Joist Drilling Expedition

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Thomas K

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So here are the 3 1/2" holes the plumber drilled through my 2 x 10 sistered joists. Anyone have any idea what I can use to strengthen these?

I thought about using some of the steel plates from joistrepair.com, , which may work on most of these holes, although I'll have to reroute the pex lines I installed to allow clearance for the plates. Image 2030 is a 4 1/2" hole, but he did drill through the sistering 2 x 8 on other side of this joist as well.

I don't think the joist repair plate will work on the holes in photos 1984 and 2036 (same joist) because the holes are about an inch from the edge. This particular joist supports the walkway of the bathroom above it.

If anyone has any better ideas, please let me know. I thought about sistering with a new joist, but it still needs the same hole for pipe to run through.

Thanks for any replies!
 

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Breplum

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Holes of 3-1/8" are allowed in 2 x 10 joists.
If only in a sistered joists are drilled and you have structural Simpson screws sistering, then, maybe it is ok.
Or to get some plywood on both sides and screw it further.
 

wwhitney

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Where you don't have clearance for the joistrepair solution, the following would probably work, although this is seat of the pants and should be analyzed with some engineering calculations:

The initial idea would be this (but probably needs to be modified as noted later): If you have, say 1-1/4" clearance from the pipe to the edge of the joist, then get some 1-1/4" perforated steel tube (use the largest size that will fit in both places you need to reinforce). Use a length that is sufficient for the required fasteners and center it over/under the hole. Use some 1/4" SDS fasteners to connect the tube to the joist, with full penetration through the joist. Say 3 on each side of the hole, keeping the fasteners say at least 2" apart, and at least 2" from the projection of the hole width onto the tube.

You'll need to confirm that the holes in the perforated steel tube are the correct size; if they are too large, use a washer under each SDS screw. More importantly the above would probably put the SDS fasteners too close to the edge of the joist. So instead you can stack a short piece of tube above/below the full length piece on each side of the hole. That piece would get the SDS fasteners to the joist in every other hole. Then you can connect the short tube segments to the long tube segment with some vertical bolts and nuts, 1/4" (or 5/16" or 3/8" if that fits better in the perforations).

Probably two bolts per side would suffice, as the tube-tube connection would be stronger than the tube-wood connection. That would mean your short segments would only need to be 5 (full) holes long. You'd need to either leave clearance for the bolt head at the edge of the joist (reducing the tube size), or if possible, slide the nut down into the long tube and thread the bolt through the short tube into the nut.

Cheers, Wayne
 

Jadnashua

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I think, technically, it's too close to an edge. You can think of a joist sort of like an I-beam...the major strength is in the two outer edges...the middle is there to keep them properly separated. There are rules about how big, how close to the edges, and how close to an end point that you can drill holes in a joist.
 

Jeff H Young

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thomas how can a 3 inch pipe (31/2" diametor) with a fitting on it fit through a 3 1/2 inch hole with an inch of slop? you sure that aint a 4 1/2 " hole?
I cant advise on a fix for your joist as Id be guessing and sure my fix wouldnt be legal even if functional.
 

Tughillrzr

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thomas how can a 3 inch pipe (31/2" diametor) with a fitting on it fit through a 3 1/2 inch hole with an inch of slop? you sure that aint a 4 1/2 " hole?
I cant advise on a fix for your joist as Id be guessing and sure my fix wouldnt be legal even if functional.



He’s has both drill hole sizes.

Could you not slide in a new joist entirely?

Show a larger view of joists .
 

Thomas K

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Span of joists is 8'. I think I could slide in a sister joist, but I don't know what to do about the holes necessary for piping. Images 2058, 59, and 2060 are of the same joist, just different views. These are 2 x 10s sistered with 2 x 10s. I sistered them just to give them more strength, as they weren't sistered originally. I know they look like 2 x 6s or 2 x 8s, but that's because that insulation is hiding part of the joist. Those blue and red Pex pipes sit directly in the center of the joists.

I don't know if the heavy duty 2x stud shoe in photo would be strong enough for the thin areas of joist.
 

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Jeff H Young

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Span of joists is 8'. I think I could slide in a sister joist, but I don't know what to do about the holes necessary for piping. Images 2058, 59, and 2060 are of the same joist, just different views. These are 2 x 10s sistered with 2 x 10s. I sistered them just to give them more strength, as they weren't sistered originally. I know they look like 2 x 6s or 2 x 8s, but that's because that insulation is hiding part of the joist. Those blue and red Pex pipes sit directly in the center of the joists.

I don't know if the heavy duty 2x stud shoe in photo would be strong enough for the thin areas of joist.
I would not think the specs for a stud shoe are of use for a floor joist. This is kind of a billybob fix doubt any of this is legal but someone who really knows structure (not me ) might know a proper redkneck fix . ultimately of cource your the engineer on this
 

wwhitney

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Could you not slide in a new joist entirely?
Only if he demos out the piping and then redoes it afterwards, which will only be a significant improvement if he can drill the holes smaller with greater edge distance. A lot of work for little gain.

Where the holes are too close to the edge, the solution is to parallel the thin portion of wood with steel, and fasten the steel to the undamaged sections of joist on either side of the hole. That means you need a "U" shaped piece of steel. Bolting together some perforated tube as I suggested would be a pretty easy and pretty effective way to do that. If you want to do better, you'd need to get an engineer involved to design a solution, and get a steel shop to fabricate it.

