Concrete garage floor - cutting through it, building on it

[cskrimshire]

I need to install a drain underneath an existing concrete garage floor - ab out a 5 metre run. This seems to be a daunting task.

Would cutting through a channel using a motorised disc cutter be a viable m ethod? The floor is about 4-5 inches thick. I would be interested in hearin g of any experience with this.

As another task, I want to remove the up-and-over garage door and replace i t with a brick wall, having a normal door opening in it. Would it be safe t o build a brick wall (dimensions typical of a single garage door opening) s traight onto the floor, or would some form of footing be advisable? If norm al brick would be too heavy, I guess lightweight blocks and rendered would be OK.

Thanks.

Chris

[Tim Watts]

On Friday 28 June 2013 18:26 [e-mail] wrote in uk.d-i-y:

It would be possible - a lot of dust will result. You can hire push along water lubricated diamond cutters - like they use on the roads. But with a hand held 12" cutter, I would estimate it will take you a few hours to make the cuts but that's a bit of a guess.

But the notion of slotting out the trench is a good one and will allow the floor to be made good neatly and you will cause less damage compared to trying to smash it out the hard way.

It will be fine as the wall will only be supporting itself (as opposed to the roof). I have internal walls in my house that just sit on the floor slab. Brick should be find too - it's not *that* heavy.

[Fredxx]

I think you'll both these works are notifiable. If there is any chance of selling the house in the next 10 years or so, having a certificate saying it is done to standard may save an awful lot of heartache later on!

My experience of "rules" is that underpinning would be required for a permanent brick wall.

[Lobster]

We had a single-skin, single storey, block garage built about 12 years ago, on our drive so that one sidewall forms the boundary with next door. Now next door is actually about 18" higher than us, and there was (is) in effect a concrete step of that height running the length of our drives.

Building Control agreed that the 'upper level' concrete was substantial enough for the boundary wall of the garage to be built directly onto the existing drive, without having to away all the 'step' and digging out new footings (and the garage has certainly been fine).

Our garage wall of course bears the weight of the tiled garage roof, so takes much more load than the OP's proposed wall will exert.

[Roger Mills]

When we converted a built-in garage into a kitchen a couple of years ago, we replaced the door with a cavity wall with quite a large window in it - and left the original lintel in place, to hold up the second storey. Nevertheless, the BCO wouldn't let us build on the slab. We had to remove that bit of the slab, and put two concrete lintels across - supported on the foundations of the side walls.

Since your work will be notifiable, ask your BCO what will be acceptable.

[Farmer Giles]

I've done exactly what you plan to do - the drain that is. After asking around, I hired a Stihl saw with a diamond blade (about £60/£70 for a couple of days if I remember correctly). A lot of dust, get some protection, but a doddle - like a knife through butter (well almost!).

[Tim Watts]

On Friday 28 June 2013 18:39 Fredxx wrote in uk.d-i-y:

The drain might technically be - but I doubt if anyone's actually that bothered. OTOH the notification fee may be quite small for such a job and that can buy you quite some good advice from a decent BCO.

My advice to the OP there would be to drop in a single 6m pipe to avoid joints under the floor and don't forget to surround the pipe with 10mm pea shingle. That will pretty much guarantee nothing will ever go wrong with it.