Roof boarding.

[Gilesda]

Hi all.
I'm looking to overboard my flat garage roof before laying a new covering. I'm doing this because the roof currently has floorboards and if I use EPDM then they won't be much use.
I want to keep the boards as thin as possible because of where a cooker hood exit grill is located just above the roof level. Would 6mm ply sheets be ok to use or are they likely to warp?
Thanks.

 

[sircerebus666]

No, 6mm is far too thin , that would give you issues with drainage when it rains and cause pooling causing the roof to sag , same when it snows and you could never use ladders or stand on your roof as you would in all likely go straight through it

Why do you want to keep it thin because of an extract pipe that doesn't make any sense , it's no different cutting a hole in 25mm board as it is cutting one in 6mm board

 

[oldbutnotdead]

Sounds as if the grille comes through the wall rather than the roof...
Ideally your 'flat' roof should have some fall towards the guttering (or drainhole if you've got parapet walls).
That grille will be a pest to weather as well, how much of a chew would it be to lift it by 200mm or so? Other options are going to look odd and be a pain to weather

 

[Alastairreid]

6mm ply is too thin, you won't get the edges to sit neat enough.
You need a minimum 11mm to overboard.

 

[oldbutnotdead]

Your easiest way out is probably to lift the old felt and roof boards, that'll buy you enough depth to put some chunky boards down

 

[catlad]

You mean like a proper roofer should do?

 

[oldbutnotdead]

You mean like a proper roofer should do?

Yep, but seems lots either don't want to know whats under the felt or don't want to have to dispose of the rubbish....

 

[catlad]

Or bring the insulation up to current standards.

 

[oldbutnotdead]

Or bring the insulation up to current standards.

Yeah that too

 

[Gilesda]

I didn't get any alerts for this thread and thought I'd had no replies.
Thanks to everybody who did reply.
Sircerebus666: I was talking about overboarding the existing floorboards that currently form the roof. Not taking them off and replacing with 6mm ply which as you say I'd likely fall through.
Also the grill comes through the wall just above the deck. Obviously if I add more boards onto the existing then I'll have even less of a flashing then I have now which is only about 40mm below the grill.

Sounds as if the grille comes through the wall rather than the roof...
Ideally your 'flat' roof should have some fall towards the guttering (or drainhole if you've got parapet walls).
That grille will be a pest to weather as well, how much of a chew would it be to lift it by 200mm or so? Other options are going to look odd and be a pain to weather

The ducting for the extractor runs through the void formed by the kitchen ceiling and the upstairs floor. It then exits straight through the house wall to just above the garage roof deck. It will be impossible to lift it any higher for obvious reasons. I could half the size of the grill which would give me another 50mm or so.
I think I'll do what you said, completely remove the old deck and board it with 18mm osb. I'll be no worse off if I do that.

 

[catlad]

It will also give you the option of seeing what insulation you have, and whether or not you can improve it.