I have a floor joist that I noticed has several large knots that have split vertically through the joist. I am going to sister this joist with an identical sized joist (2X10) over its full length.
My plan is to use construction adhesive and tack it into place with nails. To permenantly secure the joist I will use 1/2 inch carriage bolts in sets of 2.
My question is, what should my fastening schedule be? a set every foot, 2 foot, etc…
Thanks in advance.
Replies
I'm not an engineer, but it is my understanding that nails share loads better than bolts do. Why not just nail it off with sets of 5 nails every 16"? The glue is a good idea, too. Others will be by to add info, or to tell you to hire an engineer.
Bill
Use a bunch of nails and liberal glue. Gorilla glue would work well, but you need to dampen the wood first. You could use some screws or bolts to draw the two joists tightly together, but common nails will work very well. If they poke out the other side, clinch them over.
"When asked if you can do something, tell'em "Why certainly I can", then get busy and find a way to do it." T. Roosevelt
I'm not an engineer either but I would glue and nail it. I've had to replace many joists that were hacked up and as long as the inspectors see globs of glue dripping from between the joists they seem happy.
I'm an Inspector. And I LOVE glue!
Don't use construction adhesive -- it has bad creap. Gorilla glue (or another brand of expanding urethane glue) is good for this job. Humidity helps set the glue, so, as was stated, dampen the glue if it's dry there.
Be sure to spread out plastic under the beam to catch the drips -- GG is REALLY messy.
If the beam were simply overloaded then three carriage bolts would be all you needed, but for a cracked one you want more frequent fastening. It isn't a bad idea to use three bolts or lag screws, though, to do the initial fastening -- often easier than trying to get it nailed off with just clamps holding things. (Do have several clamps on hand, though, to assist you.)
Remove as much load above as possible when installing. One trick that can be done with the three carriage bolts is to install one in one end and one in the middle, leaving the other end dangling down an inch or so (amount depending on any existing sag). Then jack up the free end and install the last bolt, before nailing off everything. (You'll need to plan ahead and work fast due to the glue.)
Nail off with 16d nails. (Be sure to check the other side of the joist for wiring before nailing. Probably a good idea to pry loose any wires stapled to the side before beginning this whole procedure.) The nails will protrude through the far side -- bend these over ("clinch" them). This assures they'll never wiggle loose.
Alternate nails top/bottom, or top/middle/bottom. A nail every six-eight inches should suffice, with them a little closer near the ends. (A power nailer will really help.)
Note that you may have to change your plans based on nailing clearances -- not enough room to swing a hammer, etc. In some cases bolts will be all that's practical, in which case probably one every 12-18 inches (alternating top/bottom) should suffice.
If there are wires going through the joist, and this is an unfinished (and essentially unfinishable) basement, cut the wire (after cutting power) at the adjacent joists and install junction boxes -- usually you'll need two boxes, and a short piece of new wire, but occasionally there's enough slack to be had that one will suffice.
Of course, if pipes go through the joist then other arrangements are needed. If the pipe isn't in a seriously weak spot, and is not too near the bottom of the joist, the sister can be notched around it, and then (after sister installation) a wedge glued into the notch.
happy?
DanH,
Why do you say construction adhesive is crap?? Just wondering? Ive had varying experiences with different brands under different conditions??? Usually stick with the PL brand (PL400 or PL Premium Polyeurethane).
m2akitaLive by the sword, die by the sword....but choose your sword wisely.
LOL... creap not crap. It allows slight movement and that is somthing to avoid in this situation.
Construction adhesive is plyable after setup because it is rubber based. Great for holding down subfloor and filling little gaps along the joist. Not so good for holding large loads w/o movement. It's the whole inertia thing, once somthing is started in motion it takes less energy to keep in motion.
Garett
LMAO!!! Guess I need to learn to read better. Whole time Im writing original reply Im thinking '#$%%, they found that this stuff doesnt work, how'd I miss this,.....
Very good point about being pliable. Im assumeing (big danger), that something like the PL Premium Polyurethane would be o.k. as its polyurethane based. Ive got nothing against Gorilla Glue ( love the stuff), just thinking how much easier it would be to apply the PL from a caulk gun opposed to squeezeing out the Gorilla glue from a bottle.
-m2akitaLive by the sword, die by the sword....but choose your sword wisely.
I said it CREAPS. It's good for what it's good for, but not good in shear.
If ignorance is bliss why aren't more people
happy?
I just finished up the job.
I ended up using a liberal amount of gorrilla glue along with 16D nails. I fired the nails in vertical rows of 5 nails spaced at roughly 12". It is clamped in 3 places right now with C clamps. I will let them sit over night. I also drove 2X4 braces between the sister and the adjacent joist to apply pressure where the clamps wouldn't reach.
I will draw the free end in with carriage bolts tomorrow.
I wan't to thank everyone for the advice.
I will draw the free end in with carriage bolts tomorrow.
You want to explain that? Did you glue and nail only part of the new joist?
