Garage base - insulation, depth ,suggestions..

[alex s]

I am about to start to build a new detached garage at the bottom of my garden as the first stage of a general reburb of our house.
The size will be 4.5m x6.5m.
I am getting a man in with a digger to dig out for the base.
So 3 questions.

First, I am going to use the garage year round for working on the car and also to do some woodwork, so it needs to be fairly warm, with regards to the base, can I put kingspan underneath the concrete base(was thinking of 150mm reinforced slab)if so , should I lay it on a bed of compacted type 1. Is it worth adding a DPM(if so at which level)
will it be ok bearing in mind the weight of cars etc?

Second question, this maybe should go in electrical.. while I have the guy with the digger there I was going to get him to dig a trench to the house to lay some cable in (16mm T+E for the supply, 2 coax for sky and cctv, and a cat5e just in case and a 15mm cold water pipe) how deep should I ask him to go? Also can these all be put in the same trench(eg electric and water, can I use standard 16mm T+E if I run it in conduit(plastic).

Last question, the garage is going to be timber frame, do the outside walls on the boundary line need to be of a fireproof nature? As I was going to clad in feather edge boards. Make up of walls will be (from inside out) 12.5mm te plasterboard, vapor barrier,150mm studs at 400centers full fill with 150mm insulation,15mm osb, tyvec breathable housewrap,2x1 battens finally fe boards. IS this spec going to be ok, heat wise and fire wise.
Any suggestions or other options I have missed ?
Will be doing all the construction work myself to keep cost down.
Thanks in advance.

 

[hotrod]

Hi alex

First, I am going to use the garage year round for working on the car and also to do some woodwork, so it needs to be fairly warm, with regards to the base, can I put kingspan underneath the concrete base(was thinking of 150mm reinforced slab)if so , should I lay it on a bed of compacted type 1. Is it worth adding a DPM(if so at which level)
will it be ok bearing in mind the weight of cars etc?

150mm reinforced slab should be fine for domestic cars. I would include a DPM - your construction should be as follows, Type1, blinding sand, DPM, kingspan, concrete.

Second question, this maybe should go in electrical.. while I have the guy with the digger there I was going to get him to dig a trench to the house to lay some cable in (16mm T+E for the supply, 2 coax for sky and cctv, and a cat5e just in case and a 15mm cold water pipe) how deep should I ask him to go? Also can these all be put in the same trench(eg electric and water, can I use standard 16mm T+E if I run it in conduit(plastic).

I'm pretty sure your services can go in the same trench. You will need a min 750mm depth for the water and 600mm for electrics with appropriate warning marker tape. Not sure you should be using T&E perhaps SWA - but I'm sure a sparks can confirm that.

Last question, the garage is going to be timber frame, do the outside walls on the boundary line need to be of a fireproof nature? As I was going to clad in feather edge boards. Make up of walls will be (from inside out) 12.5mm te plasterboard, vapor barrier,150mm studs at 400centers full fill with 150mm insulation,15mm osb, tyvec breathable housewrap,2x1 battens finally fe boards. IS this spec going to be ok, heat wise and fire wise.

You may need Building Regs for this as "If the floor area of the building is between 15 square metres and 30 square metres, you will not normally be required to apply for building regulations approval providing that the building is either at least one metre from any boundary or it is constructed of substantially non-combustible materials" So if you're on the boundary, your sizes take you over 15m2 - however, I'm not sure how they classify "substantially non-combustible materials". I am sure someone like Woody could enlighten us.

hope this helps somewhat



[/quote]

 

[alex s]

Thanks for that.
If I go the BR's route, before I start talking to them, what part of the building regs applies to the construction, so I can look it up and base plans around this.
Will it have to be to the same standard as a habitable building?
Thanks
Alex

 

[hotrod]

If the Regs apply and I'm not sure they do, the building is likely to be exempt from certain parts that would be required for a 'habitable' building. Here's a few links that may help you out:-

http://www.planningportal.gov.uk/england/genpub/en/1115315233162.html

http://www.planningportal.gov.uk/england/professionals/en/1115314269469.html

I'm sure a phone call to your local BCO could clear this up for you. The key issue is really the definition of substantially non-combustible materials as you're using timber frame. If you were using traditional brick / block you would be exempt.

