We are going to be building a single story garage 8.2m x 4.8m with a pitched roof. Is having a cavity block construction in a garage/shed needless, should I just go with 6″ block? What insulation should you use for the roof/ceiling to try and prevent condensation? What’s the benefit of doing a strip vs concrete pad foundation, does it depend on ground conditions on site? I’m totally clueless!

That’s about the same size as our workshop.

[url=https://flic.kr/p/daJJhs]The finished slab![/url] by brf, on Flickr

[url=https://flic.kr/p/dquzPL]Alan Day #4[/url] by brf, on Flickr

[url=https://flic.kr/p/dtvtXR]1st beam on post[/url] by brf, on Flickr

[url=https://flic.kr/p/duKBXF]Rafters in place[/url] by brf, on Flickr

[url=https://flic.kr/p/dyeVBo]Danny Upton at work[/url] by brf, on Flickr

[url=https://flic.kr/p/dz8YPz]1st shipment of Celotex (38/68 sheets)[/url] by brf, on Flickr

[url=https://flic.kr/p/dzLqXE]First insulation later complete[/url] by brf, on Flickr

[url=https://flic.kr/p/dQF6K8]Freshly skimmed walls[/url] by brf, on Flickr

[url=https://flic.kr/p/dZhZUo]Both benches in situ[/url] by brf, on Flickr

[url=https://flic.kr/p/n2LN6Z]Trellis, Gate and Fence[/url] by brf, on Flickr

We are going to be building a single story garage 8.2m x 4.8m with a pitched roof. Is having a cavity block construction in a garage/shed needless

Based on the size I would recommend it, plus it future proofs the construction for later conversion / adaption. Also damp through the walls need to be considered (exposure etc) . The cavity is ideal.

should I just go with 6″ block?

No. A good 100mm wide close textured concrete block will be suffice

What insulation should you use for the roof/ceiling to try and prevent condensation?

Depends on the roof construction. Are you putting an heat(energy) into the building? Typically I wouldn’t bother on the basis that I could retrospectively apply insulation if converting.

What’s the benefit of doing a strip vs concrete pad foundation, does it depend on ground conditions on site?

Assume you mean mass fill rather then “pad”. (Don’t go along the raft route) If so working constraints and time. (Easier to mass fill a trench)

I’m totally clueless!

You are only just over the limit for building without building regs. A quick calc says its by a couple of square metres if you do go for cavity walls. I’d be tempted to reduce it slightly to have a 30m2 internal floor area to save a few quid and a bit of hassle. You’ll need planning too. All this is assuming its in England/Wales.

Cavity makes sense or you’ll likely have issues with damp. Strip is generally considered to be easier and cheaper. Raft tends to be for problem ground.

Trench fill.

Trench fill…..doh. I didn’t think mass fill sounded right but I couldn’t think of a better word.

Architects 🙄
😉

@footflaps – that steel/roof is fair overkill isn’t it, was it just the logistics of handling a larger steel section that dictated that design?

Depends on the roof construction. Are you putting an heat(energy) into the building? Typically I wouldn’t bother on the basis that I could retrospectively apply insulation if converting.

There’s no heat going into the building so I’ll just leave it out and I can add the insulation at a later stage if required.

You’ll need planning too. All this is assuming its in England/Wales.

Planning already approved and in Ireland

Strip is generally considered to be easier and cheaper. Raft tends to be for problem ground.

Cheers!

Some appalling Health & safety standards in those pics! 😯

Call the HSE!!

Your strip founds cant really be decided on till you put a bucket in the ground. As a rule of thumb they should extend 150 either side of construction.
ie 100 ext brick/block 100 cavity 100 int block, would require a 600mm strip. Basically 2ft bucket. This would be the optimum construction method on a traditional build in my mind to then convert into anything at a later date.
Get digging.

Architects

Go and wash your mouth out! I’m a Technician!

Wrightyson – If I have a aggregate (8″) with 6″ rebarred concrete on top platform (it’s 17’x13′ area) – can I build a block garage?

I’m looking to build a single block layer (to raise the barrel board away from the splashback) with wooden structure on top (up to 14′ or so) but if I could build all blockwork I’d be happier.

14 feet high? 😯
You can’t go that high or that floor plan in single skin without incorporating plenty of piers.
Again regarding the slab it all depends on what we’re sitting on.
In theory a simple slab on good consolidated ground is fine. For something that size and weight I’d be looking at getting a simple design from an engineer. It may require slight thickenings (and an extra rip of mesh) to the slab around the perimeter to allow for the added weight of the block work/roof.

Sorry, 14′ would be including the roof, was looking at 7′ walls (want to be able to stand the bikes upright and then a pitched metal roof.

The platform is an existing one with 2 sets of mesh (1 near the top and 1 near the bottom, thought that was called rebar) that’s been in place for 7 years with a metal shed on top with no bother.

Sounds like i’d be borderline and I’d prefer overbuilt so I don’t have to worry 30 years down the line.

If in doubt overbuild everything!

Rebar/bar is just single legnths of cut and bent steel of varying (usually bigger than mesh) diameters that are then set out as req’d, mesh is preformed in sheets for speed.
Seems a bit overkill initially just for the shed so I’d say with the two layers in it would be perfectly (disclaimer) acceptable strong enough. You’ll still need some piers in tho with that floor plan size.
See footflaps original epic build thread for an idea of the piers as an example.
Is your original slab still nice and level no sign of cracking etc.

Original slab is “imperial level” – 1″ drop per 6′ and no cracking or movement.

It is massively overbuilt for what was put on there (I think the builder thought I was wanted to put a car on there and he was very confused with the ground anchor, although as is the way with sheds it’s rammed with stuff now).