Floor Joist Damage & Splices
Floor Joist Damage & Splices
(OP)
I was asked to look at some floor joists - nominal 2x8'as @ 24" o.c. spanning 12'3". The joists are damaged at one end. The damage extends from the face of the foundation wall inward 5'. The damage is located in the bottom third of the joist. Some of the joists may have damage up further into the joist. There is likely damage at the location where the joist is in contact with the wall (bearing location).
Is it worth trying to design a splice with side plates and through bolts or just go with replacement?
My first inclination was to replace. Add new joists to carry the loads between the existing joists or along side the existing joists.
Whether splicing or replacing, there will be ducts, pipes, and wires that will need to be taken down for the installation work.
Is it worth trying to design a splice with side plates and through bolts or just go with replacement?
My first inclination was to replace. Add new joists to carry the loads between the existing joists or along side the existing joists.
Whether splicing or replacing, there will be ducts, pipes, and wires that will need to be taken down for the installation work.





RE: Floor Joist Damage & Splices
RE: Floor Joist Damage & Splices
RE: Floor Joist Damage & Splices
Also, adding new wood to this would only be a temporary fix if they don't cure the bug issue.
RE: Floor Joist Damage & Splices
RE: Floor Joist Damage & Splices
What is 2x4 PT?
RE: Floor Joist Damage & Splices
I would be providing a new joist sistered to each affected joist. Although Boo1's idea of only providing a 2x4 at the bottom of the current joist is a nice solution as well. provided all you need to do is improve shear resistance of the affected joist.
RE: Floor Joist Damage & Splices
So for a 5' long portion of the joist starting at the bearing location (foundation wall), there is approximately 6.75 sq. in. of area (1 1/2x4 1/2) remaining. So no attachment to the bottom.
shear resistance would need improvement
moment resistance would need improvement as well
and the connection to transfer the forces
RE: Floor Joist Damage & Splices
RE: Floor Joist Damage & Splices
RE: Floor Joist Damage & Splices
So if I look at installing a 2x4 or 2x6 on each side of the damaged 2x8 floor joist.
The new members would have to be at the top of the damaged member.
The damaged members would have to extend beyond the damaged portion of the existing or are you saying go from support to support?
The connection design would be similar to reinforcing a steel beam.
If the new members are only partial length, what is the connection design of the members once you are past the damaged portion?
Avoiding the hassle/expense of taking down the obstacles would be helpful.
RE: Floor Joist Damage & Splices
scab repair would be along the bottom edge of the joist.
Width of the 2x is to get back to good wood.
If you can get away with the scabs being not flush, allow it
Length of the scabs is min 4 feet past the damage area to allow the forces to be transferred back to the joist. If you can get full length scabs installed with out too much trouble specify it
RE: Floor Joist Damage & Splices
thanks for the explanation
this would be a splice type fix
The scabs would bear on the foundation wall, extend approximately 5' (length of damage) plus an additional 4'
No connection of the scabs in the 5' length
connection in the 4' length to transfer shear and bending
RE: Floor Joist Damage & Splices
Am I the only one that is skeptical of this?
If I were looking at someones floor and this was the repair detail, I'd likely specify it gets removed.
RE: Floor Joist Damage & Splices
I am asking questions so that I can understand what is being suggested.
How you see it is what I am dealing with.
I ask the questions in case there is something that I am overlooking.
RE: Floor Joist Damage & Splices
I still have a hard time believing you will get a full moment splice using 2x4, regardless of the length of splice. and at a 9 foot piece of lumber already you may as well just go the entire way, use lvl to stand a chance of working for strength.
I feel as though the existing 2x8 is damaged beyond use and therefore should be neglected for having any strength.
RE: Floor Joist Damage & Splices
RE: Floor Joist Damage & Splices
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Floor Joist Damage & Splices
Of course we prefer to replace with new material, but the interferences makes that difficult.
But I would think the owner wants a lowest cost (easiest repair).
RE: Floor Joist Damage & Splices
I envision you sitting at home at night, sipping crown on the rocks, dreaming up details that at first glance seem crazy but after further review, appear to work.
RE: Floor Joist Damage & Splices
I suspect that plain old sistering will win the day. With regard to that, 2x6 sisters would be no harder to fish through than 2x4, right? Both would go in weak axis and get flipped upright I imagine.
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Floor Joist Damage & Splices
how would you quantify the capacity of the bolts?
Should there be any concern with causing tension perpendicular to the grain caused by the bolts in the existing joist?
"God grant me the serenity, to accept the things I cannot change, the courage to change the things I can, and the wisdom to know the difference" -Reinhold Niebuhr
RE: Floor Joist Damage & Splices
Bearing, edge distances, group action factors, Hankinson formula... the usual stuff.
It would definitely be a concern in the new, moment connected members. I don't see it in the existing members.
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.