Can I Build over concrete?

sebastianj

I have an outside wall, through which I am planning to fit a door and build a kind of enclosure on the outside (a utility room).

The outside space is already concreted over, if I have another 6inches added to it, then is it possible to build an enclosure? The total area is about 990 cubic feet which I believe does not require planning permission. Do I need any damp protection between concrete and the outside wall?

Your help most appreciated as I cannot afford to have it done, I am using the Bricky tool to do that, hope I survive till it is built.
rgd
seb

ukwoody

You could really do with ascertaining just what the existing concrete is like, regarding depth and footing. Now I'm not a brickie or a builder, I speak as experinced chippie, so I'll be a bit careful what I say, and allow other trades to comment more.

Theoretically anoth 6" over the top, especially if you put some re-inforcing in place may well be sufficient for a very basic utility area, but I have many worries. By adding that much concrete over the top you are adding a LOT of weight to the are, plus the brick wals, plus roof. Thats probably several tons of weight. This could mean that the existing conrete basically sinks in the ground under the weight of it all, thus taking the new build with it. Thats basically subsidence.
Yes you will need a dpc layer.

You quite possibly do not need planning permision but may well need to meet building regs - unless you can prove it is a non permanent structure - ie can be removed.
You may also have real problems in the future trying to sell the property if any surveyor cares to take a look at it and you dont have the paperwork ness. I had real problems about 5 years ago selling my old house. I bought it with an existing extention no probs. Due to a change in planning laws, they can now be back dated, when I triedo sell it on I got hammered by 3 different surveyors as there was no paperwork to prove everything was legel and built correctly. I had to pay for a structural engineers report then an Insurance policy for the new buyers that indemified them against various possible future actions. The cost? £1700 in total plus 3 lost sales, plus £20k off the asking price to shift it.
Never ever again!

Woody

sebastianj

Many thanks UKWoody for your help,
May be concreting over the whole area is not such a good idea, what about concreting only under where the bricks are going, about 1 foot or so?? I could try and support the walls with wooden structure and plaster boards on the inside?

I will check with the planning next week, perhaps involvement of the building control is a good idea as I have no confidence in my DIY as long as it looks good, its OK.

What do I use for DPC? this has never made sense to me, I have seen builders putting polythene sheeting in between wall, is that DPC?

rgd
seb

ormus

you really need to dig some inspection holes next to the main house to see what depth the foundations are at present. if you do the same you should be safe enough.
although new regs may require deeper foundations. ie 130cm deep is not unknown. all areas are different, esp if subsidence is known in the locality.
(i helped in one extension a few yrs ago and the depth req was 1100mm.)

re the dpc. that is usually placed a few courses above base level. see your present house and use the same level.
you may not require PP, but you will certainly need to follow building control regs.
http://www.wickes.co.uk/DPMs/Damp-Proof-Course/invt/152856

sebastianj

Many thanks ARMUS,Cant see how inspection holes will help, House wall is one side, opposite is a partition wall with my neighbor. So what I am building is about 2x5 foot strip of walls. If I put in a door to one side and fit a small window on the other end, then the brick work will be very little, I just need some encouragement.

I thought of using wooden structure, but now I have got this Bricky tool, got to use it, seriously though, there is no subsidence issues in the area I live in. This structure will not add any weight to the original house, its 1928 brick built. Is there a good book I can read before I do this? I am so confused.
rgd
seb

Morty_007

sebastianj wrote: »

Is there a good book I can read before I do this? I am so confused.
rgd
seb

:eek: Yes, it's called the yellow pages!!:eek: :rotfl: good luck!

tanith

I really don't think this is a DIY project for someone who seems to have little knowledge of building... its ok building two walls and putting in doors and windows but you have to consider lintels over the door and windows and of course then there is the roof ... how are you going to support the roof and what will you use for roofing material.. it takes some experience to be able to make a roof waterproof... I really think you are taking on more than you are able to deal with... but good luck with your project...

peediedj

sebastianj wrote: »

Many thanks UKWoody for your help,
What do I use for DPC? this has never made sense to me, I have seen builders putting polythene sheeting in between wall, is that DPC?

rgd
seb

thats dpm,usually blue or black

sebastianj

Well, I think I am now convinced that this project is not for me. If I can't tell the difference between DPM and DPC then what will my cement mix like. Thanks Morty, tanith and peediedj.

rgd
seb

Morty_007

sebastianj wrote: »

Well, I think I am now convinced that this project is not for me. If I can't tell the difference between DPM and DPC then what will my cement mix like. Thanks Morty, tanith and peediedj.

rgd
seb

Relieved to hear you say that! :T

DPM = Damp proof membrane
DPC = Damp proof course
Your DPM forms a part of your DPC

Some things are best left to the pro's!

ukwoody

sebastianj wrote: »

seriously though, there is no subsidence issues in the area I live in. This structure will not add any weight to the original house, its 1928 brick built.seb

Seb, it's not the weight adding to the original house. It's the slab of concrete you want to build on thats the problem. Beleive me, that can move/sink/subside/crack all on it's own. It might only be 2" thick which is why Ormus(i think) said drill some exploratory holes.

If you go to a house, lets say 30 years old. Got a concrete path down the garden. I bet it's cracked and got holes or the edges have gone on it. Why? Probably becaues it's only 3" thick concrete on a poor base. That could be exactly the same as the bit you wanted to build on.

I see you haver decided not to go ahead with it. OK thats fair enough, BUT since you've got the urge, since you've got "The bricky", do you know of a friendly builder who might pop round, take a look and give some general advice? However it must be said given your description of the strip I rather suspect it would be of no worth what so ever to risk building on it as it sounds like a glorified path.
Woody