Drilled Joist

A contractor drilled a joist on which I’d like some advice. This is a 4 story brick masonry structure on a 43’x53’ footprint. The joist is 2-7/8" thick by 11-1/2" deep (tall). The drilled hole left 2-1/2" of wood remaining at the bottom and 4" remaining at the top. In other words, the hole is about 4-1/2" in diameter. This was done for a 2" c.i. pipe which means that he had problems. Now I read on this site and elsewhere that holes may not be greater than 1/3 of the measured depth of the joist. In this joist’s case, that would be 3.83" whereas it’s actually 4.5".

Here are my questions: 1) How big a problem is this? 2) Can I cure the problem by sistering around it? 3) I could also place thick plate steel on either side with bolts into (not through) the joist. Your thoughts appreciated.

The d/3 formula is a standard applied to nominal framing lumber for ex. a 2"x12" joist which is 1-1/2" x 11-1/2". Fortunately the joist you describe is nearly twice the thickness of a standard joist. While I’m certainly not an engineer but with that said if the joist is carrying only the floor load for a single floor you are probably fine. Another factor is how long the joist is spanning between supports and what area of the home is being supported by the joist. For example typical design standard would call for he joist too support a live load of 40psf and a dead load of 20psf if it were in the main area of the home but if it were located in a sleeping room the live loading would be reduced too 30psf

Mark, many thanks for your input. Here’s some additional detail. The subject drilled joist is in the 2nd story ceiling. It is approx. 16’ long and it was drilled in the very middle of its length. Above one-half of its length, on the 3rd story, is a 7-1/2’ x 13’ bathroom. Owing to Victorian building style, its tile floor lies atop 5" of concrete. Also above that half length, on the 4th story, is a 7’ x 7’ bathroom with similar flooring. I have no idea how to calculate the load that is placed on the drilled joist.

At one end, the drilled joist lies atop a 10" deep x 7’ long steel I-beam that runs between a chimney and an exterior brick masonry wall. At its other end, it lies atop a wood plate that lies atop a stud wall. Below that wall, on the 1st floor, is a heavier wall that includes two 5-1/4" square posts that flank an arch that accommodates pocket doors. Above the said posts lies a 10" deep x 10’ long steel I-beam. That (pocket door) wall is in turn supported in the basement by three cast iron 5-1/2" diameter columns above which is a 10" x 24’ steel I-beam.

You asked about ‘the area of the home that is being supported by the joist.’ The answer is about 368 s.f. on each of the 3rd & 4th floors. That’s 368 x 2 = 736 s.f. Including the basement, the home’s total area by exterior dimensions is 10,600 s.f., or about 8,741 s.f. by interior dimensions.

I’d rather not replace or do a full 16’ sister of the joist. My thought is to place 3" x 10" angle iron on both sides of it (with a hole drilled in each for the pipe. I’m not yet sure whether or not I will be able to get the 3" part of the angle iron under the joist as there is a non-load bearing wall under it that might be difficult to disturb. If not, the 3" part of the angle iron would be “flying” out to the side parallel to the bottom of the joist. The angle iron on both sides of the joist would be affixed to the joist with adhesive and lag screws.

The thing I can’t figure is 1) is using two pieces of angle iron a decent fix, 2) the gauge of steel that I should use, 3) the depth (height) of the angle iron, and 4) the length of the angle iron. I will tomorrow talk to an iron / steel shop to gather their thoughts. I wish that I could afford a structural engineer, but I know that it would cost me another $500, so my thought it to just go overkill on the steel if it’s a viable fix.

While all of the home work you have already done most probably your most inexpensive way out would be too consult a “PE” My guess would be that the required repair will be minimal if required at all. In my opinion you are getting indegistion over nothing


You may be right. I’ll call one on Monday. Thanks again.