franky
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| posted on 24/8/14 at 07:40 AM |
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Oak framed garages....
Has anyone got one? Pro's/con's etc?
I'm looking at something about 7m wide, 5.5m deep, 2 sets of doors with a slight annex area. If you've got one did you have to go
though building control and if so what do they specify for footings etc? Any pics?
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mark chandler
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| posted on 24/8/14 at 08:23 AM |
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I,m building one at the moment, 6m x 4m do not expect it to be cheap!
I called the council, as long as it is more than 1m from the neighbours fence, sits behind the front line of your house and is no more than 4m tall
assuming a pitched roof you can build a massive 'shed', talk to the neighbours first 
As I am going for a peg tile roof I have laid strong foundations, so far 10sqm of concrete have gone through my mixer and two pallets of engineering
bricks so I am already at nearly £1000 before the frame arrives.
As a shed there is no specification for footings but you do not want the slab to crack so have a good google, I went for around 800mm deep 400mm wide
footings then laid two courses of engineering bricks on top, scraped out the centre and back filled and whacked (buy a whacker and sell when done) in
4" of type one, then poured a concrete slab inside this to the top of the bricks with plenty of mesh placed in, the slab is around 5"
thick, mesh is in the bottom third.
For doors I went to the local salvage yard and got some really nice oak mews doors for £100 each, the frame is being constructed around these, also
two sets of doors as it's by the side of my house so I can drive through if required.
I would estimate I have 10 meters of soil to have removed, big pile at the front of my garden so need a grab lorry to collect.
This is hard work!!! I purchased a digger and dumper off eBay, I would not think about doing this by hand, even then I have spent maybe 14 days on it
but now have a dwarf wall built so am just awaiting the frame moving the spoil is just as hard as pulling it out.
Note that's 5 days digging and shifting, you will spend maybe £1000 on hire for digger and dumper so purchasing makes sense or get someone else
in for this bit?
Regards Mark
[Edited on 24/8/14 by mark chandler]
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franky
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| posted on 24/8/14 at 08:30 AM |
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quote:
Originally posted by mark chandler
I,m building one at the moment, 6m x 4m do not expect it to be cheap!
I called the council, as long as it is more than 1m from the neighbours fence, sits behind the front line of your house and is no more than 4m tall
assuming a pitched roof you can build a massive 'shed', talk to the neighbours first
As I am going for a peg tile roof I have laid strong foundations, so far 10sqm of concrete have gone through my mixer and two pallets of engineering
bricks so I am already at nearly £1000 before the frame arrives.
As a shed there is no specification for footings but you do not want the slab to crack so have a good google, I went for around 800mm deep 400mm wide
footings then laid two courses of engineering bricks on top, scraped out the centre and back filled and whacked (buy a whacker and sell when done) in
4" of type one, then poured a concrete slab inside this to the top of the bricks with plenty of mesh placed in, the slab is around 5"
thick, mesh is in the bottom third.
For doors I went to the local salvage yard and got some really nice oak mews doors for £100 each, the frame is being constructed around these, also
two sets of doors as it's by the side of my house so I can drive through if required.
I would estimate I have 10 meters of soil to have removed, big pile at the front of my garden so need a grab lorry to collect.
This is hard work!!! I purchased a digger and dumper off eBay, I would not think about doing this by hand, even then I have spent maybe 14 days on it
but now have a dwarf wall built so am just awaiting the frame moving the spoil is just as hard as pulling it out.
Regards Mark
Its got to go closer to the road than the house and 50cm from next doors garage so I will need planning etc  Thats why I thought i'd go for a
2.5bay size one. I'm doing the maths against a block and clad built one, I'll ring building control on tuesday to see what they'd
expect for foundations etc.
Are you having oak soleplates and/or oak cladding? Doors are an expensive part of the cost, in oak they're coming in at about £3k a pair so
finding some would be good! I have asked about having a roller door fitted and I've been told its fine but will require thicker posts along the
front to enable mounting etc. I do like the look of a quality roller door behind the oak posts and braces.
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mark chandler
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| posted on 24/8/14 at 08:55 AM |
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I have built a dwarf wall that the oak frame will drop on, 3 posts on each long side which will be pretty substantial, 6" square I think with
softwood studding inbetween and softwood roof structure.
The cladding will be scots pine, this all comes in at around £4000 erected, I then have to felt, batten and tile at my own expense + insulate, oak
frame is not any cheaper than getting one built in blocks but it's still a shed so no planning.
