Height from top of foundation to existing dpc

[ashworth108]

Hi I am about to set out my level for my foundations. Would you advise me to put my finished hight 225mm below the level of my existing dpc or 450 ? Many thanks

 

[noseall]

We set ours at 525mm down from DPC. This is so that we can finish with a single course of bricks on the inner leaf after laying the two courses of block.

Having this single course of bricks on top means that we can knock off the bricks in any door openings later on, when it comes time for screeding.

Setting at this depth also means that you have ample room for bottle gullies etc and have the potential of four courses of brick on show externally.

However, provided that the external ground level is pretty consistent and that there are no external gullies or such like to worry about then 450mm is acceptable. This would mean showing three courses of brick externally having laid a single course of block.

 

[^woody^]

Noses method makes sense regarding the door thresholds, but I'd say that its easier and cheaper to pour as much concrete as possible before starting the walls.

 

[ashworth108]

Thanks for this information. I take it I have to make my new
Dpc level the same as existing? It's just that my dpc level is about 2 courses below finished floor level. When I do my floor slab does that membrane below the concrete have to tie in with my dpc or can I make it higher? Many thanks

 

[noseall]

but I'd say that its easier and cheaper to pour as much concrete as possible before starting the walls.

Generally yes.
Just be aware that a higher concrete level can be prohibitive and can lead to some expensive breaking out later on.

 

[ashworth108]

Thanks for this information. I take it I have to make my new
Dpc level the same as existing? It's just that my dpc level is about 2 courses below finished floor level. When I do my floor slab does that membrane below the concrete have to tie in with my dpc or can I make it higher? Many thanks

 

[^woody^]

Thanks for this information. I take it I have to make my new
Dpc level the same as existing? It's just that my dpc level is about 2 courses below finished floor level. When I do my floor slab does that membrane below the concrete have to tie in with my dpc or can I make it higher? Many thanks

No, the new wall DPC should be level with floor level and the new DPM lapped under it. Step the new DPC down where it joins the main house, to lap the existing

 

[ashworth108]

Thank you all for replys. Woody I have only just seen yours and after doing research I'm still not 100% sure I've done the right thing; I laid the foundations on Saturday at around 460 below existing dpc which I am now having a few issues figuring out how to build up to floor level! My main issue is I know your outside floor has to be 150 below dpc. That will mean allot of soil to come out in the garden. If I raise the dpc it would make it much better for me. My height from the top of my foundations to the internal floor level is 650mm . I am hoping to have flush thresholds for my byfold doors that will go out onto decking (where the floor under decking will be 150 mm). If I do bring my dpc exactly to the height of my internal floor surely this cannot be achieved? Any ideas would be great? Thanks

Untitled

• ashworth108
• 25 May 2015
• 1

 

[^woody^]

You're making it harder than it needs to be.

Ground floor level is the datum to work to. All brickwork is gauged up and down from there, and thresholds worked out based on floor level.

Ground floor level is also DPC level.

You ignore the existing DPC and just lap the new DPC into it.

At thresholds, the DPC is taken down and under the cill

 

[ashworth108]

Thanks woody, yeah think I've made a balls up already but to be fair at the side I wouldn't have been able to go much higher unless I made shuttering. So I'll have to cut blocks to suite. Just to confirm it's to make it level with the top of my floor boards inside? Thanks for your help

 

[^woody^]

Timber floors higher than the DPC have thrown many people.

I'm presuming your new floor will be concrete. Mark the floor level on your trench corners (timber profiles) and when you gauge down, you only have to gain 15mm which is nothing. Three course of blocks will work on the inside, or all bricks if that's what you have. If blocks, leave the top course off at any openings, and run two course of bricks there instead as per noseall's post. Go for a slightly big joint on the first course on the concrete. That will be most if not all you need to gain.

 

[ashworth108]

Hi woody yes my new floor will be a concrete slab. After your previous post I was looking at using 2 blocks which would take me to 450 then cutting another one down to 190 in hight to get to my 650 internal floor level. So on the opening for my bi fold doors leave the cut down block and return to
It when it's ready to be fitted so I can work out the floor threshold? Feel like I've proper messed this first stage up as my old foundations are lower then new foundations due to the way I gauged this! just hoping a good brickie will sort this out!

 

[ashworth108]

Just to note it's all pebble dash so have no worries about bricks on show.

 

[noseall]

Just to note it's all pebble dash so have no worries about bricks on show.

What, even those below DPC?

 

[ashworth108]

No they are just rendered ,