Caravan act Build - Technical source?

[Galileo]

Not sure which category this goes in, design and planning or construction, hope i got right. I've a notion of building to caravan act standards, mostly because I'm poor(!) and it looks like I would have more of a free hand with the layout and materials. So I'm basically looking at building a very well insulated wooden box on a skid base, in two halfs, on some peaty ground.

 

There is a lot of really good high level information in the forums, and I've been a member for quite awhile and soaked in a lot of just by searching, but one part that eludes me is the technical how. What I mean by that is I have the idea of how to do what I want, but no idea on what to specify for framing the base, ridge beam sizing etc. Are there any recommendations of places to look for people that have already done this, or perhaps publications that will guide me, would any of the TRADA publications cover such a thing as building a "static caravan"? 

 

I'm not a stranger to building, plumbing and electrical work, having tried my hand at most things with success, except plastering, but it's all been small scale like a workshop, sheds, house renovation etc. I'm looking to build in a coastal location, with a lot of wet and a LOT of gale force winds, so I really don't want to cut corners or screw up on the structure specifications, as I'm keen on not waking up floating in the Atlantic for want of a cunningly placed Simpson Strong-tie. If the simple answer is employ a structural engineer, all good but any advice gratefully received.

[Declan52]

Your going to need to get the base correct first so do you happen to know the depth of the peat. This will play a massive part in the type of base you can put in. If it's within 2/3m you could dig it out and trench fill with concrete. Anything deeper and your looking at some kind of pile. Could be a driven pile or screw pile. 

After the base is in then your just constructing a basic shed in 2 halfs.How big the joists need to be will depend on the span. For the walls 4*2 filled with insulation plus OSB, membrane and whatever you intend to use as the outside layer, cedar/shiplap etc. The size of the roof timbers will also depend on the span. 

[A_L]

46 minutes ago, Galileo said:

places to look for people that have already done this

 

perhaps try this one time buildhubber

 

https://forum.buildhub.org.uk/topic/16414-caravan-act-compliant-home-eligible-for-vat-claim-back/?tab=comments#comment-266730

 

https://forum.buildhub.org.uk/topic/13305-looking-for-advice-log-cabin-caravan-build-scotland/page/2/?tab=comments#comment-222442

[Crofter]

My wee cottage was built to this sort of spec, as a portable building within the definition of the Caravan Act.

The whole attraction of going down this route is that you are not constrained by building regs and can design and build it just the way you want, so long as it satisfies the planners.

 

I did a fair bit of first-principles calculations on things like wind loading and how that impacted on the foundation system. I also used the JJI joist spacing online tool to spec the floor joists. But other than that, it was pretty much a case of 'if it looks right, it is right'. If you want to put a meaningful amount of insulation in, then your timbers are always going to end up being pretty massive. I never really made my mind up about the roof structure, for example, and it ended up being a heavy ridge beam with cut rafters, some of which were then braced to become trusses. I think that's a sort of hybrid of three different ways of building a roof, but what the heck it is still standing and doesn't so much as creak when a gale of wind is blowing outside (which is more than can be said for most 'professionally built' houses I've lived in).

 

I used Sketchup (free 3D drawing software) to work out the minutiae of the little details, like floor to wall junctions. Well worth spending a few hours getting your head around the software as it was very useful for me.

 

 

This build route does have some downsides. The most obvious one is that, as non-standard construction with no completion certificate, you won't be able to mortgage it. That has a massive effect on future resale value. Secondly, in a more technical vein, the building cannot be built up from conventional foundations. It must be possible to lift it off the site in no more than two pieces, so if you have to leave the floor behind that's not going to comply. In my case I chose to keep it as a single monolithic box, meaning that my floor joists had to do the whole width of the building in a single unsupported span. If I had a sleeper wall at the mid-point, my joists could have been a fraction of the size, and I would have had a less bouncy floor. I could have split the building down the middle, which would have traded an easier floor for a much more complex roof.

