Broken Joists

[Bubba Fett]

Well I walked into my Man Cave/Office, and noticed the floor felt weird. Also noticed my speaker towers were leaning a bit away from the wall, as is a chest of drawers which hold DVDs and Blu-Rays. I put a ball on the floor and it quickly rolled to the center of the room. Uh oh.

So I crawled underneath the house, and took a look around. I have 4 cracked joists, all next to each other. I reckon I had too many tools, speakers, CDs, etc. in there.

So I plan on filling the cracks with wood glue, and use a couple of jacks and an 8-foot 4x4 beam to lift the joists up all at once, then sister the joists with 2x8 boards. I'm planning on building new supports with concrete blocks to prevent this from happening again, using the 4x4 to spread the weight.

But folks, moving those blocks, and wood to the location is not as easy as I had thought. There isn't much clearance under there, and it's a hell of a lot harder to pick up a block while lying down. I did find the lower section of an old A/V cart, which lets me roll them, but the ground is uneven. Anyway, I got most everything where it needs to be, but I was worn out, so the actual work will have to wait.

Does this sound like a decent plan? Should I use gravel or quick-crete to make a footing before stacking the blocks?

Thanks!

 

[toolmiser]

Well I walked into my Man Cave/Office, and noticed the floor felt weird. Also noticed my speaker towers were leaning a bit away from the wall, as is a chest of drawers which hold DVDs and Blu-Rays. I put a ball on the floor and it quickly rolled to the center of the room. Uh oh.

So I crawled underneath the house, and took a look around. I have 4 cracked joists, all next to each other. I reckon I had too many tools, speakers, CDs, etc. in there.

So I plan on filling the cracks with wood glue, and use a couple of jacks and an 8-foot 4x4 beam to lift the joists up all at once, then sister the joists with 2x8 boards. I'm planning on building new supports with concrete blocks to prevent this from happening again, using the 4x4 to spread the weight.

But folks, moving those blocks, and wood to the location is not as easy as I had thought. There isn't much clearance under there, and it's a hell of a lot harder to pick up a block while lying down. I did find the lower section of an old A/V cart, which lets me roll them, but the ground is uneven. Anyway, I got most everything where it needs to be, but I was worn out, so the actual work will have to wait.

Does this sound like a decent plan? Should I use gravel or quick-crete to make a footing before stacking the blocks?

Thanks!

How about putting the materials on a kids plastic sled and moving them like that?

 

[mm08822]

Light on the details.....

Are these 2x8's that cracked?
What is the span?
What is the sheathing?
How wide is the area?
How much head space exists in this crawl space?
Will you be able to get the new 2x8's into the crawl space? rotated up into position?

How much weight is the floor seeing?
Any shock loads - dropping, banging things?

What is the soil you plan to bear on?
Concrete wouldn't move and you could adjust it's height with a form.

A 4x4 isnt the best choice for a beam. At least 4x6, or build up 2xX's.

 

[mm08822]

Layout plywood strips or 2x's and slide a tote or tote lid on them. Even 5 gal buckets of concrete (mixed outside) will move pretty easy.

 

[Rusted Nut]

Most of the plan sounds OK. but glue isn't going to do anything.

 

[eejack]

It might just be easier to empty the room and pull up the floor. Can't imagine after all the flexing the floor will still be sound and end up flat.

 

[mm08822]

It might just be easier to empty the room and pull up the floor. Can't imagine after all the flexing the floor will still be sound and end up flat.

At least select planks or panels.


NEED

 

[Bubba Fett]

Light on the details.....

Are these 2x8's that cracked?
What is the span?
What is the sheathing?
How wide is the area?
How much head space exists in this crawl space?
Will you be able to get the new 2x8's into the crawl space? rotated up into position?

How much weight is the floor seeing?
Any shock loads - dropping, banging things?

What is the soil you plan to bear on?
Concrete wouldn't move and you could adjust it's height with a form.

A 4x4 isnt the best choice for a beam. At least 4x6, or build up 2xX's.

I have about 2 feet of crawl space, some of which is occupied by HVAC ducting, so it's tight. I'm also not as thin as I used to be. The existing joists are 2x8, and they are about 10 feet long. The house has two beams, basically under the hall. The sheathing is diagonal wooden boards. It was built in 1972.

The new 2x8's will be shorter than the existing ones, because there is no way to get full-length boards to where they need to go, due to obstacles. They new ones are about 4 feet long, and will be attached with construction adhesive and nails. This is the main reason I plan on making new piers. I figure between the two methods, it should be fine.

