Joist Sistering

[cgallery]

Another solution, assuming the bearing ends of the joists were in good condition, would have been to sister on a single piece that was as long as practical -- let's say 11'-4", centered on the existing span, with a 4" allowance for bearing (on the stated 12' span) at each end.

Why would anyone do it the way the contractor did it in this case and not the way you describe above?

[Hellrazor]

Larry,

No conclusion was ever made to the source of the joist deflection. This could mean undersized or weak joists are in place or as simple as insufficient mechanical crossbracing. He also mentioned he planned to install a tile floor. This implies hardiboard and tile would be installed on top of the existing subfloor which increases the static load. The joists are already undersized since they are only 2x8's. Typical floor framing is 2x10.

[Woodshark]

If it was me I would sister another 2x10x12 to each joist with construction glue & screws. Yeah, it'll cost you another $200 but if the floor is not solid then later on the tile job could start cracking.

Think about how much time and $$$ that will cost to redo.

[jking]

Larry,

No conclusion was ever made to the source of the joist deflection. This could mean undersized or weak joists are in place or as simple as insufficient mechanical crossbracing. He also mentioned he planned to install a tile floor. This implies hardiboard and tile would be installed on top of the existing subfloor which increases the static load. The joists are already undersized since they are only 2x8's. Typical floor framing is 2x10.

Crossbracing typically would not much effect on the joist deflection in this situation. Unless the joists were cracked somewhere, the source of the deflection is due to undersized joists for the situation. I'm not sure why the decision to use 8' & 4' sisters for the reinforcement, but, I don't know there's anything wrong with it. Disclaimer: Being adequate & meeting code are two different things.

An optimized beam will have material only where needed. In steel structures, it is not uncommon to see beams which are deeper in the middle than the ends. It's not something done with dimensional lumber joists, but, certainly done with fabricated trusses. It is common to reinforce or repair wood trusses by adding plywood to the sides where needed. I see no reason to be concerned with the repair if it accomplished its goal (sounds like it did), or, you are concerned about it being code compliant. The code compliance issue could have liability or insurance implications if something ever happened, though. Your insurance company might hire an engineer to do an investigation in that type of situation.

I'd recommend you have your local code official take a look at it if you are concerned. I'd hate to spend the effort & $ to fix something that does need to be fixed.

[jking]

If it was me I would sister another 2x10x12 to each joist with construction glue & screws. Yeah, it'll cost you another $200 but if the floor is not solid then later on the tile job could start cracking.

Think about how much time and $$$ that will cost to redo.

The original joist was 2x8, he couldn't do anything full length deeper than that.

[Hellrazor]

It is common to reinforce or repair wood trusses by adding plywood to the sides where needed. I see no reason to be concerned with the repair if it accomplished its goal (sounds like it did), or, you are concerned about it being code compliant. The code compliance issue could have liability or insurance implications if something ever happened, though.

I have multiple concerns. Code compliance is one because it is a liability if something happens or he tries to sell. A home inspector is not going to like that at all.

I also have issue with the way it was done when the intent was to place tile floors on top. I am assuming he is talking ceramic,etc tile and not some vinyl peel and stick. If the joists are undersized in the first place, scabbing the boards did nothing to prepare it for the heavier load of a tile floor. I don't want to see someone install cement board & ceramic and have it crack out.

The truss example is a good one, but a truss handles loads completely different then a joist. The plywood or steel ties are used to help secure a connection the same way a hurricane tie does.

[LarryG]

I also have issue with the way it was done when the intent was to place tile floors on top. I am assuming he is talking ceramic,etc tile and not some vinyl peel and stick.

I did not read it that way but if that is the intent, I share your concern in this one area.

It is always a risky proposition and a bad idea to put hard tile on a wood floor (we basically never do it, in our projects: too many problems). It is an especially bad idea to put hard tile on a wood floor that was not designed specifically with that in mind.

[jking]

I have multiple concerns. Code compliance is one because it is a liability if something happens or he tries to sell. A home inspector is not going to like that at all.

I also have issue with the way it was done when the intent was to place tile floors on top. I am assuming he is talking ceramic,etc tile and not some vinyl peel and stick. If the joists are undersized in the first place, scabbing the boards did nothing to prepare it for the heavier load of a tile floor. I don't want to see someone install cement board & ceramic and have it crack out.

The truss example is a good one, but a truss handles loads completely different then a joist. The plywood or steel ties are used to help secure a connection the same way a hurricane tie does.

I've designed trusses, I know how they work. The basic concept of reinforcing is pretty similar whether it's a truss or dimensional lumber. You reinforce the member(s) as needed to handle the additional load. There are numerous ways this can be accomplished. My point with the trusses was mainly to point out the falacy that the reinforcement absolutely needed to be full length to be effective. I'm not disputing "better", only "effective".

You statement that since the joists were originally undersized therefore the reinforcment as installed provides no value...well, this is simply not true. The discontinuous pieces are surely not the same as a continuous piece, but they do something. The fact that most of the observed deflection is gone demonstrates this. Whether its adequate for a tile floor, I can't make a determination since I haven't seen the exact setup.

I have the same concerns you do about code compliance & liability. I'd hate to see the tile crack, but, I'd also hate to see him spend alot of effort & $ to make additional repairs to something that might be ok. This is why I suggested having the local code official review what was done. The code official can make a decision on compliance & should have a handle on adequacy for tile floors. He/she will reject it if it is non-compliant, and will recommend a course of action if it is not. This is what building/code officials for.

Home inspectors are fine for electrical & plumbing issues, but, I've grown skeptical when it comes to structural issues. I've seen certified home inspectors ok things that as an engineer I would require repairs to.

[jseklund]

Thanks to everyone for the replies! It has been very helpful in making my decision. Sorry I have not had time to reply, between work and this house, I'm just straight out busy. I appreciate everyone's concern and help greatly!

Having LarryG confirm with a structural engineer what others had stated and what I thought on my own- the scabbing on of the boards was a solution to the original problem (deflection), was great. It put my mind at ease at least knowing that wasn't a total screw-up.

However, as others have stated, there were two concerns left:

1. What would an inspector say if they saw it?
2. The tile floor issue.

I ALREADY had the tile floor down (we rushed to get the joists done because I was planning to tile that night when we noticed the deflection- DOH!). So taking the scabs off, since they were glued and screwed in, was not an option it appeared. So, in the end, I figured it would be better to sandwich the scabs between the old joist and a new full-sized, continuous joist.

Obviously, the real issue is that the 2X8's are undersized, and I was concerned that over time the undersized joist will fail and the scabs will become useless, even if they are providing benefit now. So, a second full-length 2X8 and the scab, and the original joist, I figured would be the best issue. a 2X10 was considered, with notches- but it just seemed impractical. The 2X8's, glue, nails, screws ran me about $200 and my mom paid a guy about $400 to put them in. While he was at it, he also ran sisters, full length, on the other side of the house. The hardwood floors were squeeking and I just knew deep down that the joists were a major part of the problem. Everyone, including the guy doing it, said it was because the floor was butted to the wall, must have taken on water, etc.- but since it's been sistered it only squeeks in one spot now- and it is obvious the plywood under is not nailed in that spot because you can feel it binding.

The floor, I think and hope, is in good shape now. Thanks again for all the help!