stone wall support 2

I am going to be adding 4-6" stone veneer over a wood frame house. I'm wondering about the need for buttresses on the front and back walls. It's a 37 foot run on a Saltbox design. The peak is around 20 feet with windows below on the first and second floors. I plan to use L shaped lag screws to tie the wall into the 2x6 framing through the plywood sheathing. If I am going to need buttresses I need to deal with the footings and block so I would appreciate any advice.

 

[ishvaaag]

I have given a look to old DIN 1053 and 1045 that deal with wall masonry construction and your stone thickness wouldn't be approved if loading. It does not, and so such code then limits for the size of continuous panel (without buttress) to 8 m2 for elements with proportion 2:1, giving for your height of about 6 m separaation between buttresses 1.25 m for an even lesser and worse ratio (out of the table). In short, as long as the wood behind normally does not have stiffness enough to oppose wind pressure and suction without risk of the stone breaking, buttresses are needed and those needed would be specified so close that simply it may make more sense start with thicker stone wall. If your house is stiff enough against lateral deformation (wind), may be exists the possibility of reinforcing the stone behind, towards your wood skin, a calculation would indicate. Another solution is to build trays on your wood frame and attach or fix by layers the stone to the wood frame...that more likely would need then to be strengthened.
Last, if you go for buttresses, better align them with walls and leave a first section of 2 ft of buttress contiguous to your wall.

 

[JAE]

stonejockey,

If you are simply adding "veneer" to the house, and properly tying it back to the walls, then buttresses make no sense. The concern is the vertical support of the stone veneer...on what does it rest? Is there a ledge or foundation to support it? Has the ledge and foundation been designed to support it?

Normally, for a two-story salt-box house, the typical wood stud framing should be adequate for lateral support (L/600) of the veneer. Be sure to properly flash and weep the veneer at the bottom.

The tie-backs to the wall should be installed per the code requirements in your area. These usually specify a single anchor per a certain maximum area of wall. In our area, it is approximately 1 anchor per 2 1/2 sq. ft. of wall surface area.

 

The house will be built on a full basement of 12" blocks sitting on a 3000 psi footing. The 2x6 framing will be placed on the inside edge of the wall leaving a 5-6" ledge for the stone veneer. Will the block be strong enough if left hollow or should the hollows be rebarred and filled. Any more insight on flashing would be appreciated. I understand about weep holes but am not familiar with flashing at the base of stone work.

 

[LPPE]

Is the foundation reinforced with rebar in solid grouted cores? I would at least use a bond beam as the top course.

 

[ishvaaag]

I doubt plywood or wood will be delivering anywhere 1/600 undeformability. Furthermore masonries start to break (something many don't want to hear about) from about L/1500.
The non engineered more or less DIN code is clear in that of course as a standing wall something 6 m tall and 10 to 15 cm wide can't stand, that's pure common sense. So again the question is maybe not if the thing will stand -many things not made to current codes stand- but if it will meet the proper conditions of safety and serviceability. From my viewpoint, except proper proof says otherwise, a common outer layer of wood maybe under 1 inch thick rarely will be being stiff enough as to properly restrain in compatible way against damaging deformations a weak stone wall. Proof may be gained, but without that, I won't support with my advice such construction.

 

[JAE]

ishvaaag,

There are perhaps millions of residential homes all over the U.S. that use wood stud walls with brick veneer and they have been performing well. Most of the residential homes in the U.S. have walls only 8 ft. high (2.44 m) so the deflection really doesn't amount to much.

For a 20 psf wind - 8 ft. span and 16" stud spacing using 2x6 studs - I get an approximate lateral deflection at midspan of about .09" = 2.3mm. L/600 = .16"

Agree with pylko that the top course should be a bond beam. Whether or not the walls need reinforcing is based upon the lateral earth pressures on the basement walls. Usually (in my location) the local codes require some reinforcing when 8" block is used. For 12" block you'd just have to check it using concrete masonry design procedures. This would include lateral moment on the wall and any vertical dead loads, live loads, or wind uplift.

 

[LPPE]

JAE - Ever analyze a 2x4 stud?! Doesn't work, yet millions of homes are still standing!

 

[JAE]

Yes, isn't it amazing that we structural engineers get confronted with structures that are under-designed and yet stand for years. Its hard to tell an owner that his building isn't safe....yet has stood firm for 20 years.