dpm

[A Trowel]

where would my ventilation go?

So as to give air flow to the void under the joists

 

[electrified]

So as to give air flow to the void under the joists

what if i didn’t. as outside is being rendered.

 

[A Trowel]

what if i didn’t. as outside is being rendered.

Doesn’t matter if you’re getting banksy to paint it, no vents no building regs approval.

 

[electrified]

ok i understand this. but as i said earlier when the dpm goes up the wall can i penetrate this now and again with 2 screws for joist hangers? if not how else am i going to keep the joists in place?

 

[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

Also you say here that the dpm and dpc are not linked for a suspended timber floor??

 

[A Trowel]

ok i understand this. but as i said earlier when the dpm goes up the wall can i penetrate this now and again with 2 screws for joist hangers? if not how else am i going to keep the joists in place?

You’re planning on fixing joist hangers with 2 screws good luck with your project and even better luck with Build Control ( perhaps use private rather than local authority).

 

[electrified]

You’re planning on fixing joist hangers with 2 screws good luck with your project and even better luck with Build Control ( perhaps use private rather than local authority).

four screws then, either way i’m asking about penetration of the dpm.

 

[^woody^]

You don't have a DPM with a timber suspended floor

 

[electrified]

You don't have a DPM with a timber suspended floor

so just 50mm blinding sand and then concrete underneath?

why wouldn’t i need a dpm as damp could rise couldn’t it? would there be any harm in putting one and butting it to the brickwork instead of connecting it to the dpc?

is there a diagram you can point me towards?

 

[^woody^]

Search the NHBC or LABC standards, there are several illustrations

 

[A Trowel]

Timber ground floors:

Timber used for suspended ground floors should be treated or naturally durable, in accordance with Chapter 3.3 ‘Timber preservation (natural solid timber)’, and the ground below the floor covered with:

• 50mm concrete or fine aggregate on a polyethylene membrane laid on 50mm sand blinding, or
• 100mm concrete.

 

[electrified]

Timber ground floors:

Timber used for suspended ground floors should be treated or naturally durable, in accordance with Chapter 3.3 ‘Timber preservation (natural solid timber)’, and the ground below the floor covered with:

• 50mm concrete or fine aggregate on a polyethylene membrane laid on 50mm sand blinding, or
• 100mm concrete.

is this for timber laying on the concrete? not sub raised floors?

 

[A Trowel]

What does the first line say ?

 

[electrified]

What does the first line say ?

timber ground floors. so a floor with timber, raised or non raised

 

[electrified]

Timber ground floors:

• 50mm concrete or fine aggregate on a polyethylene membrane laid on 50mm sand blinding, or
• 100mm concrete.

So you do have to lay a membrane????? which one?