Foundation Cost and requirements - is BC being too picky

[hmpmarketing]

Hey guys,

 

On my journey to build my garden / office I have been chasing quotes for a SIPS structure, (supposedly lightweight).  A couple of suppliers have already indicated that I would need 300mm footings and a 1500mm slab to sail through B.C. A quick email to my private BC (that approved my house) and his reply was :

 

"If the building was a garage the proposed footings would suffice, if the building is for another use full strip footings of at least 1 metre depth are required."

 

FIY, the approved building is a garage but changing it (variation of a condition) to a garden / office. Is he being too picky or should I consider another one? Wondering if the SIPs bit he did not understand! Outbuilding is 8m x 6m

 

 And what would be the approx cost for a 300mm/150mm slab vs 1000mm/1500mm one (south east england)

 

Any input appreciated! Cheers everyone

Edited February 15, 2018 by hmpmarketing

[nod]

29 minutes ago, hmpmarketing said:

Hey guys,

 

On my journey to build my garden / office I have been chasing quotes for a SIPS structure, (supposedly lightweight).  A couple of suppliers have already indicated that I would need 300mm footings and a 1500mm slab to sail through B.C. A quick email to my private BC (that approved my house) and his reply was :

 

"If the building was a garage the proposed footings would suffice, if the building is for another use full strip footings of at least 1 metre depth are required."

 

FIY, the approved building is a garage but changing it (variation of a condition) to a garden / office. Is he being too picky or should I consider another one? Wondering if the SIPs bit he did not understand! Outbuilding is 8m x 6m

I’m guessing that when you say 1500 mil slab You mean 150 mil

In any case 300 for a strip foundation would be very shallow for anything other than a garden wall

750 would to 900 would be about right for a garage

Depending on the ground

Even with an engineers drawing telling you to dig 750 down BC may inspect before you pour the foundation and request another 300 or more to be dug

On something that size you are not talking a massive difference in laboure or materials

I would budget to go down a metre and if you don’t need to go as deep you may save a little bit of money on concrete and muck away 

I’m not sure what labour rates are were you are But the two depths you have mentioned would be dug and concreted the same day

So it’s just working out your outlay for concrete 

29 minutes ago, hmpmarketing said:

 And what would be the approx cost for a 300mm/150mm slab vs 1000mm/1500mm one (south east england)

 

Any input appreciated! Cheers everyone

 

[bissoejosh]

1500mm for a slab must be a typo surely?!

[ProDave]

Exactly what size of office are you building?

 

Why are building control even involved?

 

You can build a building up to about 100 square metres and my making it "portable" it becomes exempt from building regulations (it is treated for BC as a "caravan" and does not need to be on wheels for that)

 

I have wired many such portable buildings, real sturdy well insulated houses but built with a few rules in mind that makes them "portable" even though they are intended as a permanent home. I certainly would not be involving building control for a garden office.

[hmpmarketing]

6 hours ago, bissoejosh said:

1500mm for a slab must be a typo surely?!

 

Sorry I meant 150

 

4 hours ago, ProDave said:

Exactly what size of office are you building?

 

Why are building control even involved?

 

You can build a building up to about 100 square metres and my making it "portable" it becomes exempt from building regulations (it is treated for BC as a "caravan" and does not need to be on wheels for that)

 

I have wired many such portable buildings, real sturdy well insulated houses but built with a few rules in mind that makes them "portable" even though they are intended as a permanent home. I certainly would not be involving building control for a garden office.

 

8m x 6m box (most likely SIPs), flat roof, so 48m2 (hence B.C.)...I call it "office" because thats where I plan to setup my computer and music practice. 

 

Can you clarify how I could make such a building portable if I need to sit it on some sort of foundation?  

Edited February 16, 2018 by hmpmarketing

[Ian]

@hmpmarketing

The best guide I've seen online is available as a free download here:

http://www.ecomobilehomes.com/planning/

It will tell you all you need to know

[ProDave]

This is Highland Council's definition of a "caravan" https://www.highland.gov.uk/downloads/file/1346/bst_018_caravans_and_mobile_homes

 

Note that in England and Wales a "caravan" can be larger than we are allowed in Scotland because at some pint the Caravans act was updated there, but not in Scotland.

 

As long as the building is capable of being moved in 1 or 2 pieces it can be classed as a "caravan" it does not have to be on wheels. @Crofter  is building his holiday home under this ruling and the Highland Council confirmed that being able to be picked up by a crane and put onto a low loader is sufficient to make it qualify as  a "caravan" as far as BC are concerned.

 

The only practical difference in your  case would be make the frame it sits on strong enough that it won't disintegrate if you put a couple of scaffold tubes under it an picked it up with a crane.  It would typically sit on pads or on a slab.

 

There was a Grand Designs house a few years ago that built a 100 square metre portable house building right to the limits of the definition of a caravan.

 

If you have a drainage connection, that will be subject to building control but nothing else will be.

[hmpmarketing]

32 minutes ago, Ian said:

@hmpmarketing

The best guide I've seen online is available as a free download here:

http://www.ecomobilehomes.com/planning/

It will tell you all you need to know

 

Thanks for the link, downloaded the PDF and will read :-)

 

17 minutes ago, ProDave said:

This is Highland Council's definition of a "caravan" https://www.highland.gov.uk/downloads/file/1346/bst_018_caravans_and_mobile_homes

 

Note that in England and Wales a "caravan" can be larger than we are allowed in Scotland because at some pint the Caravans act was updated there, but not in Scotland.

