Wall Removal

[Contraflexure74]

Hi,
A client of wants to build on a single storey extension onto the rear of a 2 storey house. He wants to interconnect both rooms which means taking out 50% of the original rear wall of the house at ground floor level on one side of the house. Should I be concerned about lateral stability along this line. Should I put in a steel portal structure in this zone to stiffen up this zone or am I being too conservative?

 

[KootK]

Should I be concerned about lateral stability along this line.

Yes.

Should I put in a steel portal structure in this zone to stiffen up this zone or am I being too conservative?

Difficult to know without more details and/or your analysis. One thing to be careful with is that, unless it's a very stiff moment frame, the lion's share of the lateral load may end up going to the remaining wall segments whether your put the moment frame in or not. Moment frames struggle to compete with the stiffness of walls.

 

[TehMightyEngineer]

At a minimum I'd suspect you're going to need to demo some of the siding prior to the design to verify what you have for existing shear wall construction. You'll also likely be turning one shearwall into one or two smaller shearwalls which may require more nailing or holddowns to be acceptable.

If you're not experienced in wood shearwall design I'd brush up on that as you'll likely have to run the numbers to prove that the new system works. Your new structure will also be adding load onto this wall.

I'd also make sure you'll have a sufficient member to act as a shear collector above the opening to take the lateral load from the second floor and get it into the remaining first floor wall.

Overall it sounds like a fun project that's not too difficult but definitely one you'll want to make sure is feasible before you make any promises.

Ian Riley, PE, SE
Professional Engineer (ME, NH, VT, CT, MA, FL) Structural Engineer (IL)
American Concrete Industries

https://americanconcrete.com/

 

[TLHS]

You don't necessarily have to put in a lateral restraint in the existing location, although it would make everyone's lives easier. You can also try to push the load out to the new exterior wall using a floor diaphragm or something similar. This is going to shift loads around in general though, so you'd have to consider the full effects of things like the eccentricity of the lateral loads on the floor above and the fact that you'll need to deal with diaphragm flange forces in both directions, as well as tying those back into the building.

 

[Contraflexure74]

Hi All,

Thanks for your input. See attached existing and proposed plans. As you can see we are just infilling back left section of house with a single storey extension and you can see the 2 walls which are coming out.

 

[Contraflexure74]

Also attached photo of rear of house to give you a better feel for this. Any comments welcome.

 

[TehMightyEngineer]

I'd suspect you're all set; especially if you're just opening below the window or deleting that corner area. If you're removing an entire wall panel in one of the corners you may have a minor issue but I suspect it works in practice and could be made to work within your engineering codes.

Can you sketch the wall(s) to be removed?

Ian Riley, PE, SE
Professional Engineer (ME, NH, VT, CT, MA, FL) Structural Engineer (IL)
American Concrete Industries

https://americanconcrete.com/

 

[Contraflexure74]

Walls to be removed are highlighted on the attached sketch.

 

[Contraflexure74]

Attached is what the extension will look like from the rear.

 

[oldestguy]

I don't like the idea of a post in the open area, even if at a counter. Can one of the beams be extended to far wall? Loads are light so it should not be a problem with ceiling height.