Lap joint a cantilever timber

[angelboy]

I'm building a shed, 3.6m x 2.7m using 4x2 timber framing and was thinking about extending the roof on for another 1.2m to provide a sheltered area.

I'm doubling up on the wall plate and I already have some 4.2m lengths but not 4.8m lengths. I've read the general rule of thumb for a cantilevered beam is that you don't go more than a third the full size of the timber.

So could I lap joint the bottom timber, at say 4m with a 800m short section, which falls about the door frame and then stagger the next timber at around 2m to be above the opposing side of the door frame?

The roof at the over hang will just have a 3mm onduline covering with exposed rafters underneath so very little weight (other than snow of course).

I have some old porch brackets but I only wanted to add them as decretive as I'm not sure the state of the timber.

I don't know if you can see the lap joints above the door frame on this shot.

 

[MikeG.]

With proper braces this isn't a cantilever, and you can do your top plates anyhow you like (although I would keep the joint well away from the end wall of the building). However, this does mean doing the gallows brackets properly, not just as a decorative feature.

Please, you will curve those brackets the other way, won't you. That looks awful that way.

 

[angelboy]

With proper braces this isn't a cantilever, and you can do your top plates anyhow you like (although I would keep the joint well away from the end wall of the building). However, this does mean doing the gallows brackets properly, not just as a decorative feature.

Please, you will curve those brackets the other way, won't you. That looks awful that way.

I just thought I needed to have the joint above one of the uprights but if it can go anywhere then I can move the back joints closer to the middle.

The brackets are from a Victorian property I think. I bought them years ago so the sketchup drawing isn't supposed to be exact replicas, they were just to give me an idea of the dimensions. I'll take a photo later to show you. I wasn't sure of their structural capabilities to be honest. I'll investigate tomorrow.

 

[angelboy]

As promised - this is one of the brackets. Maybe they can be used for the support as they're quite substantial.

The top is rotten but I can trim the timbers down. The rest of the timbers seem solid enough.

 

[MikeG.]

If you can get those fixed in place securely (ie bolts rather than screws or nails), then those would be fine. I don't think I'd be extending the plates more than 300mm or so out from the top of the brackets, though, so you may have to rein in your overhang ambitions somewhat.

 

[angelboy]

Thanks Mike, I really appreciate your response.

I'll be able to bolt them into the frame by turning the corner posts round.

The planned roof was 380mm further than the brackets so I'll bring it back a touch.