A joist below my bathtub was severeley cut for the bathtub drain plumbing.
You can see where it rests on the sill plate at the right. There's only
about 2" of joist left at the sill plate.
The bathtub is out. The vertical stub went up to the bathtub overflow.
The bathtub sits perpendicular to the joists, so the drain is between
The cut would have been done 50 years ago.
I'm thinking of strengthening it, partly because I'm planning to put a stone
or tile floor in my bathroom and I don't want it to crack if someone fills
the bathtub and the floor sags. I'm not sure whether strengthening
the joist is necessary.
Rather understandably, the joist is sagging. The LH side sags
about 1/4" below horizontal, and the joist sheared slightly at the edge of
the sill plate.
It seems like the best way of strengthening it would be to attach 2" steel
angle - L-beams - on both sides of the joist, with the legs of the L's
sticking out horizontally.
I'm thinking of jacking up the sagging part so it's straight before
attaching the steel angle, though. How would this be done? The joist is
over my garage. Could I raise it a little by hammering in a 2x4 under it
that's a little longer than the distance between the joist and the garage
On Jun 2, 9:33 pm, firstname.lastname@example.org (Graven Water) wrote:
Get rid of the antiquated trap and lead bends, install a proper tub
trap, and sister on a full depth joist that's glued and screwed to the
existing compromised joist, that sits on the wall plate and extends
~2' minimum past the notched area. Drill holes or notch as per code
Just because the plumbing is old school doesn't mean it all needs to
be replaced. That's soft copper pipe, not rigid. Bending it is ok.
Make sure you bolt the angle iron on at multiple locations. And run
it several feet out from the cut in the joist. You can't transfer a
lot of load to it and then expect one bolt hole near the edge of the
joist to carry it without splitting the joist where you attach the
I get the impression that the leg of the angle adds strength. The
joist is both bending where it was cut, and shearing a bit at the
edge of the sill plate. I'm not sure whether the leg of the angle adds
shear strength or bending strength, but both seem to be needed.
I would have to clamp the steel angles on. Drilling one hole through both
angles seems like a good idea. Since the joist is 2" wide, I would need
clamps with at least 6" gap.
Could it be straightened out with a jack, though? Or since it's a small area
that's bent a lot, is it permanently like that now? I guess I could try
jacking it up a bit and see what happens.
On Jun 3, 11:36 am, email@example.com (Graven Water) wrote:
the vertical bit of the steel provides the most strength in the sense
of keeping the joist from bending and the floor from sagging. So if
you can get an asymmetrical L-channel it should be installed with the
long leg lagged to the joist. C-channel would be another option. But
Bob is right in that for strengthening an existing joist, a plate is
almost as good...
On Jun 3, 11:40 am, firstname.lastname@example.org (Graven Water) wrote:
You don't need to bolt the iron to the joist where the joist has been
cut. And if you use angle iron you don't need to bolt it to the joist
where the joist sits on top of the sill plate either. The horizontal
side of the angle iron will sit on top of the sill plate. Carry the
angle iron a good several feet past the cut and use 3 or 4 bolts along
that part. As another poster suggested angle iron on both sides
bolted so it clamps the joist would be good. If you can't do that use
good sized washers.
yep sounded like pipes were in way, and as far as thickness heavier is
always better, who cares its cheap and extra thickness shouldnt
and yeah i had this problem at home sale time, the home inspector went
nuts, required jack posts, but just on floor, not on a footer.
what a waste in my case the joist hadnt sagged, and 50 years was a
A 2x4 might work. You could also try using a 2x6, 2x8, 4x4 or 6X6. If
hammering doesn't work out well you could try putting a jack under it.
Perhaps a bumper jack would allow you to stabilize the assembly by wrapping
some rope around the board and the top of the jack. The best technique
would to place cribbing on the floor until you are high enough to put a jack
under the joist. You can look here for pictures and methods.
Normally when a joist is cut adequate support is restored by adding a cross
member to the adjacent joists. This would allow you to open up more space
for plumbing. Here is a link to a picture
Your plan of using angle may work too. You should replace all those old
drain pipes with new.
DO NOT use a bumper jack or Jack-all on a 2X4 for this job. There is a
tool made for the job, called a jack-post. It has a screw-jack built
into the one end, and is (generally) adjustable for rough height bu
telescoping and installing a big pin. Any contractors equipment rental
place should have them available - or worst case you buy one from home
despot, lowes, or who-ever.
On Fri, 03 Jun 2011 21:56:21 -0400, email@example.com wrote:
That's what I was going to say. Knocking a 2x4 into place is okay for
something that won't crack if you push it too far, or something that
can crack and it's okay, but Laura needs a lot more control about how
high she lifts it. None of those jacks give enough control either.
With a jack-post she'll be able to lift a millimeter at a time when
it's getting near the right spot.
I don't think it's okay if the joist cracks, plust there is other
stuff around it which has never flexed in the opposite direction.
Lowe's has a "steel adjustable building column" that they tell me will
work for jacking a joist up a small distance. See
Item # 210169.
