Reinforcing Wood Floor Joist

[TRAK.Structural]

I've got a client who needs a fix for a wood floor joist that had a hole cut too close to the top edge of the member (see below). I'm considering trying to analyze this with a 2x6 spliced on to each face of the existing joist. My thought is that as long as the flexural and shear stresses of the effective section at the hole (essentially (3)2x6) are within the allowables that this works. Obviously I need to provide enough fasteners to justify composite action but I think that is do-able.

Any other approaches folks have used in the past?

I've seen some of the metal reinforcing plate products for holes and notches but seems like those have very specific situations where they have been tested which limits the applications where they can be used.

 

[SWComposites]

Sister a new joist on one or both sides and drill a new hole in a proper location.

 

[fp23]

Typically when I've done this in the past I've sistered the additional members for almost the full length (usually stop around 1' from the ends since you don't need it for shear) of the joist but this has usually been with a bigger hole or notch. if you do a shorter segment your really moment connecting it to the joist, so you need 2 groups of fasteners that are pretty far away from each other (i'd recommend like 18"). you could model it in risa. forte also does holes in lvl's but i'm not sure if it'll check 2x material with holes. Also, i'd recommend using LVL so it doesn't shrink relative to the member it's being sistered to.

If it were me i'd sister a 5 1/2" lvl full length the joist if the numbers check out (maybe both sides if you need it) and be done with it. The cost of the lumber is going to be less then your time for analyzing it. My old boss used to say "just throw lumber at it" and i think that is very applicable to this situation.

 

[lexpatrie]

If this is residential there's a light gauge metal product that screws into the existing but I forget the name. Has an ESR.

 

[TRAK.Structural]

SWComposites - Unfortunately, because of the existing plumbing the new hole needs to be where it is for gravity to do its part with draining the lines.

fp - Using LVL's is a good idea. Full length may be a tough sell to avoid removing more subfloor or potentially ceiling below, but the numbers need to check out before I decide on length

lex - Yea I think I have seen that product, but if I recall correctly I think I need a minimum of 1 5/8" from top of hole to edge of joist which I am just shy of.

 

[KootK]

Is this being done to a single joist in a field of them? Or to a bunch of joists in a row? The answer affects the risk proposition.

If we are talking about a number of consecutive joists then I vote "no" on the proposed reinforcement for the following reasons:

1) We normally tend to frown upon attempts at composite reinforcement in wood because, with most fasteners, fastener slip will tend to neuter whatever composite behavior we were going for. The use of glue can help to some degree.

2) That sad little flexural compression block will be pretty fragile. Given the uncertainties involved with reinforcing a loaded structure, or jacking the structure to unload it, I would struggle to ever feel great about the compression block's survivability.

I don't think that I would allow this for my own home if it were multiple joists that were affected.

 

[TRAK.Structural]

KootK - It's a single joist and the stresses aren't particularly high in flexure because it's not that close to mid-span. The dead load of the sheathing and floor finishes has been removed as part of the bigger project so these repairs can be made with only the load of self weight of the member and the ceiling below currently in place. Your point about fastener slip is valid.

 

[KootK]

Meh, go nuts then. A system like this will not be greatly compromised by the loss of one joist. So the risk is acceptable in my opinion.

..the stresses aren't particularly high in flexure because it's not that close to mid-span

The stresses are high enough that the reinforcing is required. Almost by definition, I feel that means that the compression zone over the hole is heavily taxed.

If this is in the outer 1/3 of the span, would be possible to just treat the situation as being your two reinforcing pieces moment spliced with the original member near the hole?