As you have to apply then block work may be the way forward, I wanted the oak frame look, could have done this far more cheaply.
Regards Mark
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Sam_68
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| posted on 24/8/14 at 09:24 AM |
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I'm Design & Technical Manager for a timber frame company that sells a range of them, as it happens.
You will need Building Regulations, as your floor area is over 30m2.
I'm afraid to say that Mr Chandler seems to have squandered a lot of unnecessary money on foundations: oak frame garages are post-and-beam
structures, so the only structural loads on the foundations are point loads from the posts. As such, strip foundations are technically the wrong
solution: the 'logical' and correct solution if you're not building off the slab would be individual pad foundations under
each post. Conversely, a 5" slab is right at the lower end of what I'd consider acceptable (but of course does nothing to bear the loads
of the actual structure, if strip foundations are used).
In most cases, though, people just build off the slab. If you've got half reasonable ground conditions, all you need is a slab with edge
thickening to form ground beams at the edges, with suitable reinforcement. A slab min. 150mm thick, thickened to min. 300mm. along the edges, with a
single layer of mesh generally and an extra strip of mesh toward the bottom of the edge thickening (but with min. 50mm cover, of course), is perfectly
adequate, even for a room-in-roof garage, in most cases, but your frame manufacturer will be able to advise better, depending on the design of the
structure (size of structure; spacing of posts, etc.) and weight of roof covering.
Building Control will not 'design' your foundations for you, though. The best they will give you is an assessment of the ground bearing
capacity of your subsoil. It is then up to you to provide a foundation design to them, which should be based on the point loads calculated by
the manufacturer of your oak frame: Approved Document A to the Building Regulations doesn't offer 'standard' solutions for
post-and-beam structures, so you will need engineering calculations to 'prove' the structure, which your oak frame supplier will
(or should) provide to you on request.
Do be clear about why you want oak. Unless you spend a fortune on air-dried oak, the timber you will be using will be 'green' oak, which
has a very high moisture content and which will distort and develop noticeable shakes (splits) as it dries out. This is perfectly normal, part
of the character of the wood, and something you should expect. It's great if you want the 'authentic' distressed look of an old
building, to sit in context with a 200-year old cottage, but alongside a sharp-edged mock-tudor executive home from Charles Church (or whoever), it
can end up just looking a bit ramshackle!
You can do the same structure in douglas fir or redwood (both softwoods), which are dimensionally much more stable, substantially cheaper, and
will still last more than a lifetime if they are treated with a clear timber preservative every few years (oak requires less treatment, but will
benefit from the same care).
Our standard spec for cladding and doors is softwood (larch or douglas fir feather-edge cladding; douglas fir for the doors) for the same reasons: oak
is much more expensive, and the dimensional instability of oak is even more pronounced with thinner sections of timber. Green Oak will split and twist
like buggery in small sections, so you will have to use air dried oak for the doors (which is why your quote for doors is about four times
what we would charge for a custom-sized pair of doors in douglas fir). We will happily sell customers oak doors and cladding if they want it, of
course, but we do like to be clear about the pros and cons with them, before parting them from large quantities of their hard-earned cash for no
reason!
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Sam_68
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| posted on 24/8/14 at 09:28 AM |
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quote:
Originally posted by mark chandler...I then have to felt, batten and tile at my own expense + insulate
Be careful about how you do this: without a VCL and breather membrane, it's easy to create problems that will lead to the panels rotting out
fairly quickly.
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franky
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| posted on 24/8/14 at 10:01 AM |
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quote:
Originally posted by Sam_68
I'm Design & Technical Manager for a timber frame company that sells a range of them, as it happens.
You will need Building Regulations, as your floor area is over 30m2.
I'm afraid to say that Mr Chandler seems to have squandered a lot of unnecessary money on foundations: oak frame garages are post-and-beam
structures, so the only structural loads on the foundations are point loads from the posts. As such, strip foundations are technically the wrong
solution: the 'logical' and correct solution if you're not building off the slab would be individual pad foundations under
each post. Conversely, a 5" slab is right at the lower end of what I'd consider acceptable (but of course does nothing to bear the loads
of the actual structure, if strip foundations are used).
In most cases, though, people just build off the slab. If you've got half reasonable ground conditions, all you need is a slab with edge
thickening to form ground beams at the edges, with suitable reinforcement. A slab min. 150mm thick, thickened to min. 300mm. along the edges, with a
single layer of mesh generally and an extra strip of mesh toward the bottom of the edge thickening (but with min. 50mm cover, of course), is perfectly
adequate, even for a room-in-roof garage, in most cases, but your frame manufacturer will be able to advise better, depending on the design of the
structure (size of structure; spacing of posts, etc.) and weight of roof covering.
