What's Wring With This Picture: Bored Holes in Floor Joists?

Here is a photo I shot during a Code Inspection this past week.

What you are seeing are 3" PVC pipes going through 2x10 sawn lumber joists of the second floor. (30lb live load)

The joist spans are 13’ 6" and the bores occur in the exact middle of the joists (top to botttom) and in the end 3rd of the joist spans nearest the exterior bearing wall.

The bored hole sizes were 4 1/2" in diameter. The outside diameter of 3" PVC pipe is ~3 1/8".

Is there anything wrong with this construction? Any Code Violations?

Your question would be answered as yes, and no.

Per R502.8 the maximum hole size could not have been any greater than 3 & 11/64"s, so yes it is in violation. Since it has been reinforced as shown, the IRC does not reflect that and in my opinion, based on the capacity of these floor joist, I would not be worried.

This is only my opinion.

Marcel :slight_smile: :slight_smile:

Just last fall while I was installing an HRV in a client’s house, the local code inspector recomended and accepted a fix like that for 4-5 cut joists by, of course, the plumber. The funny thing here is that the plumber was a part timer, his fulltime job…a butcher!!! Just got to cut, cut cut!! and cut, cut, cut

I wouldn’t have any idea if that were OK. I guess it looks like it might be OK, but I’d recommend a qualified contractor and he might want to accept the liability or he might recommend an SE.

Put a big waterbed above it, send the kids up to roll around and see of it’s OK.

Well here’s the ‘rest’ of the story…

3" PVC is disallowed in 2x10s because the maximum boring of a floor joist according to the IRC Code is limited to D/3, or Depth divided by 3.

In the case of 2x10s, the actual depth of the joist is 9 1/4".

9 1/4" divided by 3 allows for a maximum bore size of only 3 1/16".

The diameter of 3" PVC pipe exceeds the maximum bore size allowed for 2x10s.

So I informed the plumber that his 4 1/2" bore sizes were a code violation…when he smiled smugly…went to his truck…and handed me a 4 page stamped engineered design complete with all the load, moment. deflection and all other calculations…

The 2 foot ‘sisters’ had been calculated to be able to handle the load for the span and location and themselves were engineered using a specifically designed 9 screw pattern on each side of the hole on each side of the joist.

Engineered designs are perfectly acceptable alternatives to the prescriptive limits imposed by the Code text.

I had no choice but to ok this installation…and learned something in the process…:slight_smile:

Thanks for the education. I noticed the screw pattern, it looked like someone new what they were doing.

I just think the bored holes needed a little excitement. :wink:

Since when is boring permitted in the middle third of the joist? Does sistering the joist make it OK? Inquiring minds need to know. :wink:

Too much weekend. I was thinking of notching. :cool:


The joist spans are 13’ 6" and the bores occur in the exact middle of the joists (top to botttom) and in the end 3rd of the joist spans nearest the exterior bearing wall.


When and only when a deviation of the IRC is noted, will it be acceptable upon receipt of a Structural Engineers Report Certificate on the acceptance of the remedial repairs for upgrading non-standard Construction activity that might cause concern to the integrity of the framing structure members.

Other than that, you should report what is observed, reccommend further evaluation by a reputable Contractor or Engineer an move on.
Since our job is to not quote code unless it pertains to Life Safety, I would just do the reccommendation thingy.

Marcel :slight_smile: :slight_smile: :stuck_out_tongue:

I suppose if it was stamped, it should work. The stamp means someone has come to the conclusion after calculation that the sistering is acceptable. My concerns are that they are in the middle third of the joists and it spans at least three in a row. But I am no structural engineer.

It is also hard to tell from the picture, but is that a horizontal tee in the drainpipe?

Dear Homebild,

No notching is allowed in the middle third. As a licensed home inspector, that’s all I really need to say.

Sistering is an interesting approach, but I’m not convinced that it overcomes the problem created by the -shall we say- extreme notching in the middle third.

I’m not citing any code. See p. 70, “Essentials of Home Inspection-Home Reference Book,” Carson-Dunlop & Associates Ltd. c. 2003.

Again, not wishing to offer any engineering advice, I would like to reiterate the following comments about joist strength. (quoting ibid, p. 27)

“It is interesting to note that the strength of a joist comes largely from its depth. Doubling a joist by putting another of the same size beside it will double its resistance to bending. Doubling the depth of a joist increases its deflection resistance eight times. For example, the equivalent strength… of two 2 x 10s compared to four 2 x 8s can be compared by multiplying the base times the height cubed. It is interesting to note that two 2x10s are more resistant to deflection than four 2x8s for conventional house framing purposes.”

The point being, depth trumps thickness. If you do the math (base times height cubed, actual measurements) you might be surprised.

Even though I think it’s strange, if I were in your shoes I’d have done the same thing.

It isn’t “notching”, it’s “boring”. Two different things. Notching is cutting away the top or bottom of a joist. Boring is making a hole in the joist. Neither notching or boring is permitted in the middle third of the length of the joist. Bored holes are permitted in the end one-thirds of the length of the joist but only in the middle third of the depth of the joist, and only to the extent of one-third of the joist depth. (unless, of course, an alternate method is engineered)

Only 2 of the spans appear to be in the center assuming the El on the left is the end of the piping. The rest are near a wall. Looks plenty strong to me though I’d like to see some wood/construction adhesive in the sistering also.

Bored holes and notches are not the same thing.

Only notches are restricted to the end thirds or rafters or joists.

Holes can be bored anywhere along the length in a sawn lumber joist or rafter according to building codes.

The exception is for truss joists which can be bored only in locations specified by the manufacturer.

The engineered design required using adhesive and adhesive was used.

Hi I just found this site and had a question, I’m a first time home buyer and have chosen to go with a builder for a new home, I’m at pre dry wall stage, everything in the home is wood foundation, frame… Should I be concerned that the thin large wood block on the floor have a hole about the size of a dollar coin, not sure if I’m being very picky but it really bothers me… Any help would be very appreciated! Thank you!!