I was running some new gas pipe and I notched one floor joist and drilled a hole in another. I have now learned that this is not appropriate. This was in the forbidden zone of the middle 1/3rd of the joist.

The joist is 7 inches tall and the notch is 1.5 inches tall. I think the wood is redwood. The span is roughly 100 inches. This is an old house, built in the '40s.

  • Here's a photo from the day I made the notch: drilled joist
  • Here's a quick sketch of the situation: sketchup diagram

I went back a few days later and took a close-up picture. There are some horizontal cracks. If you look very closely in the original photo, these cracks were pre-existing to some degree.

  • Here's a close-up of the cracks enter image description here

This joist is close to the foundation (as you can see), and the notch is under a bedroom closet. I'm not sure if the closet wall is load-bearing.


  1. I've heard that I can glue/screw a 2x4 to the bottom of this joist to make it an upside down T shape. Will this restore enough tensile strength?
  2. Otherwise, does this need to be fully-sistered (with the pipe relocated)?
  3. How urgent is this repair?

Note that I've seen other questions about joist notching on this site. I believe my situation is sufficiently different to merit its own answer.


5 Answers 5


Good on you for leveling up your knowledge and learning where not to drill or saw on joists. On that same note, here's an excellent summary from BuildingAdvisor titled Guide to Notching and Boring Joists:

  • Don’t make any holes with a diameter greater than 1/3 the depth of a joist.
  • No holes closer than 2 inches to the top or bottom edge.
  • No holes closer than 2 inches to any other hole or notch.
  • No notches in the middle 1/3 of the joist, but holes are permitted here.
  • No notches deeper than 1/6 the joist depth.
  • No end notches (where the joist is supported) greater than 1/4 the joist depth.
  • The length of a notch should not exceed 1/3 the joist depth.
  • Do not make square or rectangular cutouts. Also avoid square cuts in notches — angled cuts are better, as shown. Square cuts tend to start cracks.
  • No notches are allowed in the top of a large beam (greater than 4 in. thick), except at the ends.

I've heard that I can glue/screw a 2x4 to the bottom of this joist to make it an upside down T shape. Will this restore enough tensile strength?

A glued and screwed 2x4 fastened to the bottom of the joist would increase the tensile strength. Enough? You shouldn't trust anyones advice on that but a structural engineer, and I'm a different type of engineer. That's not among the fixes I've seen employed in the building trades.

Does this need to be fully-sistered (with the pipe relocated)?

That's one option. There are others.

  • Sister the first unaltered joist, making it a trimmer. Then, temporarily support the 2nd and 3rd improperly altered joists, cut them off on either side of your steel pipe, and run new double 2x8 joists (aka: headers) from the rim joist to your sistered trimmer. Add in the requisite joist hangers, remove your temporary supports, and you're good.
  • Add flitch plates to the cut joists.
  • Add a support beam beneath the two cut joists, near the cut. Voila, now the holes/cuts are no longer in the middle third of the span and the span is roughly half.

How urgent is this repair?

  • Unless you're planning to park a fridge in that closet, this is unlikely to be urgent.
  • It looks like your 2x8 is wider than 1-1/2"
  • A modern 2x6 would suffice for your span, which is what you made your 2x8 into.
  • Your subfloor looks like 1", those boards will help distribute loads across joists.
  • The cracks are normal. No big deal. Search on "Checks and Splits in Lumber" for details.
  • The closet walls are unlikely to be supporting. Supporting walls are atop framing that carries loads down to footings.
  • Try a deflection test. Have a helper eyeball the floors deflection as you jump above the cut and uncut floor joists. Does the floor feel more squishy above the cut joists? Does it deflect more?
  • Thanks for the thorough reply. I don't see any deflection with a helper and I don't feel any deflection myself.
    – Peter
    Commented Nov 21, 2019 at 14:06
  • If it helps, here is a photo of the room above. The joist is approximately under the back left corner of that closet, where the wood is stacked against the wall. imgur.com/a/gv26b5V
    – Peter
    Commented Nov 21, 2019 at 17:57
  • 2
    The photo helps. Notice how the ceiling joists run parallel to the closet wall? That's big clue #2 that the closet walls are not load bearing. Also, your hardwood flooring is running perpendicular to the 1" subflooring. And it's near the wall. Those factors combine to lessen the impact of weakening those joists. You've got a strong floor system. I'd file this one under, "when I get a round tuit." Commented Nov 21, 2019 at 21:56
  • Got it. Thanks again!
    – Peter
    Commented Nov 21, 2019 at 22:11

You’re lucky, sort of...

First, the joists are 1 5/8” x 7 1/2” not 1 1/2” x 7 1/4” if the house was built in the 1940’s.

Second, the joists are not Redwood (thank goodness) they’re Douglas fir.

Third, I’d classify them as No. 1 or Select Structural grade. (There’s only one grade better: Dense Select Structural.)

Fourth, those hairline horizontal lines are from the wood drying out and are located in the “neutral axis”. The neutral axis is that portion of the joists that has neither tension nor compression (prior to you drilling the holes).

You didn’t indicate the spacing of the joists, but assuming the worst, 24” on center, a 2x6 could support a code required minimum of 40 lbs. per square foot and span about 9’, which exceeds your span of 8’-3”....you’re lucky.

However, there are two issues: 1) There isn’t a load bearing wall on these joists, and 2) you are not storing any heavy items in the closet directly above.

  1. You indicate closet walls above this area, but this area is very close to the exterior walls. So, I doubt the closet walls are load bearing.

