Thread: Floor Joist Sagging

First time post. I bought a house and noticed two floor joists that were split. I am pretty handy but not an expert on floor joists. I hired a private inspector before purchasing the house and he told me to jack the joists and sister a board next to each of them. I did so and now the joists next to those I repaired look saggy. Is it more possible they sagged from the extra load they may have carried since the old joists were split, or could I have jacked the joists to high. Any advice would be appreciated, thanks.

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Welcome Kyle,

Pictures before and after would be helpful.

A good start would be to check the level of the affected areas.
* laser, bubble or if you can ( hard surface ) drop a golf ball from a fews inches and see if it rolls to a low point.
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My guess is that you really spliced the floor joists.

The probable reason the ones next to the split joists are sagging is that they carried the extra load before the "repair". They carried too much weight, causing the sag. Just a guess of course with no pictures.

I don't think that you caused any sag. If you jacked the joists up too much, you probably would have heard a snap, crackle, and/ or pop as boards broke, fasteners pulled free, etc.

My question is: What caused the joists to become damaged originally? (design issues, giants living in the house, etc.)

Originally Posted by kyle major

First time post. I bought a house and noticed two floor joists that were split. I am pretty handy but not an expert on floor joists. I hired a private inspector before purchasing the house and he told me to jack the joists and sister a board next to each of them. I did so and now the joists next to those I repaired look saggy. Is it more possible they sagged from the extra load they may have carried since the old joists were split, or could I have jacked the joists to high. Any advice would be appreciated, thanks.

What is the span (how long are the joist)?

What room are the joist for?
Bedroom...water bed?
Living room...piano?

I would say that it is unusual for properly sized floor joist to split under normal conditions, "checking" maybe but not splitting.

A drop sill might be the best solution to remove the sag for that section of joist.

As mentioned above a picture is worth a thousand words.

This can be like tunning a piano. don't try to do it all in one day. this may take some time. set up some 10ton floor bottle jacks and do one at a time working them back and forth.

You may need to set up a string from one end to the other and adjust the joist as needed.


Best

Ron

Originally Posted by chris mcintyre

What is the span (how long are the joist)?

What room are the joist for?
Bedroom...water bed?
Living room...piano?

Kitchen...fridge?

Before I put down my hardwood floor I repaired a sagging joist. The floor looks better now than it did before but now the one next to the repaired joist looks sagged. It just got tired from doing the work of the bad joist as well as carrying its own load.

Ok. Thanks for the replies.... Today I ran a string in the basement across all the joists in my kitchen and ran a line level. The string is level and all the joists seem to be even. But when looking at the kitchen floor two joists look sagged, I cant get any good pictures. When looking at the kitchen floor you can see it dip in two spots, but when looking at the joists in the basement everything looks fine even with the string. I am at a loss. I think I am gonna jack the joists up the next couple days and see if it evens out. Ill wait a little while to see what you guys think, maybe a leveling compound will be the best bet when I replace the tile?

Originally Posted by kyle major

Ok. Thanks for the replies.... Today I ran a string in the basement across all the joists in my kitchen and ran a line level. The string is level and all the joists seem to be even. But when looking at the kitchen floor two joists look sagged, I cant get any good pictures. When looking at the kitchen floor you can see it dip in two spots, but when looking at the joists in the basement everything looks fine even with the string. I am at a loss. I think I am gonna jack the joists up the next couple days and see if it evens out. Ill wait a little while to see what you guys think, maybe a leveling compound will be the best bet when I replace the tile?

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If you start Jacking Your going to crack the Tile.

If the Joist are level Why Jack them up?

Sub flooring may have a sag and not the as You say Level Joists.

If your going to replace the tile Floor leveling compound would be my suggestion.
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I had a sag in my kitchen floor. Underneath the back door in the kitchen, the box beam, and the sill plate were completely rotted. Once I had the repair done, the floor got even again. The sag was caused by the sill being rotted, and the floor joisted sag about 1".

I find it is difficult to visually judge levelness from below.

If you are going to risk intalling ceramic tiles then invest in LVL's or glulams for sistering.

and even better also put down a mud job with steel mesh lath nailed to the floor and carefully screed it. And whatever you do don't install thin 12 inch tiles. go for thick 9 inch tiles.

Roll a golf ball across the floor from one side to the other side, if it rolls straight, the floor is level 'in that direction'. Roll the golf ball across the floor perpendicular to the first test and check for levelness in that direction.

If there is a low area, the golf ball will curl around and roll to the low area, and there may be more than one low area.

In addition to repairing the floor joist I would consider adding in a girder/beam below the floor joists supporting the joists mid-span. That will reduce the span of the floor joists by half and then they should not be any problem.

As stated above by others, when leveling a floor, level from the bottom but measure from the top - the floor joists may not all be the same exact thickness and some may have sagged more than others.

Set a laser up above the floor and shot it across the room, measure out from the laser in short increments and if you always get the same reading, the floor is level in that direction, now, like the golf ball, measure in the other direction.

I always recommend setting the laser beam at a nice even 12" above the floor, you should read 12" where the laser beam strikes the tape measure all the way across the floor (provided, naturally, that the level the laser is on is really "level" - you will probably need one of those new electronic levels which reads down to the nitty-gritty and forgo the 'bubble' levels where you 'guess' if the bubble is centered or not ... if the laser is pointed up even slightly the laser beam will get higher and higher the farther away you get from the laser.