foundation/extension queries

[thomp1983]

Hi All,

I'm looking into the idea of building an extension to the side of our chalet bungalow above the garage and have a few questions that hopefully someone can help with.

The first picture is our house as it currently stands, the second picture is a house further around the estate that has already a similar extension to what I'm thinking the main difference will be that I shouldn't need to have the hipped end to the extension, the neighbour had to do it that way due to the neighbour complaining about loss of light, to the left of our property is a footpath and the neighbours house to the other side of the path is a normal 2 storey house that has windows in the gable end looking towards our property. As I don't think we would require the hipped end I plan to build the extension up into a triangluler gable similar to that in the third picture.

Now for the questions,

1, The extension with hopefully run the full length of the house (approx. 8.5m) and the width between the house and fence is a touch under 3m, I know i'll need to remove the block paving along the edge upto level with the front and dig a strip foundation but what are the odds of the original garage foundations being deep enough to be able to build the extension straight on top or am I looking at demolishing the outside wall of the garage to allow me to dig full length foundations?

2, Where the outside of the garage wall will need extending forward would it be possible to either just build 2/3 pillars with a rsj on top to support the extension so I could fence in between to keep things visually similar or at least build 4ft walls between a couple of pillars, my concern is if I just build a brick wall 12ft forwards and at the same heoght as the current outside garage there will be a massive loss of light to the area in front of the garage which is where the front door and hallway are.

3, At the rear of the property the garage which is currently a flat roof extends back past the end of the house, where the rainwater would run off the rear of the new roof is it acceptable to just allow it to run onto the remaining flat roof which would then run into the garage guttering.

Thanks
Chris

 

[^woody^]

You'll need to gig a trial hole for the foundations.No-one here will know and neither will you unless you do.

Yes that's technically feasible to build piers and span a beam. Whether is aesthetically pleasing or acceptable to planners is another matter.

Yes you can run rainwater across a flat roof. Again whether it's the best thing to do is another matter, but it can often be the easiest way.

 

[frutbunn]

The foundation even if deep enough may not be wide enough if the JCB driver changed the bucket, although if you're intending to erect piers you will probably need new pad foundation anyway.
There is a potential problem with the open panels on the boundary, some building control bodies may take the view that this is unprotected area for fire space separation, so I would contact whoever you are using to establish this.

 

[thomp1983]

Thanks for the replies.

What sort of foundation depth/width would I be looking for if I dig a test hole? Presumably 600mm wide but how deep would be acceptable were on fairly solid clay where we live.

I only intend to build piers in the 12ft forward of the garage which is currently the 6ft fencing, for this area I would dig a 12ft trench foundation as this covers any eventualities ie. Building the piers so we can fit fencing and the wife then deciding she wants 4ft walls etc.

I hadn't thought about the fire aspect I'll have to check this with the local building control department once I finalise the idea.

Thanks
Chris