Building Control will not 'design' your foundations for you, though. The best they will give you is an assessment of the ground bearing
capacity of your subsoil. It is then up to you to provide a foundation design to them, which should be based on the point loads calculated by
the manufacturer of your oak frame: Approved Document A to the Building Regulations doesn't offer 'standard' solutions for
post-and-beam structures, so you will need engineering calculations to 'prove' the structure, which your oak frame supplier will
(or should) provide to you on request.
Do be clear about why you want oak. Unless you spend a fortune on air-dried oak, the timber you will be using will be 'green' oak, which
has a very high moisture content and which will distort and develop noticeable shakes (splits) as it dries out. This is perfectly normal, part
of the character of the wood, and something you should expect. It's great if you want the 'authentic' distressed look of an old
building, to sit in context with a 200-year old cottage, but alongside a sharp-edged mock-tudor executive home from Charles Church (or whoever), it
can end up just looking a bit ramshackle!
You can do the same structure in douglas fir or redwood (both softwoods), which are dimensionally much more stable, substantially cheaper, and
will still last more than a lifetime if they are treated with a clear timber preservative every few years (oak requires less treatment, but will
benefit from the same care).
Our standard spec for cladding and doors is softwood (larch or douglas fir feather-edge cladding; douglas fir for the doors) for the same reasons: oak
is much more expensive, and the dimensional instability of oak is even more pronounced with thinner sections of timber. Green Oak will split and twist
like buggery in small sections, so you will have to use air dried oak for the doors (which is why your quote for doors is about four times
what we would charge for a custom-sized pair of doors in douglas fir). We will happily sell customers oak doors and cladding if they want it, of
course, but we do like to be clear about the pros and cons with them, before parting them from large quantities of their hard-earned cash for no
reason!
Thanks for the reply Sam.
I've a new 'project' house, which is a 3-400 year old Devon Farm house, built mainly of the local stone thats rendered over, with
a small portion being cob. I'm thinking about an oak frame as it'll sit nicely with the house once its weathered down over a few
years.
Who is it you work for? As someone with lots of knowledge in this area what would the 'perfect' spec be, Oak frame and Larch for the
cladding? Regarding the doors, thats where i'm struggling as I'm slightly limited on turning circle so roller doors would give some much
needed space, I've seen a nice oak building with an anthracite/dark grey door which looked nice(all relative).
With an oak frame what would be the best door type to use if I went for wooden side hung doors? I don't mind if the building needs tlc but
ideally no more than every 3 years ish.....
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franky
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| posted on 24/8/14 at 10:03 AM |
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Ps, thanks in advance.
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Sam_68
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| posted on 24/8/14 at 10:38 AM |
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To be fair, then, you can certainly justify oak frame in your own case, as the 'distressed' character will sit comfortably alongside your
main property. It'll cost you about a grand extra, compared to douglas fir, though.
I wouldn't necessarily worry about oak cladding, but that's your call; if it were me, I'd be happy with larch. I'd be happy
with douglas fir for the doors too, given the stupid cost of oak (you're paying mainly for the fact that the sawmill has had to leave the timber
air drying for several years, so you're paying for their investment, though there's a labour cost due to the fact it's harder to
work, too). For comparison, in douglas fir we'd charge about £230 for a pair of doors to suit a standard 7'0"x 7'0"
opening, and about £700 for a pair of bespoke doors to a non-standard width (I wasn't clear if your price of £3K was for one pair of doors or
two? obviously, you'll need 2 pairs of side-hung doors for a two bay garage).
Roller doors are doable (we've fitted them with our standard sized posts, which are 6" square, with a little faffing about to accommodate
the gear, but yes, it's easier with a heavier frame section), but of course they are not at all in keeping with the rest of the building. Again,
your choice, and I can understand your reasons for wanting them, but to me it would look a bit like a set of Kahn chromed alloys on Morgan
3-wheeler!
If space is a problem, have you considered whether you need doors at all? If the garage is for car storage, maybe just leave the main part open, and
make the half bay into a lockable store? The ventilation is healthier for a car than a fully enclosed structure, truth be told.
You need to allow at least 6 metres (preferably 7.5m) clear, unobstructed space in front of the garage for turning, and to line up on the door
opening, if entry and exit are not going to be a major pain in the arse.
