Foundations for mobile home

[Jilly]

I have a redundant riding arena (20m x 40m) and would like to put a mobile, caravan compliant, granny annexe on it.

 

The ground beneath is clay with hedging at the sides.

 

The build up is: 150mm carboniferous limestone topped with about 50mm silica sand layer and shredded rubber. It's never moved at all, drains completely (into a pond) , has had horses, vehicles, huge lorries driven on it, and a shipping container is sited there. 

 

My question is, is this likely to be sufficient foundation for a mobile home? My instinct is that it is, but how can I test/prove this? 

 

 

[ProDave]

I think it depends of it is literally a static caravan, which tend to be quite lightweight, or are you building a properly engineered well built well insulated "house" that happens to fit the legal definition of a "caravan" (it does not need to be on wheels to legally be a "caravan") which might be very much more substantial and heavier?

[Jilly]

I was thinking of something good, if I can get it through planning. 

[saveasteading]

1 hour ago, Jilly said:

but how can I test/prove this?

If it is to sit on the metal jack legs alone, then they put a very concentrated load down. They will indent , or even break into, the surface you describe. But spread by blocks or timber baulks it should be fine.

Bigger 'caravans' have bigger jack legs. presumably more of them too. 

Tell us more and we can answer better.

[ProDave]

My static caravan sits on 12 pillars of concrete blocks, so a well spread load, but it is only about 2 tons of caravan son not a lot of weight. I don't use the puny wind down legs at all.

 

For a more substantial build I would probably do a number of concrete pads a decent depth.

 

 

[Jilly]

Thank you. I haven't chosen anything, I'm just trying to get a feel for things. Would I need it to be designed by an SE or are such things available? 

 

A structural engineer visited about something else and thought we need piles, which obviously is a massive deal and would cost as much as the structure, so I'm keen to explore every avenue to avoid that and get more opinions

[saveasteading]

11 minutes ago, Jilly said:

thought we need piles

For a caravan? 

[Jilly]

 

18 minutes ago, saveasteading said:

For a caravan? 

That’s what I thought. But actually the caravan compliant builds can look pretty substantial.

[ETC]

Piles for a caravan - I’ve heard it all now!

[SuperJohnG]

The wind down legs are just to steady it. 

 

My static is up on 8 (albeit should at at least 12) static Jack's. I jacked it up with a standard bottle jack till it was high enough and levelled it. 

 

It's on 400mm of type 1, then some wooden pads then the static jacks

[Andehh]

I would think several large 40mm+ concrete paving slabs under various structural points would be plenty to share the load. Ensure all are level using a biscuit mix of concrete/sand to help as well.

[SteamyTea]

Easiest way to find out is to ask a Structural Engineer, what they do.

[saveasteading]

2 hours ago, SteamyTea said:

Easiest way to find out is to ask a Structural Engineer, what they do.

If i was contacted with this question I'd  be giving the same answers, free, on the phone.

If it really is a caravan, not a house in disguise, then prop on slabs or baulks. If it moves, it can be adjusted.

If not really a caravan, then it is has to be as a proper submission, or I decline to be involved. 

[Jilly]

Thank you all. I'll investigate some of the companies, as they come as kits with plans and calculations etc so they are likely to advise on foundations.