 

[^woody^]

The interpretation of "constructed of substantially non-combustible materials" means exactly that and if it is timber frame then it will require b/regs approval.

But by the sound of things the proposed timber frame construction is sufficiently fire-resistant structurally, however the use of timber cladding may not meet the requirement for external surface spread of fire. if it is within 1m of the boundary.

Its not a habitable room, and so there are no insualtion requirements. The BCO is mainy going to be looking that it is structually sound - ie wont fall, blow or burn down. Even damp prevention is not a requirement for a garage, buts its worth while!
Basically all the b/regs apply if you are incorporating controlled work. If your water supply is to just wash the car then thats fine, if its to a wash basin, then you will need drainage too.

 

[alex s]

Thanks Woody.
So will I have to provide plans and calcs?
I was planning on a sink, using a saniflow to connect it to the sewer via the trench back to the house, is this allowed?
To comply with the fire regs what could I use instead of the timber cladding, would it only have to be on the side that is within 1m of the boundry(eg could i still use timber on the side in the garden facing the house.
Sorry for all the questions.
Thanks
Alex

 

[^woody^]

If you know what you are doing, then you can do it on a building notice without plans. You would not normally need and calcs, unless you have non-standard roof timber spans.

You could have fire retardant treated timber to the boundary side, or fibre cement board like superlux or masterboard - you may be able to fix this behind the cladding, but it depends on the BCO. Precautions are to the boundary side only

You may also be able to get this rule relaxed if there is no neighbouring building on the other side of the boundary, and not likely to ever be one, so again ask the BCO

You will have to confirm distances/falls and pump rate of the saniflo. and again confirm with the BCO. As long as the waste will get to the sewer and no smells come back up, then it should be fine. Will probably have to be via a proper drain though and not the 2" saniflow pipe

 

[noseall]

You may also be able to get this rule relaxed if there is no neighbouring building on the other side of the boundary,

not if you are next to a field!

the fire risk rules still apply even next to a farmers field. it is true to say though, farmers can grow flammable produce.

 

[^woody^]

Yes, there is nothing like a flame grilled steak

 

[martyc]

youll need SWA and you should zig zag it a little to allow it to stretch if required due to ground heave...warning tape aswell as someone else said.
No prob with laying them all in the same trench
marty.

 

[JohnD]

I know nothing about these things, but a relation who had her large rural garage burnt down found that the quotes to rebuild it timber frame, were more expensive than rendered block (which seems to me to be a better building)

 

[alex s]

I know nothing about these things, but a relation who had her large rural garage burnt down found that the quotes to rebuild it timber frame, were more expensive than rendered block (which seems to me to be a better building)

Two problems with rendered block, I can build the timber frame, would have to pay for a brickie and plasterer. Also the block would need a lot more insulation to be as warm as the 150mm frame filled with insulation.

 

[alex s]

You may also be able to get this rule relaxed if there is no neighbouring building on the other side of the boundary,

At the boundary is a unmade access road to my neibours garage(which i own half of and have access over). Fingers crossed

 

[alex s]

youll need SWA and you should zig zag it a little to allow it to stretch if required due to ground heave...warning tape aswell as someone else said.
No prob with laying them all in the same trench
marty.

Thanks for that. If the cable is in conduit 750mm below ground, would i still have to use SWA, as the run will be around 35m and need to be either 10mm, or for overkill 16mm, guessing SWA 16mm is going to be very expensive. if it is the case, any suggestions where is the best place to get this.
Thanks
Alex

 

[^woody^]

At the boundary is a unmade access road to my neibours garage(which i own half of and have access over). Fingers crossed

In that case you should be OK. The reasoning behind the 1m gap is to keep a space between the buildings, so that flames can not jump across to an adjacent building. If its a road, then this regulation would not apply