The room is just a bedroom, used as an office/music/hobby room, so I don't expect any shock loads, or anything like that. From what I can tell, the existing piers (which are concrete block) appear to be resting right on the ground, but there may be concrete under the dirt, which is pretty hard. I'll move some vapor barrier away from one of them and probe/dig.

While I'm under there, I'll be adding some more vapor barrier to cover spots that are exposed to the dirt. I have a little mold under there, which I plan on addressing with fungicidal spray. I may also redo an outdoor spigot that's nearby.

The new vapor barrier I have already added seems to help the low-rider cart roll a bit better. I have been looking for a sled, but we almost never get snow, so I rarely see them.

Edit: Looks like the floor has sagged about half an inch. I have a bottle jack and a couple of screw jacks, and a laser level. I plan to jack the joists back into place slowly, using the 4x4 to raise them all at once.

I wish my crawlspace was like this:

 

[nadogail]

I remember Wards selling adjustable posts, with big screws in the upper end that could jack a beam back into its original position. The newly straighten beams could then be sistered.
When the White House was renovated in the late 40's or early 50's, dome was jacked back up into position with hydraulic jacks and those jacks were later encased in concrete.
Rather than struggle moving heavy pier blocks into position; slide a inexpensive hydraulic jack into position and after pushing the load into position, then encase it in concrete.

 

[dscheidt]

I have about 2 feet of crawl space, some of which is occupied by HVAC ducting, so it's tight. I'm also not as thin as I used to be. The existing joists are 2x8, and they are about 10 feet long. The house has two beams, basically under the hall. The sheathing is diagonal wooden boards. It was built in 1972.

The new 2x8's will be shorter than the existing ones, because there is no way to get full-length boards to where they need to go, due to obstacles. They new ones are about 4 feet long, and will be attached with construction adhesive and nails. This is the main reason I plan on making new piers. I figure between the two methods, it should be fine.

The room is just a bedroom, used as an office/music/hobby room, so I don't expect any shock loads, or anything like that. From what I can tell, the existing piers (which are concrete block) appear to be resting right on the ground, but there may be concrete under the dirt, which is pretty hard. I'll move some vapor barrier away from one of them and probe/dig.

Use as long joists as possible. Don’t bother with glue, construction adhesive creeps in shear, so it is a waste of time and money. The piers need to bear on undisturbed soil below the frost line.

I would also add bridging between the joists. It helps the joists to share load and greatly increases stiffness.

 

[Bubba Fett]

Most of the plan sounds OK. but glue isn't going to do anything.

The wood glue won't do much structurally, but it can't hurt. I will use construction adhesive on the sistering boards, along with clamps, to hold them in place while I nail them in. (That sounds raunchy.) I feel like that should be be pretty solid.

One thing that I think could have prevented this, is proper blocking between the joists. There is just bridging, which is better than nothing, but not enough, IMO. I have also noticed that a lot of the nails on the bridging boards have worked their way loose over the years. I will try to carefully hammer them back into place.

Perhaps adding blocking in between the joists will be a future project. I may build some more piers under the living room, because there is a large area under there without any.

 

[red]

It might just be easier to empty the room and pull up the floor. Can't imagine after all the flexing the floor will still be sound and end up flat.

Agreed, with the floor removed you'll be able to do a much better job.

Personally I would remove the existing floor, run strings from one end of the room to the other to jack them up to the correct height. Then I would add full length crowned 2x8's nailed top & bottom every 12 inches. Then maybe install the beam down the middle. Also you can add a 2X4 under the bottom of the joists, that will create an i-beam. Reinstall your old flooring or spend the money for new plywood. Much better job and less damage to your back and rest of your body.

It had to be a lot of weight to crack 2X8 with a 10ft span. Good luck

 

[whateg01]

I have a question about glue and why it won't work. In every discussion about wood glue, it's said that the glue joint is stronger than the wood around it. In this case, it would be impossible to get the glue into every part of the crack but shouldn't the area that is fully glued be stronger than the 2by was to begin with?

 

[mm08822]

Round over 2 opposite ( or all 4) corners with a 1/2" router bit over each bearing surface to make it easier to rotate the 2x8s in place.

 

[mm08822]

I have a question about glue and why it won't work. In every discussion about wood glue, it's said that the glue joint is stronger than the wood around it. In this case, it would be impossible to get the glue into every part of the crack but shouldn't the area that is fully glued be stronger than the 2by was to begin with?

Glue can't hurt, but injecting it into a fracture and trying to get all strands on each side to align is fruitless.

 

[Bubba Fett]

Glue can't hurt, but injecting it into a fracture and trying to get all strands on each side to align is fruitless.

Agreed. I realize it's not that important, but I figured at least sealing the cracks would make me feel better. LOL.

