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pleasedrivefast 05-31-2012 03:39 PM

Sister Joist - Notch Question
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My town building inspector keeps referring me to the UCC code for floor notching:

My question is surrounding sister joists attached to the original joists. The original joists appear to follow the code referenced in section 502.8.

However the sister joist is heavily notched well beyond the allowed code. The code does not specify if sister joists must follow this section.

The question lies in that the notch appears in the middle third and is approximately 1/2 the depth. The original joist and sister are 2x6. They span roughly 15' from load bearing top plate to outside wall support.

Does this need to be corrected or does the original joist hold the support? Above is a bedroom.

Pics are below: 551 is the original joist view. 553 is sistered notch view.

Maintenance 6 05-31-2012 03:53 PM

The sister joist is a part of the floor joist construction and needs to follow the same notching rule. What would be the point of adding a sister and then weakening it by notching it wrong? The joist with the notch around the armored cable is useless. It has been compromised and is just adding weight to it's sister, not helping to strengthen it. At 15 feet, the 2x6 joists are way over spanned as well.

bob22 05-31-2012 03:56 PM

Notching the new joist would seem to me make the benefit of adding it in useless since it is weakened by the same factors that would apply to a single joist. Best way to do this is pull the electrical cables out, put in the new joist, rebore holes, reinstall cables.

packer_rich 05-31-2012 04:10 PM

bob22 is right. Why go through all the work of sistering joists and basically cut one in half?

pleasedrivefast 05-31-2012 04:36 PM

Thanks for the replies. I was thinking this would be the case once I saw this after opening the ceiling.

Gary in WA 05-31-2012 11:04 PM

You will want a closer nailing pattern than what is pictured (30"), this is above Code minimum:


Maintenance 6 06-01-2012 06:21 AM

As additional info: You can see that one of the sister joists with a notch has already split at the base of the notch, so it obviously is overstressed. This is exactly why the notching is spelled out in the code. Also the joists to the right of the top picture appear to be bearing on 2x4s layed flat against the masonry without a plate to tie them together. Unless they pass through openings in the block wall (hard to tell from the picture), this means that the bearing surface is less than the minimum required. There is no bridging or blocking mid-span or at the ends to prevent the joists from rolling. If the header above the window is bearing the floor joist load, it is way undersized. Whoever built this was clueless, which is why we have building codes and permits.

hand drive 06-01-2012 07:27 AM

like another poster posted, remove wire and add a new sister to the bad one. nail really well together to make a strong double joist member, consider re nailing all of the other sistered joists with many many nails. to check if the 15' span is really bad, at one side of the joist stick your head up into the joist cavity and sight across the bottom edge of the joists. if it is sagging you will see it.

pleasedrivefast 06-01-2012 07:50 AM

Again, thanks for all the replies. I've determined to hire a liscensed professional to take care of this job as I need it done right.

@Maintenance 6

The original joists are tied into the block through an opening and then with mortar around the joint. The sister is just nailed to the original and not tied to the wall.

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