dpm

[electrified]

extension. will have footing then 3 blocks flat on footing, then will have 2 blocks upright going to dpc. my question is that once i have put 50mm of sand then my dpm on the floor, when i get to the blockwork can i cement this into the nearest mortar joint. i was thinking of putting a few blocks then doing the dpm so i can put in under there nice and then carry on bricking up, kind of like putting in the dpc. the reason for this is because i will stud the floor which will be lower than the dpc. if i only butt the dpm up to the blockwork it is going to leave a section where damp can get up. so having it as like a second dpc below this will stop damp even more? i have left a diagram that might help you. thanks in advance

 

[^woody^]

look closely at the bit of wall between the dpc and the dpm.water will get across the wall there.the dpm needs to join the dpc.

 

[A Trowel]

“ stud the floor “, “ lower than the dpc” if you mean you are constructing a suspended timber floor, the dpm and dpc are not linked. There are a multitude of illustrations of the detail to be found online and ,bless them, the NHBC 5.2.10 covers damp and ventilation for this

 

[conny]

Basically what they are saying is your dpm must meet the dpc. Easiest way is to run your dpm up the wall and then overlap under the dpc.
Look for the NHBC rule that A Trowel has posted. This should explain the best way to do what you want to do.

 

[A Trowel]

Basically what they are saying is your dpm must meet the dpc. Easiest way is to run your dpm up the wall and then overlap under the dpc.
Look for the NHBC rule that A Trowel has posted. This should explain the best way to do what you want to do.

But it doesn’t for a timber suspended floor, in-situ concrete yes but suspended not

 

[^woody^]

But it doesn’t for a timber suspended floor, in-situ concrete yes but suspended not

Yes, there is no DPM but for a timber floor, the DPC must be below the floor.

 

[A Trowel]

Yes, there is no DPM but for a timber floor, the DPC must be below the floor.

Not necessarily, dwarf walls built off a suitable oversite concrete so the timber doesn’t come into contact with the actual shell is acceptable to many BCO

 

[Notch7]

Yes, there is no DPM but for a timber floor, the DPC must be below the floor.

Are you saying the internal DPC would be lower than external?

 

[electrified]

i have added to my diagram shown below. so i know i need a 150mm gap from concrete. my floor level will most likely be around the height of the dpc. is the diagram correct?

also say i was going to put joist hangers to the wall, would it be ok the penetrate this with maybe two screws for every joist hanger as the dpm is going up to the dpc.

 

[electrified]

“ stud the floor “, “ lower than the dpc” if you mean you are constructing a suspended timber floor, the dpm and dpc are not linked. There are a multitude of illustrations of the detail to be found online and ,bless them, the NHBC 5.2.10 covers damp and ventilation for this

in a suspended floor why are these not linked (going up the wall to the dpc). you will still have that small bit where water can get across.

 

[^woody^]

Are you saying the internal DPC would be lower than external?

The levels of the DPC in each leaf may be determined by the floor and ground levels, with a tray as necessary. However normally they would be at the same level if possible

But what I was saying is that a timber floor would typically have the DPC lower than the floor surface and the floor joists. Otherwise if there is a higher DPC there is a risk of damp ingress in the space between the floor and higher DPC. Yes, this situation can be dealt with via tray, but in principle that's how it is.

 

[^woody^]

Not necessarily, dwarf walls built off a suitable oversite concrete so the timber doesn’t come into contact with the actual shell is acceptable to many BCO

But it's still bad design, unless it is the only option.

 

[A Trowel]

i have added to my diagram shown below. so i know i need a 150mm gap from concrete. my floor level will most likely be around the height of the dpc. is the diagram correct?

also say i was going to put joist hangers to the wall, would it be ok the penetrate this with maybe two screws for every joist hanger as the dpm is going up to the dpc.

So where is your ventilation?

 

[electrified]

So where is your ventilation?

where would my ventilation go?

 

[A Trowel]

But it's still bad design, unless it is the only option.

Retro fitting you play the hand you’re dealt, BCO in hxxxley insists on ledgerboard wrapped in dpc, timber to timber hangers and damn mineral wool insulation, I mean why make life easy