Gina's Observatory

[Astrokev]

That sounds better Gina.

Just my 2p worth !

Just noticed - I'm a Proto Star ! Oooh!

[Digz]

Thanks Gina.

I think if you could incorporate the up stand into your dividing wall that would be best.

[Bizibilder]

Have you considered a rubber strip as in the attached redo of your sketch (garage door seal, I think) It doesn't have to touch the lower roof and will prevent 99% of splashing entering the join. The "upstanding" felt inside the joint should cope with the other 1%.

One good thing about my own metal shed is there are quite a few (deliberate!!) ventilation slots in the roof - this keeps the whole thing cool and airy all year round.

[Digz]

To be honest, in this detail you could probably get away with nothing depending on your construction tolerances i.e. how tight you make the gap between the two roofs.

That is the slope on the warm room roof will direct all water away from the joint. The lapped felt on the inside will stop any wind driven rain which will only get blown into this space through the gap and will run straight back out when the wind stops. You probably wont get any build up of moisture associated with snow as snow is not going to get in there.

Of course, there is nothing wrong with belt and braces

[Gina]

Here is a design suitably beefed up to take the extra stress when the roof is closed. Two 4x2 timbers, part of the main structure will take the load. I doubt extra sealing will be required as has been said.

I've now got the omega profile strip - it's very light and flimsy - too much so IMO. I'll find another use for it.

[malc-c]

To be honest, in this detail you could probably get away with nothing depending on your construction tolerances i.e. how tight you make the gap between the two roofs.

That is the slope on the warm room roof will direct all water away from the joint. The lapped felt on the inside will stop any wind driven rain which will only get blown into this space through the gap and will run straight back out when the wind stops. You probably wont get any build up of moisture associated with snow as snow is not going to get in there.

Have to agree 100%.

I've taken advantage of a warm summers evening and have my ROR rolling. When closed the bottom of the frame pulls in tight against the felt at the top of the pent roof, butting up nicely against a lip at the top of the pent roof. I have no seals in place, and as the frame is 63mm thick at that point the gap at the open end is only a few mm. If I get chance I'll take some more images tomorrow

[malc-c]

Gina,

One thing I've noticed in my build is that despite the best made plans, often things fall into place as you go, seeing things physically in front of you helps, and when they don't go to plan you work through that problem and come up with a work-around...

Lets hope the weather improves in your part of the world and you can get started on the build... I'm really looking forward to seeing how your design works out

[Gina]

Thank you Malcolm The site is still a mud bath but the weather is fine today and things are drying up. More rain forecast in the next few days though

I want to get the design as worked out as possible so that I can order all the timber in one go, or at least have as little extra to buy as I can. I should easily make the £300 for free delivery. Yes, I know I shall need to "adjust" the design as building proceeds.

I've nearly finished the design - working on the roof frames and extra bits ATM plus the partition wall.

[Gina]

Roof structures.

1. Roof frames.

2. Elevation showing how roofs overlap. Obsy room end wall in blue, roll off roof in green, dividing wall in brown and warm room in red.

[nightvision]

A great design, looking forward to the build.

[Gina]

Does anyone know how long exterior grade plywood will last when used as the walls of a shed. I can get pressure treated ply which would help but I don't remember seeing any garden sheds with plywood walls, however cheap. Solid timber (eg, shiplap) is a lot dearer but I'm wondering if it would be false economy to use plywood. Of course, shiplap looks much better but I'm not concerned about that, in fact, a really grotty looking shed would look less like it contains anything worth stealing. This is a smallholding (very small farm) and ramshackle sheds are the norm. We have some pieces of old corrugated galvanised iron roofing sheets but not enough for the whole shed.

[JamesF]

I've used 12mm construction ply (birch, perhaps?) for making my chicken houses Gina, and that seems to be holding up fairly well. I do give it a good splash of creosote at least every couple of years though, and even then it doesn't like sitting in damp.

James

[malc-c]

I used 18mm exterior grade ply for the flooring, and even with a coat of wood preserve the top veneer has bubbled in parts where it got soaked before I could get a tarp to give it some protection. It would probably hold up, but as it's made from layers there is far more chance of it lasting just a few years rather than decades if continiously exposed to the elements.

I agree shiplap is expensive... I paid out £450 for 55 lengths of 5.4m rebated 12mm Redwood shiplap for my build. Where by comparison 12 boards of ply would be around £340, and if i had gone down the feather-edge route it would of been £260. But then I wanted something that looked like a normal shed and something that would last with little maintenance.

It depends on what your budget is...

[Astrokev]

Malcolm,

You mentioned Redwood shiplap. Is this a grade easily available and is it recognized as being superior to the "normal" Wickes shiplap for example?

[Digz]

Personally I wouldnt use ply in an exposed situation like that unless it was Marine Ply. I cant find any costs for marine ply at present but Im guessing it might be just as expensive as shiplap.

WBP ply is supposed to be suitable for external use but the top layer must be sealed. Having said that it wont stand up to repeated moisture and drying cycles for very long. It wont last very long with harsh freezing as well.

I would personally go for either feather edge or shiplap. Another option, however, might be to see if you can source some PVC strips, maybe in a brown colour instead of white, to clad your obsy in.

This is for use in bathrooms in showers not externally, but might do the trick?

http://www.diy.com/diy/jsp/bq/nav.jsp?action=detail&fh_secondid=9976796&fh_location=//catalog01/en_GB/categories%3C{9372016}/categories%3C{9372053}/categories%3C{9372276}/categories%3C{9392113}/specificationsProductType=cladding

HTH

[Gina]

I used 18mm exterior grade ply for the flooring, and even with a coat of wood preserve the top veneer has bubbled in parts where it got soaked before I could get a tarp to give it some protection. It would probably hold up, but as it's made from layers there is far more chance of it lasting just a few years rather than decades if continiously exposed to the elements.

