Timber framed garage - my plans & 3D model

[helvellyn950m]

Hi chaps,

after a lot of wasted time looking into a concrete sectional lean-to garage, I've decided to go down the DIY timber-framed route. This way I'll get exactly what I want, cut out the planning permission & building regs, and save a small fortune too...if all goes to plan!

This is a detached building to be exempt from building regs and 2.5m high with a 15 sq.m floor area to stay away from planning permission.

It's pretty complicated spot to the side of my house; a myriad of (private) foul and surface water drains underground, utility cupboards and a foul downpipe from the bathroom on the gable end, a wonky boundary and a really tight squeeze for a standard 7ft up & over door!

I wanted to post up my plans for the framing people to see. Have I overlooked anything?

It's following a principle I found in an American book for building timber structures; they called it a 'Pole barn' where the vertical pillars are sunk into concrete:

(There's a 7' x 7' up & over door to the front of the house)

The pillars are spaced oddly, but this is necessary to dodge the drains underground.

Please excuse the inaccuracies in these 3D models - I'm still getting to grips with the software:

I'm using treated timber for the frame throughout, but I'm not sure what sizes to use? I have available: 6x2, 4x3, 3x2, 4x2, 4x1 in the lengths I need - what would people recommend for various aspects of the frame & roof? I wanted 4x4 for the pillars but I can't get them in lengths over 3m locally. Maybe two 6x2's glued and screwed together?

I plan to frame between the pillars at 600mm centres with 3x2 before cladding over (maybe with cement fibre board) and maybe some 3x2 diagonal runs between for rigidity. The building is going to be weakest at the front end, so I plan to sneak in a steel bracket to brace it against the house. Does this all sound sensible?

Cheers,
Chris

 

[Jasonb]

I really would not put the posts into the concrete, even with treated timber they will rot out in 10-12yrs.

Your joinery does not look ideal, the head plates are fixed to teh sides of the posts so all load is through the fixings, far better to put the plate on top of the posts so loads are transfered directly

Personally I would lay a coupel of courses of brickwork, make a 4x2 stud walls, 4x2 should also be OK for the roof joists. Clad the outside, ply & felt the roof and just add a few diagonals or metal strap banding fixed to the studs to triangulate the walls.

Just done an oak clad one but not take pics yet, if you can wait a few days I'll take some.

 

[helvellyn950m]

I really would not put the posts into the concrete, even with treated timber they will rot out in 10-12yrs.

Yes that's something I'd thought too. I was going to soak the bottoms in a creosote substitute and then coat in bitumen paint. I'll pop one of those post savers on too (heatshrink with mastic lining) to lengthen the life but ultimately they are going to rot. 10-12 years is OK for me.

I guess the concrete idea is a little unusual but is a way of giving a bit of extra stability to make up for my average DIY joinery skills.

Your joinery does not look ideal, the head plates are fixed to teh sides of the posts so all load is through the fixings, far better to put the plate on top of the posts so loads are transfered directly

You're right, I'd not thought of that. All the weight between spans will be borne by 4 coach bolts. I imagine the timber about these will break under load. I'll adjust my plans there, thanks!

Just done an oak clad one but not take pics yet, if you can wait a few days I'll take some.

Yes please!

 

[foxhole]

If you have a concrete base there is no need to sink any timber below, a frame screwed to the concrete would be fine, 3x2 or 4x2 could then be used for all the framing and lining the inside with osb would give great stability and strength.Fixings at high level to the house would also ensure a sturdy structure.Polythene sheet under cladding and it should all be water tight.

 

[foxhole]

If you have a concrete base there is no need to sink any timber below, a frame screwed to the concrete would be fine, 3x2 or 4x2 could then be used for all the framing and lining the inside with osb would give great stability and strength.Fixings at high level to the house would also ensure a sturdy structure.Polythene sheet under cladding and it should all be water tight.

 

[^woody^]

This is a detached building to be exempt from building regs

Your proposal will not be exempt - it is too close to the house and the boundary, to be built from timber

It needs to be at least 1m away from the building or boundary if built in timber, or you need to build it from "substantially" non-combustible material - ie masonry walls and a tiled roof.

