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technique for accurate placement of ledger

Posted by sequoia_2007 (My Page) on
Mon, Jul 6, 09 at 2:25

I am replacing a ledger that supports a 4x6 beam as part of a repair project. I will be using 5/8” hot dipped galvanized threaded rod imbedded 7” into the 8” thick grouted CMU wall using Simpson SET-PAC-EZ Adhesive.

QUESTIONS:

I have to drill ¾” holes horizontally in the grouted CMU wall to insert the 5/8” hot dipped galvanized bolts. This will leave a 1/8” space between the top of the threaded rod and the top of the ¾” bored hole and no space between the bottom of the threaded rod and the bottom of the hole. I don’t see any way to center the 5/8” threaded rod in the ¾” hole. Does it matter if the threaded rod is not centered on the axis of the ¾” hole?

The placement of the new ledger needs to be very accurate so there is a tight fit between the top of the ledger and the new 4x6 beam and the joists the beam supports. What is the best way to accomplish this? I was thinking about waiting for the adhesive for the 5/8” bolts to set then sliding the new 4x6 ledger into position and taping it just hard enough to mark the exposed ends of the 5/8” threaded rods so they leave an impression on the 4x6 ledger. Then I would locate the center of the 5/8” impressions and drill 5/8” holes. Is this a good method? I suspect the accuracy of this method could be hit or miss.

Thank you for taking the time to read my post and consider my questions.

Howard

EXISTING LEDGER

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REPLACEMENT LEDGER

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Follow-Up Postings:

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RE: technique for accurate placement of ledger

Wedge anchors would probably be better.

The hole in the wood and base material are the same size.

You can use tapcons to hold the wood in place temporarily while drilling a hole through the wood and into the masonry.

Any 'play' between the fastener and the wood could allow the ledger to slip downwards. You want solid contact of the ledger on the anchor shaft right from the start.


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RE: technique for accurate placement of ledger

You're right that your method will be hit or miss: slight alignment problems can make this difficult. If I understand what you're doing, I think I have a more accurate approach.

My suggestion: 1) put the new ledger in place and butt it up to the beam with a jack, or a post and wedges; 2 ) drill 5/8" holes through the ledger and the wall; 3) remove the ledger; 4) drill 3/4" holes into the CMU; 5) put adhesive into the holes and slide the threaded rod in; 6) put your ledger back up, using a mallet to drive it up against the wall; 7) hold in place like you did before; 8) put on the nuts when the adhesive has set.

Let me know if you think this will do what you want. I have more ideas if this won't work.


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RE: technique for accurate placement of ledger

Thank you for taking the time to respond.

My latest thought is to do what you are saying, but instead drill " holes through the ledger into the CMU wall, then use the " centers to drill 5/8" holes in the ledger and " holes in the CMU wall. I only have ", " and " hammer drill bits. I do not have 5/8"

How do you feel about this approach?

Howard


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RE: technique for accurate placement of ledger

Howard-
Sounds like a good solution to me. You might want to drill the 1/4" holes through the ledger with a regular wood bit (preferably in a drill press, but not absolutely necessary). Then, put the drilled ledger in place as described and use your 1/4" hammer drill bits to drill the CMU. Go into the CMU as deep as you can with the ledger in place so the holes in the wood and the holes in the CMU are on the same axis. Then enlarge the holes as you described. Good luck...should work fine.


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RE: technique for accurate placement of ledger

OK, sounds like I am good to go. I have 8 feet of pressure treated 4x6 so I guess I repeat this several times to get it right if necessary.

Thanks


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RE: technique for accurate placement of ledger

Can you find a suitable bushing material to go down to 1/2 from 5/8? If there is no load on the 4x6 as the epoxy sets up, you could overfill the hole so the epoxy becomes the bushing.
We have used Hilti fasteners where the drilled hole is the same size as the shank. The Hilti-poxy is something. Goes off in less than 5 minutes.
Casey


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RE: technique for accurate placement of ledger

Do you have a link to the Hilti fasteners that don't require an 1/8" oversize hole when used with epoxy?


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RE: technique for accurate placement of ledger

I do not like the OP's nor any other repair method suggested so far.

I would not consider any type of mastic or wedge anchors to hold threaded rods and the ledger in place.

Unless the OP can grout J-Bolts into hollow CMUs to properly support the ledger or use threaded rods long enough so that they go completely through the new ledger and the CMU wall, I would consider nothing short of a column mounted on a concrete footing to support this beam end.

Tapcons and mastic installed rods just don't cut it in most cases, and in most cases would not pass a code inspection without an engineer or architect's approval.

Use a simple column and your worries are over.

Otherwise, consider replacing the horizontal beam with a longer one...one long enough to be set into a pocket cut into the core-filled CMU wall...and your worries are over.

Just my buck three-eighty.


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RE: technique for accurate placement of ledger

I dont recall mentioning wedge connectors or mastic anchored bolts for this application. In addition, the CMU wall is grouted.

I had a structural engineer review this and do the calculations. He said the method and components are code compliant. I also talked with a Simpson applications engineer about this. He will be surprised to hear their RFB#5X12HDG-R bolts chemically anchored with their SET-PAC-EZ Epoxy Adhesive installed per their instructions cant meet code requirements. I believe the real limiting load factor is the amount of load the ledger can handle with the bolts perpendicular to the grain. The structural engineer did the calculations and we are well within those load limits.


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RE: technique for accurate placement of ledger

Howard-
I'm not a structural engineer, but, looking at the specs and the illustrations in the Simpson literature for this product, it seems like this is an entirely appropriate application of the adhesive for your purposes.


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RE: technique for accurate placement of ledger

Simpson strong bolts are listed, but the AHJ may want to see an engineer stamp off the load calculations.

Here is a link that might be useful: Simpson strong bolt listing


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RE: technique for accurate placement of ledger

Just got the phone with our building inspector. He gave his OK for the design and method. Only change is he wants a 1/2" air gap between the end of the new 4x6 beam and the CMU wall.

Thank you to all those who responded and tried to help.


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RE: technique for accurate placement of ledger

"Only change is he wants a 1/2" air gap between the end of the new 4x6 beam and the CMU wall."

He is worried about moisture wicking from the CMU into the wood, and end grain is especially bad.

This will also reduce the bearing surface to only 1 inch x 3.5 inches.

It may still be enough, but the ledger will need to have a decent compressive strength.
Douglass Fir may be adequate depending on the loads on the 4x6.
A piece of 1/4 inch steel plate 1.5 wide x 8 long between the ledger and the beam would help spread the load.


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RE: technique for accurate placement of ledger

Brickeyee,

The bearing surface will be reduced from 3.5" x 3.5" to 3.0" x 3.5". The bearing will be more than adequate.

Thanks,

Howard


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RE: technique for accurate placement of ledger

I did not initially notice you are using a 3.5 inch ledger.


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