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Bizibilder's (New) Roll off roof Observatory build


Bizibilder
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I've finally started my new "improved" observatory build - the whole project will take all summer but at least i've started.

My first design ideas can be found here:

http://stargazerslou...er observatory and http://stargazerslounge.com/topic/172431-a-quart-out-of-a-pint-pot/page__hl__%2Bbizibilder+%2Bobservatory and http://stargazerslounge.com/topic/52029-bizibilders-roll-off-roof-observatory/page__hl__%20bizibilder%20%20observatory

My original build was a modified metal shed, the new one will be entirely timber and to my own design. The current observatory is nominally 6'6" by 6'6" and, whilst adequate, can be quite cramped. The shed sits on a base that is around 5" larger all round than the shed. The new building will fit to the limit of the base in width and I intend to extend the base by 2'6" to the North to provide somewhere for me to have a small bench for the computer etc - probably not a full "warm room" but certainly more space. The new shed will therefore be 7 feet wide by 9 feet long - in my case width is East-West and length is North South.

The fence you can see behind the observatory is perfectly North - South, with North to the right.

The first job was to remove a conifer that was going to be in the way:

Now you see it post-4502-0-97414700-1370099188_thumb.jp Now you don't post-4502-0-95156600-1370099204_thumb.jp

Then dig out the new extension to the concrete base: post-4502-0-45664600-1370099277_thumb.jp And a general view of the old Observatory post-4502-0-73269300-1370099309_thumb.jp

I've also been to the local timber merchant and started to price materials.

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Was the original build a metal foam sandwich? Actually looks quite a neat and tidy observatory, apart from rebuilding to get the increased dimensions did you have bad condensation problems, prompting the new design/build in wood?

Good luck with the build and hope you can still get some observing in over the summer months!

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The original is simply a metal shed (skin) over a simple timber frame, necessary as the seperate roof makes the original metal shed design unstable. I've never had condensation problems with the old observatory - there is quite a bit of ventilation in the metal shed roof design (deliberate!) that seems to keep things OK.

The old building is now four years old and is still perfectly OK - it's just that I need a bit more room. (I'm not as young as I was and not quite as slim either :smile: ). There are also a few new toys to install - so we can all look forward to a cloudy autumn :clouds2: :clouds2: .

I've just done a bit more digging to make room for the shuttering:

post-4502-0-43875700-1370112579_thumb.jp post-4502-0-80164200-1370112586_thumb.jp

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Progress is slow at the moment due to work but I managed to get the shuttering for the base extension done this weekend. The trick is to get this stage dead straight, level and to dimension - it makes life so much easier later!!

post-4502-0-44051800-1370795225_thumb.jp post-4502-0-90194700-1370795231_thumb.jp

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  • 2 weeks later...

Awful weather (heavy showers and clouds) prevented any physical progress - so it was "thinking time". A swift play with Sketchup shows the basic framing and runners:

post-4502-0-80098700-1372004121_thumb.jp

I've been mulling over the roof design for a few weeks now and have decided to make it flat. It will run on rails that are outside the main "box" to make weatherproofing easier (on three sided at least!). I did think of a pent roof for a while until I discovered that I woud have to exceed 4 feet wide on each side of the ridge - thus I would need double the number of 8x4 ply sheets and a considerably larger sheet of EDPM rubber - not to mention the extra timber for the framing.

The shed will be a nominal 7' x 9' and will have a small "work area" about 2'6" wide partitioned off across the end opposite the door - not really a warm room as such.

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I finally had time, and the weather, to do the concreting. A quarter of a ton (250Kg - 10 bags of 25Kg) all mixed by hand - poor old Bizibilder is suffering for that! (He's not as young as he used to be).

As easy as 1-2-3 :p

post-4502-0-30020700-1372352114_thumb.jp post-4502-0-69764200-1372352120_thumb.jp post-4502-0-98919300-1372352129_thumb.jp

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A bit more thinking time this weekend! Also I have ordered the rubber for the roof, some Stainless steel nails and a new cordless drill (as the batteries on my old one have finally given up - it must be nearly 10 years old so I can't complain!).

This is the basic framework, it all looks a bit flimsy but you have to imagine a outer covering of shiplap and internal panelling of 4mm plywood. These should make things quite sturdy.

