Foundation Under Garage Door?

[Tomsbuild29]

Good morning all! 

 

We are due to begin our garage conversion in the next month or so but wanted to ask the question before we start digging. 

 

Bit of background info: The garage is attached to the house and the back half of the garage has been converted (over 10 years ago) to an office and has been knocked through to the main house. The plan is to convert the front half of the garage into a WC/utility area. The foul drain is by the front door so the project will involve digging a new trench for a waste pipe, and also a trench for a water main from the kitchen at the front off the house, round the corner to the garage. 

 

My question is, is there likely a foundation below where the garage door was? A few people I have spoke to have loosely mentioned the need to lintel between the two. I didnt give it much thought at the time, but as the project comes closer I'm starting to think about it. I have interpreted what they said as - The foundation won't continue under the garage door (no need for it originally), and we'll need 2 lintels to bridge the gap between the 2 foundations. This could work well as we would then run the services under this lintel.

 

As most garages do, it has a concrete slab. The plan was to put 100mm PIR on top of the slab with 22mm t&g flooring. I'm hoping this will be approved by BC. 

 

Ps. Lots of homes on the estate have converted their garage and I can get it done under permitted development. 

 

Cheers!

Tom

[Nickfromwales]

I doubt there will be an existing found there tbh, and last garage conversion I did had to have one dig in and poured to satisfy the BCO before the dwarf wall under the window could be installed. 
Was some specified curing time for the concrete also, iirc.

Not sure how practical lintels would be vs pouring a found, as these will need concrete pours each end to take them anyways.

Maybe direct the pipe work / services after digging out, then protect them to build over, then do a pour. Depends if you can get lintels in, services under, and pads each end I guess. 
Are you DIY’ing? If not, make it the builders problem   

[saveasteading]

  On 31/10/2024 at 07:38, Tomsbuild29 said:

is there likely a foundation below where the garage door was

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No. It would have been a waste of money, so 95% there isn't. Probably easiest to do a full dig out and pour.

[Tomsbuild29]

  On 31/10/2024 at 08:37, Nickfromwales said:

I doubt there will be an existing found there tbh, and last garage conversion I did had to have one dig in and poured to satisfy the BCO before the dwarf wall under the window could be installed. 
Was some specified curing time for the concrete also, iirc.

Not sure how practical lintels would be vs pouring a found, as these will need concrete pours each end to take them anyways.

Maybe direct the pipe work / services after digging out, then protect them to build over, then do a pour. Depends if you can get lintels in, services under, and pads each end I guess. 
Are you DIY’ing? If not, make it the builders problem   

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Yes I'm DIY'ing! 

 

Interesting to hear! My neighbour laid straight on top of the concrete slab and it was all passed by BCO. 

 

I think pouring a new footing is going to be the answer, it's not exactly going to be a huge amount of concrete.

 

Cheers

[Tomsbuild29]

  On 31/10/2024 at 09:47, saveasteading said:

No. It would have been a waste of money, so 95% there isn't. Probably easiest to do a full dig out and pour.

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Yeah you're right. I think this is the best option. Just shutter round the services and lintel over. 

 

What about the concrete floor? Would you take this up and put a new insulated screed in? 

[saveasteading]

  On 31/10/2024 at 21:21, Tomsbuild29 said:

Would you take this up and put a new insulated screed in

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What is the ceiling height? Can you put a thin insulation down and screed over that. Put the bulk of insulation elsewhere.

check door heights too.

[Nickfromwales]

  On 31/10/2024 at 21:20, Tomsbuild29 said:

 

Yes I'm DIY'ing! 

 

Interesting to hear! My neighbour laid straight on top of the concrete slab and it was all passed by BCO. 

 

I think pouring a new footing is going to be the answer, it's not exactly going to be a huge amount of concrete.

 

Cheers

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Some are ok, some are jobsworths, that’s the problem. 
The info needs to come from your inspector not us tbh.

I’ve had one pass without, as you say, but we used Timberframe not brick and block to build back up. 

[Tomsbuild29]

  On 01/11/2024 at 07:13, Nickfromwales said:

Some are ok, some are jobsworths, that’s the problem. 
The info needs to come from your inspector not us tbh.