 

As long as the building is capable of being moved in 1 or 2 pieces it can be classed as a "caravan" it does not have to be on wheels. @Crofter  is building his holiday home under this ruling and the Highland Council confirmed that being able to be picked up by a crane and put onto a low loader is sufficient to make it qualify as  a "caravan" as far as BC are concerned.

 

The only practical difference in your  case would be make the frame it sits on strong enough that it won't disintegrate if you put a couple of scaffold tubes under it an picked it up with a crane.  It would typically sit on pads or on a slab.

 

There was a Grand Designs house a few years ago that built a 100 square metre portable house building right to the limits of the definition of a caravan.

 

If you have a drainage connection, that will be subject to building control but nothing else will be.

 

What if I have electrical connection to it, would it be subjected to BC? you mentioned drainage (wont have that), wondering about a permanent connection to a switchboard.

 

Im still puzzled why the SIPs supplier mentioned 300mm footings but BC is against this, Im having a call with him today, but dont want to give away too much

[ProDave]

In England and Wales, the electrics will be notifiable under Part P. Just use an electrician signed up with one of the self certification schemes and they will notify it for you. No need to contact building control.

 

I would have thought a simple foundation slav is all you need with this building sitting (not fixed) on top of that.

[hmpmarketing]

3 minutes ago, ProDave said:

In England and Wales, the electrics will be notifiable under Part P. Just use an electrician signed up with one of the self certification schemes and they will notify it for you. No need to contact building control.

 

I would have thought a simple foundation slav is all you need with this building sitting (not fixed) on top of that.

 

Well 150mm and 300mm footings would be considered simple I believe.....

 

Just reading the PDF form the site @Ian provided , regarding Caravans and Mobile Homes, reading the sample description letters:

 

 

If the SIPS panels are bolted to the slab, wouldn't it invalidate the whole argument of it being a mobile home?

Edited February 16, 2018 by hmpmarketing

[ProDave]

21 minutes ago, hmpmarketing said:

 

 

Just reading the PDF form the site @Ian provided , regarding Caravans and Mobile Homes, reading the sample description letters:

 

 

If the SIPS panels are bolted to the slab, wouldn't it invalidate the whole argument of it being a mobile home?

Yes.

 

Instead, make a free standing base say of 6 by 2 timbers that just sits on the slab, and fix the SIPS panels to that, making a rigid self contained building that is demonstrably portable by picking the whole thing up as one lump.

 

You can insulate between the joists of that base so it is instantly better than just sitting on a cold uninsulated concrete slab as your floor.

[hmpmarketing]

3 minutes ago, ProDave said:

Yes.

 

Instead, make a free standing base say of 6 by 2 timbers that just sits on the slab, and fix the SIPS panels to that, making a rigid self contained building that is demonstrably portable by picking the whole thing up as one lump.

 

http://www.valuemobilehomes.com/mobile-home-southampton-sip-panel-production/ 

[Crofter]

My 'portable building' sits on eight concrete piers, each about 450mm square and of heights varying between 150-900mm due to the slope of the site. These piers are themselves cast atop individual concrete bases measuring around 800mm square and of whatever depth was needed to reach firm soil (minimum 500mm from memory).

The building itself is a big monolithic box that should, in theory, be capable of transport by crane or low loader, just as a container would be.

BC have shown zero interest in my project, and I have had no contact with them other than my initial query to check if my proposal would be exempt.

[hmpmarketing]

Thanks guys for the feedback. In theory , footings for a mobile home are 300mm or less? or just a flat slab would do?

[hmpmarketing]

1 hour ago, Crofter said:

My 'portable building' sits on eight concrete piers, each about 450mm square and of heights varying between 150-900mm due to the slope of the site. These piers are themselves cast atop individual concrete bases measuring around 800mm square and of whatever depth was needed to reach firm soil (minimum 500mm from memory).

The building itself is a big monolithic box that should, in theory, be capable of transport by crane or low loader, just as a container would be.

BC have shown zero interest in my project, and I have had no contact with them other than my initial query to check if my proposal would be exempt.

 Similar to this?

 

https://swiftfoundations.co.uk/shop/swift-foundation-raft/

Edited February 16, 2018 by hmpmarketing

[ProDave]

1 hour ago, hmpmarketing said:

Thanks guys for the feedback. In theory , footings for a mobile home are 300mm or less? or just a flat slab would do?

My static caravan sits on a base of 300mm compacted MOT1 topped with a layer of gravel to make it look nicer. It sits on 12 piers of concrete blocks on their sides. There are 4 lengths of steel angle driven into the ground and it is strapped down to those at each corner to ensure it stays where it is when the wind blows.

[ProDave]

1 hour ago, hmpmarketing said:

 Similar to this?

 

https://swiftfoundations.co.uk/shop/swift-foundation-raft/

That would do. But I would not pay that much. Some timber from a builders merchant and those concrete pads look awfully like garden wall pier toppings, again from a builders merchant for a lot less no doubt.

[hmpmarketing]

Thanks @ProDave!