I agree shiplap is expensive... I paid out £450 for 55 lengths of 5.4m rebated 12mm Redwood shiplap for my build. Where by comparison 12 boards of ply would be around £340, and if i had gone down the feather-edge route it would of been £260. But then I wanted something that looked like a normal shed and something that would last with little maintenance.

It depends on what your budget is...

Budget is verging on non-existent I'm beginning to think I've taken on a hobby/pastime a bit beyond my means. Guess I'm in too much of a hurry to get things done It'll just have to take a bit longer that's all - I'm not giving up now! I get these big ideas at times

Anyway, I had 6mm plywood in mind and I'm thinking that wouldn't last long. We are in a very exposed position here.

[Digz]

I think you would find 6mm would not be sufficient in any case, I would personally go for 12mm.

I know what you mean about taking things on though....Im not in a position to build my own observatory but Ive been designing it on and off for the past couple of months, its the excitement that I like planning something new and then, hopefully watching it come to fruition.

[Gina]

Personally I wouldnt use ply in an exposed situation like that unless it was Marine Ply. I cant find any costs for marine ply at present but Im guessing it might be just as expensive as shiplap.

That's what I thought. I know marine ply is very expensive - I used to go dinghy sailing in my younger days. Good quality wood and waterproof glue. Anything less is just not going to be up to it for the exterior of a building.

I would personally go for either feather edge or shiplap. Another option, however, might be to see if you can source some PVC strips, maybe in a brown colour instead of white, to clad your obsy in.

This is for use in bathrooms in showers not externally, but might do the trick?

http://www.diy.com/diy/jsp/bq/nav.jsp?action=detail&fh_secondid=9976796&fh_location=//catalog01/en_GB/categories%3C{9372016}/categories%3C{9372053}/categories%3C{9372276}/categories%3C{9392113}/specificationsProductType=cladding

HTH

uPVC shiplap would be ideal except that it's twice the price of wood (or more). I'm not sure interior grade plastic would stand up to UV and might disintegrate. That B&Q cladding is about the same price as Wickes wood shiplap.

I've just phoned the sawmills I'm getting the other timber from and their prices are lower than Wickes, and theirs is 19x150mm whereas Wickes is only 12x121. Also, I was quoted for treated timber. I don't know if Wickes is. Price us just under £2 a metre.

A quick estimate works out at £360.

[Digz]

Ah that's a good point it will almost certainly degrade in UV. We have brown uPVC guttering and down pipes which were installed about 8 years ago and even they are fading now.

I guess a bigger size of timber will mean less is used which is a bonus and if it's treated and cheaper it sounds good.

[malc-c]

Malcolm,

You mentioned Redwood shiplap. Is this a grade easily available and is it recognized as being superior to the "normal" Wickes shiplap for example?

Yes it should be available from any decent timber / builders merchant. It's basically pine, but with a tinge of red in it's grain. The difference between the stuff I used and that from Wickes is that it isn't tongue and groved, just rebated like the example below

It also comes in longer lengths, up to 5.4m - and unlike wickes, most are not warped, twisted or have chunks missing

[Gina]

I read the reviews of the Wickes shiplap. It was not complimentary (except for one person, I think). Very lightweight, knot holes, splits easily, warped, etc... It is NOT treated for rot! The shiplap from the sawmills near here comes in 3.6 and 4.8m lengths, is 19x150mm (Wickes 12x121) costs just under £2 inc VAT per metre, similar price per metre to Wickes but being wider is less per square metre and therefore cheaper overall. oh, and that price is for treated timber.

[malc-c]

The shiplap I purchased cost £1.30 +VAT per metre making that £8.43 inc vat per 5.4m length. There was only one length that had a slight bit of damage on it and that was on the end so I was still able to get the two end lengths out of it, so couldn't complain..

Forgot to add, that was for 12mm x 125mm, not the deeper size Gina has been quoted for

[Astrokev]

Yes it should be available from any decent timber / builders merchant. It's basically pine, but with a tinge of red in it's grain. The difference between the stuff I used and that from Wickes is that it isn't tongue and groved, just rebated like the example below

It also comes in longer lengths, up to 5.4m - and unlike wickes, most are not warped, twisted or have chunks missing

Thanks Malcolm.

I'll bare this in mind when I eventually get round to my build.

I'm in a similar position to Digz. Lots of planning going on but, since I'm currently job-hunting following recent redundancy, I need to watch the pennies!

I'm also planning the rebuild of my old 6" Dob. Pages of drawings and SketchUp designs, but no action yet for the same reason . One day soon, hopefully!

[Gina]

I think I'll go with shiplap even if it means waiting a bit longer to collect the funds together. Best bet in the end. Also, it gives more flexibility in the dimensions. My first thought for wall height was 4ft - the width of a sheet of plywood. That's a bit low, particularly with the obsy roof being over 7ft at it's highest. To have the walls higher would mean a join in the plywood - somewhere for the weather to get in. With shiplap, I can easily have higher walls. I was unhappy at having a 3ft high roll off section which couldn't be braced at the wall/roof intersection as it had to clear the warm room roof. "Racking" could only be prevented where it went past the dividing wall and at the other end by the flap, when closed. (Darren's design uses thick steel angle plates to brace the wall/roof intersection, which I haven't been able to source.) I'm now thinking of having 4'6" high south wall and 5'6" north wall (where the sky is restricted by trees and buildings). The east wall can also be 4'6" with the flap down.

Site progress is awaiting a spell of dry weather to dry up the ground. I have run the rotavator over it to break the mud up and help it dry out.

Cloudy tonight so no moon and no sight of the eclipse

[Gina]

Cross-section of obsy showing roll off and base section main timbers and rollers.