I’ve had one pass without, as you say, but we used Timberframe not brick and block to build back up. 

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Yeah I am getting that impression.

 

I've submitted our proposal to the local council and they have just come back with the fees associated with BC. Typically when would the BCO visit? Would they come out before the job begins so that we can discuss our proposal? 

 

Cheers! 

[Tomsbuild29]

  On 31/10/2024 at 23:39, saveasteading said:

What is the ceiling height? Can you put a thin insulation down and screed over that. Put the bulk of insulation elsewhere.

check door heights too.

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ceiling is 2520 from slab. Other half of the garage FFL is 155 higher. 

 

Cheers

[Nickfromwales]

  On 01/11/2024 at 11:32, Tomsbuild29 said:

Yeah I am getting that impression.

 

I've submitted our proposal to the local council and they have just come back with the fees associated with BC. Typically when would the BCO visit? Would they come out before the job begins so that we can discuss our proposal? 

 

Cheers! 

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You employ the BCO, so the sooner the better, but not before you have detailed construction drawings. 
The BCO will dictate the spec, and will tell you when they want to visit etc. 

[Tomsbuild29]

  On 01/11/2024 at 14:25, Nickfromwales said:

You employ the BCO, so the sooner the better, but not before you have detailed construction drawings. 
The BCO will dictate the spec, and will tell you when they want to visit etc. 

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Detailed constuction drawings for a Garage conversion? Is that really necessary? I was hoping for a D&B type project. 

[DevilDamo]

  On 01/11/2024 at 14:25, Nickfromwales said:

The BCO will dictate the spec,

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No they will not or should not, especially since the implementation of the BSA.

[DevilDamo]

  On 31/10/2024 at 07:38, Tomsbuild29 said:

The plan was to put 100mm PIR on top of the slab with 22mm t&g flooring. I'm hoping this will be approved by BC.

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Approval only comes via a Full Plans application, which in my opinion is a little overkill for a garage conversion. And the thickness of insulation is dependant on the P/A figure.

[Nickfromwales]

  On 02/11/2024 at 21:23, Tomsbuild29 said:

Detailed constuction drawings for a Garage conversion? Is that really necessary? I was hoping for a D&B type project. 

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For the structural stuff, I would. SE needs to be involved to spec, BCO to indirect and approve then sign it off. 
 

  On 02/11/2024 at 22:04, DevilDamo said:

No they will not or should not, especially since the implementation of the BSA.

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Agreed, sorry. As per above 👆 

SE needed then BCO. 

[kandgmitchell]

Is there much "structural stuff" in a garage conversion? At worst just dig a new foundation to match the existing so as to fill in the gap. The rest is sensible damp proofing and insulation. Save the SE's fees and put them towards the carpet!

[Tomsbuild29]

  On 04/11/2024 at 10:20, kandgmitchell said:

Is there much "structural stuff" in a garage conversion? At worst just dig a new foundation to match the existing so as to fill in the gap. The rest is sensible damp proofing and insulation. Save the SE's fees and put them towards the carpet!

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My thoughts exactly, won't be needing a SE! 

[Tomsbuild29]

  On 04/11/2024 at 10:20, kandgmitchell said:

Is there much "structural stuff" in a garage conversion? At worst just dig a new foundation to match the existing so as to fill in the gap. The rest is sensible damp proofing and insulation. Save the SE's fees and put them towards the carpet!

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I think we'll go with this approach, dig a new foundation and lintel over the services. Can't see why this wouldn't be signed off 

[Tomsbuild29]

  On 02/11/2024 at 22:06, DevilDamo said:

Approval only comes via a Full Plans application, which in my opinion is a little overkill for a garage conversion. And the thickness of insulation is dependant on the P/A figure.

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Yeah agreed, shouldn't need plans for a lowkey job like this. 

What's the process when they're are no plans? When would BC need to do their first visit? After trenches dug for foundation and services? 

[DevilDamo]

  On 05/11/2024 at 13:28, Tomsbuild29 said:

After trenches dug for foundation

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Correct.