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No subfloor, now what?

We've got a 1921 colonial. I was removing the kitchen ceiling to sister a 2x8 joist. An overzealous plumber had taken a 4" diameter chunk out of the joist to run a 2" pipe through. :eek: The cast iron tub didn’t mind but the floor outside the bathroom did. It has a slight sag, noticeable with a bounce when you walk over and by creaking.

After taking down the ceiling, I noticed that the 1” thick x 2” wide tongue and groove oak flooring is nailed directly to the joists with no subfloor. The joists are 16” OC, 2x8. Any suggestions? I was thinking to put up a ¾” plywood subfloor from underneath, in between the joists, wedge between 2x4s running along the length of the joists and the flooring itself. Thanks!

Re: No subfloor, now what?

I don't think you need to worry about adding a subfloor since the house has been like that for a very long time. The oak flooring is plenty strong enough with 16" oc joists. Sistering the joist however will definitely help with lessening or eliminating the bounce. You can get rid of the sag by jacking up the joists that are sagging before sistering them. Hope this helps you out.

Re: No subfloor, now what?

I'll try the jacking and sistering first and then see if it needs more. Appreciate the input.

Re: No subfloor, now what?

a plumber butchered a joist??? Imagine that...LOL.
Your 1x2's is your subfloor. Thats how they built em' back then.
Like sabo said jack up the sagger N' add your sister...
as in new joist... lol.
If it were me...I'd use some PL Premium glue (comes in caulking
tubes from your lumber yard or box store) that I'd put sandwiched
between the new and existing joists and nail'r up...then again I
always go for over kill :D

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