new flat roof..timber

[george765]

Hi,
What sort of timber shold I be asking for, to build a new flat roof ?
joists need to be 170x50 and the plates 100x50.
I don't kmow anything about timber.
thanks for any advice.

 

[Deleted member 174758]

Ask for C16s for the joists. C16 is a structurally graded timber suitable for the job. The wall plates can be a lower grade, just rough sawn softwood - just tell the yard that you need them for wall plates - and make sure that everything is reasonably straight. How are you securing the wall plates and joists? Steel straps and truss clips? Or are you going to cross nail your trusses?

 

[george765]

thanks J.....
I am planning to strap down the wall plates and cross screw the joists down to the wall plate with my impact driver....sound ok ?

 

[Deleted member 174758]

I am planning to strap down the wall plates and cross screw the joists down to the wall plate with my impact driver....sound ok ?

Yep, sounds good to me

 

[Harbourwoodwork]

It sounds like your on the right track. I'll throw in my twopenneth. Any bent timbers put the curve to the top. Don't forget vapour barriers, insulation. Its a good idea to use tanalised timber

 

[foxhole]

Don't skimp on the noggins

 

[george765]

thanks all

some more questions....
the vapour barrier I need to put on before the insulation..is it anything special, like a breathable purpose made, or just a sheet of plastic ?
.
I will be using an impact driver and about 100mm screws...not used this tool much before, do I need special stronger screws so they don't break ?
.
I am going to board over before the insulation, then again after... what sort of board should I be buying for this pupose ?

george

 

[Harbourwoodwork]

Screwfix have vapour barrier. Use this on the warm side (inside) of the insulation. For roof boarding, any exterior grade boards. Impact drivers can shatter bits when driving big screws hard. Impact bits and bit holders help Just use standard wood screws with a rust proof coating, but getting the correct size screwdriver bits is half the battle, the screws you have chosen could be Pozi size 3 ,

 

[george765]

thanks h....very helpful....I think I'm ready to tackle the flat roof now (when the rain stops)

 

[foxhole]

I find these best for structural work, no broken/ stripped screw heads.
http://www.screwfix.com/p/timberfix-plus-exterior-timber-screws-6-3-x-100mm-pk50/80050
You can drive the 6 inch version straight thru timber without any pre-drilling etc.