 

I'm not sure what the best course of action is for you with building on peaty ground. As your build will likely end up being quite light, it would be tempting to simply sit it on the ground, as you say on skids- but perhaps it would sink over time? I think a trial hole to see if there is any solid ground underneath would be worthwhile. I hand dug eight holes and then poured concrete pillars and sat the building on top of those, but I had good ground conditions and it wasn't any harder than digging a hole for a strainer post. The holes also didn't fill instantly with water as yours probably would!

[Galileo]

22 hours ago, A_L said:

 

perhaps try this one time buildhubber

 

https://forum.buildhub.org.uk/topic/16414-caravan-act-compliant-home-eligible-for-vat-claim-back/?tab=comments#comment-266730

 

https://forum.buildhub.org.uk/topic/13305-looking-for-advice-log-cabin-caravan-build-scotland/page/2/?tab=comments#comment-222442

Thanks for those, had already read the first but somehow had missed the bottom one!

[Galileo]

Thanks for taking the time for the detailed reply @Crofter

 

A mortgage does not concern me as this will be built on a croft and I'm not keen on decrofting at the moment as there's the old croft house (a ruin) that I could get around to restoring. There is though admittedly the question of conforming to the housing grant requirements from CAG if that's still going to be available next funding round. I've no intention of selling when built, I've done a fair few house moves and sworn that this will be my last before the old peoples home or pushing up the daisies occurs.

 

Rounded down 18m x 6m, 108m², seems a lot of space when a 1 bed place with a shower (don't like baths) could be built in 60m². I've learnt recently to be able to live small, and as long as I have storage for my hobbies which can be a seperate barn sized workshop,  as one of them is unloved Triumph cars of the 70's. I'm quite happy.

 

I had in my mind a 15m x 5m box, constructed as two "pent" style roof halfs at 2.5m each. Was also thing that dividing walls could be breaks, so that it would not be a 15m ridge beam. Also, the pent halfs ridge beams could be bolted together to create the final "in place" ridge beam for maximum strength? I had similar thoughts on rafters, and using a mixture of braced truss in the middle, unbraced towards the gables.

 

There was a kit that I kind of liked the look off, http://www.cottagekithomes.com/design/bluebell/ but at £23k for the basic kit, which is not a bad price, I felt that someone not in a hurry with some skill could do something similar for far less. One of the reasons for the caravan act approach was that apart from saving a £1k on paperwork and warrants, I would also be able to slowly complete the interior fit out as time and money allowed for. 

 

The ground will need some test digs, I've no idea how far the peat goes down, could be quite away and will definitely fill up and need a former if a concrete pier was used. The old croft house was right by the sea on a small flatter section of land, I'm hoping to build a bit further up.

 

I've used Sketchup for 3d printing, I shall give it a try and turn my thoughts into something more concrete (if not actual concrete!).

Edited December 2, 2020 by Galileo

[A_L]

25 minutes ago, Galileo said:

Rounded down 18m x 6m, 108m², seems a lot of space

 

I believe the Sottish dimensions have been 'harmonised' with the English ones, i.e. 136m²

 

https://www.gov.scot/publications/business-regulatory-impact-assessment-caravan-sites-act-1968-amendment-definition-caravan-scotland-order-2019/pages/1/

 

https://www.legislation.gov.uk/ssi/2019/295/made

[scottishjohn]

13 hours ago, A_L said:

 

I believe the Sottish dimensions have been 'harmonised' with the English ones, i.e. 136m²

 

https://www.gov.scot/publications/business-regulatory-impact-assessment-caravan-sites-act-1968-amendment-definition-caravan-scotland-order-2019/pages/1/

 

https://www.legislation.gov.uk/ssi/2019/295/made

are you allowed to have a real sewage treatment plant and other service  connections 

as what you propose would be a wonderful solution to make one at top of the quarry part of my plot 

would have same view as my house 

 and 130sq m is plenty for a house 

  I presume  you can also then have other sheds  on the site 

like a workshop ?

