Novice shed build

[jc78]

Hi I'm gearing up to build a wooden shed and am stuck on a few things - hoping someone here might be able to help..?

I want to make something that will last and potentially be repurposed as a usuable (small) working space in the future. From research this feels doable for less than I'd pay for a half-decent ready-made shed online. Famous last words...

Plan is to frame in 3x2 treated with 4x4 corner posts, skin in 6mm ply then clad in feather edge. I was given some Cromar vent 3 light so figured would wrap between ply and feather edge, and on roof. Roof will be an apex with ridge beam in 4x2 and rafters in 3x2, and skinned in 12mm ply/osb. Would like metal corrugated roof if I can find a good deal - might tarp over for now.

We have a concrete slab measuring 3m wide and 2.5m deep. Has dpm (2 actually!). The builders did this for us end of summer 2022 but it's taken ages to get round to the shed. Seems ok despite being exposed to the elements for so long.

Q1. Given the slab has dpm already, do I still need bearers? If not, would it be worth either laying another membrane over the whole slab or a damp proof course/some kind of barrier tape on underside of the timber frame?

Q2. What is the best way to fix rafters to ridge beam here? And is there a trick for avoiding nails/screws that are fixing the opposing rafter?

Q3. For fixing frame to concrete slab I bought some concrete frame screws (7.5x102mm) by ForgeFix but when tested didn't get great purchase so am now leaning towards a screw and plug option that I hammer in once drilled, then screw down. If anyone has a particular recommendation I'd be really grateful.

As I said, I'm a novice - but I'm keen - any help much appreciated!!!

 

[Letsgetitdone]

With question 2 assuming you're using hammer and nails pre nail the nail into the rafter so that it's into the rafter timber at the top bit where the plumb cut is but don't drive it through so that the sharp bit of the nail is poking through the surface of the plumb cut. Once pre nailed offer the rafter up into the correct position and drive the nail through to the beam. It's a similar process for the seat cut.

I don't know about nail guns, I was taught by an old time roofer who treated it more like an art than a trade.

With hitting the opposing rafter its very unlikely, perhaps you are over thinking it.

 

[jc78]

Thanks Letsgetitdone

With the nail should that be horizontal into the ridge beam or any angle?

Sorry

 

[Letsgetitdone]

Over thinking it, the objective is to get the nail through the rafter and then a good length of the nail into the meat of the beam, to achieve that it will be closer to the horizontal. No one's measuring angles of nails! Another way to do it is use ridge to rafter connectors, I'd recommend using those or do a basic carpenters course before doing your project.

 

[noseall]

Q1. Given the slab has dpm already, do I still need bearers?

A DPM under the slab, won't be worth a jot, if the surface can get wet. Only when the footprint of the shed exceeds or matches that of slab (plus cladding or exterior finishes), does this work practically.

We dropped a large piece of DPM down on the slab. Placed sheets of 50mm Celotex on the DPM, then fixed a timber (100mm x 50mm) ring beam around the Celotex. We then built the shed on top of the ring beam, then wrapped the excess DPM up the sides of the shed exterior, prior to cladding it.

20221203_133018.jpg

• noseall
• 4 Dec 2023

shed.jpg

• noseall
• 4 Dec 2022

 

[noseall]

Q3. For fixing frame to concrete slab I bought some concrete frame screws (7.5x102mm) by ForgeFix but when tested didn't get great purchase so am now leaning towards a screw and plug option that I hammer in once drilled, then screw down. If anyone has a particular recommendation I'd be really grateful.

As I said, I'm a novice - but I'm keen - any help much appreciated!!!

You won't need to fix it down. However, if you want to steady the sole plate, then plug and screw with some 100mm 5's or 6's, 7mm drill, brown plugs.

 

[jc78]

A DPM under the slab, won't be worth a jot, if the surface can get wet. Only when the footprint of the shed exceeds or matches that of slab (plus cladding or exterior finishes), does this work practically.

We dropped a large piece of DPM down on the slab. Placed sheets of 50mm Celotex on the DPM, then fixed a timber (100mm x 50mm) ring beam around the Celotex. We then built the shed on top of the ring beam, then wrapped the excess DPM up the sides of the shed exterior, prior to cladding it.

20221203_133018.jpg

• noseall
• 4 Dec 2023

shed.jpg

• noseall
• 4 Dec 2022

Thanks for this @noseall

I've tweaked my design so that it will overhang the slab by an inch all round, which is the combined thickness of the ply sheathing and feather edge cladding.

I'll lay a dpm and run the excess up the sides and also make sure the cladding comes down lower than the top of the slab.

Also planning to insulate the floor - can I just check, when you mention the 'ring beam' do you mean you had the 4x2 running round the inside edge of the slab with the wide (4") face down?

 

[jc78]

Shed looks great by the way

 

[jc78]

You won't need to fix it down. However, if you want to steady the sole plate, then plug and screw with some 100mm 5's or 6's, 7mm drill, brown plugs.

Thanks for this as well - I would like to anchor it somehow as have kids and while it's unlikely they'd be able to budge it I'd rather be safe than sorry

 

[jc78]

Thanks for this @noseall

I've tweaked my design so that it will overhang the slab by an inch all round, which is the combined thickness of the ply sheathing and feather edge cladding.

I'll lay a dpm and run the excess up the sides and also make sure the cladding comes down lower than the top of the slab.

Also planning to insulate the floor - can I just check, when you mention the 'ring beam' do you mean you had the 4x2 running round the inside edge of the slab with the wide (4") face down?

Sorry @noseall if any chance you could spell out exactly what you did with the timber ring beam that would be a massive help...

 

[noseall]

Sorry @noseall if any chance you could spell out exactly what you did with the timber ring beam that would be a massive help...

More of a sole plate really.

Placed four pieces of 75mm x 50mm pre-cut lengths of timber flat, on top of the membrane (on top of the concrete pad), in a rough rectangle shape and pinned them together at the corners with some lengthy (125mm) screws. Squared it up and braced it, then filled out the space with 50mm thick Celotex. Floated the deck on top and pinned the edges to the sole plate with 50mm 5's (screws).

 

[jc78]

More of a sole plate really.

Placed four pieces of 75mm x 50mm pre-cut lengths of timber flat, on top of the membrane (on top of the concrete pad), in a rough rectangle shape and pinned them together at the corners with some lengthy (125mm) screws. Squared it up and braced it, then filled out the space with 50mm thick Celotex. Floated the deck on top and pinned the edges to the sole plate with 50mm 5's (screws).

Thanks for explaining, makes sense.
The one area I'm unsure of now is whether to fix it down or not. You say above that it's not needed - and that's good as it seems daft to puncture the dpm - but guess I'm just worrying about it slipping off/bad weather etc
Is your view that the overall weight is enough to keep it all in place?
Thanks as always

 

[noseall]

Is your view that the overall weight is enough to keep it all in place?

None of my (lighter) shed blew away. Mind you, they were also full of shoite!