Floor joist sistering question


N

Neil

I have a floor joist that is sagging where the joist was drilled
through to allow for passage of the hot water heat pipe. Naturally
this hole was made in pretty close to the exact center of the joist
and they never sistered it as they should have done to begin with. To
make matters worse, the previous owner had a grand piano sitting on
this spot.

There's no splitting or cracking, but the joist is clearly sagging
about 1/2" in the middle. It's the end joist, and the floor has
settled enough that the quarter round now dips slightly below the
baseboard.

I've jacked up and sistered rafters before but am a little unsure how
to approach this since the hot water pipe runs directly under the
joist preventing me from jacking up the joist directly.

Is it acceptable to lift the joist with a sistered member attached to
the half of the joist with the pipe and then fasten it to the other
once it comes up to level? If so, how do you gauge an appropriate gap
on the new member so that you can jack it up correctly?

Thanks for any advice. We moved some furniture around so that it's
visible and it's driving me crazy.
 
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D

Doug Miller

I have a floor joist that is sagging where the joist was drilled
through to allow for passage of the hot water heat pipe. Naturally
this hole was made in pretty close to the exact center of the joist
and they never sistered it as they should have done to begin with. To
make matters worse, the previous owner had a grand piano sitting on
this spot.
The piano is the cause of the sag, not the hole (unless it's a really *huge*
hole). The exact center of the joist is precisely where the hole *should* be.
There's no splitting or cracking, but the joist is clearly sagging
about 1/2" in the middle. It's the end joist, and the floor has
settled enough that the quarter round now dips slightly below the
baseboard.

I've jacked up and sistered rafters before but am a little unsure how
to approach this since the hot water pipe runs directly under the
joist preventing me from jacking up the joist directly.
Above, you said the joist was drilled for the pipe. Here, you say the pipe is
*under* the joist. Do you mean the joist was notched at the bottom?
Is it acceptable to lift the joist with a sistered member attached to
the half of the joist with the pipe and then fasten it to the other
once it comes up to level? If so, how do you gauge an appropriate gap
on the new member so that you can jack it up correctly?
"the half of the joist with the pipe"?? Isn't the pipe attached to (or passing
through) *all* of the joist?
Thanks for any advice. We moved some furniture around so that it's
visible and it's driving me crazy.
First advice is to post a picture of the joist and pipe somewhere. Your
description doesn't make sense.
 
P

PJx

Remove the pipe temporarily while you properly fix the joist. Use
strings in both directions in the room and jack til it is slightly
above level as it will settle over the weeks ahead.
PJ
 
N

Neil

The joist is drilled through vertically, not horizontally. The hot
water pipe goes straight down thru the joist from the baseboad in one
room and runs underneath before turning back up (through the another
joist) to go to a baseboard in another room.

A top view would look like this ...
_______________
______O________


and a side view like this ...


_________''_______
''
''
_________''_______
=========''
 
G

George E. Cawthon

Neil said:
I have a floor joist that is sagging where the joist was drilled
through to allow for passage of the hot water heat pipe. Naturally
this hole was made in pretty close to the exact center of the joist
and they never sistered it as they should have done to begin with. To
make matters worse, the previous owner had a grand piano sitting on
this spot.

There's no splitting or cracking, but the joist is clearly sagging
about 1/2" in the middle. It's the end joist, and the floor has
settled enough that the quarter round now dips slightly below the
baseboard.

I've jacked up and sistered rafters before but am a little unsure how
to approach this since the hot water pipe runs directly under the
joist preventing me from jacking up the joist directly.

Is it acceptable to lift the joist with a sistered member attached to
the half of the joist with the pipe and then fasten it to the other
once it comes up to level? If so, how do you gauge an appropriate gap
on the new member so that you can jack it up correctly?

Thanks for any advice. We moved some furniture around so that it's
visible and it's driving me crazy.
Just a comment first, What kind of idiot would have drilled
through the joist instead of movingthe pipe a little bit?
Assuming the joist is 1-1/2 x 8 inches and the pipe is 1
inch outside diameter, the plumber made it into a 1/2 x 8
inch joist. Jees!

Yes you can jack the sister. Attach the sister with two
3/4" bolts about 3 inches each side of the hole for the pipe
and about 1/3 of the way from the bottom. The dimensions
are not critical but the closer you get to the center of the
joist and the closer you get to pipe the better pivot you
have and the less push end wise. To reduce the push end wise
as you jack, make the hole in the original joist slightly
larger than the bolt or cut the holes with a chisel on the
outside edges to make the hole more of a slot and use large
washers at the head and nut ends and don't tighten so that
they dig into the wood. You need to keep the bolts back
aways from the pipe and in the lower half of the joist.
Jack the sister slowly. I would use a level on a straight
board on the floor and watch the baseboard crack. When you
get it finally up your sister will be fairly parallel with
the bottom of he joist, but the top won't touch the floor
because you started with a sag. Nail, screw, or bolt the
sister to the original joist when you get it where you want
it.

If you want to get really wild, sister two pieces with a gap
of about 1/2 inch at the hole. Put a board under this and
jack up. When level sister another piece on top of your
split sister. That would give you three joint thicknesses.
 
D

Doug Miller

The joist is drilled through vertically, not horizontally. The hot
water pipe goes straight down thru the joist from the baseboad in one
room and runs underneath before turning back up (through the another
joist) to go to a baseboard in another room.

A top view would look like this ...
_______________
______O________


and a side view like this ...


_________''_______
''
''
_________''_______
=========''
Wow. That's amazing. The plumber who installed that is an idiot.

OK, here's what I'd do:
1. Get *two* 2x8s (or whatever size your joist is) by at least six feet long.
2. Attach one on *each* side of the drilled joist, aligning the centers of the
sisters with the drilled hole. Attach each sister with only about six nails,
in rows of three about six inches each side of the center.
3. Place jacks under *each* sister, right next to the drilled hole, and raise
the floor *slowly* (1/8" per day **maximum** rate) until it's level.
4. After the floor is level, nail the sisters to the joist along the remainder
of their length.
 
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G

George E. Cawthon

Curtis said:
Naturally this hole was made in pretty close to the exact center of the
joist > >

If the hole was centered in the depth of the joist the effective strength
has barely been reduced. The sagging most likely was due to the dead load
over time.

Spars in aircraft wings have lightening holes for nearly the total span.
If you read his second explanation you find out that the
hole is center in the narrow edge and reaches from the top
to the bottom of the joist. This would effectively change a
1-1/2" thick joist into a 1/2" thick joist assuming the hole
is 1' in diameter.
 

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