Hello all its been a long time since I have been around. I have a question in regards to a mid span support. I have an existing kitchen that is 11×24. Currently it is supported along the 24′ walls underneath by the foundation and center beam. The floor joists are 2×8 and 11′ long. If I install a mid span support under the 2×8’s made from 3- 2×12’s nailed together and used only one mid span support what would the deflection limit be in the middle of 12′ runs? I want to install natural stone on this kitchen floor and need a limit of 720.
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Replies
What's the center beam?
The existing center beam is supported by a wall. Its 4- 2x12's. The new mid span support(3-2x12's) would cut the existing 2x8 joist leangth in half to 5' 6".. That support would be supported in the middle at 12'. What would be the deflection of that new beam in the center? I would assume the existing beam would not calculate into the equation since it is supported already. It would just be a dead load of the floor and its contents. Its a kitchen.
Something tells me that you or someone has calculated this and you are double checking or you are a damn good guesser. That is almost exactly the deflection on the 3-2x12 beam you suggested based on a normal 40 lbs/sf live and dead load with a beam span of 12'-0. Using the properties of # 1 D Fir or YP or equal.
However, you say that you are going to lay a natural stone flooring. I don't know what stone you are considering, but that is likely to increase the loading. 3-2x12 may not do the job. You might consider use LVL's. They are much stiffer.
Disclaimer: The use of the above information is at the users own risk. If you have not had a registered engineer do the calculations, you should do so prior to construction.
just a dang good guesser. I am a builder by trade who has no engineer friends......lol . All of the homes I build are spec already.