Small cantilevered porch

[Jilly]

Our extension (3.5m x 6m) has a small cantilevered porch (3.5m x 1m) on the short side, on the planning permission drawings. The SE and architect's technician seem to have overlooked it, and I paid and finished up with them ages ago. 

 

I have emailed the SE but they are always slow to reply. The builder thinks they are likely to design something expensive with steels and has suggested turning the last few roof joists round to overhang and put an unobtrusive  post in for support. I'm not averse to this, but is he correct? I'd rather have the SE's opinion.

 

The main reasons I'm worried are that I can imagine the overhang levering the end of roof off if it isn't done correctly and the differential movement between the post in concrete and the extension with 6m plies. 

 

Any suggestions/thoughts anyone? 

[markc]

A 1m cantilever is nothing in structural terms, assuming the porch is inline with the rafters/joists then I would go with your builders suggestion. If you were in a blown high snow load area then I would be looking into the loads a bit more.

[George]

Could you post some pictures? hard to visualise.

 

If there's a useful backspan for a cantilever, that's always preferable to trying to get an attachment to the a wall (pure cantilevers are very difficult to make work on masonry).

 

Otherwise putting a post in is a safe bet. 

[Russell griffiths]

Depends what it’s holding up. 

Flat roof or pitch with tiles. 

[saveasteading]

Would this be an extension fixed onto your existing joists  or all part of the original structure ( longer joists). 'Turning some joists round' concerns me. As above...a sketch please.

[Gus Potter]

On 02/10/2022 at 20:32, Jilly said:

and put an unobtrusive  post in for support. I'm not averse to this, but is he correct? I'd rather have the SE's opinion.

Hi Jilly.

 

Yes builder is onto something here. It might be worth seeing if you can fix a bearer to the external wall. Use that to support the high end of the roof. At the outside corners on some thing like this you could use a couple of essentially galvanised scaffold tubes to support the outside corners. If these look too slender then you could use a 76mm circular hollow section to get the appearance right.

 

Your issue is going to be the ground if BC get involved. The loads are really small so you if you need to get this by BC you could say.. look this is a canopy, if so you may need to decouple from the dwelling and argue that it is akin to a smoking shelter and if it settles then so what. Here as the loads are so small you could go back to your driveway design and say.. hey the area under the canopy is the the same make up as the drive and this is designed for a 5.0 tonne axle load so the canopy on a concrete platt will be ok?