"When asked if you can do something, tell'em "Why certainly I can", then get busy and find a way to do it." T. Roosevelt
sorry...bad english.
I glued and nailed the entire span...including the free end. since i had enough fun for one day...backing wires out, redrilling, pulling,etc...i am saving the final step of installing carriage bolts until tomorrow evening.
again...it is glued and nailed from the free end all the way over the header 10ft away.
iS THE NEW BOARD ONLY 10 FT LONG?
"When asked if you can do something, tell'em "Why certainly I can", then get busy and find a way to do it." T. Roosevelt
The board is roughly 12 ft but precisely 142inches.
Ok, so you glued and screwed 10 ft of a 12 ft board. How do you plan to get glue between the boards for the last 2 ft? And if the glue is already there, it's probably set by now, and you won't be able to pull the boards together.
"When asked if you can do something, tell'em "Why certainly I can", then get busy and find a way to do it." T. Roosevelt
I glued and nailed the entire span...including the free end. since i had enough fun for one day...backing wires out, redrilling, pulling,etc...i am saving the final step of installing carriage bolts until tomorrow evening.
You did the same project?
"When asked if you can do something, tell'em "Why certainly I can", then get busy and find a way to do it." T. Roosevelt
I had access to all 12ft. The entire length was glued and nailed
Is the joist with the knots/cracks sagged significantly more than the other joists (check this by running staight edge or stringline perpindicular along bottom of joists)??? If so, you might want to jack up that joist (little bit over period of time) before sistering to it.
Also, if the joist that you are going to be using as the sister is the same dimensions (2x10 the full lenght of span) as the bad one, I dont think you have to worry a hole lot about shear strength attachement, your new joist should be able to carry the load on its own just as all the other joist.
Good luck trying to get a full lenght joist in, it might be a little tight (Im assuming your getting access to the old joist from the basement, and its resting on a mudsill.) You may have to cut it a bit shorter than the full length and chop a little off the top corners to get it in. As little as possible.
m2akita
M2,
my house is on a slab foundation. it also turns out that the house is balloon framed. I am remodeling a small room and half bath. the room has been stripped down to the studs...obviously. I cannot get the sister joist to recess into the wall cavity on the one end...that is why i need a fastening schedule.
i also want to point out that there is no sag in this joist currently. there is, however, 3 sizable/noticable cracks through these knots.
You should have said that from the beginning! If one side of joist is unsupported carriage bolts should be used with glue, nails etc. You'd want the bolts on the unsupported side two,three verticle pattern.
No way to support that end??
If hammering nails is problematic for that space, consider McFeely's 2 7/8" Promax screws. They are self drilling #10 screws (similar to 10D nails) that have an extra long shank - 1.5" of shank. This allows face fastening of two boards without a gap. They also have a washer head so they really snug up the wood instead of splitting it. Great for gluing!
Elmers Polyurathane glue costs much less that GG, but does the same job as far as I can tell. For this job, you might even want to consider a two part epoxy in a paired syringe tube.
Rebuilding my home in Cypress, CA
Also a CRX fanatic!
You're right on the Elemrs glue. I was using Gorilla glue as a generic term. The one advantage to urethane glue is the long open time. I spary one board to get it damp, then spread glue evenly on the other board, and then assemble. The open time is long enough that there's no reason to hurry, except for the dripping glue.
"When asked if you can do something, tell'em "Why certainly I can", then get busy and find a way to do it." T. Roosevelt
Don't forget the simple palm nailer - It saved my butt when doing the same job with some damaged joist in a basement.JT
Don't forget to use joist hangers at each end. Get the double for the appropriate joist size and make sure you nail it off completely.
I would but the house is balloon framed. There is no rim joist to attach a hanger to.
How does the weight load reach the wall? Did you notch the ends of the new joist to fit? How does the existing cracked joist bear its load to the wall? I am not sure that adding more weight to an already compromised joist is going to fix the problem, regardless of your nailing and bolting schedule. I know I'm a day late and a dollar short here, but next time........;D
A beam of uniform cross-section is weakest in the middle, from a standpoint of strength vs forces present. Sistering just the middle 50% or so will add significant overall strength. And if the defects in question are that area it adds much more.
If ignorance is bliss why aren't more people
happy?
those defects are in that area.
my cracked joist was not failing or sagging. I noticed 3 significant splits that transversed half the height of the joist. Adding the sister was nothing more than good preventative maintanence while I had access to the beam.
12' long @53#/ft is about 600#.
6 16d nails total, perhaps 3 near each end is all that were needed.
Glue does nothing to help the load transfer.
the original joist had a nice combination of bow and twist. i used glue to keep the sister joist tight to the original. The C clamps pulled them together and held the joists until the glue set. The nails were to transfer the load. Now I won't have to worry about the sister joist trying to pull the nails out.
Technically, The new joist is going to carry the load by itself. I is not required to be a built up assembly. Attaching it the the existing joist and subfloor will aid in preventing squeaks.
The new joist is only supported at one end. Therefore, it did need to be built up in order to transfer the load