Cantilevering a garden building floor deck

[danlightbulb]

Hi,

I am planning to build a garden outbuilding. Essentially to be used as a large shed/storage area.

There used to be a concrete sectional garage on the site so there is an existing brick perimeter wall that this used to sit on, at ground level. The width of this foundation is 2.4m (8ft).

So I could very easily span this with say 2x6's. But I would like a 3m wide building.

I am thinking, therefore, of keeping the foundation as is, but placing 3m 2.x6's on it. So there would be a supported span of 2.4m and a cantilever of 0.6m.

Which I think would be fine if it was a simple deck on its own. But, the front wall of my outbuilding will be sitting on the extremity of the cantilevered part of the floor, not directly above the foundation brickwork. The wall will be 2x4's with OSB sheeting and cladding, and on this side incorporating a door and possibly window. The back wall will be the same size, but sitting on directly over the foundation brickwork.

Hopefully makes sense. Is it ok to do the cantilever like this?

 

[DAZB]

As you have 80% of your building on solid ground and 20% overhanging i would say you are well within the limits of stability. I personally would not worry but you could always double up your joists over all or some of the length, coach bolted together with double sided spiked timber connectors, if you want peace of mind.

 

[Harry Bloomfield]

Hopefully makes sense. Is it ok to do the cantilever like this?

You might have to limit, the loading over the cantilevered end.

 

[danlightbulb]

You might have to limit, the loading over the cantilevered end.

The internal loading you mean, from items I put in there? That's fine I can do that, obviously the structural wall and transference down of the roof load will be by far the heaviest thing sitting on the cantilever.

 

[carmanmemoranda]

Can you put in additional supports under the exposed end ?

 

[Dereekoo]

Stability wise it has a FoS against overturning of 4 so no problem there and as long as any stored stuff is not all placed on the overhang and none on the other then again ok. Deflection of the 6x2s could be a problem depending what spacing you have them, obviously the more you have the less load each has to take, bolting them together or just laid side by side makes no difference to their structural capabilities.

 

[foxhole]

Easy enough to put a couple of brick or slab piers under corners of overhang .

 

[freddiemercurystwin]

Easy enough to put a couple of brick or slab piers under corners of overhang .

Agreed, removes any doubts then, it would only need a few. A cantilevered approach whilst entirely feasible will always lead to a bit of bounce unless the whole floor is super beefy.