sistering floor beams

[JHZR2]

Hi,

In my home, the previous owners had installed some weight equipment, and had to cut into two of the 2x8 or 2x10 floor beams.

They didnt remove more than 1/3 of the beam, but they did cut it, and the cut is about 2-3 inches down the beam. There is no evidence of cracking or breakage.

Both my real estate agent and the home inspector suggested that I sister these two beams, just for reassurance.

OK, fair enough, whether its needed or not, its an easy job, and it really doesnt cost much at all, so Ill do it!

So I need some expert help. I have just a few questions:

1) nails, screws or bolts with washers and nuts?

2) How far on either side of the cutout compromise area should the sister extend? One foot? two feet?

3) One sister per floor beam or two?

4) if only one, since its two parallel beams, should the sisters go both on the inner sides of the two compromised beams? Or should they go both on the outer sides of the compromised beams? Or should they be both on the same side of each beam, so one is on the inner side between the two, and one is on the outer?

Thanks in advance for the advice!

JMH

 

[labman]

Ain't home ownership fun? Now you have a garage to work on your car. Trouble is, the (*&^#$%^(*&$%^*& house takes up all your time plus mowing the grass.

Don't think which side makes much difference. Nails would do, but you hardly have room to swing a hammer. I would use screws or lag bolts. Harbor Freight has good deals on angle head drill adapters.

 

[Auto-Union]

True sistering means going the full length to each wall and into a pocket cut into the masonary or the framing. You can just attach a section with nails extending 18" inches in either direction, a "scab". Cutting a few inches out of the joist is no biggie, the rest of the floor system supports it. Just a "scab" piece should be sufficient. Got a pic?

 

[JHZR2]

Thanks!

I didnt think about the space restriction... nailing may be tough, and if Im drilling for bolts, then I might as well save a step or two and just drill wood screws right in (or are pilot holes necessary anyhow?)

Thanks again!

JMH

 

[JHZR2]

quote:

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Originally posted by Auto-Union:
Got a pic?

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hopefully on the 28th...

Yes, a scab is what they described. How many nails would I want to use? one ever 2-3 inches? two or three vertical over the 8 or 10" joist?

Thanks again!

JMH

 

[Auto-Union]

Drywall screws work too, if you have a good enough drill. Just put in a few, a coupla inches apart, as far as possible toward the end of the board will give the best leverage. PS the size of the scab does not have to match the original joist. Apply upward force on it as you nail/glue it...a singe 2x4 shoring will jack it up a hair.

 

[Auto-Union]

If you can add a few nails through the floor from above into the scab, that will tighten it too. Not worth damaging the finish floor though.

 

[Amkeer]

The correct way to transfer the loads from a joist that is compromised is to extend the peice to a beam on either side. You will then lag bolt or bolt and washer 2 bolts every 24 inches. The problem is if there is deflection in the floor you first have to temporarily support the middle span to reduce deflection then install member. No easy task!

 

[Bret Chase]

what is the span of the floor? if you've got 2X10's@16"OC and the span is less than 10' I really wouldn't worry about it. if you are worried about it, get a sheet of 3/4" plywood, a couple of tubes of construction adhesive and a couple of pounds of 2" drywall scres. take the plywood and rip down 2 strips 8' long by the depth of your joists. take the adhesive and coat one side of the plywood strip. make a puncheon out of couple of 2x4's and put some up pressure on the joist. then clamp the strips up on either side of the joist and screw off the sheets on a 4"X4" pattern. this repair is far stronger than the unmolested joist ever was.

 

[JHZR2]

wow, so many options to consider. I do know that due to running of some old knob and tube, pipes, etc., I might have a hard time running pieces for that long...

Ill have to take measurements and update when Im able...

Thanks all for the ideas and advice!

JMH

 

[drm7]

Please correct me if I'm wrong, but I thought drywall screws were pretty weak? I would think you would want to use a better screw if you dealing with something structural (even if you do use glue).

 

[Oldmoparguy1]

Use the treated deck screws with the square drive. Much stronger and easier to drive. Also easier if you pre-drill the new piece.

 

[Schmoe]

I'd listen to oldmoparguy, that's exactly how I'd do it.

 

[1sttruck]

Before building some large shelf frames out of 2x4 I experimented with different fasteners, fastening a couple of pieces of 2x4 with an offset and then hitting the end with a hammer. I could pop the coated deck screws every time as they were pretty brittle, while nails, regular wood screws and obviously bolts did just fine. I ended up using nails for shear loads and deck screws for compression, which is what they're really designed for anyway. The square drive stainless deck screws don't appear to be as brittle, but I'd still use something else for shear loads.

 

[1sttruck]

Another item... I always pilot drill for screws, even deck screws. You can often get away without doing it on green wood, at least while it's still green, but good, seasoned wood is prone to splitting.

 

[Bret Chase]

quote:

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Originally posted by drm7:
Please correct me if I'm wrong, but I thought drywall screws were pretty weak? I would think you would want to use a better screw if you dealing with something structural (even if you do use glue).

---

all you're doing is providing a clamping force until the construction adhesive cures. one it cures, the screws are irrelevant. besides, you're not going to break the 72 screws per side.. it's just not going to happen.

 

[1sttruck]

"...you're not going to break the 72 screws per side.. it's just not going to happen."

But if it gets inspected it might end up being a code issue, as deck screws don't seem to commonly be considered acceptable for load bearing construction. Do whatever you want when building shelves or whatnot, but it's worth looking into what would be approved otherwise.

 

[Bret Chase]

it's not an issue with BOCA '96, IBC2000 or IBC2003, the 3 codes that I deal with regularly.

 

[1sttruck]

The codes probably aren't going to state 'don't use deck screws for this application', instead they'll either state to use a common shear rated fastener or it's equivalent. If that's the case then one needs to find shear vales for the non-standard fastener, the deck screw in this case, which will tend to be product and model specific a deck screws don't seem to commonly be shear rated. As I recall Simpson states not to use deck screws with their joist hangers, one needs to use nails, even though they make deck screws. Only one of Simpson's line of deck screws seems to have a shear rating.

I have lots of them, they're handy and all, but I won't trust a fastener for shear if it will pop when driving into seasoned wood, or if it hits a knot, or if I hit the joint.

 

[JHZR2]

so... that said... am i better off wth some good nails or some good wood screws? (or even big bolts at either end)?

Thanks,

JMH