New garage questions

[Misterg]

I want to put up a new garage / workshop at the end of the garden. There's enough space there that I can go for the full 30m^2 (before building regs kick in), so probably about 5.5m x 5.5m. Roughly as shown below:

I would really like rendered block with a shallow pitched roof, but everyone I talk to says to go for a prefab steel or concrete one instead. If this is the case, I'll size the base accordingly.

Can I build a block one on a concrete raft? or would I need to dig footings? If a raft is possible, how thick would the edges need to be? The ground is a mixture of existing stone hard-standing, garden / grass over deep, deep clay, but there's also an old shed base that would need to be broken up. The site is on a slope with maybe 400mm fall from left to right

Access to the garage will be off a shared service road (several houses already do this). I'd like to have a shallow ramp up onto the garage base to keep it clear of surface water - what sort of slope is reasonable? (There's about 2.5m run.)

One wall will be as close as reasonable to a boundary fence (500mm??). How best to deal with the narrow strip of land between the garage and the fence? I'm thinking to reduce the level a bit, put down a membrane of some sort and cover it with pebbles.

I'm assuming that the base will be something like 100mm compacted stone ('MOT') with 100mm 'C20' concrete with a reinforcing mesh (or would fibres in the mix be sufficient?)

Any suggestions welcome!

 

[gaz1]

your on a corner so build an apex roof not a single pitched roof

do you need to dig footings yes

and then concrete the footings and concrete raft in one

make sure the blocks stop at the concrete edges so if you use a pebble dash effect then its over the concrete raft therefore no chance of hitting the concrete raft and seeping back inside

id stay away from the boundary but because yours isnt affecting anyone then you might be able to build right on the boundary just dont go over it with your gutter but in your case really wont matter as stated yours is on a corner will not affect anyone

 

[sg66]

I put in a pre fab one in with pent roof, it's been fine, I raised pad above ground level by a couple of inches, run a shallow ramp upto it over probably 3ft, have gravel all the way round the edge, I have a narrow gap down the full side of it and nothing has attempted to grow between it and the neighbours fence.

Never had water through the sides, went around inside walls at base with cement with sika waterproof to seal walls to base

I used 4" C30 with mesh for base 150 sub base.

I went prefab for speed.

 

[gaz1]

post 7

https://www.mig-welding.co.uk/forum/threads/builder-ground-works-question.84610/

 

[keithski122]

I'll throw this in, go for a dutch barn roof, more storage space for the same space.

 

[sg66]

I was limited to the overall height of mine with it being close to the boundary, I got a list from local planning so I didn't incur their wrath if a neighbour complained, putting up a 24ft garage 3" of their fence can do that sort of thing.

 

[Pigeon_Droppings2]

Access to the garage will be off a shared service road (several houses already do this).

Make sure you have a legal right of access into the service road...worth checking as it causes a lot of issues here in London where service roads are owned and rights allocated to specific houses.

Mine is a roughly 30sqm prefab...I built the base about 4 inches out of the ground which has worked very well. Only issue with prefabs is roof height...as above we are also limited to heights depending on what roof is chosen.

 

[Misterg]

Thanks.

your on a corner so build an apex roof not a single pitched roof

D'oh - yeas, I meant apex roof, rather than pent, but it would need to be a very shallow pitch to keep the height down (as the house looks over the garden and we've got 'scenery' behind) - something like 15° over a 5.5m span. I've no idea how to construct a roof that shallow without a substantial steel ridge beam. I'd assume it can be treated as a 'flat' roof and decked with OSB / covered with EPDM.

Edit - meant to add a graphic:

post 7

Thank you - a lot of useful reading to do there - so for a slab, I don't really need 'footings' (which would be something like 600mm+ deep), just dig an extra ~100mm for a 300mm wide strip around the edge.

 

[Bobtail4x4]

dont forget the 30sqM is the TOTAL building size,

 

[Misterg]

I'll throw this in, go for a dutch barn roof, more storage space for the same space.

