Foundations and DPC

[jlaspire]

Evening all!

I know this is a Plastering forum but considering most people are really helpful I thought I would ask to see if anyone could help!

I'm trying to work out the process of extension footings and up the build to DPC? Does anyone have any knowledge of or know where I could get the best information?

Thanks in advance!!

 

[warriorupnorth]

Building control , contact your la , there 600 mm orv 900mm deep by 600 wide under normal circs in my area but that can change between authoritiesband depending on strata, soil comp, treesx, etc etc

 

[johniosaif]

I am assuming plans have been drawn up, are the not detailed? The depth is dependant on the ground and any underground pipes, build overs need permission from the water body, Thames water in my case, the dpc course would be done in engineering brick, have you spoken to the surveyor yet, the building inspector ,council or private will have to see it firstly when dug, then when poured ,then at dpc.

 

[johniosaif]

I no longer use building control from the local authority, I use my surveyor and structural and they send plans to my building inspector, more efficient and cheaper I believe

 

[raggles]

Some if not all will also require you to pin the new founds to the old depending on the nature of the build

 

[flynnyman]

run your damp in with your house or whats existing

 

[johniosaif]

run your damp in with your house or whats existing

Ground level dependant and if the old can be seen or is correct

 

[jlaspire]

Sorry should have put a bit more info in my first post. Its more just the basic principal of the set up I'm after.

Say footings are 1 meter deep, then filled with concrete to required level its the next bit I'm trying to work out.

Solid block work or brick up to dpc level. If your joining to an existing property does the new dpc have to be before the old one or set to the same level? Also does the cavity need to be filled with concrete if not using foundation blocks to this level? Does the internal concrete floor level have any criteria on the dpc also?

Sorry mixed bag of questions just trying to work it out as something I've never worked on only block and beam!

 

[raggles]

Set the dpc to same level as exsisting. once founds are set build upto dpc with engineering bricks or blocks of correct spec. Back fill area with sub base to required level and compact with whacker plate every 50 to 75mm of thickness added. Lay your insulation on top of this. Lay DPM and then fill and level with the concrete of your choice to required thickness.

 

[johniosaif]

Internal solid floor whether its screed or concrete will be a course or more below dpc.lots of this will be decided by factors on site ,ground level, existing floor, drains

 

[irish_spread]

Want a price on the plastering Marra ?

 

[Arti]

Ive got someone in mind for the dashing......................:RpS_wink:

 

[johniosaif]

Get an ugly girl , they are great at foundations and blushing

 

[User________removed]

Your footings will generally be 1m deep by .600 wide depending on ground, you don't have to fill your trench completely with concrete either, building control will advise you on what to put in, i think the last one i did i put .600 of concrete in. Start coming out of the ground with tench blocks or 7n blocks, once your close to what will be visible come out the ground with engineers blues or reds. The cavity will need to be filled with lean mix cavity fill then insulation, take your damp to marry in with existing.

 

[jlaspire]

Thanks for all the replies! If the dpc of the existing building is lower than the finished floor level of the extension (Timber floor on property) and I want a solid floor in the extension will the membrane I put down stop any issue with having the finished floor level above dpc inside?

 

[johniosaif]

Your dpm can be married into the dpc level ,also if you have a cavity you can hav a second dpc two courses higher, any ways the new dpc can be fed into the old dpc, this does not stop you raising the new dpc up a course or two.

 

[malc]

you may have to put air ducts across the oversite unless the timber floor has other air vents. you will have to put a duct through the footing if there are any services to enter the new build.
are there any trees near the new footings?
you could dig a test hole where the soakaway is going to be, then you can get some idea of the depth that needs to be dug. if it is clay you may need clayboards to protect the footings, you may need a metal cage in the founds. if you hit ironstone in you test dig break into about 6 inches then leave it get the building inspector to agree to the depth that needs to be dug.
we always go for the narrow dig, less soil to dump, and trench fill with concrete. dig in the morning fill in the afternoon do not leave the trenches open as there is a risk of a collapse.
you do know how to mark out the dig?

 

[jlaspire]

Thanks everyone for the replies. Think I've got the idea of it now. The project was for the conversion of an old conservatory which I was planning on taking down and starting again. Think I will be keeping to the old base now and just building within the limits to keep it classed as a conservatory. Will still need to add in a new dpc as the current build upto the floor level seems to be missing it. Another poor job the last owner left me with! Thanks again!