Garage

[Butcher]

I'm buying a house at the moment, which has a fairly knackered concrete pre-fab garage (with asbestos roof). I'm looking to take it down and replace with something new and less shonky.
So Hexites, input on garages please!

Current thoughts:

• 6x6m internal size
• Single wide door (4.25m)
• Brick and block cavity walls, or maybe single skin brick, but I'm concerned about excessive penetrating damp.
• Pitched tiled roof (flat roofs are leaky naff things).
• Electrical installation.

I'm looking to do it as cheaply as possibly without it being a total mess. To that end I'd like to DIY what I can, but I'm not exactly a builder, so I'm thinking getting in a builder to lay foundations and build the masonry shell, and a roofer to put a roof on it would be a good plan. I could have a crack at building it myself, but I'm worried I'd just make a hash on it.

[Zak33]

are you sure it's an asbestos roof?

[Butcher]

are you sure it's an asbestos roof?

I'm pretty sure, though it hasn't been tested.
I eyeballed it as asbestos; it's a corrugated fibre cement sheet and while possibly not original to the house (mid-50s) it must be as old as I am at the least.
Additionally my surveyor visually identified it as asbestos, specifically: "The garage is of pebbledash rendered concrete panels beneath a corrugated asbestos roof overlaid in mineral felt." Also, "it is felt that significant remedial works will be required or, if this is not viable pulling down and rebuilding."

The existing garage is an old single (so about 16x8 feet) and not well located (the drive slices the back lawn in two) so the double bonus of removing it is moving it to one side of the plot and expanding it to a more useful size.

[Ttaskmaster]

If you can afford it, I'd get it built... at least as far as the roof. Easy enough to lay ply boards down, cover with roofing felt and seal the thing.... or tile it, if you know how.

Electrickery is easier, IMO, long as you know what you're doing.

[Butcher]

If you can afford it, I'd get it built... at least as far as the roof. Easy enough to lay ply boards down, cover with roofing felt and seal the thing.... or tile it, if you know how.

Electrickery is easier, IMO, long as you know what you're doing.

I can do electrics, though I might end up getting a sparky in just for the Part P sign off. Not going to roof it myself, definitely paying a tiler for that.

[Zak33]

that asbestos isn't a DIY job.

trust me. you won't be allowed to take it to the dump for example. It will need a pro removal

I'd budget £600 +

[TeePee]

My money saving tip: If your roof hasn't been tested as asbestos, then it isn't asbestos. Don't get it tested.

Obviously be cautious with removing it, but any demolition requires caution, and mitigating dust is a good thing for any material.

Brick and block cavity walls will last forever, but are expensive and very thick, which means a smaller interior volume for the size of the building. Consider stick built construction, which is a lot easier to DIY. It's also very easy to insulate if this is going to be a work space (I hope so!), typically with more than three times the R-value of an equivalent thickness of cavity wall.

Another method to consider would be to use SIPs. More expensive than stick, but still cheaper than brick and block, with great insulation. You can DIY the assembly, which is basically an oversize jigsaw puzzle.

[Butcher]

that asbestos isn't a DIY job.

trust me. you won't be allowed to take it to the dump for example. It will need a pro removal

I'd budget £600 +

You actually can take it to the tip, as long as it's double bagged and properly labelled. I'm not sure I want to do it myself anyway, but a paper suit and masks are around £50.

My money saving tip: If your roof hasn't been tested as asbestos, then it isn't asbestos. Don't get it tested.

Obviously be cautious with removing it, but any demolition requires caution, and mitigating dust is a good thing for any material.

Unfortunately around here anything that looks like asbestos is treated as asbestos, best not to risk it. But as mentioned, I could just run it down the tip. The walls are concrete so pretty safe to knock down.

Brick and block cavity walls will last forever, but are expensive and very thick, which means a smaller interior volume for the size of the building. Consider stick built construction, which is a lot easier to DIY. It's also very easy to insulate if this is going to be a work space (I hope so!), typically with more than three times the R-value of an equivalent thickness of cavity wall.

Another method to consider would be to use SIPs. More expensive than stick, but still cheaper than brick and block, with great insulation. You can DIY the assembly, which is basically an oversize jigsaw puzzle.

Yes it's going to be a work space with occasional car storage.

Around here brick and block is about as cheap as it gets. SIPs are definitely more expensive and I'm not sure I need that much insulation, given the roof will likely be uninsulated. Timber frame is doable, but not as easy to find builders for. Cavity walls offer very good insulation when you stuff them with rockwool. Granted they are larger, but space isn't a huge issue really.

One of the things I would like is for the garage to match the house somewhat, which means brick outer and a tiled roof.

[ik9000]

My money saving tip: If your roof hasn't been tested as asbestos, then it isn't asbestos. Don't get it tested.

