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Always worth an ask in here, as there’s such a diverse bunch!
Looking at doing my second self build (genuine self build where I do most of the work)
But this one I want to keep as simple and cost effective as possible, with the goal to still have a high performance, well designed build.
I am looking at building a hebhomes kit build, so lightweight and fairly straightforward.
Just wondered if anyone had any professional knowledge or recent experience on groundwork and foundation costs?
Ideally I would have a raft foundation and the footprint is around 125m2
I know there are many variables but just after a ball park cost range at the moment, my last build was 10 years ago, so concrete and steel prices have gone through the roof since!!
I may look at standard strip foundations and slab as an alternative but I prefer the clean easy route of raft
Any ideas?
Cheers
Foundation design relies on 2 things: the load and how it is applied and the ground. These dictate the foundation type that can work. Sometimes a range of types is available, sometimes not. The only ball park costs available given the information in your post will be those by a builder rather than someone qualified to desgin foundations (sse recent thread on structural calcualtions as outlining the philosophy of similar approaches). The biggest variable is the ground. In extreme cases the ground will dictate the type of structure that can be constructed on that ground.
I can offer more advice related to ground engineering as this is my profession, but I can offer little idea on costs, but maybe able to steer you towards someone happy to assist you in a proefessional and paid capacity depending on your location.
The website you link to looks good. I am sure they would be able to provide required loads for whichever structure you wanted to take forwards as a conceptual and then hopefully detailed desgin..which just leaves you with the ground parameters together with any other environmental parameters: wind loadings etc.
What does your planning consent/ insurers/ finacers require? a signed off foundation design? If that is the case probably worthwhile engaging a professional from the get-go, ramping up their involvement and detailing of their output as the project ramps up.
Haha. Get lubed up ready for the quote.
We had a 3x2m porch poured last year, they had to go down 1 metre, insulation near the top, and a 75mm ish skim over the top.
£5k.
I think you will be very lucky to get it done for less than £20k.
The type of foundation is largely down to what building control will accept. I'd start with a chat to them, my local office is really helpful. Once you have an idea what you need you can start working out what it will cost a groundwork firm by getting local quotes for muck away/concrete etc. Use that to information to get a rough idea then get some quotes.
I poured 2 and a bit cubic meters in September and that was ~£350. If we would have had a full load then price per cube would obveously be less. Part of the cost was due to the part load. We barrowed as it pump hire was too much for a small amount. I think . Pump hire was going to be £500, there would be a time limit on this but I did not look into it anymore as it was too much minimum charge for our small job.
Digger hire is quite cheap for a small 1.5- 2 ton, something like £200 odd for a week, a dumper is about the same if needed. Grab waste removal will be the cheapest, not sure on price. 1 week should be enough.
The major cost will be the concrete and the depends on how many cubes.
You still have all the build up to maybe 150mm above ground level, drainage and maybe other services, is it a suspended wooden floor or 100mm kingspan,concrete then floating floor?
Is the site level ?
Thanks all…
I know most of what you all mention, as I have a fair bit of experience… it’s just been a while since I have dealt with prices.
I am working on assumptions at the moment but I do know building control will be happy with a toed raft and I’m a sure the ground conditions are suitable too
I have a fair understanding of the loads from the proposed builds and a standard specification raft will be more than adequate.
I have mapped out and calculated costs for connecting services, drainage and soak away. I am also ok with dealing with the remaining build up to DPC, to suit the build system.
What I am really looking for is anyone with professional or recent experience having a raft foundation for a lightweight build done.
Just to gauge ballpark costs.
I also have the option of building off pads and going suspended/cassette floor but I would rather build solid floor and start with a raft.
Just need to gauge rough costs
I was hoping sun £15k for 125m2 (setting out, pour and reinforcement)but think I may be being optimistic
Cheers all
I'm not sue how you could beat a monopoured icf footing for price/performance.
less excavation, less concrete and done in 1 visit, no flatwork.
EPS insulation too so less environmental impact as a bonus over a huge amount of concrete with XPS under
I've 3 extensions to do on my next project, 2 living spaces will be icf strips with a bag footing and joist structure above. the other (garage) will be insulated slab on grade. The garage portion will be the most expensive of the 3
suppose it depends if your kit can be built on a wooden subfloor vs a slab
a standard specification raft will be more than adequate
Have you had the ground tested to confirm that? No deep made ground? No low strength soils? No sudden change in geology in the middle of the footprint? No issues with shrink/swell clay and trees?