Cladding Parapet

[McCracken]

I'm cladding a parapet with OSB3, and was planning on running DPC up and over between it and the blockwork to keep it dry.

 

Parapet will get fibre glass.

 

I know OSB is waterproof, but I had some DPC left over and threw it in. 

 

Does anyone foresee any problems with that? 

 

Is it the done thing?

[PeterW]

1 hour ago, McCracken said:

know OSB is waterproof

It isn’t … it’s water resistant. 

[McCracken]

of course,  water resistant. I'm using DPC to separate from outer block assuming that it becomes more water resistant.

 

[Dave Jones]

id make sure to have a minimum of two outlets if its an enclosed parapet.

 

Is it a warm or cold roof ?

[McCracken]

I'm doing one per side to the front, enclosed and covered with fibre glass.

its a cold roof.. as in 100mm insulation between 6x 2 rafters.

I have run DPC down the side of parapet behind the battening for the valley and continued it up and over the block work behind the OSB.. and now Im thinking will condensation be a problem.

Overthinking is a speciality with me.. prob a thing with most DIY'ers

[McCracken]

Apols, warm roof..

[Dave Jones]

what vapour barrier are you using ?

[McCracken]

Looking at IZOPERM PLUS to the rafters for vapour and airtightness.

I'm going to install a HRV, its only 2 rooms btw.

Tyvek Supro above.

 

 

[Dave Jones]

you dont have a warm roof by the looks, you have a traditional breathable cold roof. Tyvec supro is a breathable membrane and will not stop moisture moving into your insulation.

 

You also don't need a vapour barrier with a cold roof as it doesn't really do anything apart from trap humidity inside the house.

[McCracken]

what would you recommend instead?

I was thinking HRV will deal with humidity, Izoperm was for create airtight.

 

[McCracken]

I thought cold roof was insulation in joists , assuming you don't have vaulted ceiling