Extension project

[P.J.]

Hi All ,
I currently live in a 3 bed detached house with a detached garage adjacent. There's a gap of just a few feet between the house and garage. I'm looking into extending above the garage to add a 4th bedroom and also to join the garage to the house. Both house and garage are 25 years old and of brick construction: garage single skin and house cavity wall with blocks on the interior leaf. The ground floor would become a larger garage with utility area.

My first thought is that the garage is obviously on a raft with little or no foundations so I'm going to either need to tear down the garage completely and start again with the necessary foundations, or possibly use a steel frame sat on piles on which to support the new bit of the first floor. I'm hoping to refit the garage roof on the new first floor.

If anyone can advise whether the steel frame is a feasible solution or any other widely used alternatives to those mentioned above that would be a great help.

I've tried to keep this brief so if I've left out any important info, please let me know.

Many thanks.

P.J.

 

[noseall]

Yes a steel frame is feasible, but, if the frame is to be supported on upright columns then these columns will require some beefy foundations.

This in itself can be impractical simply because of the size of the holes.

Sometimes it is better to dig down from inside the garage to create a strip foundation from which the inner skin can be built.

We recently 'encompassed' a garage by building three columns on the outside, up to first floor height. Steels and lintels then ran back to the house and along the length joining the three. From here we built a first floor extension.

 

[P.J.]

Thanks for the reply noseall, much appreciated.

So, is it OK to lay the strip foundation just under the inner leaf ? Is that because the inner leaf bears the floor loads and the outer leaf mainly just supports its own weight ?

Do you have any idea roughly the size of the foundations we would be talking about for the steel columns?

Thanks again,

P.J.

 

[noseall]

So, is it OK to lay the strip foundation just under the inner leaf ? Is that because the inner leaf bears the floor loads and the outer leaf mainly just supports its own weight ?

Correct.
The foundations will still need to be substantial enough to do the job and will probably wrap around the existing footings.

Do you have any idea roughly the size of the foundations we would be talking about for the steel columns?

1m x 1m x 1m. Probably.

 

[P.J.]

HI and thanks again for the useful advice.

The column foundations sound do-able for the layout I have. Of course I'll put everything out to the relevant pros for assessment and approval before I start hacking away with my jack hammer!

Just a thought about digging out along existing foundations: what's the normal practice for this to avoid collapse please ? I guess you have to dig and lay something like 1m long strips of foundation, 1m apart, then dig and fill in the gaps ?

Best regards,

P.J.

 

[jm2000]

Hi only last month we worked on a project like yours....25years you say, well you may want to excavate your foundation of you garage, if it was built 25 years ago 1980 onwards, it would of come under local authority and it should be substantial. your building control officer would be able to work along with your architecht and an engineer.

The building we worked on was a detatched house and garage, pretty much the same design as what you have by the sound of it.

the foundations were enlarged for the external skins, padstones were put on existing walls for the new steel framework and light weight block were used where possible.

How ever i must say it seemed like a lot of expense to go to. i would of thought it easier and cheaper to drop and rebuild the garage and extension on new foundations...than to go to the expense of bespoke steel framework and engineers reports.

 

[P.J.]

many thanks jm2000.

it will be worth checking what the garage is built on, and considering both steel and complete tear down/rebuild options when discussing with the engineer.

thanks again.

P.J.