conservatory piled foundations

[zulu705]

Hi,
I've nearly got my conservatory plans approved by BCO but they don't like my plans for basic foundations as it turns out that my house was build on made up ground and has 'reinforced concrete strip foundations spanning between vibro compacted stone columns'. I am not entirely sure what that means being a complete novice to any sort of building work.
I assume that my conservatory needs to have similar founds? The made up ground was to a depth or 2.6 m! So does that mean that I need these stone pillars to 2.6m then strip foundations between them? Where do the pillars get placed, one at each corner?

Any advice appreciated....

 

[Darkrob_DIY]

Hey,

Piled foundations are reinforced concrete piles which are either driven into the ground or the soil is removed before concrete is poured, they are able to be taken to a suitable loadbearing subsoil depth in your case 2.6m. The tops of the piles will then support reinforced ground beams from which walls are then built off. The piles will get placed in each corner of the building and then any other points such as intermediate walls.

Heres a picture;

You could possible ask your BCO about using a raft foundation as this is an alternative for filled ground as it spreads the load over a greater area.

Hope this helps

R Critchley

 

[Static]

Piles will be expensive, unless you opt for a mini pile system. Your better off aiming for a raft footing onto the made ground. This will involve getting some geotechnical info about the material and getting a bearing pressure.

 

[zulu705]

Thanks.

Yes it is the expense I'm worried about as this was supposed to be a cheap DIY job!
What is a mini pile system?

I will need to read up about raft foundations but would that mean I would need to dig 2.6m depth over the whole area of the conservatory?

The other option I was now thinking about would be the steel base systems you can get for conservatories these days, anyone have any experience of this?

 

[Static]

Urm these guys do a min pile foundation system http://www.van-elle.co.uk/News&Events/News/Offsite 2005.htm also might check Keller.
Raft footings are basically one massive lump of reinforced concrete bearing onto the made ground. You have to get the soil tested to see what loading it can take but it would be your most cost effective solution.

 

[zulu705]

Thanks static.

It all looks a bit overkill (expensive) for a conservatory

Raft sounds better, any pointers as to who/how I test the soil to see what loading it can take?

 

[Static]

Well, i would get in contact with a structural engineer and get him/her to sort the geotechnical testing and detailing of foundation.

 

[zulu705]

OK.

Can anyone recommend one in Central Scotland?
I've emailed the local ones that are on the Scottish Building satndards website so hopefully one will reply.
Anyone know how much this is likely to cost?

 

[Static]

What type of foundation did you submit in the first place?

 

[zulu705]

a basic trenchfill type
width 400mm
depth 450mm
one brick course below ground and 5 on top for a single skin wall. It has glass to ground panels so this isn't a dwarf wall just a slightly large base wall.
The 3rd side is a cavity wall firewall on neighbours boundary and I specified slighly deeper and wider founds for it.

 

[zulu705]

I've been quoted £3500 inc VAT for 9 mini piles and concrete beams for the foundations of my conservatory. Does that seem ok?

These piles still seem a bit over kill for a conservatory though ...

 

[Static]

Your other option is get the soil tested for bearing pressure. If its adequate to go for either strip footings or raft foundations. Or as said before get an engineer involved, will cost a few hundred but my save you putting in the piled option.
Get quotes for a raft and trench footing option.

 

[zulu705]

I am having trouble finding an engineer.
I have got a quote for the trenchfill founds of £4500 inc VAT but that also included building the base wall, firewall and concrete floor. BC won't accept trenchfill though.

once I find and engineer I can see if raft or piled is best.

 

[Static]

http://www.findanengineer.com/ does list all but may help.

 

[zulu705]

thanks for that link Static, just sent of a raft of emails.