Does it actually work as a jack? It has a small rod through it at the top
that turns a screw to raise and lower the top plate (not shown in the
picture). But that may not have enough leverage to actually jack up a joist.
Is this what you're talking about?
Also, should I attach plywood plates to the top and bottom for safety?
It would be resting either on my concrete garage floor or on some paving
stones that are on the floor. The metal plates it comes with are about
4-6" square. Does one need to use a plumb bob or something to make sure
Uh, no, not plywood plates. Big honkin' steel plates. If you must use
wood, use real wood at least a couple inches thick and a couple feet
long on the bottom. On the top, you want something that will keep the
post in position. And no, that dinky little handle on the Lowes post
will not provide enough leverage to do anything. What those are, are
adjustable posts, not jacks, meant to be left in place once the
offending beam is jacked into place and set back down on them. Try local
rental place, and see if they have proper jacks available on a weekly or
monthly basis at a decent price. Once the floor is all lined up, you can
figure out how to add structure to keep it that way. A common method is
to add a small beam between two of those adjustable posts, buried in
adjoining walls, or at least out of the way. Beam can be steel, or a
tripled 2x8 or whatever. But it is a lot more elegant if you can figure
a way to do it within the floor system itself, by sistering joists or
adding box sections or whatever.
Note that any permanent posts you add should have footings under them,
if there are other loads being carried down to them by the house above.
What you have is a very common problem, and the cures are usually
hillbilly at best. Framers always cringe when they see a plumber carry
in a sawzall. Stuff like this should be addressed in the design phase-
if they know a bathroom is going above, make sure there is a path for
the pipes. Either make tub centerline land on a joist bay, or header off
an opening below the wet wall.
That's what I meant too. I don't know why so many webpages don't call
things what people call them. I coudn't figure out what Home Depot
calls them, even though I know they sell them too.
**One example is the cube tap. Actually I don't know what people call
them either, the small things one plugs into an electrical outlet,
then plugs three thrings into it.
How long is it? I dont' see that in the picture, and I thought one
is supposed to provide his own jack handle or other 18" or 2 foot
heavy steel rod to turn it with. Maybe grease the threads first if
they're not greased???
This is your first post in the thread. She was only trying to lift up
her bathroom floor and hold up her bathtub. Do you really think she
needs steel plates?
Tripled 2x8's!!!. This is only to supplement** one notched joist.
It's not going to hold up other joists.
**Temnporarily I think it was so she can take the stress off the joist
and lifte it 1/4" iirc until she can sisters in a steel plate or one
on both sides.
Now footings you want!! YOu must not have read the thread. :)
The OP is not jacking up a load bearing wall, and if the adjustable
post has a 1" 10tpi thread like the 4 in my basement they WILL do a
lot of lifting. If they are 10tpi, they will lift 1/10 inch per turn
of the screw. If you use a 1 foot long handle to turn the screw, you
get a theoretical mechanical advantage of 753 to one, so 50 lbs of
force(50 ft lbs) would lift 37,650 lbs without taking friction into
account. With well lubricated threads you are looking at something
close to FIFTEEN TONS lifting force at 50 ft lbs of torque. Using a 2
foot long bar to turn the screw, it is VERY easy to input 50 ft lbs of
torque. The posts are rated for about 12000 lb at full height.(which
is less than 25 ft lbs of input force, by my calculations.
My numbers may be off - but even if I am optiminstic by 100%, the
capability of the post to handle the job is NOT in question.
I've used them for a lot worse jacking issues than what is presented
here - with excellent results.
As for the plywood - all you are doing is spreading (at full rated
load of, let's say 12000 lbs) a load of (on 8" square plate) 187 lb
per sqare inch over 1 square foot (assuming a 12" square peice of 1"
plywood) for a resulting load on the garage floor of 85 lb per square
inch. I don't have the numbers as far as the compressive strength of
plywood at hand - but 1 inch fir ply is easily up to the task - don't
know if I'd trust it on loose or copacted soil - but definitely on
My suspicion is well under 2 tons of lifting force would be more than
adequate for the job at hand. Childs play with that "adjustable post".
On Jun 5, 11:32 pm, firstname.lastname@example.org wrote:
re: "That's what I meant too. I don't know why so many webpages don't
call things what people call them."
Maybe because there's a difference between an "adjustable building
column" and a "jack post"?
I believe that most of you are recommending the use of a "jack post"
not an "adjustable column", which is what the OP posted a link to.
On Mon, 6 Jun 2011 12:09:10 -0700 (PDT), DerbyDad03
I've used the "adjustable column" to slowly bring a floor back to
level at my brother's older home. Raised it about an inch over 6
months - and that was under a wall in a 2 1/2 story roughly 90 year
old brick house. Same problem - someone had cut a floor joist and it
sagged. These were "adjustable columns" - not jack posts. The jack
post is a heavier device and is usually used to get a beam up to where
it belongs to put either fixed posts or a block wall under it - I've
used them jacking up a barn too. A bit too heavy for the "adjustable
post" to even act as a post -
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