  2. If you store books, newspapers, automatic transmissions, etc. in this closet, that is an unusual load and not accounted for in these calculations. (Dirty socks and tennis shoes are okay.)

I would not nail a 2x4 plate on the bottom of the joists. The joists do not need anymore trauma...

However, I would monitor the joists by visually inspecting them once each month, measure the width of the opening and write it in a journal. Take a pic and date it. Then, compare it to the earlier dimensions and pics. Note: Wood, in tension, is designed to fail slowly. It will crack and the hole will slowly get wider. (Wood that fails in compression will fail with a bang. You don’t want to be near that when that happens.) You’re lucky...your joists will fail in tension...slowly.

  • 1
    How do you feel about joist reinforcers? metwood.com/joist-reinforcers maybe the 210NR? Commented Nov 21, 2019 at 8:38
  • 1
    @FreshCodemonger I presume they have been tested and are U.L. Certified. However, I would caution using something that requires installing 30 nails or screws in a weakened member. There’s a tendency to split the wood with so many penetrations.
    – Lee Sam
    Commented Nov 21, 2019 at 8:54
  • If it needed to be corrected could he put a post underneath it? Commented Nov 21, 2019 at 17:12
  • @PlatinumGoose If you need to add a post, then you‘ll need to add a footing. However, the load may be small enough that the existing concrete slab may sufficient.
    – Lee Sam
    Commented Nov 21, 2019 at 18:59
  • Unfortunately the neutral axis of a rectangular section is the location of highest shear stress. Fortunately the midspan position has the lowest net shear (this is why you will usually find shear delamination starting at the ends).
    – popham
    Commented Nov 27, 2023 at 18:05

These are larger than 2x6 joists. That plays in your favor. A notch in a 2x6 is disastrous. The beams look OK for now. The cracks are horizontal so they're not concerning. Those can be caused by the drying of the boards or settling, and they could predate the notches.

Your best bet is to reroute the pipes and full sister the beam . It has the least questions. If you want maximum peace of mind, go this route. Full sistering involved getting an uncut board of the same width and gluing and bolting it to the damaged beam. Once done, it's just as if you had not cut the beam. A regular pine board should do the trick.

If you want a simpler repair, consider a metal plate (with deep screws) across the bottom below the notch. The hole can likely stand alone (it's close but should still hold) but a metal plate to reinforce can't hurt. Neither is terribly large (as a percentage of the joist)

None of this is urgent (urgent would be a vertical crack), but I would keep an eye on it if you don't repair it right away.

  • Thanks for the reply. The joists are 2x8s (~7.25 inches tall) The 2x4 would be along the bottom of the joist. Nothing would be touching the ground. Are you worried about these cracks?
    – Peter
    Commented Nov 21, 2019 at 4:50
  • 2
    The problem is the notch is on the bottom, which is the tension side. Commented Nov 21, 2019 at 7:49
  • I've heard that I can glue/screw a 2x4 to the bottom of this joist to make it an upside down T shape. Will this restore enough tensile strength?
  • Otherwise, does this need to be fully-sistered (with the pipe relocated)?
  • How urgent is this repair?

It's not urgent. You think your notch is problematic? Look at this guy's project! I've seen entire sections of studs and joists removed without adverse effects. Given that your project is non-load-bearing, and given the relative dimensions of the removed material, I'd be surprised if you see any deflection over time. Part of that is what you have above it. Heavy bookshelves loaded to the max? I once used a bottle jack to lift a girder which was only a 2"x 6" that was spanning over 130" under a load-bearing wall. Did the house collapse? No. Did it sag more than 2" over 60 years? You betcha! When you deform wood, it's not like steel. It doesn't suddenly fracture and rip apart. It slowly deforms makes a lot of creaking and crackling and splinters first. Using jacks, for instance, is done slowly over time, poco a poco.

To buy special hardware seems a little overkill. If you really are worried, you can get by with lumber and a nail gun. I'm also surprised no one else noticed but this isn't a question of tensile strength. Deflection is known as bending to engineers. Will adding reinforcing members prevent sagging on this supporting element? Sure. Is actually going to sag? I doubt it. But if you want to see, draw a horizontal line above it with a straight edge, and come back periodically with the straight edge and compare. You'll tell in a heartbeat if there's deformation. You already have bracing running to the sill plate. If you really are worried, just run one on the other side to the next joist inboard. Those two members will transfer force to whole members.

I've never heard of retaining a structural engineer to assess such a small deviance from standard practice, and I've seen plenty of this sort of thing. (But of course, I'm not a structural engineer and nothing I say can ever be trusted!)

And next time just run your black pipe past and then attach your elbow and rise. You'll save yourself the grief. If space was an issue, don't be afraid to use a union.

  • 1
    Thanks so much. This was definitely a learning experience. It's a long crawl and a low crawlspace, so I went with the easy decision -- which was wrong. That's another lesson learned (or rather, re-learned).
    – Peter
    Commented Nov 21, 2019 at 22:15
  • 1
    Exeperience is the best teacher! I just wanted to put your mind at ease. I hope the photo put things in perspective! Good luck.
    – J D
    Commented Nov 21, 2019 at 22:25

On a scale of 1-10 (10 being highest concern, I’d rate this a 2. Based on the location of the joists, size and age of the joists and lack of bearing partitions above I would not worry about these failing. If you want to be done with this concern with the least investment of energy the simplest solution would be to support the joist pair with a post. Run a small beam (double 2x4 minimum) across the joist pair and support them vertically with a post and solid footing. Do that and enjoy your new gas supply!

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