[ProDave]

47 minutes ago, scottishjohn said:

are you allowed to have a real sewage treatment plant and other service  connections 

as what you propose would be a wonderful solution to make one at top of the quarry part of my plot 

would have same view as my house 

 and 130sq m is plenty for a house 

  I presume  you can also then have other sheds  on the site 

like a workshop ?

Yes you can have services connected. Any treatment plant will need a building warrant but the "caravan" won't.

 

you will need planning permission though. The caravan thing only exempts you from building control for the "house"  This is where it gets intertesting and debatable.  Do you apply for PP for a "caravan" or do you apply for a house with a pretty picture of what it looks like, and the "house" then happens to get built complying with the regs for a "caravan" wgile still looking like the picture in the planning?

[Temp]

 +1

Would help to know more about why you want to build a "caravan"?

[A_L]

13 minutes ago, Temp said:

Would help to know more about why you want to build a "caravan"?

 

1) May be possible to get PP for a caravan but not a house.

2) As said above, exemption from building regs for 'caravan'.

 

 

44 minutes ago, ProDave said:

This is where it gets intertesting and debatable.  Do you apply for PP for a "caravan" or do you apply for a house with a pretty picture of what it looks like, and the "house" then happens to get built complying with the regs for a "caravan" wgile still looking like the picture in the planning?

 

@Crofter, perhaps you could detail your planning process? TIA

[Temp]

I was asking because some people propose building caravans and houses from containers thinking thats a way of avoiding the need for planning permission. 

 

 

[ProDave]

2 minutes ago, Temp said:

I was asking because some people propose building caravans and houses from containers thinking thats a way of avoiding the need for planning permission. 

 

 

No it is not, otherwise there would be fields of them and no housing shortage.

[Galileo]

22 hours ago, A_L said:

 

I believe the Sottish dimensions have been 'harmonised' with the English ones, i.e. 136m²

 

https://www.gov.scot/publications/business-regulatory-impact-assessment-caravan-sites-act-1968-amendment-definition-caravan-scotland-order-2019/pages/1/

 

https://www.legislation.gov.uk/ssi/2019/295/made

 

Good spot, thanks! I knew that it was being discussed some years back but had not noticed that it has now become law, so you can tell how long I've been planning this for. Might have a think to see if the larger dimensions alter my thinking in any way.

 

Watched a Youtube video on how one of the park house companies make their houses, was surprised by the small timber sizes and so strength that was in the floor, I'm taking it that the 'undercarriage' must add a lot more. Probably not the right route to look for inspiration on timber sizes for framing!

[scottishjohn]

 I suppose it depends on if the PP requirements for siting a caravan are different than  a house--i would think not --

If yuo want a very strong and light subframe then make up plywood box beams  and if you want them rot and bug proof -- sheath in GRP

I am guessing 

but do not know 

that they expect it to be made up off site in maximum of 2 parts ,then transported to site 

 so how about you make up the 2 parts not on actaul foudations -- but very close by then slide the 2 halfs onto final founds 

then it has been made off site and transported to final location 

 as for building on a bottomless peat bog 

 

 why not dig it out and use 1m cuubes of polystyrene -as they do in the artic circle ,where permofrost and sinking  in summer is a problem 

 2 metre deep and the whole foot print in ploystyrene will support a lot of weight 

 

maybe only needs 1 layer each block will displace 1 tonne of water  so support that amount of something else  ?

will be alot easier getting blocks of that to site  than 100tons of hard core 

  I say blocks you could just sheet stuff  piled

 maybe a be a silly idea 

I leave you to ponder 

 

 

 

 

 

[ProDave]

It does not say anywhere that a "caravan" has to be made off site.  It can be constructed in it's final position if you want to.  The only stipulation is it must be capable of being moved, so it must be built in such a way it won't all just fall apart if you try moving it.  It has been tested and proven that lifting it onto a low loader with a crane is a valid means of moving it.  so it boils down to the "chassis" must be stiff enough that you can somehow move it.

