Noob - questions and (eventually) progress pics

[hamfist]

First off, great site. I've a 1924 Craftsman with a main floor full bath (another full upstairs installed recently) that we're going to begin a reno on this week. We're hiring out the surround and tub install (I know my limits; I'm good at rough carpentry and electrical, just getting started tiling) but I will be doing the balance, including flooring, stool, vanity, wiring, etc. The wife wants tile, but we've springy floors in parts of the house. Here are the specifics:

1. 2x8 (varies actually from 7.25 - 7.75) Doug Fir joists, 16" oc, 13' 6" unsupported span. L/221
2. From the basement, I've got 1x9 tongue and groove subfloor, under 1x3 white oak then various layers of vinyl, 3/8 ply, etc. I plan on going down the the subfloor and working my way back up from there.
3. Floor in the bathroom is roughly 4' 6" x 5'.

I know that L/221 is rated for only wood or vinyl but along the bathroom wall furthest from the house center support beam (perpendicular to the joists) is a wall that creates a small room in the basement. I've yet to take a peak inside of the wall, but it is framed with 2x4s. This wall effectively cuts the floor joists under the bathroom in half, such that the springiness that's evident in the front of the house is all but absent in the back quarter where this wall is. Is there any easy way to take this wall into account for the calculation of the floor deflection? Is it possible that this wall makes the deflection of the relevant floor joists past L/360?

Thanks for you help. LMK if you need any more information or a drawing.

Ryan

[cx]

Welcome, Ryan.

You need to determine whether the basement wall is capable of acting as a support for your joist system above and thereby effectively reducing the unsupported span.

You need to consider what the wall is sitting on, whether the studs are directly under the joists or that you have a doubled top plate, whether the top plate is actually making contact with each joist to provide support, whether the wall is sheathed on at least one side, etc.

If it's a support wall, you measure the longest unsupported joist span with that in mind and enter that figure into the Deflecto.

My opinion; worth price charged.