Exterior Wooden Building

[d438a1]

Hi, I am hoping to construct a wooden out building next spring all going well and I have started planning for it. I have not decided upon sizes properly, but i want to try settle on a design specification. But for my first prototype design, i have used 6m x 4m.

I have take some screenshots of my design in 3D and put them on photobucket as explained below. When viewing these images, it is best to try zoom in using the browser to see them clearer

Screenshot 1 shows the zoomed out view:-

http://i241.photobucket.com/albums/ff165/d438a1/1.jpg

Screenshot 2 shows the detail of a through wall and a butt wall meeting: -

http://i241.photobucket.com/albums/ff165/d438a1/2.jpg

Screenshot 3 shows a detail around the window, this method is used for the other windows and door: -

http://i241.photobucket.com/albums/ff165/d438a1/3.jpg

Screenshot 4 shows a zoomed in view of the roof: -

http://i241.photobucket.com/albums/ff165/d438a1/4.jpg

Screenshot 5 shows the typical dimmensions of the building: -

http://i241.photobucket.com/albums/ff165/d438a1/5.jpg


So i was hoping that people could give me some feedback on my design - dont worry about being critical! If you need any more information or screenshots, i will provide that on request.

I am also planning to build this on a concrete slab, with j bolts embedded to anchor the walls.

A further note, the majortiy of timber is 50mm x 100mm, with 50mm x 150mm used for the window header and window sill ,and 50mm x 200mm used for ridgeboard

Thanks in advance for the comments.

 

[Ossy]

Looks like you've had some fun with a 3D package

There're just a couple of things that would concern me from a structural point of view:

There's nothing to prevent eaves spread. The rafters will have a horizontal reaction where they meet the wall plate which will be trying to push the walls outwards. You can avoid this by having a decent sized ridge beam (probably the 200x50 would be enough, but it'd need a calc or two to check). If the ridge beam is 'man-enough' then the two end supporting rafters will have a much larger horizontal force where they meet the wall plate. You'll have to make sure that the connection into the horizontal beam along each gable is also strong enough to tie them together. This might be going a bit OTT for what you're building, but if you had a heavy snow sat on that roof for a while and hadn't though about it then you might have a problem.

Secondly is stability. I assume that this will be clad in timber of some sort. As long as this is fixed adequately to each frame and horizontal then it'll effectively provide bracing to the structure. If not, then you could do with putting in some diagonals from floor to roof on each wall.

All that said, I may be telling you stuff you've alreay thought about....

 

[joe-90]

John is right, you need to to strengthen the roof. If I were you I'd change a few of the rafters into 'A' frame trusses by adding ties beams across them. You can then store timber overhead.

 

[d438a1]

Yeah, it will all be clad in either plywood or osb ,then finished off ,possibly with cedar.

I did a quick mock up of a ridge beam and a tie, is something like this ok?

http://i241.photobucket.com/albums/ff165/d438a1/7.jpg

 

[joe-90]

That's the right sort of idea but you need more of them. As John pointed out snow can be very heavy and all the force is against the walls.

 

[big-all]

some very messy pictures of my shed














if you look the "A" frame is made up from 3x2" and 12mm ply either side of the joints
the cross bracing is 3" up to give extra head height so with 6ft sides you get 6ft3" head height thus keeping the overall hight down

are you aware that there are restrictions you need to comply with to avoid needing planning permission!!!

 

[Deluks]

Resting the base on concrete or even dpc on concrete could cause problems later on because of the ground contact.
Consider building a low (2 or 3 course) brick wall, or a single course of conc blocks, and build the timber frame up on this (on dpc)

You can still fix it to the ground, either by fixing the studs in between the concrete blocks (careful setting out required) or using L shaped restraint straps, fixed to the upright studs, with the shorter section bolted to the ground.

Don't know what you're planning for roof covering but a couple of rooflights are a very good idea.

 

[d438a1]

Some nice pictures there! I like the idea of the little hatch doors to get access to the roof storage!

Ok, so i will do some work on the roof plans to strengthen it and post a drawing soon.

I have not yet fully investigated the restrictions to avoid planning permission. Are they universal, or does each council have variations?

For the base, if there was a dpm underneath the hardcore before the concrete goes on, and the cladding overlapped the concrete base, could i get away without having a course of bricks?

Thanks for the replies

 

[big-all]

fairly standard i think

some are must be less than 30 sqare m
less than half the garden !!!
less than 3m flat roof or 4m slopping

more than 1m from the boundery
more than "x" m from the public highway!!!

are some of the requirements the ones with question marks the exact amount i am not shure about!!

 

[JohnD]

A couple of courses of bricks underneath will be a great help in keeping its feet dry, and so lasting longer. You can shape the cladding to throw water off so it can't get onto the tops of the bricks. Do what you can to prevent water being able to lie on the slab. If you only have a dpm under the slab, it will still get damp from the ground contact at the sides unless you put in in a tray.

If you are going to clad it in ply, think about dimensions that will suit 8x4 sheets with minimum cutting. These dimensions will also suit slab insulation. If you are using fibreglass, space the studs to suit roll width.

You might consider shutters for the windows as you will probably have valuable tools inside

run a couple of ducts for power and comms before you lay the slab. this is also a good time to run polypipe for a garden tap and your kettle while you have the trench open.

 

[Ossy]

When I said that the ridge would probably be good enough - ignore me - I don't think I'd grasped the 6m span.

I've just had a play with a spreadsheet and using a ridge beam in this situation really isn't an option, unless you've got access to some pretty damned big bits of timber.

The most the ridge will span without undue deflection is 2m (using some very rough guesstimates) i.e. you'll have to fit ties to the end rafters and two others at equal spacing along the roof. You should put these ties as low as you can, ideally at wall-plate level, as this will form the 'magic' triangle.

And joe-90 - not sure who you think I am, but my name's Dave, not John

 

[joe-90]

Are you sure about that? I'd ask matron just to be on the safe side.

 

[d438a1]

Ossy, you are completely right!

How stupid, the thought never occurred to me that i had put a 6m ridge beam in! I will have to make some major adjustments to the roof!

JohnD, excellent point about ducts for power and water, etc. If there is a DPM under slab, and i put a strip of DPM underneath the bottom plate on the walls, surely the water would not be able to rise up the walls?

Thanks

 

[JohnD]

dwarf walls under the wall plate with dpm will protect the wall plate.

but slab will be damp unless it is dpm under and edges.

One way is to build the dwarf wall on a strip and lay the slab inside it with DPM folded up at edges.

A damp slab will make the shed damp inside.

 

[d438a1]

OK, so I have some new sketches, I hope they aren't too hard to work out.

Having realised my near brainless mistake of having 6m lengths of wood, I have now reworked the plans.

I have incorporated most peoples suggestions and important structural improvements.

For the roof (Image 1), I have made it in to 3 sections (Image 3), with 3 main ties embedded in the top wall plate and birds mouth of the rafter (Image 4). There are also 3 other extra ties which are placed a bit further up the rafters (Image 2).

There is also created an overhang for the gable ends (Image 5).

For the walls, these are now in sections (Image 6) and are tied together with a second wall plate.

Image 1 -


Image 2 -


Image 3 -


Image 4 -


Image 5 -


Image 6 -


I hope this gets closer to meeting peoples structural approval! I look forward to the critical responses!

Thanks as always