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House Ext - wall on existing floor q
Simon - 18/1/12 at 06:15 PM

Chaps,

I have permission to extend out house, one aspect of which is building on top of the existing garage to put another bedroom/shower room.

The garage is single skin so will need a second inner lining wall. Now, subject to a couple of test digs to ensure existing footings are ok, can I then build the second inner lining wall straight onto garage floor or should I remove this down to footings, build on that then backfill garage floor to new wall.

Hope this clear

Cheers very much

ATB

Simon


Ben_Copeland - 18/1/12 at 06:44 PM

Best to ask your building inspector. Almost certainly they'll want the wall rebuilding with cavity ties etc.

It would also depend on the construction of the original wall too.


snapper - 18/1/12 at 06:44 PM

It's got to bond with the footings which may not be wide enough and the new wall should be insulated and bonded to the old.
In reality it is easier, quicker and in the long run cheaper to knock the old wall down and start again.
Building regs on this must be followed


bigfoot4616 - 18/1/12 at 06:45 PM

can't you build the second skin on the outside? save you losing garage space.

wouldn't think you will be able to build of the garage floor. it will possibly only be 4" of concrete on top of a bit of hardcore.

its a few years since i've had anything to do with this sort of work but last time i did something similar building control made us dig down to the bottom of the original footings and pour more concrete to create new footings for the extra wall


zilspeed - 18/1/12 at 07:21 PM

I've done this before.

You have no way of verifying the suitability of the garage floor for carrying the additional load, short of cutting through it, but that' doesn't confirm what steel if any is in there.

The one we did, we had to cut a channel out of the floor, dig down to foundation level, tie new foundations to the existing and then build off that.


silverback - 18/1/12 at 09:01 PM

You have to dig down to the bottom of your footings to make sure that you have the right depth and width of the footings to be able to take the safety of your new building above. See a builder who will tell you what depth and width you will need to be certain that it passes building regs.
Once that you are positive that your footings is correct you can start building, don't forget the cavity, and as you are building up you will need to put ties in to strengthen both skins.
This is the hard way. The easy way will be to knock down and start all over and be right from the word go.
One thing I advise is to keep in with all building regs and the planning department.


zilspeed - 18/1/12 at 09:09 PM

quote:
Originally posted by silverback
You have to dig down to the bottom of your footings to make sure that you have the right depth and width of the footings to be able to take the safety of your new building above. See a builder who will tell you what depth and width you will need to be certain that it passes building regs.
Once that you are positive that your footings is correct you can start building, don't forget the cavity, and as you are building up you will need to put ties in to strengthen both skins.
This is the hard way. The easy way will be to knock down and start all over and be right from the word go.
One thing I advise is to keep in with all building regs and the planning department.


One bit I disagree with here.

A builder knows how to build stuff, not how to design stuff.
An engineer is required for the design.

Granted there are a great many that would get it right, but you're asking him to do a job that he's not qualified to do.
You need an engineer, that way you're buying liability insurance.


silverback - 18/1/12 at 09:53 PM

quote:
Originally posted by zilspeed
quote:
Originally posted by silverback
You have to dig down to the bottom of your footings to make sure that you have the right depth and width of the footings to be able to take the safety of your new building above. See a builder who will tell you what depth and width you will need to be certain that it passes building regs.
Once that you are positive that your footings is correct you can start building, don't forget the cavity, and as you are building up you will need to put ties in to strengthen both skins.
This is the hard way. The easy way will be to knock down and start all over and be right from the word go.
One thing I advise is to keep in with all building regs and the planning department.


One bit I disagree with here.

A builder knows how to build stuff, not how to design stuff.
An engineer is required for the design.

Granted there are a great many that would get it right, but you're asking him to do a job that he's not qualified to do.
You need an engineer, that way you're buying liability insurance.


Yes sorry I was getting ahead of myself. I do apologise.


zilspeed - 18/1/12 at 10:00 PM

I don't think there's actually any need to apologise, so please don't.

P.S. Welcome to the forum.


silverback - 18/1/12 at 10:26 PM

quote:
Originally posted by zilspeed
I don't think there's actually any need to apologise, so please don't.

P.S. Welcome to the forum.

Thanx for welcoming me to the forum.


ssc28 - 18/1/12 at 10:48 PM

Firstly, it is not acceptable to build off the existing floor slab in most instances, I'd suggest that you should investigate the existing foundation, it will probably be of insufficent width to accomodate the additional leaf of masonry.
It has already been said about builidng your new leaf of masonry on the outside of the garage and this is the way I would normally recommend. It will result in the garage not being reduced in size and the new room above will be in the order of 300mm bigger in each dimension.
Should the foundation be of insufficent width it is very simple tp overcast the scarcement and dowl into the existing to provide a suitable foundation. Additionally you will not need to break out the garage floor and a dig to the outside of the garage is likely to be easier too.


rachaeljf - 18/1/12 at 11:19 PM

We need to see some drawings/photos to properly help you explore your options.

Cheers R


Simon - 18/1/12 at 11:26 PM

Ours is on the left, neighbour on right did what we are planning to do - except our garage will be extended roadward by 10 feet and the porch by 5 feet

Neighbour has converted garage to study, we won't be.


[img] house
house
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Appreciate about tieing walls and insulation etc.

Prob best to place new wall on footings rather than onto floor or garage. Next door built new wall outside existing.

Will be doing building regs drawings soon so will mentioned to regs officer.

Cheers chaps

ATB

Simon

[Edited on 18/1/12 by Simon]


rachaeljf - 18/1/12 at 11:47 PM

Copying what the neighbours did will certainly be looked upon kindly by the local authority. When you say "permission" did you mean planning permission or other half's permission?

You've done well if you got planning permission to extend the garage forward, that's not generally allowed. I suppose you don't have enough space to widen the garage, developers always make their garages too bloody narrow to be useful


Simon - 19/1/12 at 12:24 AM

Planning permission granted Ours and the neighbour being in the round bit of the close are set back from the neighbours to the left of our house by about 25', so we are behind any sightlines.

Means I'll have a nice size empty garage (gotta sell toy car to help pay for it) but plenty of room for the next project

ATB

Simon


slingshot2000 - 19/1/12 at 12:37 AM

quote:
Originally posted by Simon
Chaps,

I have permission to extend out house,
Simon


1, who exactly do you have permission from ,

and

2, are you extending; an !"out house" or are you extending "out from the house" ?


Simon - 19/1/12 at 01:06 AM

The people I sent the plans and my money to - Tunbridge Wells Borough Council

No "out house", that was a typo that should read "our house"

ATB

Simon