Cheers, Wayne
 

Jeff H Young

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Just one of those repairs where a decision needs to be made, I have the luxury of total trust in my brother a carpenter of 35 years . We have made decisions before that might not quite be legal but were very confident in the safety and integrity of building. but totally an individual owners /builder liability
 

Thomas K

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This is what I had in mind for the holes that weren't so close to the edge-up to 6" hole, and around $60 per plate. I think Wayne's idea of using perforated steel tubing to support joists cut too close to edge is excellent. I wouldn't have to reroute Pex pipes if I do that.
 

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WorthFlorida

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As suggested plywood screwed to the joist is easy and strong. Another way is use a 1.5" angle iron. Drill holes in the angle iron for wood screws about every 8". Use it at the bottom of the stud with one part under the joist, the other next to the joist. L shape. Since the bottom of the joist is under tension, steel is at its strongest under tension.

https://www.homedepot.com/p/Everbil...teel-Angle-with-1-8-in-Thick-800957/204225776
 

wwhitney

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As suggested plywood screwed to the joist is easy and strong.
Easy, yes, strong no. For joist repair, it is about half as strong as an equal thickness of solid sawn wood, as half the plies are oriented in the wrong direction. OK, since the face plies are in the correct direction, maybe it's only one third oriented wrong. So a 3/4" thick plywood sister would be comparable at best to 1/2" of solid sawn wood, or ~ 1/3 the strength of the same size piece of 2x sister.


Another way is use a 1.5" angle iron. Drill holes in the angle iron for wood screws about every 8".
It would be nice to skip the fabrication of drilling the holes. I checked the minimum edge distance for SDS screws and SPAX Powerlags, I think 3/4" edge distance would be OK. So with 1-1/2" clearance from pipe to joist edge, using a single layer of 1-1/2" perforated tube would be fine, my initial idea. Or you could use a slotted angle or a slotted channel.

If the pipe distance is smaller than 1-1/2", I suggest using 1-1/2" slotted angle with part of the vertical leg cut away to provide clearance for the pipe. The horizontal leg goes flush with the joist edge.

Cheers, Wayne
 

Thomas K

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Just a thought...What if I sistered these joists with 2 x 12s, notching them to make them 2 x 10s on the end, where they rest on the cement block wall? I'd have to add 1 1/2" spacers to other joists to have even drywall ceiling, but it might work.
 

Reach4

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If I sistered joists, I would screw and glue the wood together. That is stronger than just fasteners.
 

wwhitney

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Just a thought...What if I sistered these joists with 2 x 12s, notching them to make them 2 x 10s on the end, where they rest on the cement block wall? I'd have to add 1 1/2" spacers to other joists to have even drywall ceiling, but it might work.
You could do that, but it's more work than the slotted angle, and I'm not sure it's better. Most people wouldn't want to lose 1-1/2" to 2" of headroom. If you're worried the slotted angle is insufficient, do it on both sides of the joist (offsetting the fasteners).

Cheers, Wayne
 

Thomas K

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You could do that, but it's more work than the slotted angle, and I'm not sure it's better. Most people wouldn't want to lose 1-1/2" to 2" of headroom. If you're worried the slotted angle is insufficient, do it on both sides of the joist (offsetting the fasteners).

Cheers, Wayne
Photo 2059 is the one I'm worried about. There is half an inch between pipe hub here and edge of joist. 3/4" on the other side of same hole between pipe and edge.

There is 1 1/2" between pipe and edge in photo 2036. Plenty of room there for slotted angle iron. Don't know what to do about that 3/4" problem. If regular angle iron is stronger than slotted, I'd have no problem drilling holes, but like you said, the screws would be close to the edge.

I don't think it's going to collapse; I can jump up and down on the subfloor above it, but I'd feel better with a little steel support. I know why he drilled holes so low. He was making sure drain pipe had 1/4" slope, but I think he should've drilled a little higher.

Oh. Almost forgot. Measured height from floor to bottom of joists. 91".
 

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wwhitney

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Don't know what to do about that 3/4" problem. If regular angle iron is stronger than slotted, I'd have no problem drilling holes, but like you said, the screws would be close to the edge.
The screws don't have to be close to the edge. Use 1-1/2" angle iron, maybe 1/8" thick, with the horizontal leg below the pipe. The vertical leg gets a shallow arc cut into it to clear the pipe (trickiest part). Then drill screw holes for SDS fasteners on either side of the pipe, say 1" above the edge of the joist/angle (1/2" from the top).

Cheers, Wayne
 

Thomas K

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That means cutting a 1" half moon in iron. I can cut it at work; we have cutting wheels and grinders. I don't dare use an acetylene torch because it might weaken the steel. Wouldn't it be wise to have the angle iron span both holes with one piece of angle iron on each joist? 4' x 1 1/2" x 3/16" angle iron at Home Depot is around $20.
 

wwhitney

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I don't follow "span both holes". I haven't done the calculations, but my engineering intuition says that a single piece of 1/8" x 1-1/2" angle iron is a sufficient repair. 3/16" on both sides would be overkill.

Cheers, Wayne
 
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