Trusses

[rosinante]

Hi Chaps ,
I am building a porch , dwarf walls with glazing above , it will have a pitch roof with concrete tiles , cut into a facing pitch roof. I will have to form 2 valleys . What size timbers will I need for the trusses , span is 2 metres , the depth about 1.8 m inc front overhang , they will be on 16 inch centres . Roof pitch is 35 degrees or there abouts .
I am hoping to have a vaulted ceiling . It's on a bungalow which has low soffits just above the front door so a ceiling that height would seem claustrophobic. Also I plan to have laminated 100mm sq posts at front corners , the wall plate supported on these , another query what shape, section should this be please , I have ordered drawings but am fed up with waiting for them , any help advice most welcome ,
Thanks
Chris

 

[baldkev]

For a span of 2m 4x2 should be fine. Wall plate would be 4x4 to match the post. A 4x2 on its flat won't be enough over 1.8m. Are you going to want the valley rafters hidden or visable? Remember that the centre of the valley rafter is the centre of where the 2 pitches intersect both top and bottom, so when setting the rafter, it'll be lower than the common rafters.

 

[rosinante]

For a span of 2m 4x2 should be fine. Wall plate would be 4x4 to match the post. A 4x2 on its flat won't be enough over 1.8m. Are you going to want the valley rafters hidden or visable? Remember that the centre of the valley rafter is the centre of where the 2 pitches intersect both top and bottom, so when setting the rafter, it'll be lower than the common rafters.

Thank you gor your reply, Well I have never done this before , I was thinking that a vertical blanking above the house wall plate would trim that.
Armed with the dimensions and sections I am hoping to make a decent job of it, the 4x4 timber available would have to be glued and screwed to laminate the section up. I was just going to use galvanised ironmongery to secure the wall plate to posts and also strap the structure to wall, foundation .As for seating the wall plate on the corner posts would a simple mitre suffice? Or is there a more robust way? Again thank you for advice ,
Chris

 

[baldkev]

If i understand what you are doing correctly, you will end up creating a u shape of 4x4 material to go over the posts to take the rafters and tie the front gable together. You can cut the ends of the timbers on the wall plates to allow the front crossmember to join in. It could be a half lap, fixed down through into the posts.
Of course all of the above is just my opinion and i am not a structural engineer

 

[Jameshow]

A picture or sketch would tell a 1000 words!