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Unread 02-14-2021, 09:49 AM   #1
KarenA01
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Floor deflection question

This NOT about my bathroom but about a possible next renovation project (kitchen) after we get that done money permitting, which is why this is in a separate thread

Right now there is vinyl sheet flooring that need to be replaced over what is likely another layer of vinyl and under that a layer of linoleum.

When we get to redoing the kitchen, we are considering going with a tile floor.

To that end I went into the basement to look at the floor joists in that part of the house to use the Defecto calculator here... but I am not sure if it applies to the situation I found.

The joists themselves are 2" thick and 10 inches tall and 16" on center and look to be in good shape though I don't know the wood type ... but the joists are not supported by the walls directly in that part of the house...

We have steel I-beams that go across the width of the house and the joists run length wise. At the end of each joist the bottom is notched just enough so the end can fit on the lip of the I-beam.

The joist spans vary by the spacing of the I-Beams. A NOT TO SCALE diagram is shown below to make clear what I mean. The span where the kitchen is is 11 ft... and each I-beam has a separate joist on each lip.

The kitchen is located directly above the middle section in the diagram.

But as I assume the I-Beams themselves have some flex, and the edge of the joists are notched to fit into them, I don't know if the Defecto calculator here would apply.

Does it?

Thanks
-Karen
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Unread 02-14-2021, 10:08 AM   #2
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Karen, I had to laugh at "Defecto". A different thing from "Deflecto", the defecto is something, innate or learned, that resides inside of good craftspeople.

To you question, no, the Deflecto can't do what you're describing. The fact that there's steel would suggest some engineering took place when originally built. But the actual 2" lumber dimension suggests an old structure, where things were often done SOP (seat of pants).

It may be a situation where it would be worth it to hire a structural engineer to have a look/see and some advise.
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Unread 02-14-2021, 12:22 PM   #3
PC7060
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Hi Karen,

The flex of the steel beam are insignificant and can be ignored. Run your floor span through the Deflecto tool using the nominal 2x10 (1.5x9.25 actual) selection and see what it come up at. I’m thinking you should be in good shape. - incorrect information!

Edit: Oops, just ran the numbers and you are a bit long at 15’ if your kitchen is over that section. Can you verify the actual unsupported span of the joists? Also a markup showing footprint of kitchen when tile is planned would be useful.

What’s the age of the house? Given you’ve got steel I beams I’m thinking it’s less than 50 years. Also please verify the dimensions of the framing. I assumed the actual size was nominal 2x10 but your post does say full size 2x10. Post a picture of the framing to steel beam connection if you can.

Last edited by PC7060; 02-14-2021 at 12:32 PM. Reason: Correct stupid assumptions.
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Unread 02-14-2021, 01:14 PM   #4
KarenA01
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Peter ,

Glad my typo made you laugh!

A structural engineer might be a good idea to check out a few things about this house!

PC,

The house was built in the mid 1950s so it is in it's mid 60s. The joists are actually 2" thick NOT 1.5". The kitchen is over the 11" ft span

See the picture below for where the joist meets the I-beam... Not a great picture - My cell phone does not have a good camera.

I added a second picture with a measuring tape showing the joist is actually 2 full inches thick... Sorry for being blurry... I could not hold the phone steady for that long above my head.
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Unread 02-14-2021, 05:26 PM   #5
PC7060
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Thanks for the pictures. The tape “taped” to beam was helpful You should have no problems given you are in the center between the beams. It can be a concern when the floor bridges a beam due to potential uplift of rafter ends so glad to see that is not a issue.

I’ve included the results below:

Quote:
Originally Posted by Deflecto
Thank you for using the John Bridge Forums Deflect-O-Lator :-)

For joists that are Unknown wood, but in good condition, 10 inches tall, 2 inches wide, 16 inches on center, and 11 feet long between supports, the deflection calculated is 0.157 inches.

This translates to a deflection of L / 840.

Since the maximum deflection for tile is L / 360, and for natural stone is L / 720, your floor is rated for Ceramic tile or Natural stone, Congratulations!
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