Workshop\Shed Construction

[wizer]

Well after nearly a year i'm back to planning a workshop. It's been a bit of a nightmare what with kitchen plans, garages and useless builders, etc etc (I won't bore you with the details).

So following on from this old thread, i've now made a firm decision to build it out of wood and do it myself.

Briefly, it is a wooden lean-to building with roller doors at the front and double doors at back. External dims roughly 4.6m x 2.4m

I'm currently designing the roof and wondered if I am on the right tracks:

Is this the right sort of joint for the rafters?

 

[Jake]

The simplest way to attach the rafters to the house wall would be to rawlbolt a beam along it, and hang the rafters off that with joist hangers - saves all that other timber you have against that wall (and space).

 

[Freetochat]

The simplest way to attach the rafters to the house wall would be to rawlbolt a beam along it, and hang the rafters off that with joist hangers - saves all that other timber you have against that wall (and space).

Unless you are going to insulate and line with boards rather than a brick face?

 

[Jake]

Unless you are going to insulate and line with boards rather than a brick face?

Why would you insulate what is becoming an internal wall?

 

[wizer]

yeh cheers, it will be insulated and ply lined, so for aesthetics it will be best to have the extra frame work.

 

[wizer]

Unless you are going to insulate and line with boards rather than a brick face?

Why would you insulate what is becoming an internal wall?

sound insulation more than anything

 

[Shady]

Wizer, having read the 'old' thread, 2 observations:

1) Agree with the point about needing to access the gap between fence and shed for maintenance: who 'owns' the fence, and how 'friendly' is the neighbour: I say this because the best way of solving this and maximising every inch of space would be to replace that section of fence with the workshop's 'outer side'. You could make it look almost unchanged with careful design, I suspect. Offer to re-proof the whole fence once a year in return??

2) Light: I'd make the entire roof out of the 'see-through wriggly perspex' stuff. It makes a tremendous difference, and is a cheap way of doing one. I've just used some to make a quick lean to for bicycle storage. With proper rafter spacing, it's quite strong and permanent enough. Good luck!

 

[Jake]

In which case, you'd be better hanging the rafters off the wall, and stepping the internal wall off the house wall by a cm or two leaving a gap between the two - decoupling is the most effective form of reducing vibration/sound.

 

[wizer]

Shady:

1) I have considered this... what about the gutter overhang? I think to save any complications i'd rather keep the fence in place. The fence panels slide out easy enough so re-treating wont be much of a problem. I need to consider how to finish the 'unseen' side. Felt?

2) Light is somehting I do need to think about. My father suggested the same stuff. Will it be prone to leaking? How would you fix it to the rafters?

Jake, cheers I will look into that idea.

 

[Shady]

It's very waterproof - impervious, in fact. IIRC, you allow a 2 'wriggle' overlap where sheets join - could always run a bead of clear silicone in for absolute assurance, I guess.

Fixes with special screws/plastic washers/spacers, sold in packs wherever you get the materials from. (Travis Perkins seem reasonable) Also available are shaped 'end pieces' that fill the gaps so that it's draft-proof. If light's an issue, I'd take a long hard look at this stuff: it's easy to work with, very quick to install, lightweight, and will maximise your light. I think it's also got a 10 year guarantee, from memory... I'll try and find the website - lost it just now...

OK - found some stuff: Flashing advice here:

http://www.cavitytrays.co.uk/pdf/damp_proofing/Type F.pdf

General advice here (a good link for an overview, with details on overlaps, fixing etc):

http://www.diydata.com/projects/cor_roof/cor_roofing.htm

Initial costing info here:

http://www.casupply.co.uk/acatalog/pvc_roof_sheets.html

From the same site, accessories, fixings etc:

http://www.casupply.co.uk/acatalog/corrugated_fixings.html

 

[wizer]

Blimey, thanks so much Shady, something for me to read up on. I like the idea alot.

 

[Shady]

No Probs: the only downsides that I'm aware of are

a) it's not very aesthetically pleasing... (!)

b) thermal properties: check on UV absorption/siting of your shed with respect to the sun: you might broil yourself in summer - although if it's that hot, nice to work with the doors open - and it won't offer a lot of insulation in the winter - but a shed that size should be nicely heatable with some sort of thermostatically controlled wall heater, I'd think...

 

[Jake]

A more expensive, but more aesthetically pleasing (and better insulated) option would be to use twin-wall poly like a plastic conservatory - look in Screwfix for example - twin wall stuff

.

 

[wizer]

Looks good too Jake. I'll have to look into how to install it. Do they have a flashing solution as per the corrugated stuff?

 

[SketchUp Guru]

I'm wondering how you'll close the join between the wall and roof next to the brick wall. Have you given that and thought?

I think I would change the rafter joint up at the top of the high wall. As it is now, it looks like a split waiting to happen. Perhaps a ledge or blocking (like a bracket) run underneath each rafter would take care of that.

I like the "wriggly perspex" idea for letting light into the shop. Here in the US it's fiberglass. there is a wooden strip available that is milled to fit the corrugations. If that is available, suppose you put two pieces back to back on top of a layer of the W.P. and another layer of W.P. on top of that. It would give you an airspace to act as an insulator

You could also make some isulated shades to open or close to control how much light you get in and how much heat comes in or out.

 

[Shady]

I'm wondering how you'll close the join between the wall and roof next to the brick wall. Have you given that and thought?

Over here it's called 'flashing' Dave: for traditional roofs meeting brick (which the majority of our houses are) you cut a channel into the mortar between two courses of bricks at the appropriate height, and press/hammer in the top edge of lead sheeting, which then lays down onto the roof. It's then mortared into place. For these sort of things, there are plastic alternatives: I suspect they'll need some sort of silicone gunk along the top edge - haven't used them myself...

 

[SketchUp Guru]

Thanks Shady for the explanantion. Actually I wasn't thinking about that join but rather between the shed wall and roof.

The flashing does make sense to keep water from runnning down in between.

 

[wizer]

grr after spending a day on more shed design, sketchup decided to not save when it said it had! :evil: I've tried to recover the changes, but no luck.... back to square 1 (or rather square 3 or 4)

Partly my fault I suppose as I was running it on Windows Vista Beta 2

I'm not really sure where the problem lies in that joint Dave? Where is the weakness?

 

[SketchUp Guru]

I could be wrong but it seems to me as if that notch would be a great place for a stress riser--a place where a crack could easily start--if there is much of a load on the rafter. Of course I'm thinking of snow loads such as we commonly get here in Minnesota in the winter (and once in awhile in the summer. )

 

[wizer]

ah ok cheers Dave I see it now. Not sure wether this is a problem or not. We do get snow but not often and not often that heavy. I suppose the solution is to just sit the whole rafter on top of the frame work