Good idea, but I should have said that I'm limited on height in this case.

Thanks.

 

[Misterg]

I put in a pre fab one in with pent roof, it's been fine

Thanks - I'm also interested in the speed aspect.

Was yours a concrete one?

 

[gaz1]

as goes for your garage

mines in red



public and service rd can be built right on the boundary so the garage becomes the boundary wall

the bottom side i presume is the neighbours boundary try to stay away by the regs

i get a wider front and because its smaller on its lengths needed you can beam it differently

 

[gaz1]

Thanks - I'm also interested in the speed aspect.

Was yours a concrete one?

it depends on how you build it

one month for the base to set enough

walls in your case 2 days for hip height build 4 - 5 blocks high 2 days again for the last 4-5 blocks high

depends on your builders speed

roof 4 days large span

 

[Misterg]

Make sure you have a legal right of access into the service road

Good point - There are 6 houses that share it and it's in our deeds that we all have access. We're the first one, so everyone else has to drive past ours. (The road isn't surfaced.)

Neighbours is another reason I'd like to keep the height down - we are on good terms and I'd like to keep it that way. What I'm planning isn't out of keeping with what others have done, but if I put up a 3.5m high apex roof it'd stick out like a sore thumb.

mines in red

That would be well over 30m^2! (I believe it's floor area rather than the footprint of the building?) and I don't want to get into building regs.
We'd also like to keep some access to the garden past the garage (the shed shown in grey will be taken down as part of the job).

Off to read the thread that @gaz1 linked to...

 

[jo1010]

One of the problems is the 400mm fall - options are excavate down (which will also reduce overall height of structure) but had it's problems with waterproof tanking of the walls OR you'll be into a lot of fill and compaction ( not without it's own risks - inadequate compaction leads to future instability of the floor, even on 6" of concrete).
And an 18foot span is a big one for trusses without a steel inserted - talk to truss manufacturers who have calculation programs to guide you.

 

[gaz1]

That would be well over 30m^2! (I believe it's floor area rather than the footprint of the building?) and I don't want to get into building regs.
We'd also like to keep some access to the garden past the garage (the shed shown in grey will be taken down as part of the job).

Off to read the thread that @gaz1 linked to...

30 meters in any shape of floor area is the regs

 

[bricol]

I went prefab for speed - used old panel and some new seconds, used steel C-section roof beams mounted on angle higher than the walls to get the flat/sloping roof at the max height allowed, meaning good internal head room. Infilled the gap between panel with ply and steel cladding. Cheaper than a block built garage too. I used a local bloke to sort the base - my next door neighbors son-in-law , meaning if he bust her greenhouse right next to it . . .

Mine did leak at the bottom after a number of years when the cement fillet all the pre-fab makers suggest failed. Since ground chamfers on the inside and outside of the panels and used sealant for sealing slurry pits, sewage pipes etc, so fingers crossed, no more leaks for a while.

 

[Misterg]

One of the problems is the 400mm fall -

I wouldn't want the ground higher than the base, so am thinking about having a path next to, and slightly below the slab and either grading the 'lawn' down to this, or building a low (~300mm high) "retaining" wall on the far side of the path (only it wouldn't be retaining much).

 

[gaz1]

from another build

Fabrication shed

Last year I'd just got the house to the point where it was 80% finished (100% finished in bloke terms), and then my partner and I had twins. I'm a car guy, and had a shared unit on a farm for cars and fabrication, but the 30 minute trip clearly wasn't going to work with babies at home. I figured...

www.mig-welding.co.uk

 

[caprinut]

Mine had 15% sloping roof to the long sides, one side covered 3/4 of the length the short side at 45% was glazed with twin wall sheet to allow light in the east elevation the west end had an up and over door. the roof was in Bituminised OSB covered in corrugated felt and left open allow free flow of air to reduce condensation.