 

[Bubba Fett]

Agreed, with the floor removed you'll be able to do a much better job.

Personally I would remove the existing floor, run strings from one end of the room to the other to jack them up to the correct height. Then I would add full length crowned 2x8's nailed top & bottom every 12 inches. Then maybe install the beam down the middle. Also you can add a 2X4 under the bottom of the joists, that will create an i-beam. Reinstall your old flooring or spend the money for new plywood. Much better job and less damage to your back and rest of your body.

It had to be a lot of weight to crack 2X8 with a 10ft span. Good luck

Well, I did kinda have some tool boxes in there, and kept adding tools a little at a time, not realizing how heavy it had gotten. I also had some old, very heavy speakers in there. So I had too much weight in one spot. Live and learn, I suppose. That said, I do think true blocking would have prevented this.

When I crawl under there, I'm using elbow and knee pads, which does help tremendously. I have thought about removing the flooring, but my space is limited, so that will be difficult. I will be jacking up the joists slowly, and periodically checking to make sure everything is good. The walls have not cracked, which is a good sign.

 

[The Cobbler]

If all i had was 2' crawl space, I'd be cutting out the floor so I could mostly work top down, not bottom up

 

[dscheidt]

The wood glue won't do much structurally, but it can't hurt. I will use construction adhesive on the sistering boards, along with clamps, to hold them in place while I nail them in. (That sounds raunchy.) I feel like that should be be pretty solid.

just use a couple screws. Much faster, and cheaper.

Agreed. I realize it's not that important, but I figured at least sealing the cracks would make me feel better. LOL.

Just dirtier.

 

[AC-WC]

Did you ever think about lag bolts to sister instead of nails? Regardless of which you decide to use you should fasten in a W pattern to prevent splitting of the sister joist.
Per This Old House they also recommended gluing the crack prior to straightening the broken joist. Wood glue nothing special.

 

[MoonRise]

Although a PROPERLY glued wood joint is indeed usually stronger than the wood itself, some cracked floor joists still in place are unlikely to let you achieve a PROPERLY glued wood joint.

What is the spacing of your 2x8 floor joists? What wood species and Grade are those joists? What is the EXACT span of those floor joists? Details matter.

Your general plan of jack up the sagging flooring to level things, sister new 2x8 pieces (use as LONG of a 2x8 as you can) to the cracked existing 2x8 floor joists, and attach them together is the usual general plan.

But again, the details matter.

Spread the jacking force on your 4x4 across more than just the cracked joists, reach to at least one intact floor joist on either side of the cracked floor joists (helps you even out the jacking force and keeps the floor more in plane).

You really can't jack up broken floor joists directly, so you are probably looking at two 4x4's (one on each side of the crack in the existing floor joists, perpendicular to the floor joists). And one jacking device on the end of each 4x4, so four jacks needed.

Each jack has to sit on a firm level surface that will not sag, shift, tilt, or sink as the jacking forces are applied. Not insurmountable, but something to keep in mind and plan for. Can't really just put a jack on dirt and lift the floor joists.

Fasteners to sister the floor joists together can be framing nails (do you have a pneumatic or electric framing nailer, or have access to one? Because pounding framing nails by hand with a hammer lying on your back in a tight crawl space is NOT my definition of fun.

Or structural lag or framing screws.

Tutorial for Understanding Loads and Using Span Tables

Using span tables to size joists and rafters is a straight-forward process when you understand the structural principles that govern their use.

awc.org

 

[Uncle murph]

The wood glue won't do much structurally, but it can't hurt. I will use construction adhesive on the sistering boards, along with clamps, to hold them in place while I nail them in. (That sounds raunchy.) I feel like that should be be pretty solid.

One thing that I think could have prevented this, is proper blocking between the joists. There is just bridging, which is better than nothing, but not enough, IMO. I have also noticed that a lot of the nails on the bridging boards have worked their way loose over the years. I will try to carefully hammer them back into place.

Perhaps adding blocking in between the joists will be a future project. I may build some more piers under the living room, because there is a large area under there without any.

There’s a hundred ways to skin a cat but if it was me (I do these types of repairs regularly) I would go ahead with your plan but using the longest possible board and don’t nail or glue anything until the floor has been jacked back to straight.There’s nothing wrong with x bracing but use whatever works for you. I would also suggest using a adjustable screw column instead of the blocks,you can tweak it perfectly and if it ever needs adjustment you will have that option.

 

[Bubba Fett]

Excellent advise, everyone. I'm thinking an I-beam might be better than a 4x4. The screw columns might be a better way to go, at least as a temporary brace until I get the blocks properly seated. I'll see what I can find.

I greatly appreciate the feedback.