Estimated costs for a garage concrete slab

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Thanks @sovietspybob, I've obtained three quotes; for non-insulated, just the roof insulated and roof and walls insulated. The difference in each is quite a lot due to the increase in materials, effectively skinning the inside of the building again. To go from non-insulated to fully insulated is about £6k of a difference, that buys a lot of 50mm Kingspan and OSB. I think I'll be opting for only the roof insulated (hardest part to diy) and insulate the walls myself like you.

Did you get the supplier to erect it for you? All the companies want around £5k to put it up which seems a lot for what is a kit of parts. I know there's a bit of fettling required with steel buildings and some working at height but I suppose those quys know what they're doing so they'll be less mistakes and it'll be built quicker.

Still considering reducing the height of the garage as it'll reduce costs but then again I could work on a larger car in the future. Plus extra height means I could build a simple mezzanine area for storage later.
 
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Thanks @sovietspybob, I've obtained three quotes; for non-insulated, just the roof insulated and roof and walls insulated. The difference in each is quite a lot due to the increase in materials, effectively skinning the inside of the building again. To go from non-insulated to fully insulated is about £6k of a difference, that buys a lot of 50mm Kingspan and OSB. I think I'll be opting for only the roof insulated (hardest part to diy) and insulate the walls myself like you.

Did you get the supplier to erect it for you? All the companies want around £5k to put it up which seems a lot for what is a kit of parts. I know there's a bit of fettling required with steel buildings and some working at height but I suppose those quys know what they're doing so they'll be less mistakes and it'll be built quicker.

Still considering reducing the height of the garage as it'll reduce costs but then again I could work on a larger car in the future. Plus extra height means I could build a simple mezzanine area for storage later.

Yeah i kinda wish i got my roof done, i just had that done in that weird fleece backed stuff which at least stops it dropping any moisture.

I got mine erected by one of the suppliers builders, mine was only £1800 from memory to erect which like you'll have found went up a lot if i wanted insulated, i think it was nearer 3k if i went for fully insulated. plus the extra 3k for the building too so wasn't worth it to me as i reckon i could do the whole thing myself in Kingspan for around a grand.

I would say from watching the guys doing it that it looked a fairly fiddly job if you're not used to working with steel buildings, quite a few bits needed cutting on site and things like getting the roller doors to line up and operate smoothly looked like it could turn in to a nightmare if you didn't have the experience.

I build a simple long storage shelf in mine re-using the shuttering and that's been super useful. It's 1.2m deep and 4.8m long, think its about 2.5m high so i've got lots of rack shelving under it currently and its tall enough that you could work under it without it being in the way.
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Looks great, that storage is exactly what I have in mind but with maybe steps if space allows. Nice ride on train?! Best not show that to my lad!

Perhaps I won't save much with getting my own crew to assemble after all. Rough calculations of four people at £250 a day for four days is £4k and they'll have all the equipment and knowhow, think I'm sold on them putting it up.
 
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I did a thread about my railway here, need to update it really as I've done a bit more since then:
https://overclockers.co.uk/forums/threads/garden-railway.18890402/

But yeah get them to put it up is my advise, it took 2 guys 4 days to do mine, would have been 3 but some of the wrong bits turned to to begin with. Also make sure the slab is spot on, the guy doing mine says most issues are because the slab isn't true in one a aspect of another and it's makes it a nightmare. Mine was less than 10mm out on the back edge and he said the guy who did mine deserved a medal, so aim for that!
 
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Given the size, will you need a building control application?

Building regs scuppered our plans for doing a timber-frame garage. If you do need building regs, a simple concrete base might not be sufficient depending on your soil conditions and the proximity of any trees.

We’re moving house now, so we’ve shelved the garage build, but it was quite a learning experience.
 
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blimey ..soviet ive rented units smaller than that, well jealous:) keep telling myself i must try and get the back half of my garage roof higher really does restrict my ramp height, currently have to stoop slightly being nearly 6ft when under a vehicle.:)
 
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I did a thread about my railway here, need to update it really as I've done a bit more since then:
https://overclockers.co.uk/forums/threads/garden-railway.18890402/

But yeah get them to put it up is my advise, it took 2 guys 4 days to do mine, would have been 3 but some of the wrong bits turned to to begin with. Also make sure the slab is spot on, the guy doing mine says most issues are because the slab isn't true in one a aspect of another and it's makes it a nightmare. Mine was less than 10mm out on the back edge and he said the guy who did mine deserved a medal, so aim for that!

You do need to update your railway thread! I've bumped it for you ;).

Most of the quotes I've received have stated the installation costs are 30% of the building cost which is quite a lot. Great advice on the slab dimensions, hopefully the team putting in the slab will be as experienced as yours! Thought about getting the slab done first then getting the building designed to those dimensions. Sad thing is one building supplier has already got in touch to say they're putting up costs by 20% for orders signed after June and I presume others will follow suit. Seeing as planning permission won't be granted until after that it's another cost that probably means I may have to delay my build to next year once things have hopefully calmed down. Building a workshop albeit a large one, is expensive.

