening I did manage an hour though. I stuck down the edges of the EPDM to the side of the track rail with contact adhesive. I can now trim this which will enable me to make the catchment structure and check for clearance along the entire length of roof travel. The other big news is that I've now decided to put an OSB skin on the outside walls and then put cladding on top of this. This will make the building much more secure and will remove any risk of gaps caused by shrinkage of the cladding. The downside is I'm going to have to remove the breathable membrane I'd already put up, as this needs to go on the outside of the OSB. Started this this evening; a slow job trying to remove the clout nails without damaging the membrane, but well worth it.

Looking really good James. I like the fact that you're fixing the wall frames directly to the joists, and not through the floor boarding. This is similar to my build and means any future issues or changes you want to make to the floor can be dealt with without taking the walls down! A much more flexible approach.

OK, so off came the rafters and noggins, ridge beam and N & S beams cut back by 17mm, rafters and noggins put back on. I'm now back to where I was at 9.00 this morning - except that the capture structure should be a much better fit ? . Following the suggestion by @nightvision I'm now pondering on whether to skin the obsy in ply or OSB before I put on the cladding. Much as though I'd like to get the OSB and EPDM on the rolling roof, it will probably be easier if I can clad the gable ends first, so this is now top of the priority list....

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?