Building a Large Shed

[perky416]

Hi Guys,

Background:
Im thinking about building a large shed in my back garden, outside dimensions to be 5.4m x 5.4m, with a pent roof, the highest point being 2.5m tall.
I will build the shed from scratch, im thinking about using a timber frame and shiplap.
Ive built sheds in the past, and literally screwed the 4 sides together, however nothing anywhere near this size.
The roof will likely be cement fibre sheets.
For the roof beams, Ive looked at span charts, and for a a 0.5-0.75 knm2 dead load, I can span around 5.5m using 220x75mm c16 timber, with a 400mm joist spacing.

Questions:
1 - With regards to the roof, what dead load would I use, and would I need to factor in a live load, such as snow? Im hoping to use the shallowest timber I can get away with to maximize head space inside the shed.
2 - Are there any special considerations I need to factor in with building a shed of this size (i.e. wind resistance etc)?
3 - Will it be acceptable to simply screw the 4 sides of the shed together and secure it to the foundation? Or should I sink posts into the ground and secure the sides to the posts?

Thanks

 

[big-all]

square is the worst off all for economical timber usage
sheet material is 2.440x 1220mm
long plank material can be quite expensive and not as easily available
buildings between 15-30sqm mostly wont need planning permission but may need to meet building regs [correction to include the building regs ref]
you need a fairly massive garden to fit in a 30sqm [greater than 60 with other buildings extensions garages etc coming off you 50% allowance]

 

[oldbutnotdead]

Have you costed your timber yet? 220 x 75 x 6m will cost a fortune- you'll be better off with engineered joists (JJ I-beams or similar) - can get them up to 20m irrc & a lot lighter than solid timber.
What are you going to build the frame with- 3 x 2 CLS or something more robust (that might take the weight of your fairly heavy roof).
Personally I think you'd be better off doing the walls with concrete blocks. Plus if you build with blocks you can have the thing within a metre of your boundary.

 

[John D v2.0]

yes you need to handle snow load as it can be as much as the dead load. dead load is just the total of the weights of the materials. I saw a video on youtube from a chartered SE who suggested breaking up the span with a flitch beam. This will save on timber and improve headroom, at the cost of steel and calculations. If your shed is small enough and/or non combustible you won't need to prove it formally, although you will need to know it's good enough.

 

[perky416]

Have you costed your timber yet? 220 x 75 x 6m will cost a fortune- you'll be better off with engineered joists (JJ I-beams or similar) - can get them up to 20m irrc & a lot lighter than solid timber.
What are you going to build the frame with- 3 x 2 CLS or something more robust (that might take the weight of your fairly heavy roof).
Personally I think you'd be better off doing the walls with concrete blocks. Plus if you build with blocks you can have the thing within a metre of your boundary.

Good point, i completely overlooked the non combustible material rule, this will be 60cm from the boundary in 3 directions. Looks like building it out of block is my only option.

Good idea about the JJ I beams. I will take a look.

Thank you

 

[freddiemercurystwin]

You can treat timber cladding with flame retardant coatings which will achieve the necessary fire rating. They can be overcoated in stains or paints etc.

 

[conny]

From experience I will never buy/use shiplap again! I don't know if it's due to poor workmanship from the supplier, (looked very good on delivery), or if it's something to do with the changing weather patterns we now seem to get, but one side of my shiplap shed is separating and creating gaps between the boards. It only seems to be happening on the south/west side as the others are still looking quite good after 3 years. It was given 3 coats of FenceLife+, and then a coat of some waterproofing clear finish, (both recommended and supplied by the supplier). Their excuse for the failing is the wet from the rain then the heat from the sun causing rapid expansion/contraction of the joints. I've given up arguing with them and will now be cladding it in either T&G or feather adge, making sure all the joints are securely fitted before re-coating
Two other shiplap sheds that were here when we moved in over 7 years ago are still in quite good condition for their age.

If I had the money, I would go for a block/brick structure every time.

 

[big-all]

Shiplap is brilliant iff affixed properly and the correct moisture level
if its overly wet when installed it will shrink too much as yours has
assuming its 6" planks the coverage should be about 134mm[shoulder to shoulder]

 

[mrrusty]

What you going to use it for? It has a bearing on how you build.

 

[noseall]

Shiplap is pants and needs ongoing maintenance.
Cedral cladding is the way to go....

shed.jpg

• noseall
• 4 Dec 2022

 

[JohnD]

But what does it cost?

 

[noseall]

But what does it cost?

The maintenance? Hundreds, especially when you factor in it will all need replacing (the low stuff always rots).

The shed wasn't cheap John, no. But I built it to last and to be largely maintenance free.

The Cedral alone cost £1'067 and I fetched it myself. That included the trims. I used odd-leg window/door (£1'150 fitted) so that I could save money finishing around those openings. I suppose you are looking at a £10k shed by the time you add the labour. I lined the inside with ply also, to keep the missus happy.

 

[John D v2.0]

But what does it cost?

Looks like about 35 pounds a square metre from a quick Google for the cladding planks itself, add in fixings trims and ancillaries

 

[Odds]

The maintenance? Hundreds, especially when you factor in it will all need replacing (the low stuff always rots).

The shed wasn't cheap John, no. But I built it to last and to be largely maintenance free.

The Cedral alone cost £1'067 and I fetched it myself. That included the trims. I used odd-leg window/door (£1'150 fitted) so that I could save money finishing around those openings. I suppose you are looking at a £10k shed by the time you add the labour. I lined the inside with ply also, to keep the missus happy.

you cannot put a price on a job to keep the missus happy, right?