3/4" holes in Floor Joists
3/4" holes in Floor Joists
(OP)
Hello, my floor joists have one 3/4" holes in 10 of the floor joists (in a row, with PEX tubing in them). The problem is that they are located only 1" from the bottom of the joists! the Joists are 2x8 wood on 16" cetres. They span 12 feet.
Do I have a structural issue? If so, how do I repair the problem?
thanks in advance for your advice/discussion!
Do I have a structural issue? If so, how do I repair the problem?
thanks in advance for your advice/discussion!





RE: 3/4" holes in Floor Joists
If these were 2X10's there would be no problem. Normally, the holes should be in the center of the joist depth for no structural issues.
Mike McCann
MMC Engineering
http://mmcengineering.tripod.com
RE: 3/4" holes in Floor Joists
The 1" is closer than the 2" minimum edge distance recommended for all 2x joists by the WWPA (Western Wood Product Association) Notching and Boring Guide.
Now a metal strap will not transfer any load until the joist fails. Unless you can install the metal strap while it is under tension. But they may keep the floor from total collapse due to domino effect.
But whether your joists are structurally sound depends on too many factors to address here. (How far the hole is from the bearings. How close are knots and other holes to it. The grade and species of the joist. The stress in the joist at the hole. The location of the joists per the framing plan. Etc.)
Now there are many safety factors in wood design. So you may never have a problem show up because of the holes. But I cannot tell from the information given. I will say that the closer the holes are to the bearing the better.
Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.
RE: 3/4" holes in Floor Joists
Handle appropriately
RE: 3/4" holes in Floor Joists
My friends think I'm crazy for worrying about the structural integrity of the house... but I am worried!
thanks again.
RE: 3/4" holes in Floor Joists
RE: 3/4" holes in Floor Joists
From what I can tell, and correct me if I'm wrong. The joists have now become 2x6's, which according to code, Douglas Fir 2x6 joists can span 11 feet? so everything is fine and I'm crazy and should redirect my energy?
RE: 3/4" holes in Floor Joists
Again you may or may not have a problem. Depending on many factors. Do you know the company that drilled the holes? If you do I have them fix it or provide an engineers calculation on it. If you do not know. Than I would recommend that you buy ten 2x6x10' Sel Struc or No.1 & Btr DF-L to nail to the joists centered as best you can over the holes. It should be cheaper than hiring your own engineer to look at it.
Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.
RE: 3/4" holes in Floor Joists
This assumes a 40 psf Live Load and 15 psf Dead. Ratio it if you want.
So - the steel strap idea is not a bad one!!
RE: 3/4" holes in Floor Joists
RE: 3/4" holes in Floor Joists
Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.
RE: 3/4" holes in Floor Joists
I don't think the deflection being over the allowable is a concern. You have a "2x6" only locally at the hole, so for deflection purposes the beam is really a 2x8.
Personally, if you are concerned, I'd stitch nail another joist as recommended, the strap in my opinion is just a bandaid...
RE: 3/4" holes in Floor Joists
I realize this is your opinion based only on the information given.... I appriciate the input.
RE: 3/4" holes in Floor Joists
RE: 3/4" holes in Floor Joists
If Mikes calculations are correct and your beam is 30% overstressed I say this puts you in a grey area. As an engineer, yes I would recommend you repair it and if it was your plumber who made the mistake it should be on his dime. Now with that said, we've worked on remodels of a lot of houses where the existing floor joists or rafters should be significantly overstressed but don't fail. Now if this is because they never reach their design loading or if there is significant safety factors implied in our design I'm not sure. From what I remember from school I believe the wood allowable stresses are based on the average minus a standard deviation or two so there is a good chance your wood is significantly stronger than assumed. Just my two cents.
In the end if it's uncovered. Seems like it woul be fairly easy to stitch nail another joist on...
RE: 3/4" holes in Floor Joists
Regardless - at a 40 psf live loading - a 20'x 20' room could support 16,000 lbs of load. Assume the average person weighs about 175 lbs (including women and children - not just us fat boys), you are looking at 90 people. Try putting 90 people in this space and you would have a riot on your hands!!
So, part of the answer is it will probably NEVER reach design load!!
RE: 3/4" holes in Floor Joists
Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.
RE: 3/4" holes in Floor Joists
So for the purposes of determining the allowable stresses in the NDS they take the average of a group of species and then subtract out 2 standard deviations. According to Breyer's Book the purpose of this is to provide an AVERAGE safety factor of about 2.5.
How's this relevant to the discussion? Probably not at all, just perked my interest so I decided to look into it, and this was the thread that started it. For the OP's question -- I wouldn't consider any of this if it was my engineering license on the line. If it was my house... well my answer may/may not be different.
RE: 3/4" holes in Floor Joists
I do tend to agree but with 3/4'' plywood and 16'' oc you are going to get a lot of load sharing unless you are putting all your load through the tip of a crow bar.
Everything ALWAYS needs to be checked.
RE: 3/4" holes in Floor Joists
RE: 3/4" holes in Floor Joists
Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.
RE: 3/4" holes in Floor Joists
RE: 3/4" holes in Floor Joists
Put the straps in place like Mike McCann says...then have your orgy.
RE: 3/4" holes in Floor Joists
Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.
RE: 3/4" holes in Floor Joists
Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.
RE: 3/4" holes in Floor Joists
I think Ron might have a point about the extra 40psf live actually getting the strap to engage though. I think a quick check would be able to see the validity of that assumption.
See what the 40psf live load will cause in deflection, if the joists are long enough the elongation along the bottom of the joist might be enough to engage the nails and strap.
Although, off the to top of my head I am not sure what a 10d nail will slip in a condition like this... So maybe this check would prove the strap useless.
RE: 3/4" holes in Floor Joists
Had a million dollar plus home with rich Italian marble on the floor that was highly mis-treated by an electrician. I read him the the riot act and made them fix the joists. NOBODY is going to crack my marble!! And it hasn't in 15 years!!
RE: 3/4" holes in Floor Joists
Most nailings of straps that I've seen don't hit the center of the hole. Further, the holes are sized to use either 10d or 16d nails. If 16d nails are used, there's little slip required to mobilize the shear in the nails and then the tension in the strap.
Strains between steel and wood are so incompatible that I feel mobilization would occur long before it could be predicted by analysis.
RE: 3/4" holes in Floor Joists
Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.
RE: 3/4" holes in Floor Joists
RE: 3/4" holes in Floor Joists
RE: 3/4" holes in Floor Joists
http://www.ntis.gov/
If you type in "ADA013987" it comes up.
Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.