Given the size, will you need a building control application?

Building regs scuppered our plans for doing a timber-frame garage. If you do need building regs, a simple concrete base might not be sufficient depending on your soil conditions and the proximity of any trees.

We’re moving house now, so we’ve shelved the garage build, but it was quite a learning experience.

I'm not sure, I'll find out when my pre-application goes to the Highland Council. I do have a lot of trees to consider. I have two areas I've considered putting the building; the first one my groundworks guy didn't recommend due to the number of trees that would have to come down and thus the amount of groundworks required. The other area only has two trees that need to come down and the earthworks would be less. Is it the roots of trees that are the cause for concern with building control?

While on the topic of concrete garage slabs, what would you expect a standard 3m x 5m slab to cost?

I'd take a guess between £500 to £1k depending on lots of things like condition of ground, depth, access, type of concrete, size of team (2 or 3 man) and where you are in the country.
 
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You do need to update your railway thread! I've bumped it for you ;).

Most of the quotes I've received have stated the installation costs are 30% of the building cost which is quite a lot. Great advice on the slab dimensions, hopefully the team putting in the slab will be as experienced as yours! Thought about getting the slab done first then getting the building designed to those dimensions. Sad thing is one building supplier has already got in touch to say they're putting up costs by 20% for orders signed after June and I presume others will follow suit. Seeing as planning permission won't be granted until after that it's another cost that probably means I may have to delay my build to next year once things have hopefully calmed down. Building a workshop albeit a large one, is expensive.



I'm not sure, I'll find out when my pre-application goes to the Highland Council. I do have a lot of trees to consider. I have two areas I've considered putting the building; the first one my groundworks guy didn't recommend due to the number of trees that would have to come down and thus the amount of groundworks required. The other area only has two trees that need to come down and the earthworks would be less. Is it the roots of trees that are the cause for concern with building control?



I'd take a guess between £500 to £1k depending on lots of things like condition of ground, depth, access, type of concrete, size of team (2 or 3 man) and where you are in the country.

So worst case scenario maybe 2-2.5k?
 
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I'm not sure, I'll find out when my pre-application goes to the Highland Council. I do have a lot of trees to consider. I have two areas I've considered putting the building; the first one my groundworks guy didn't recommend due to the number of trees that would have to come down and thus the amount of groundworks required. The other area only has two trees that need to come down and the earthworks would be less. Is it the roots of trees that are the cause for concern with building control?

As I understand it, it’s not so much the roots themselves but more to do with how thirsty the trees are, the size of the trees, the trees proximity to the proposed structure and the type of soil you’re building on.

Trees ‘drink’ more in the spring/summer and less in autumn/winter. It tends to rain less in spring/summer and more in autumn/winter. So the soil tends to dry up (shrink) in spring/summer and get saturated in autumn/winter (expand). Over time, this cycle of soil movement can damage your foundations.

Certain soil types are more prone to ‘shrinkage’ due to this effect. The closer the trees are to your site and the more thirsty the trees, the more pronounced the effect.

Google ‘NHBC guidance for building near trees’ and you will find details of the different tree types and sizes, soil types and how to determine foundation depth based on the distance of the tree(s) to the site.

In our case, our soil is mostly clay (classed as High Shrinkage) and we had two large willows (classed as High Water Demand) within a couple of metres of the site. This meant that if we had used a traditional strip foundation, the trenches would have had to have been deeper than 2.5m, which is a lot of earth to move.

We got a structural engineer to design pile foundations with a block and beam floor instead, which would have been fine except the quotes we got back to build it were over £16,000!

In the end, we found out we wouldn’t need building regs if we built a brick garage instead of a timber-frame. This is due to the proximity of the garage to the boundary and fire regulations. Without the requirement for building regs, we could build a much simpler slab foundation. It seems crazy that a heavier structure wouldn’t require building regs but there you go.

Now, you may still need building regs but get away with a simple slab foundation. If your soil is Low Shrinkage, your trees are Low Water Demand and they aren’t too close, you might be ok. Or you may find that you don’t need building regs at all, in which case you can pretty much do what you want (although I think with the size you’re proposing you will need building regs). Equally, if you cut down all the trees it might not be a problem anyway. Just bear in mind that if circumstances are against you (like in our case), the foundation costs could spiral.
 
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Thanks for the detail @Irish_Tom, much appreciated, you've steered me in a good direction. I can see why my mate with the digger who's dug foundations in the past was reluctant to put the slab where there are currently a lot of trees. I've looked over the NHBC chapters and charts, especially Chapter 4.2 and the NHBC Foundation Depth Calculator app is very useful. According to the app, my location allows a depth reduction of 0.45m, so with the trees in consideration the foundation needs to be 1.1m deep. However, it's best to get an experts opinion and line up a few quotes.
 
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