Flat roof dilemma

[PeterW]

37 minutes ago, pritch said:

So how many of you did your own flat roof..just the timber part? 

I'm being quoted some crazy prices by chancers who think you have deep pockets because you live in a nice house.  

I'm very much hands on but I thought I'd leave this to the experts. 

I'm now seriously thinking of having a go myself.  

 

What size is it, and are you talking the rafters or just the boards and firrings..??

 

Most timber yards will cut to size for you on firrings to get the falls. Not difficult to then glue and screw in place. Boards are a two man job - depending on the final finish then OSB and Ply each have their own benefits. Marine ply is not required, all you need is WBP ply, sometimes called Malayan Ply. 

[Onoff]

6 minutes ago, PeterW said:

 

What size is it, and are you talking the rafters or just the boards and firrings..??

 

Most timber yards will cut to size for you on firrings to get the falls. Not difficult to then glue and screw in place. Boards are a two man job - depending on the final finish then OSB and Ply each have their own benefits. Marine ply is not required, all you need is WBP ply, sometimes called Malayan Ply. 

 

Does a ply flat roof need ventilating underneath in the same way OSB does?

[PeterW]

A cold roof needs ventilation every time. It’s a warm roof that doesn’t where the insulation is on top of the deck. 

[pritch]

Hi

It's 45 sqm kitchen extension coming off the back of the house.  9.5m wide and 5m out . 

250mm x 50mm c24 ,osb 120mm insulation, osb.

The things that worry me the most is the firrings strips and the hidden gutter.

I'm not sure if I need a trimmer plate bolted to the wall or should the trimmers go into the brick work? 

Thanks 

 

Edited June 7, 2019 by pritch

[PeterW]

Any penetrations through the roof such as roof windows ..??

 

Whats the final weather surface, GRP or Rubber..??

 

if it’s a hidden gutter, does it have a parapet roof ..??

[pritch]

Hi

Yes it has a 4x2 lantern in the middle with a grp surface. Sorry not sure what you mean about the parapet roof. (See drawings) 

Anyone dealt with this company before ? 

Their c24 in 6m lengths seems very cheap.... not sure if I'm missing something?? 

Thanks 

 

[mvincentd]

Consider your timing and if viable have your membrane contract in place and scheduled so you can properly weatherproof the osb deck fairly soon after it's laid.  I had a stressful fiasco:

 

[Laith J]

On 30/05/2019 at 14:28, Russell griffiths said:

You need the over hang,  facia finishing level with wall looks crap imho, what you do is reduce the depth of the joist after it has rested on the wall plate, so the non load bearing part gets reduced in depth, then build up another course of bricks to allow a slimmer more elegant facia

some of these new builds with there deep rafter depth and high roof trims end up looking like a supermarket. 

 

Russell do you have some sort of drawing as to how you would achieve a slimmer overhang (and fascia) on a warm roof? My current extension roof build up will be 8x2 joist, firring strip, 18mm OSB, VCL, 150mm Celotex, 18mm OSB and finally EPDM with traditional gutters, but im struggling to find a way to reduce the overhang thickness. This is all sitting on block - cavity - block

[Russell griffiths]

You will still end up with a 300mm facia

trim the 200x50 down to 100 at the end. 

So you will have 

100 timber 

18 osb 

150 insulation 

18 osb