 

[scottishjohn]

18 minutes ago, ProDave said:

It does not say anywhere that a "caravan" has to be made off site.  It can be constructed in it's final position if you want to.  The only stipulation is it must be capable of being moved, so it must be built in such a way it won't all just fall apart if you try moving it.  It has been tested and proven that lifting it onto a low loader with a crane is a valid means of moving it.  so it boils down to the "chassis" must be stiff enough that you can somehow move it.

 

 must be more than that -- cos they move complete houses even brick ones

 

[ProDave]

37 minutes ago, scottishjohn said:

 must be more than that -- cos they move complete houses even brick ones

 

A caravan can only be single storey so even if portable, a 2 storey home would not be possible under the caravan regs and would have to be a proper building with building regs.

[joe90]

38 minutes ago, scottishjohn said:

cos they move complete houses even brick ones

Yes, but they are not designed “to be moved”.

[scottishjohn]

17 hours ago, joe90 said:

Yes, but they are not designed “to be moved”.

well if start wanting SE survey and report that the structure is strong enough to be moved etc --then that will kill it 

and would mean you would have to have full drawings before you start --so savings soon vapourize .

think you need a very agreeable local planning dept - 

so that will be a big NO for D&G

 

[Jilly]

18 hours ago, scottishjohn said:

 must be more than that -- cos they move complete houses even brick ones

 

I recall some  people in NZ speaking of moving their 'actual' house sometimes, so they must've been referring to some variation of this. 

[ProDave]

2 hours ago, Jilly said:

I recall some  people in NZ speaking of moving their 'actual' house sometimes, so they must've been referring to some variation of this. 

It happens in Australia.  North of Brisbane on the Bruce Highway is a sales yard where you can go and buy a second hand timber Queenslander type house and they will transport it and re erect it.  These were never built to be portable but they literally cut them in half and stick some girders under them and transport them on low loaders.  I saw a tv program about it, they have to travel at night with a police escort as abnormal loads.

[joe90]

14 minutes ago, ProDave said:

It happens in Australia.  North of Brisbane on the Bruce Highway is a sales yard where you can go and buy a second hand timber Queenslander type house and they will transport it and re erect it.  These were never built to be portable but they literally cut them in half and stick some girders under them and transport them on low loaders.  I saw a tv program about it, they have to travel at night with a police escort as abnormal loads.

not round uk lanes! ?, they struggled to get my 10ft wide static to my site ?.

[Crofter]

On 03/12/2020 at 13:03, A_L said:

 

 

@Crofter, perhaps you could detail your planning process? TIA

 

I applied for PP for a "one bedroom dwelling". My choice of wording. I did not say anything to the planners about construction method. In their response, they said they had assumed, from the size and style, that the build would be some sort of pre-fab, but they acknowledged that this had not been specified- it was just a throwaway remark from them rather than any sort of conditon.

 

I also contacted my local BCO to confirm that what I was doing would be exempt from BRegs.

The access/bellmouth and the sewerage system still had to comply with regs.

 

I deliberately did not want to be pinned down to any particular restrictions, so I didn't say anything about it being a holiday let (in case my plans changed in future).

[Crofter]

On 04/12/2020 at 15:57, scottishjohn said:

 must be more than that -- cos they move complete houses even brick ones

 

 

It's all there in the Caravan Act, and in local interpretations of it (e.g. Highland Council planning note 018, from memory).

 

You could make it from brick if you wanted, but it would have to be on a massive steel chassis. Literally the only stipulations are:

- max length 18m

- max width 6m

- max ceiling height 3.048m

- movable in one or two sections

 

Interestingly, the building can still qualify even if there is in practise no way of moving it. The test case for this was where somebody's portable building had been, over the years, encroached upon by other building work to the point where you could now no longer get a crane in and remove it from the site. In that case it was ruled that the characteristic of portability was inherent to the building rather than being a combination of the building and its surroundings, so just because other factors prevented access did not mean that the building lost its claim to be portable.

And of course you could hire a Chinook if you really wanted to make the point...