Very Tired and Leaky Workshop/Shed

[leevis]

Hi
I have a workshop/shed in my garden which is around 20ft by 12ft. Its a pitched roof on the long side.

Felt is knackered, leaks a lot
Shiplap has a few gaps
Original door is leaking and rotting the floor
Windows are the normal pane of glass
Strengthen the roof

What I want to do (as cheap as possible but need it to last) is to make it water tight maybe put on a decent door and windows. Fix the floor and insulate.

1. Maybe put some OSB over the existing roof
2. Use EPDM on the roof (seems to be the cheapest/best solution)
3. Put in some decent joists to carry the roof
4. Put down some 18mm or 22mm chipboard flooring over what is there (fix the rotten bits first)
5. Put some insulation in the walls and ceiling (not too sure of what or how thick)
6. Put a membrane on the inside of the shed - as. I understand it, the insulation needs to be on the inside of this so might have to move these steps around
7. Buy a couple of window sets and a door and fit them

Does this sound about right?

 

[freddiemercurystwin]

What's under the felt? Why wouldn't you strip that off first and se what state the roof deck is in? You don't want chipboard anywhere near a garden shed. Fitting a membrane behind the cladding is a floored, you'd need to strip off the cladding then fit the membrane over the face of the studs, then refit your cladding. Got some pics?

 

[leevis]

Not too sure what is under the felt, pretty sure it is chipboard though. I can certainly get the cladding off, is it really worth it though?
I'll get some pics when I can get out there

 

[foxhole]

Not much point insulating unless it’s heated? Epdm is fairly bulletproof when applied correctly .

 

[leevis]

its going to be partly used as a home gym and workshop, will be heated in the winter when someone is in there. Unsure of whether to insulate or not

 

[oldbutnotdead]

Is this a timber shed? With the worlds thinnest chipboard for the roof deck?
Before you go beefing the rafters up, see what's supporting them- don't be surprised if the frame is 2 x 1 at the biggest.

 

[leevis]

Yes its a timber one, frame is 2 x1, maybe slightly bigger. Roof is thin. Walls seem to be sturdy enough but again probably not thick enough.

Still not too sure which way to jump here, to gain some space I think the end result will be an L shaped shed with individual rooms contained within ie one for garden equipment, one for camping equipment and then a workshop and a gym with whatever is left.

I can quite easily knock it down , the difficulty will be moving the contents somewhere in the meantime whilst it is being built. The only option I think I have here would be to create the new half (lefts call it), move all the stuff in there (and have a good clear out at the same time) and then knock down the original one and rebuild.

Couple of questions.

1. I am going to need a few doors for the different sections, would it be easier to build these or buy them. Probably will need two double doors and at least two single ones.
2. Wall thickness - what is a decent thickness these days? At the moment mine are just the tongue and groove probably 10mm thick. I would assume these would need to be thicker with some boarding on the inside?
3. Joist thickness. I will need to get out there and measure the spans etc, are there calculators that can be used to work out the roof joist thicknesses?
4. Roof thickness and material. What is suggested to make up roofs, I have about a 10mm thick chipboard up there which was felted.

Thanks

 

[oldbutnotdead]

Sort your budget out first. If it's going to be used all year round as a room with people in you need to look at house levels of insulation (80 + mm pir in the walls, 100 + mm in the floor, 300mm rockwool in the roof space.

Structurally you can beef the side walls up with 3x 2. Doors- depends what you want but again for a habitable space you want draughtproof, not a shed door. Likewise with windows. Start looking at Facebook Marketplace and Freecycle for surplus uPVC doors/windows.

Chipboard as a roof deck is an invitation for disaster. Plywood or OSB, not sure you'd need 18mm, 12mm might be ok but 18 will give you better snow loading. Felt it if you want, EPDM probably best bet.

 

[leevis]

Odd question, would it be better to knock down and start again or beef up the existing?

 

[oldbutnotdead]

Depends how much of the rebuild you can do yourself. Size is inside pd limits (need to keep an eye on the height though) and small enough to not require building regs.
I suspect that putting up a proper building (cavity walls, insulated etc) might cost a bit more up front but will be way cheaper on annual bodges to keep the rain out not to mention lower heating bills, better acoustic performance, generally being a nice place to be rather than 'oh no, got to go to the shed again'

 

[leevis]

OK defo going to take down and rebuild.

Looking at the regs though it looks like I can only go up to 2.5m which isn't the end of the world. I am going to do a flat roof.

The current shed sits on a raised concrete slab of around 140mm . I will be extending the shed so part of it will be on the slab and part of it not on the slab. I understand that there needs to be airflow under the building but don't want to lose loads of height if I can help it as the 2.5m will be taken from the ground level.

What I was thinking was to use blocks etc to raise the level outside of the slab and then use the slab as the base. Not too sure what else I can do here but it does mean that the joists will be on the slab and not raised. Is there a minimum height I can get away with here?

 

[oldbutnotdead]

Price your timber replacement up. Then price up the cost of blocks for a masonry wall (there are calculators, cavity wall will give best performance) and see where you get to.