I'm not quite sure how i'm going to join the main frame timbers (all the 90° joints). I think I may use 100mm stainless screws put in at an angle - two to each joint. Anybody got a better idea?

post-4502-0-89611500-1372612491_thumb.jp post-4502-0-63497300-1372612499_thumb.jp

And a front view to show the "outboard" runners. The roof frame clears the main frame by 5mm all round.

post-4502-0-19663300-1372612506_thumb.jp

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Looks very nice Roger and good sketchup skills as well. Lots of options on the joints, though by the time you've lapped and panelled both sides out I'm sure it will be stiff enough. Not so keen on screws for this as they tend to split out the end grain on the posts, oval nails might be preferable. Personally I think stainless steel screws would be overkill, though if you have a chop saw (or strong arms and patience) and really want to add some strength then you could cut some triangular shoulders. I'm a big fan of water proof foaming adhesive (Everbuild lumber jack), which sets almost as strongly as epoxy, convenient to use with a frame gun and importantly cheap and easy. I used this once to reface the dead wood to fit a new prop shaft to my 1936 motor sailer - 10 years in a salty/oily bilge and still going strong!

Fixing it down to the concrete is more important and you will need to be careful with drilling or using expanding plugs so close to the edge of the concrete. I'd be tempted to put the horizontal base timbers down on some damp proof (type used in block/brick walls), drill down through as far from the edges as you can (perhaps at a slight angle in) and then epoxying lengths of M8 threaded bar down in to the concrete. Once this is set you should be able to bolt the frame down securely and the epoxy will protect the bolts from damp below the membrane. Again I like the self mixing frame gun cartridges, which are a little expensive, but are very quick/easy to use - the only catch is that the epoxy sets very quickly once mixed so its best to have everything cut, measured, drilled and in place before doing the epoxy in a single go.

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Surprisingly good for the price, and as its a foaming gap filling adhesive it allows for less than perfect carpentry skills. It needs a little damp to work best, so I'll often slap a wet paint brush around to dampen one side of the joint. Only major draw back is you will end up with some on your fingers/hands which leaves black marks that take a couple of days to wear off.

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I'm not quite sure how i'm going to join the main frame timbers (all the 90° joints). I think I may use 100mm stainless screws put in at an angle - two to each joint. Anybody got a better idea?

If you are talking about the noggins, I just drove in Wickes deck screws.

Drive in at an angle but not to close to any ends.

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I used ScrewFix Gold screws straight in but I drilled pilot holes so that the wood wouldn't split. To attach the frames to the main corner posts I used 10mm galvanised coach bolts.

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I just used those black screws used for plasterboard for making the framework up... they are thin enough and long enough (60 or 70mm from memory) to secure the lengths of wickes studwork. I would also recommend diagonal bracing in the framework rather then parallel noggings all the way through.

IMG_0252.jpg

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I would also recommend diagonal bracing in the framework rather then parallel noggings all the way through.

Great advice, which I followed on my build - definitely made the frames more rigid. I did use parallel noggins as well though.

For screwing everything together I got through quite a few boxes of these: http://www.screwfix.com/p/quicksilver-countersunk-prodrive-8-x-3-pack-of-100/16498?_requestid=76466

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Oh agreed, a mix of parallel noggins an diagonal bracing works well. You can see in that image that staggered horizontal bracing was used as well as the diagonals. The Diagonal bracing stops the frames turning into parallelograms :)

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Ok, definitely with you on cross bracing the corners, though given the frames are braced by the cladding and ply/shutterboard additional staggered bracing is starting to sound a little over engineered. That said probably a good idea to have some extra support on the hinged side of the doors.

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though given the frames are braced by the cladding and ply/shutterboard additional staggered bracing is starting to sound a little over engineered.

Have to disagree somewhat. Due to the nature that the roof is mobile and not fixed to the framework the structure needs to be well braced. This is the mistake people make when purchasing a commercial shed and then try and convert it. You also need to take into consideration the weather. It needs to withstand wind up to 50 mph, and take the weight of a good half a ton of snow (or more).

I'd much rather "over engineer" a build than "under engineer" one. The last thing you want to do is to have to remove cladding etc to fit more bracing at a later date as you find the structure moves in high winds !

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I agree with Malcolm. The wind can be extremely powerful as I know from experience! And yes, you do need good bracing when the roof isn't attached permanently. In spite of the solid construction my obsy still shakes a bit when I push the roof shut and it hits the end stop.

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