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-   -   Notched joist (2x8) and wall removal (http://www.diychatroom.com/f19/notched-joist-2x8-wall-removal-111626/)

diitrii_popov 07-22-2011 12:18 PM

Notched joist (2x8) and wall removal
 
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Hello, I need your help!
I want to remove the wall on the 1st floor. I think it's a non load-bearing type.. what do you think? Maybe it serves some structural purpose?
(The wall serves no purpose and only eats usable space... so I really want it gone :))


While inspecting I found the builders also notched at an angle part of the the joist leaving only 4 inches (they did this for a decorative small roof on the side of the house plus it's easier to install windows).

So here is some diagrams and pictures. The joist is 2x8 n1 grade.
They also displaced the purple wall to about a foot from exterior-load bearing wall...

q1. Can I remove that red wall without any trouble?? The final span would be 12', but the 2nd floor exterior wall (purple) is displaced by 1 foot... What do you think?
Look at the basement and bedroom above garage, 2x8 joist span 12 feet and there is no beams or any support.

q2. I can cut out the ceiling in the kitchen and add 3' x 7" slices of 3/4" plywood to the joist at the notched area? Is reinforcement needed? The house was built 25 years ago and there is no noticeable defects... but after I remove the red wall, maybe it needs more reinforcement???
The house has 2x4 walls, aluminum siding and there is only 1 layer of shingles... so probably not much weight.. :)

PS. I can actually remove the subfloor in the bedroom above kitchen area and sister full length 2x8 to the existing joists, but I want to avoid this, as I have too much work for me already...

Thanks!

AGWhitehouse 07-22-2011 12:54 PM

If those joists seats weren't hacked up the way they are you could just remove that wall without any worry. But the structural effectiveness of those joists has been comprimised. On the good side it's better to have cut the top than the bottom of the joist as the bottom is the tensile load and the top the compression load, but it doesn't give me the warm and fuzzy looking at it.

If you do remove the wall without touching those joists, you will likely get some kind of deflection. How much and if it'll be really undesireable I can't say. It may hold up fine, but then the bedroom floor might act like a trampoline. My suggestion would be to print out your post and grab some photos of your house from the inside and out and visit a structural engineer. You know the end goal, so he should be able to give you proper instruction on reinforcement.

The plywood scabs you spoke of may be all you need, but better to be safe and check with a professional than sorry afterwards...

diitrii_popov 07-22-2011 03:01 PM

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Thanks for quick reply!

I made a test... check the picture. I made small models of joists. I positioned both joists (notched and un-notched) the same way and started beating it with a hammer at the same spot (where 2nd floor exterior bearing wall sits), trying to use same force.
Interesting that 75% of the time the notched joist was stronger, I needed ~25-30% of hits more for notched, before it would break... Somehow the notched area is slightly longer and probably absorbs more pressure, thus stronger?

From my understanding ends of joists shouldn't bend at the ends, even if they are notched?? If extreme forces apply where exterior bearing wall sits, then maybe.

Thanks!

Gary in WA 07-22-2011 03:46 PM

Yikes! Go no further, listen to AGWhitehouse.... The joists are compromised; Fig.6; http://books.google.com/books?id=iwS...joists&f=false

Gary

Daniel Holzman 07-22-2011 03:57 PM

I like to stay out of learned discussions about the structural integrity of joists, but let me weigh in here with an observation. The loading on joists is typically uniform, meaning the maximum bending moment occurs at the center. There is essentially zero bending moment at the supports. Maximum shear occurs at the supports.

IF shear were the issue, the fact that the joists are hacked up would be important. However, in residential construction shear almost never controls; the critical factor is bending moment. In this case, the fact that the ends of the joist are hacked up has no effect on the maximum moment capacity of the joist, because the maximum moment occurs at the center, and the center was not hacked up.

The hacking up of the joist only reduces shear capacity, which can and should be checked by a competent individual. I am not going to check the shear capacity of this particular joist over the internet, that will have to be done by an individual who actually sees the joist, however these observations do explain why a "notched" joist such as the ones the OPS made models of would not exhibit reduced bending capacity under load. A better way to test them, rather than hammer blows which are impossible to measure accurately, would be to load the model joists with uniform load, say a metal bar, and measure the deflection. You should find that the maximum deflection is not affected by the hacking off of the ends of the joist.

AGWhitehouse 07-22-2011 03:57 PM

Interesting that you did a test, though it is a consistent applied load not an impact load.

Daniel makes great points!

sixeightten 07-22-2011 04:05 PM

I believe I heard once that up to one third of the joist end can be notched without compromising the strength severely. We have occasionally had to notch a few floor joists to straighten things out. Not the same as cutting the top of the joist, but I just thought I would throw it out there.

diitrii_popov 07-22-2011 04:43 PM

Thanks for your comments! I think that it should probably be just fine, since the weight is distributed amongst many joists... I just find this joist notching very not cool :)

I'll try to do another test. Maybe use some sort of vise to apply constant pressure. I'll post pictures!

Thank you, guys!

Gary in WA 07-22-2011 06:40 PM

Thanks, Daniel. Did you notice the main roof trusses/rafters are bearing within 2' of the angle cut joists? On that exterior bedroom wall....... Wouldn't that change things rather than a uniform load? So, 12' of roof load plus 2' O.H., plus 6' of ceiling joists (plaster/lath 8# s.f.?), plus 6' of floor load, plus 6' of ceiling joist.........

Gary

diitrii_popov 07-22-2011 08:45 PM

I saw Gary's post so here is more info...

Main roof is flush with exterior wall... I just drew it so it would look like roof. Actual roof is rotated 90 degrees...

Indeed the 2nd floor exterior bearing wall is offset by about 1.5 feet... From architectural book I have it is said 1 foot is the max... The bedroom size above kitchen area is 12x18. Walls/ceiling are 1/2" drywall. Ceiling - 2x4s 24" on center. The roof is 1 layer of asphalt shingles with pitch ~4:12. The walls are 2x4 16" on center with drywall sheathing and aluminum siding. The floor in bedroom will be 3/4 osb with 3/4 oak hardwood.

Thanks!


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