[JustAHack]

I have a small cottage and I would like to do a 2' bump out that is 8' wide on the on the gable end. I do not want to put in any footings.

The house is 2X4 construction. I figured I would put in a double 2X8 header to open the space up. I thought I would then put plywood coming out (at a 90 degree angle) from the house on the jack studs. I would then build a platform (made from 2X10) between the 2 pieces of plywood. The platform would extend 24" out from the wall. I would then add in another jack stud between the platform and the header. I would then build the 2x4 walls around the perimeter of the (27.5 X 8') platform.

I was wondering if this framing design works? Or if I should do it differently?

Thanks !

 

[joed]

You need something to hold up the out edge. You can't just stick 2x10s out in mid air like that. It's not even a cantilever.

 

[Msradell]

It's not very clear where you intend to use the plywood and I really don't see it in your drawing. The point being that plywood cannot be used structurally in building construction on anything except for floors. What are you going to be using this bump out for? It's going to have very little weight supporting ability because everything is just hanging off the side of your cabin. At the very least you need some diagonal members from your existing wall to the outermost portion of the bump out at the base.

 

[JustAHack]

I want to build cabinets in it and put a TV in there as well.

The plywood would be on the inside of the Jack studs, coming out the 2'. So.. It would end up being 27.5x~80" H.

I could use Simpson corner braces to secure the platform to the floor. And add in an extra Jack stuf between the platform and the header. This would resist the 3.5" overlap from pushing up due to the downward pressure on the outside wall of the bump out.

The bump out is going to be like an oversized fireplace bump out.

I have a window seat bump out in my house... I am looking to do something like this. I will take a pic of it in the am and post it.

 

[JustAHack]

This is an example of what I have on my house.

Iam I essence looking for what is done when a fireplace bump out is installed.

 

[JustAHack]

Forgot to add the pic... I think that the framer installed 3/4" plywood extending out from the Jack studs and hung the frame off that.

 

[joed]

It all depends on the floor joist direction. If the floor joists run opposite to the ones in the original picture the bump out can be cantilevered.
The original as drawn has no support for the outer wall. It needs foundation or angle braces for support without the cantilever.

 

[woodworkbykirk]

exactly joed , bang on with the upside down joist hangers too.

 

[JustAHack]

This is actually a window seat inside- so it is not cantelivered joists extending beyond the rim joist. I want to take some measrents on this though and fugue out howvitvwas canstructed.

I guess my Q is... At what point are brackets necessary? What if I did a 12" bump out with a small roof over it. This could allow me to recess my TV etc into the wall.

I know a brace is not that hard to do... It is more a matter of aesthetics.

Thanks!

 

[mikegp]

Best case scenario here would be to do it like a bay window. I don't know how much weight your bump out would have compared to a bay window though. You'll have 2x4's and sheathing where a window would have mostly glass. I'd look into that as it sounds like your best bet.

 

[carpdad]

Plywood (with exact nailing schedule) is a part of brace walls, so you can use plywood as a structural part of the bumpout. However, it is something I would ask the engineer or at least wait for someone who built such a thing. It would have to resist both downward and outward movement. I would think a lot of load would be on the top plates and the plate-jack/king stud connections. But top plates may be jointed at or near the load points as well as nailing points on the studs may be damaged/split. Even if all parts were put together perfectly, the organic parts are soft enough that all connecting points may hinge downward over time.
Reinforcing the horizontal and vertical parts with custom metal angles may be one idea.

 

[tretech]

I guess you are talking about a cantilevered wall. Can't remember where these images came from. Might have been another thread on this site.