mono pitched roof

[handyady]

Firstly I'd like to say Hi to everybody out there, I'm a first timer on this site and hope somebody out there can help.
Basically I'm constructing a single story extension to the rear of our house which origionally was to have a flat roof, after some thought and after the plans had been drawn I decided to change to a pitched roof. After consulting building control on pitch, span of rafter etc I know my rafters need to be 125x50mm on a wall plate of 100x50mm(birds mouth end).What i'm not so sure about is what dimensions the other wall plate needs to be (thats the one the top end of the rafter is attatched to).

I hope i've made myself clear

yours Hopefully
Handyady

 

[masona]

It would be cheaper, easier & quicker to have gang nailed plate trusses rafter made up which use less timber. Take the drawing plan to the truss rafter company & they will work it out what you need and comes with a instruction plan, the only details they need is the height of the pitch roof and the span. Providing I understand that you have got the okay to go ahead from the building inspector and the BCO.

 

[handyady]

Many thanks Masona
Trouble is I've already got the timber for my rafters lying in storageand to be quite honest i'm looking forward to the challenge.Any further advice would be greatly appreciated (useful or not).
As a PS Iwas browsing the general chat section when I came across your account of what happened to your son.Firstly I hope he carries on to make a full recovery and secondly I sincerely hope they catch the scum that did it.
Keep your chin up
Handyady

 

[masona]

Thanks handyady,

Quite easy to work out the roof layout, I start with the birdmouth first, the notch in a rafter that allows it to sit flat on the wallplate should be on more than 1/3 width of the timber, cut a small piece of a 4"x2" (100mm x 50mm) for the wallplate and a piece of 6"x2" (125mm x 50mm) for the top wallplate. You need to make a temporary square on the ground using 3:4:5 rule using 3 battens. Example, 3", 4", 5" or 3m, 4m, 5m and so on, which all meet on the external edge giving you 90 degree shaped like a triangle. (If you're not sure I will try & explain) The 6"x2" sample goes up whatever height you need and the 4"x2" sample wallplate to whatever span is it then the 1/3 height of the birdmouth sitting on the wallplate to give you the angle of the top rafter against the wallplate at the top. I understand what I'm writing but not easy to write it on here! The temporary rafter now become a pattern to cut more rafters. If you're still not sure I see if I can find a picture.

What is also important is that the top & bottom wallplate are dead level, if not, check with the pattern rafter each time as you goes along before cutting the next one.

 

[handyady]

Many thanks Masona

I understand exactly what you are saying and thats a great idea about doing the pattern on the ground to get the angle of the birds mouth etc.
Im starting tomorrow morning And i'll let you know how I'm getting on .
Thanks again
Handyady