# Thread: floor joist and parallel partition wall

1. Junior Member
Join Date
Oct 2007
Posts
8

## floor joist and parallel partition wall

Dear Sirs,

I have looked carefully and now I see the joist running parallel to
the cement block wall. I have found a diagram in the "Basic
Carpentry" book:

IMAGINE A RECTANGLE WITH A VERTICAL LINE DOWN THE
MIDDLE. THESE ARE THE LOAD BEARING WALLS, EXTERIOR
PLUS ONE INTERIOR. A HORIZONTAL LINE IN THE MIDDLE
OF THE RECTANGLE JOINS THE CENTER VERTICAL LINE.
THIS HORIZONTAL LINE IS THE PARTITION WALL.
.....vertical bearing
...............V
____________________________________
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lllllllllllxxxxxxxxxxxxxxxxxxxx
llllllllllllllllllllllllllllllllllllllllllllllllll l <partition
lllllllllllllllll
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------------------------------------
...............^bearing

This is the basic structure with one inside load bearing wall (vertical line).
The floor joist near the "xx" on the diagram is very rotted. Also,
the book describes how to build a partition wall. They mention that
the sole plate has to be nailed to the subfloor, and in the case of
masonry floors the sole plate of partition should be fastened with
expander bolts (anchors). My hollow concrete blocks on which
the partition sits do not seem to have any anchors or drilled holes
for anchors.

First, I want to concentrate on the floor joist, which is rotted at
one end. Would it be wise to simply place a new 2x6 beside
the old one (sistering)? In the living room I measure approx.
112 inches from wall to wall. Then if I add the width of the
concrete blocks, I get 112 plus 8 plus 8 or 128 inches
(10 feet 8 inches). Is there a standard length for a floor
joist? I have seen a joist replaced once. The carpenter
took almost the whole subfloor off and replaced the structure.
Since I have only one rotted end, is it possible to put a 2x6 joist
in position by working in the
crawl space and leaving the subfloor intact?

thanks, Paul serapions@yahoo.com

2. Junior Member
Join Date
Nov 2007
Posts
14

## Re: floor joist and parallel partition wall

I really don't follow your whole description, but in general, yes, I'd (hurry) "sister" a new floor joist next to the one with a rotted end. That may be tough is the floor is sagging a bit, so you'll want to determine that first. If it is sagging, you have anothe rset of issues to contend with: 1) do you leave it and try to support the one rotted joist in a nother place, or 2) do you jack up the whole floor to insert a new straight joist and risk messing up something else upstairs when I jack it up. Good luck.

3. Senior Member Rank 2
Join Date
Aug 2007
Location
Maryland
Posts
1,107

## Re: floor joist and parallel partition wall

I don't quite follow either, but how did the water get in to rot the joist & have you corrected the situation.
Leaving rotted structure in place isn't usually a good idea. Also be sure you don't have termites.
If you do leave the joist at least cut it back to good wood.
The plate should be replaced if rotted. If the replaced piece is relatively small don't worry about anchoring to the block, nailing or some strapping will be okay.
The existing sill is probably anchored to the block every 4' to 6'or so. The anchors may be straps or bolts imbeded in the block.
Their is no standard joist length, but the span it can handle is determined by its size, spacing and loading.

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