Obviously be cautious with removing it, but any demolition requires caution, and mitigating dust is a good thing for any material.

Brick and block cavity walls will last forever, but are expensive and very thick, which means a smaller interior volume for the size of the building. Consider stick built construction, which is a lot easier to DIY. It's also very easy to insulate if this is going to be a work space (I hope so!), typically with more than three times the R-value of an equivalent thickness of cavity wall.

Another method to consider would be to use SIPs. More expensive than stick, but still cheaper than brick and block, with great insulation. You can DIY the assembly, which is basically an oversize jigsaw puzzle.

Not in the UK I'm afraid. We have much stricter laws here on asbestos. It almost certainly is asbestos cement from the description. Send me a photo and I'll say better, but it's controlled and has to be disposed of properly. Providing it can be unscrewed without smashing it to dust, it can acutally be at the cheaper end to have removed, but you should assume it is asbestos. And legally it is not a defence to say "i didn't get it tested". Since the changes to CDM in 2015 even domestic owners are responsible for ensuring that any workers they employ have sufficient information to do their jobs safely, and that includes asbestos surveys where construction work is taking place.

NB not all tips accept asbestos cement. Mine does not.

Tee-Pee's suggestion of timber framing is less common in the UK, and can cause problems when/if you want to sell. Bricks and mortar are the norm here, particularly for large garages (rather than simple sheds). I would caution against going timber framed unless you really are confident in the quality of construction detail specified, and also the contractor to follow those details to the letter. Check with a local surveyor, but I know of people struggling to get mortgages due to the condition of lean-to extensions and garages, even when the main house was fine.

For a garage a single skin block wall, rendered externally will be fine at resisting weathering. If not rendered then better to go solid brick than solid block. (block tends to be more porous). Cavity will offer you better resistance, but it is necessary for a garage? Only you know the uses you want for it. Anything you plan on spending a lot of time in may benefit from cavity for the added thermal insulation. NB though it's only as a good as the door you put on the front of it. If that is a metal sheet with a gap all round it, then goodbye thermal performance anyway.

For a 6m internal space with tiled roof consider using timber I joists (Steico, JJI etc) rather than plain timbers. Max 600mm centres to comply with building regs. You'll get a stiffer roof for it, and they perform fine. Should make self building easier as probably need fewer members (greater spacing possible). Conventional rafters start to grumble above 4.5m - unless you want to get rather large timbers. Then just stick on a 12mm ply deck (or 18mm if you want to walk on it once it's finished). NB to consider whether you want a warm roof (insulation on the outside below the tiles), or a cold roof (insulation on the inside below the ply). Or no insulation if you don't plan on heating the space at all. (assuming it's a freestanding garage, and NOT part of the house). NB also to include ventilation to the roof space to prevent moisture build-up and timber rot. Tiles, go concrete precast. They lock together well and should last ages. They should be less likely to slip like thin slate ones provided they are mounted properly to begin with.

Foundations should be min 450mm deep, ideally 1m min, but it depends on the ground condition and whether you're building near any trees, and so on. Remember to check whether you need to notify neighbours under the Party Wall Act - excavations within 3m of a boundary can require this. Also check what planning and building control approvals your borough demands. Make sure you know about those BEFORE starting work.

Lastly, no need to separate the packages. Get one builder to do the lot. Then you have one warranty to worry about, and one person to contact if there's a problem down the road. You'll want to discuss whether you expect any NHBC backing (might not be necessary for just a garage, but more important for a new house), and get references. Written ones, and where you can go round / contact them without the builder being there. And don't pay 100% upfront. That's madness.

[Butcher]

NB not all tips accept asbestos cement. Mine does not.

My local one doesn't, but there are two slightly further away (as in 2-3 miles) that do.

Tee-Pee's suggestion of timber framing is less common in the UK, and can cause problems when/if you want to sell. Bricks and mortar are the norm here, particularly for large garages (rather than simple sheds). I would caution against going timber framed unless you really are confident in the quality of construction detail specified, and also the contractor to follow those details to the letter. Check with a local surveyor, but I know of people struggling to get mortgages due to the condition of lean-to extensions and garages, even when the main house was fine.

That does concern me, and I'm not sure the savings, if any, warrant the hassle, given I'd prefer a brick outer.

For a garage a single skin block wall, rendered externally will be fine at resisting weathering. If not rendered then better to go solid brick than solid block. (block tends to be more porous). Cavity will offer you better resistance, but it is necessary for a garage? Only you know the uses you want for it. Anything you plan on spending a lot of time in may benefit from cavity for the added thermal insulation. NB though it's only as a good as the door you put on the front of it. If that is a metal sheet with a gap all round it, then goodbye thermal performance anyway.

