Dpm + dpc

[Jake2021]

Afternoon

Could anyone advise on how I connect my dpc to my dpm please?

It’s my famous self build porch lol

I’m nearly out of the ground and upto dpc level I’m confident how to lay the dpc and also how to lay the dpm but unsure how they join to get her or if they even do on a single skin porch ?
Thanks
Jake

 

[noseall]

Afternoon

Could anyone advise on how I connect my dpc to my dpm please?

It’s my famous self build porch lol

I’m nearly out of the ground and upto dpc level I’m confident how to lay the dpc and also how to lay the dpm but unsure how they join to get her or if they even do on a single skin porch ?
Thanks
Jake

They don't join as such, rather both are laid in mortar. We cut our DPM back so that it laps about half way or more onto the masonry. We lift the poly then put a bed down and trowel the poly into the bed, then but more muck down and bed the DPC onto that. There is no harm in leaving the DPM to fully cover the masonry. I just like the thought that I've got some grip from the DPC to the top of the wall.

 

[SpecialK]

I did it as noseall describes but if I was to do it again I would use 300mm DPC and let it overhang internally. Once the wall is up a bit tape the DPM to the DPC. I'm only a DIYer and found trying to sort the overlap of DPM whilst plopping thermalites on a complete faff.

 

[noseall]

I did it as noseall describes but if I was to do it again I would use 300mm DPC and let it overhang internally. Once the wall is up a bit tape the DPM to the DPC. I'm only a DIYer and found trying to sort the overlap of DPM whilst plopping thermalites on a complete faff.

You should never breach the cavity unless instructed to do so (cavity tray - Radon etc).

 

[Dereekoo]

You should never breach the cavity unless instructed to do so (cavity tray - Radon etc).

His is a single skin wall, whether he means single skin or 1 brick thick?, but no cavity to worry about in this instance

 

[SpecialK]

You should never breach the cavity unless instructed to do so (cavity tray - Radon etc).

Breach the cavity? The 300mm DPC goes on the internal wall (stopping at the cavity) and the excess 200mm continues inside the property to tape the DPM to.

 

[Jake2021]

It’s a single skin ie no cavity just going to be single block and render
Thanks
Jake

 

[SpecialK]

Are you using some nice bricks below the DPC or will you try and render below DPC level?

 

[Jake2021]

SK I’ve used blocks under ground the I’ve changed to blues for the next 4 corses which is where I need to be for my Dpc level as my garden and house are two different levels lol

Im Still Learning a lot of stuff as I go and picking up advice off you guys which I’d be stumped without so thank you.

I may be wrong but in my head I had it that if you use engineering bricks at the bottom this in itself can act as a dpc? I’m still going to use a Dpc but thought it would be better this way? As I say I may be really wrong in my thoughts.

The other thing I’m unsure of is if you need insulation under a concrete floor? I’m extending our original porch( pvc) taking that down and building brick … I only have to extend it by around 120cm square so when I dug wh footings and trench filled I was pretty much left with a concrete base ( obviously a lot lower then Dpc so I don’t need any type 1 just sand then my layers

Thanks
Jake

 

[tell80]

Very basic Best Practice says:
1. You dont "render below the DPC".
2. You dont tape the DPC to the DPM - there's no need.

3. The DPM is spread out on the sand blinding, and allowed to run high where it flops against the masonry - high enough to have an allowance that overlays the DPC.
4. On cavity walls the DPM is cut back if it peeps into the cavity.

5. Field and edging Insulation is set on the DPM - the slab is then poured.

Any of the above might have variations depending on circumstances.

OP, before you do any work of this kind its best if you draw a full size section of what you propose to do.

 

[Dereekoo]

SK I’ve used blocks under ground the I’ve changed to blues for the next 4 corses which is where I need to be for my Dpc level as my garden and house are two different levels lol

Im Still Learning a lot of stuff as I go and picking up advice off you guys which I’d be stumped without so thank you.

I may be wrong but in my head I had it that if you use engineering bricks at the bottom this in itself can act as a dpc? I’m still going to use a Dpc but thought it would be better this way? As I say I may be really wrong in my thoughts.

The other thing I’m unsure of is if you need insulation under a concrete floor? I’m extending our original porch( pvc) taking that down and building brick … I only have to extend it by around 120cm square so when I dug wh footings and trench filled I was pretty much left with a concrete base ( obviously a lot lower then Dpc so I don’t need any type 1 just sand then my layers

Thanks
Jake

Pointless putting insulation in base slab if walls are not cavity ot insulated

 

[Jake2021]

der, I was planning on building a stud frame internally and insulated however if there is no need In the floor I can just poor my concrete thanks

 

[tell80]

Insulation in the floor is to prevent heat loss - which means its far from "pointless".

 

[Dereekoo]

Insulation in the floor is to prevent heat loss - which means its far from "pointless".

Agree if he's going down the line of insulating the walls otherwise just peeing in the wind although a floor that size is diddly squat compared to wall area. Also if he's not heating the porch there is no heat to retain.

 

[tell80]

Heating or insulated stud walls are irrelevant to the basic best practice - The Bldg Regs require that insulation goes into all interior pours.
The Bldg Regs are for now, and all future owners of the property.

The OP can do what he likes with my above explanation, such as adopting it to his preference but now he knows how to do the job correctly.