U2U me if you want more details (including my employer, who I'd rather not name on open forum: 'views expressed are not necessarily
representative of...' and all that!).
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franky
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| posted on 24/8/14 at 01:29 PM |
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U2U sent.
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mark chandler
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| posted on 24/8/14 at 05:33 PM |
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Thanks Sam
Originally I was going to use a flat slab as you have described however my house is built on clay, the ground around the house foundations is maybe
4" - 6" lower than original build so I went a bit overboard for my shed, where the posts land the foundations are considerably more solid
the slab sits inside this so no load is borne by this lump of concrete. I may want to plant a two or 4 post lift at some point so decided the
additional cost and effort at this stage should pay dividends at a later on.
Can you elaborate on the insulation please, any metal in my previous shed went rusty and attracted condensation, it had no insulation at all, for my
£££ I get the frame cladding and roof so anything I add I on top of the costs but I want to do it right, also keep the view of the internal
construction.
Regards Mark
[Edited on 24/8/14 by mark chandler]
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Sam_68
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| posted on 24/8/14 at 07:06 PM |
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quote:
Originally posted by mark chandler
Can you elaborate on the insulation please
That's a deceptively complicated question!
On a conventional shed/garage construction, you just have the cladding boards fixed to a timber frame panel, and that's it. It accepts that the
cladding panels are not truly weathertight and impermeable to moisture, and simply relies on the fact that there is enough air circulation to all
elements of the panel to dry it out quickly when it does get wet. If you were experiencing damp problems with your previous shed, the answer would be
to increase the air circulation.
As soon as you add insulation, you restrict air circulation directly over the timber and risk problems.
In simple terms, with an insulated panel as on a house, you'll have an internal 'vapour control layer' (typically polythene), then
the insulation within the frame panel, then a 'breather membrane' of breathable but waterproof fabric, then a ventilated air space, then
your outer cladding.
Each element is doing a specific job, and if you omit it, you risk problems:
* The Vapour Control Layer is there to stop warm, moisture laden air from within the building filtering out through the structure, because if it does,
the temperature can fall to dew point on the way through the structure and 'interstitial condensation' forms within the wall panel, which
will lead to rot.
* The breather membrane is there to stop water penetrating into the insulated frame from the outside, because again, once it finds its way in there,
it will become trapped and lead to rot.
* The ventilated air space between the outer cladding and the breather membrane is to allow the cladding to dry out, after it has got wet.
To be 100% sure of avoiding problems, you'd need to adopt the sort of panel construction you'd expect with a house instead of a shed,
complete with continuous VCL, breather membrane and ventilated air space behind the cladding. How much of a problem you have if you don't
incorporate these features is difficult to say, because it will depend on a number of factors (notably level of exposure of the building and patterns
of useage). Unfortunately, re-engineering the panel to incorporate a VCL and breather membrane may be more trouble than you consider it to be worth,
but you need to be aware of the risks you're taking and make an informed judgement.
One obvious point is to use a non-absorbent rigid foam insulation like Celotex (which has a foil face that will act as a VCL), rather than any sort of
absorbent insulation material, but even that won't help you with moisture penetrating and getting trapped between the inside face of the
cladding and the outer face of the insulation.
Another point worth making is that oak, in particular, is very acidic so any ferrous fixings you use should be stainless, otherwise they'll rust
like nobody's business.
Hope that helps, but unfortunately it's a very complex subject, and difficult to describe in brief.
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mark chandler
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| posted on 24/8/14 at 08:09 PM |
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Thank you for the full answer, I was looking at celotex, I was not aware of the need to space out from the cladding to retain an air gap, it may be
easier for me to build out the inside then nail on the outside cladding to retain an air gap.
Although cost is always a consideration what may be stored within my shed, my DB7 for example justifies doing it properly.
Regards Mark
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franky
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| posted on 26/8/14 at 06:25 PM |
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Now I'm really thinking about something like this...
http://www.timber-frame-building.co.uk/3-bay-garage-with-room-above-berkshire-attic-without-staircase.html
Seems to be good value for money, 2 sets of full size softwood doors, the far right bay as a workshop so enclosed with a single door. 2 roof lights
in the roof, barn ends on the roof to give a bit of detail.
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mark chandler
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| posted on 26/8/14 at 09:28 PM |
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This is where mine is coming from as way of a comparison.
http://shireoak.net/3-bay-oak-garage/4559143659
Dave will draw up what you want, if you get reclaimed doors such as I have done he will build to suit.
Regards Mark
[Edited on 26/8/14 by mark chandler]
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