Useful stuff here. Block and render is doable and probably the cheapest option (though rendering cost swallows most of the saving from not using bricks), but I'm in Manchester, land of the red brick buildings, so rendered blocks would be very out of place. I'd prefer to match the house (50s semi) as closely as possible which means brick walls and concrete tiled roof.
I could go solid brick walls, but I think given the size it would be one brick walls rather than half brick with piers. At which point a cavity wall is actually cheaper since the inner skin is blocks. I'm mainly after damp resistance to avoid everything in there rusting like crazy rather than super thermal performance. That said, it might be worth insulating the cavities when built as it adds only a small cost at the time vs massive hassle to retrofit.

For a 6m internal space with tiled roof consider using timber I joists (Steico, JJI etc) rather than plain timbers. Max 600mm centres to comply with building regs. You'll get a stiffer roof for it, and they perform fine. Should make self building easier as probably need fewer members (greater spacing possible). Conventional rafters start to grumble above 4.5m - unless you want to get rather large timbers. Then just stick on a 12mm ply deck (or 18mm if you want to walk on it once it's finished). NB to consider whether you want a warm roof (insulation on the outside below the tiles), or a cold roof (insulation on the inside below the ply). Or no insulation if you don't plan on heating the space at all. (assuming it's a freestanding garage, and NOT part of the house). NB also to include ventilation to the roof space to prevent moisture build-up and timber rot. Tiles, go concrete precast. They lock together well and should last ages. They should be less likely to slip like thin slate ones provided they are mounted properly to begin with.

Roof plan was prefab trusses and get a roofer to put on concrete interlocking tiles. Slate would be odd as all the local houses (including mine) are concrete tile anyway. From a bit of reading it seems that trussed rafters in normal section timber will do an 11 metre span which should be more than enough. I'm not sure whether to spec for a storage attic of sorts or not. Obviously not is a lot cheaper as it means just a simple roof without load bearing joists.

Insulation wise, I was thinking uninsulated, it would be a chore to heat other than by using electric heaters as it's planned to be significantly detached. The current garage is about 2m from the house (the nearest point of which is a utility room which is itself a converted attached garage). The plan is to build the new one at the far side of the plot, about 6 metres from the house. Access is from the rear so this would allow a driveway down the side of the back garden (rather than through the middle as it is now).

Foundations should be min 450mm deep, ideally 1m min, but it depends on the ground condition and whether you're building near any trees, and so on. Remember to check whether you need to notify neighbours under the Party Wall Act - excavations within 3m of a boundary can require this. Also check what planning and building control approvals your borough demands. Make sure you know about those BEFORE starting work.

I'd be looking at 1m as a starting point, plus whatever building control want. There are some trees not far away which might mean crazy depth, but without digging up the ground it's hard to tell. I don't know what the ground condition is, but it's not a clay area so hopefully pretty reasonable in terms of bearing ability and drainage.

Lastly, no need to separate the packages. Get one builder to do the lot. Then you have one warranty to worry about, and one person to contact if there's a problem down the road. You'll want to discuss whether you expect any NHBC backing (might not be necessary for just a garage, but more important for a new house), and get references. Written ones, and where you can go round / contact them without the builder being there. And don't pay 100% upfront. That's madness.

One builder for the lot adds cost though, as you're paying a chunk for them to project manage it for you. I'll be looking to get quotes though but I suspect that they may be more than I want to spend.

[ik9000]

yeah trussed rafters will give a reasonable span but are they necessary for just 6m given they'd kill off the space they create with all the internal timbers. have you had a design made up by someone? don't want to tread on their toes.

[Butcher]

yeah trussed rafters will give a reasonable span but are they necessary for just 6m given they'd kill off the space they create with all the internal timbers. have you had a design made up by someone? don't want to tread on their toes.

No designs done yet, I'm planning to get someone to do a proper design though since that will be needed for planning permission anyway.

Trussed rafters was mainly because they're an easy option and not expensive, it might be when going for a conventional roof though, or attic trusses to gain the storage space.

[ik9000]

No designs done yet, I'm planning to get someone to do a proper design though since that will be needed for planning permission anyway.

Trussed rafters was mainly because they're an easy option and not expensive, it might be when going for a conventional roof though, or attic trusses to gain the storage space.

You say you're in Manchester? Bit too far for me otherwise I'd offer to help. Sounds like fairly straightforward stuff assuming your planning dept isn't too strict. IMO needs an architect and an engineer with local knowledge employed on a time basis to do the checks. Normal route is to get planning with the architect, with very basic engineer involvement (if any) then the arch and engineer do their final design once you know you have permission to build it. (helps keep your costs down if the planners say no). You can use the RIBA and findanengineer.com websites to do a search in your area.

