1.2 metre foundation for 1m garage extension?

[Couyon13]

Hello

I’m wondering if anyone can cast any light on a problem I may have with my project.


I have a detached house with an attached single garage which I’m hoping to convert into a playroom/utility room.

To save having to move gas and electric and form a new opening for access from the house into the garage, the plan is to access this from a side door off kitchen which currently leads to the drive. In order to do this it would mean extending the garage out no more than 1 metre.


At the moment the existing garage roof is already continued right to where we wish to extend out to and this is also supported by a brick arch. I was hoping to simply brick up the arch and infill the extended part of the garage with the existing garage door so that it looks exactly as it is, just forward a little. Obviously it would all need insulting etc on the inside

The problem is, to the side of the brick arch is a manhole and a drain serving our downstairs toilet and next doors main bathroom feeds into this man hole.


Am I right in thinking foundations will be required for the infilling and therefore this will mean they’ll need to be taken down to drain invert level which I know is 1.2 metres?


Really wracking my brains on this as it’s such a small load and the arch structure is already there. I have uploaded some photos to explain.


Last week I submitted an enquiry to the water authority so hoping they are accommodating.

Also, the drain then runs downstream on the same line into our back garden and there’s a second manhole there so rodding etc could easily still be achieved on this drain and of course both manholes would still be accessible. It’s more the foundations for the little we need to come out that’s causing an issue.


Thanks so much for any help.

 

[KenGMac]

How about timber frames?

Ken.

 

[Notch7]

As it’s a public sewer you will need a build over agreement.

it’s a tricky one as I’m not sure how you could get the founds 150mm below invert without rebuilding the pillar.

if by good fortune that pillar is sitting on a foundation that’s deep enough (it could be on a pad, but my guess is the foundation is one long strip and goes under the arch) then you could put in a steel lintel and encase in concrete and build off that.

I suppose in theory you could underpin the foundation if it’s not deep enough, but not much fun there.

 

[Tigercubrider]

What about SIPS?
Or using UPVC units akin to shop fronts? Or big porches?
A place I used to work at originally had timber frames between a steel frame, with metal window frames and possibly asbestos or some other sheet material infill panels at the base to waist height.
The building was refurbed with UPVC windows and the bottom panels were replaced with solid panels that were UPVC faced but presumably had insulation.

Looking at the photos you could have a new side door fitted to the arch, retaining access, and infill the front with a UPVC window, maybe using brick slips as a facing ?

I don't know the rules but so long as you don't claim it as a habitable room, the rules are different?
A mate's detached garage is converted and is dry after 20 years

 

[Tigercubrider]

https://gardiniawindows.co.uk/blog/case-studies/new-upvc-porch-huddersfield-mr-mrs-warhurst/

 

[JohnD]

put the door at the other end of the kitchen.

 

[^woody^]

You can block that archway up (on new foundations) now without any permission from anyone. Then it's "existing" when you apply for b/regs for the conversion.

Likewise, you could put a 150mm slab in with thickened edges and reinforcement now without any permission. Or form the slab when you apply for b/regs and form a timber frame internally and brick skin externally if that's what you want, as this would normally be acceptable on a suitably thick slab