 

[helvellyn950m]

This is a detached building to be exempt from building regs

Your proposal will not be exempt - it is too close to the house and the boundary, to be built from timber

It needs to be at least 1m away from the building or boundary if built in timber, or you need to build it from "substantially" non-combustible material - ie masonry walls and a tiled roof.

It's under 15 sq. m so is essentially a big shed:

"If you want to put up small detached buildings such as a garden shed or summerhouse in your garden, building regulations will not normally apply if the floor area of the building is less than 15 square metres and contains NO sleeping accommodation."

 

[helvellyn950m]

a frame screwed to the concrete would be fine

Hmm..it was suggested by a friend in the trade that something in the ground (before concrete) would help stability as the long thin building without any real structure at one end wouldn't be that strong...but with a frame bolted to a concrete base I'm tempted to agree with you foxhole

 

[freddiemercurystwin]

edit

 

[Jasonb]

Bit late but only went to back to that job today.

This replaced an old open sided car port, the brickwork was built off the existing conc slab, DPC, 4x2 studwork, Metal strapping for diagonal bracing, tyvek and oak weatehr boarding.

]

6Mx3m so same size as yours, fixing to the existing building obviously adds a lot of rigidity.

J

 

[helvellyn950m]

Wow Jason that's really helpful, thanks, it looks a cracking job and like you say near enough the same size as mine. Nice idea with the diagonal strapping.

What was the spacing on your timbers? 18"?

I think I'll be using some sheets of 10mm cement fibreboard to skin the outsides that aren't visible, then some featheredge boards or UPVC to the front & back.

Thanks again for posting these!

 

[Jasonb]

16" cts as that suited the ply roof, each rafter is directly over a stud.

J

 

[AronSearle]

If you copy that feather clad building shown above, if building control do say it needs non combustible surfaces, you can get the timber pre pressure treated with a fire retardant, or line the structure with something else non combustible like render (not PVC).



I'm pretty sure you will need to do this if you are within 1m of another building.

"If you want to put up small detached buildings such as a garden shed or summerhouse in your garden, building regulations will not normally apply if the floor area of the building is less than 15 square metres and contains NO sleeping accommodation."

Notice "not normally" apply, not that they will not, you can't just look at one cutaway section of the building regs.[/u]

 

[helvellyn950m]

I'm pretty sure you will need to do this if you are within 1m of another building.

Thanks Aron, I'm going to check to be sure. You've got me wondering again! The word normally is a bit of a grey area I think:

Building a detached garage of less than 30 square metres floor area would not normally need building regulations approval if:
the floor area of the detached garage is less than 15 square metres.
the floor area of the garage is between 15 square metres and 30 square metres, provided the garage is at least one metre from any boundary, or it is constructed from substantially non-combustible materials.

http://www.planningportal.gov.uk/permission/commonprojects/outbuildings

I read that as saying the 'at least one metre from any boundary' criteria only comes into action if it's over 15 sq. m, which it's not, so it's exempt. The new building will fall into the same category as the wood shed that's there now.

But this page words it slightly differently:

Some building projects are exempt from the requirements to make a Building Regulations application:

Detached building - shed etc: If it contains no sleeping accommodation and has a floor area not exceeding 15m2.

Detached garages: Providing it contains no sleeping accommodation and has a floor area not exceeding 30m2. It must also be at least one metre from any boundary or else be substantially built from non-combustible materials.

http://www.n-somerset.gov.uk/Enviro...es+not+need+Building+Regulations+approval.htm

Am I building a detached outbuilding (a workshop) even though it has an up & over door? You couldn't get a car in there, it's for motorbikes. Or am I building a garage?

I asked these chaps - http://www.oakencloughbuildings.co.uk/ - to quote on building the workshop/garage too. It was too much for my budget, but he was sure building regs didn't apply because of the floor area.

If I went for a steel clad roof and cement fibre clad walls I'd be near fully fire retardant anyway, I'd just need to sort the frame.

 

[AronSearle]

To be honest I am not sure if building control even know for sure half the time.

The reason I am sure you need it done, is that I have dealt with several occurrences were such a structure was built, and then building control insisted on class 0 spread of flame for surface finishes.

Now possibly they were wrong, but if they say jump, it's often easier to jump.

Spread of flame is not the same as fire resistance, so if you are covering the building in cement and metal (both class 0), you won't need to treat the timbers behind the surface materials.