Over-garage extension

[Gooner239]

Good morning all.

I've dipped in and out on this site for a number of years and the DIY advice has been very informative and useful, but now I need some real advice on the big one - extensions.

We are looking at buying a house that has a garage on the side and would like some advice on the feasbility of an over-garage extension. While there's plenty of details over the web on HOW this is done (technically) there is one snag with this house that I am frying my brain.

The garage was built as an add-on to the original house around (we believe) the early 80's. However, on plan, the garage is not "square" to the house - i.e. the rear is wider than the front, following the bounday line of the property. The house is an end-terrace with a hip roof.

I would really appreciate some advice on the following:

(a) assuming that the floor plan of the upper floor extension was to follow that of the garage, is it feasible to extend the hip roof given the odd shape, or would we be looking at a flat roof?

(b) If it can be done (roof extended) how much grief (and therefore cost) are we looking at over a standard (square) roof extension?

(c) If flat roof is the way to go, dows anyone have any idea how planning are likely to react to this - is a conflicting roofline normally a no-no?

Really grateful for any advice of any kind, since if we are looking at lot of grief then we most likely will not put in a bid.

 

[rjm2k]

Don't forget that the garage foundations also need to be deep enough to support the additional floor.

 

[Gooner239]

rjm2k - Thanks. I'm aware there will very likely be some foundation strenghtening work needed - my query is more to do with the roof geometry and if it's possible/practical.

 

[freddiemercurystwin]

rjm2k - Thanks. I'm aware there will very likely be some foundation strengthening work needed - my query is more to do with the roof geometry and if it's possible/practical.

Actually this is more fundamental, financially and practically speaking, if the existing foundations are inadequate, it will probably be easier/cheaper to rebuild the whole lot from new foundations up rather than strengthen the foundations as you put it. Is it single skin or double skin, single I’d wager, which means you’ll need to support a floor and an inner skin at first floor level and above, potentially another deal breaker. The only way you’ll find this out at this stage is with a trial pit down to the foundations or two. Even if you happened to have Regs drawings showing a foundation likely to be adequate BC are very likely to insist you dig a hole to prove what’s there.

You’ve not said if the garage is the full depth of the house in line with the front wall or back wall or whatever? Anyway

a) Yes, though often a full height side extension would be expected to be subservient to the existing dwelling and that would mean the roof pitch were slightly lower.

b) Not much, I don’t see why it couldn’t still be done with trusses.

c) Apart from it looking awful its unlikely to meet with Local Plan guidance so likely to be rejected.

 

[luisdesign]

just to clarify, freddymurcerystwin means that the "ridge" of the new roof should be slightly lower... the pitch of the roof should ideally match the existing roof.

Incidentally, this usually also results in the extension stepping back from the main house too.

In any case, it is all doable... it's really just a matter of how much it will cost to do it. As well as how willing the planners are to play ball or what type of restriction / limitations they may try to impose on you.

As already pointed out though, it is sometimes simply much better, easier and cost effective to build from scratch...

 

[Gooner239]

Thanks to all.

Should have clarified that the garage does run full length of the house (c. 22') and the front and end walls are square to the original house external wall.

The snag with take-down-and-rebuild is that there is also a full-width ground floor extension that abuts the rear of the garage, built as an add-on to said garage.

looks like this one could be dead in the water financially, as it looks as good as a two-storey build from scratch, and I haven't got a spare £50k knocking around!