[Butcher]

You say you're in Manchester? Bit too far for me otherwise I'd offer to help. Sounds like fairly straightforward stuff assuming your planning dept isn't too strict. IMO needs an architect and an engineer with local knowledge employed on a time basis to do the checks. Normal route is to get planning with the architect, with very basic engineer involvement (if any) then the arch and engineer do their final design once you know you have permission to build it. (helps keep your costs down if the planners say no). You can use the RIBA and findanengineer.com websites to do a search in your area.

I can make it work via permitted development if required. Because the garage is in the back garden there's no issues with fronting the highway, the only planning issues are proximity to the boundary (I'd like it a metre from the fence) and height of the building (likely to be too tall for PD with the pitched roof). If needs be I could move it away from the boundary a little and reduce the roof height, but I'd prefer not to.
Given how close to PD it is to start with I'm hoping it won't be an issue.

Council is Trafford incidentally.

[Saracen]

One thing, on the "leaky flat roofs" comment, having got one on part of the house, is that modern rubberised materials seem to me to be much, much, MUCH better than the old felt/bitumen type which, I agree, tended to weather badly, crack and turn into more of a colander thsn a roof.

Aesthetically, they're still butt-ugly, of course, but they're far better leak-wise than tile .... which are not immune. Some crack. Also, as per mum-in-law, on a joint between two angles, the cement sealant eroded, and water blew in when the wind was in a specific direction, then somehow travelled about halfway round the house before dripping through the lounge ceiling. Finding that leak was a right bit.... erm, pain.

Anyway, it's an aside since you sound uninterested in flat roofs (don't blame you, by the way). This is really a sneaky way for me to ask ik9000's view on those modern rubberised flat roofs. Neighbours have had it done and are happy. I'm thinking about it, but they ain't cheap.

(*Note - Smallish area, about 4.5m x 1.5m.)

[ik9000]

One thing, on the "leaky flat roofs" comment, having got one on part of the house, is that modern rubberised materials seem to me to be much, much, MUCH better than the old felt/bitumen type which, I agree, tended to weather badly, crack and turn into more of a colander thsn a roof.

Aesthetically, they're still butt-ugly, of course, but they're far better leak-wise than tile .... which are not immune. Some crack. Also, as per mum-in-law, on a joint between two angles, the cement sealant eroded, and water blew in when the wind was in a specific direction, then somehow travelled about halfway round the house before dripping through the lounge ceiling. Finding that leak was a right bit.... erm, pain.

Anyway, it's an aside since you sound uninterested in flat roofs (don't blame you, by the way). This is really a sneaky way for me to ask ik9000's view on those modern rubberised flat roofs. Neighbours have had it done and are happy. I'm thinking about it, but they ain't cheap.

(*Note - Smallish area, about 4.5m x 1.5m.)

can be ok, but there's a real mix of quality out there, and it is much much more dependent on workmanship. I've seen some of those rubbery miracle membranes just degrade away in sunlight to the point of uselessness. Not to say they're all like that, but do your research very very carefully and check any warranty in great detail. Warranties that only cover repairing the leak but not the internal damage from that leak are not very useful IMO. I'd be surprised if you get a warranty on the rubber stuff for more than 10-12 years tops btw.

Personally, I'd steer clear as I wouldn't want the cost of the good ones. I'd aim to save my money, and go bitumen-asphalt which while it does age, I know how long it will last and I can get pretty much anyone to change/repair it in future. I'd budget the costs for future replacement and see how inspection (and posisble patch repair at 5 years) and replacements at 10 year intervals compares to Mike's Super Deluxe rubber liquid miracle seal. That or consider a metal finish - lead/zinc standing seam. That would last ages. Like any waterproofing the devil is in the detail, and workmanship is always key. Choose your contractor wisely.

Water always wins. For conventional pitched roofs tiles/slates and bitumen roofing felt all the way.

Alternatively you could consider a green roof and enjoy doing your bit for nature too.

Edit: another thing to bear in mind isif access is required onto that flat roof for any reason, eg to put ladders off to get up to other higher roof areas to clean gutters/fix tv aerials/wash windows etc. Asphalt is much harder wearing and I would have more confidence standing a ladder (with spreader boards) onto it than a rubberised membrane.

2nd edit, one of the problems with tiled pitched roofs on older buildings is that sometimes the rafters are undersized and the roof poorly braced laterally (quite common in 50s buildings). Modern tiles are thicker + heavier (particularly concrete ones if replacing old thin slate). The combination = greater deflection in storm gusts and opening-up of joints. Just because a tiled roof leaks is not necessarily a failing of a tiled system per-say. Sometimes adding some judicious bits of timber/ply internally can solve the problem!

edit 3: I'm assuming above you're talking about a poured viscous rubberised liquid membrane. Is that what you mean, or do you mean a rubberised "felt" that you roll out?