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Attaching a Deck Ledger to Lally columns

Toolin's picture

Building a deck for a customer and have run into an unusual situation. I need to attach a triple 2x12 deck ledger to two existing Lally Columns. (Third spot is the concrete foundation).
Anyone have any experience drilling holes in lally columns??
Thinking 2 or 3 1/2in holes.
See the attached pictures.

(post #84184, reply #1 of 19)

i think i'd alter it and put the new beam on top of the lally column  (cut the lally column )


jack and shore the structure until you can transfer the load


 



 


Mike Hussein Smith Rhode Island : Design / Build / Repair / Restore

Mike Smith Rhode Island : Design / Build / Repair / Restore

              www.mfsmithbuilder.com

(post #84184, reply #3 of 19)

Very interesting idea, Might do that.

(post #84184, reply #2 of 19)

The first question the building department would ask around here is what does the engineer say and will he "seal" it?

Greg

(post #84184, reply #4 of 19)

I think this needs an engineer. I suspect that drilling 2" or 3.5" holes in the existing columns will seriously compromise their strength.

(post #84184, reply #5 of 19)

I think he is indicating two or three holes, one half inch in diameter each.

(post #84184, reply #6 of 19)

Do you need to remove the existing flush beam as well?

(post #84184, reply #7 of 19)

I'd weld a ledger holder to them, or steel angle all the way across.

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(post #84184, reply #8 of 19)

May not fit into the esthetics of things but I'd say build a free standing deck - with columns right next to the existing.


Either that or get an engineer to specify how to drill the steel columns.  

Matt

(post #84184, reply #9 of 19)

Yes technically, lallys aren't rated for side loads like that, but we are talking about a deck and the connection to the lally is up near the top where these loads would be more reasonable.  The risk is the lally would be pushed by the deck causing a buckle, or that the weight of the deck would twist your ledger into the lally causing it to buckle.


With the inspectors around here, if something is not load rated for what you're doing you either need an engineer's ok, or you need to over build it so much that it's obviously going to work.


If you go ahead and simply bolt it as you had planned I think there is a very good chance nobody would say anything, and that an engineer would give his ok.  Steel holds a considerable amount of weight compared to the wood we're used to.  Perhaps it's worth a few hundred $ to have an engineer give the go ahead.


If it's you picking up the cost (a bid) I'd through bolt the lally.  If the inspector wants something official and the engineer wants the connection beefed up you aren't out anything and it would simply require a beefier post to satisfy both.


If the client is picking up the cost of what you decide, you might just have some beefier posts welded up.


 


 


 


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(post #84184, reply #10 of 19)

This forum is great resource. Excellent ideas.
I am coming down to two ideas.
1) The first one, Jack the house, cut the lallys and slide the triple between Lallys and the house frame. Probably the way it would be done if starting from scratch.
or
2) Bolt them one as I originally thought but then add a support post next to the lally down to the footing to provide additional support, and keep the twisting moment off of the lally.
Posts are getting wrapped in Cedar anyways, so not a big deal.

The footing is fairly far below grade, didn't have a shovel when I was there last and did not find it digging with my hammer. I think the choice between 1 and 2 will come to what I find for a footing. and whether I can use it for idea 2.

Side Question; the bottom of the Lallys are just buried (at least 8 inches) in the ground. Some reasonable rust on them. Is that a long term problem for the home owner? eg how long will it take for the lally to rust enough to be a structural issue. House was built in the 1980's

Thanks again.

(post #84184, reply #11 of 19)

The lally probably won't fail outright, but if it's rusting badly then now would be  good time to just bite the bullet and replace the whole thing. 

(post #84184, reply #12 of 19)

or ... if it's getting cut down anyway.... flip it and cut the  rusty end


then  coat it with a rust preventative before reinstalling it


Mike Hussein Smith Rhode Island : Design / Build / Repair / Restore

Mike Smith Rhode Island : Design / Build / Repair / Restore

              www.mfsmithbuilder.com

(post #84184, reply #14 of 19)

"Is that a long term problem for the home owner?"


 


Yup.


I was playing pool in a bar one night when a steel lally "blew out".


interresting to say the least.


at first we all went outside to look at the truck that obviously just ran into the building!


it was my idea we get a flashlight and check out the basement next.


 


found the center lally "blown" at the bottom ... looked like it was rigged with explosives. It lost about 4" in height .. and the pool table wasn't so good for the rest of the night. floor sank a good 2 to 3 inches in the middle.


it was set in a damp basement concrete floor ... at least they'd not have any trouble cutting it out.


Jeff


    Buck Construction


 Artistry In Carpentry


     Pittsburgh Pa

    Buck Construction

 Artistry In Carpentry

     Pittsburgh Pa

(post #84184, reply #15 of 19)

Thanks to all for your hints and thoughts.

Here's how it turned out.
I dug down about 15" and found a very solid wide concrete footing under the columns, Looking at the rust in more detail it wasn't that bad.

So rather than jack the house(risk cracking plaster) I went with a 4x4 post sistered to the column, sitting on the concrete footing.
Then put the ledger on top of that and for stability attached it to the column with two 1/2" galvy carriage bolts.

Did something interesting with the first ledger board, I wanted to increase the contact area between the ledger and the lally, and I wanted the 4.5" ledger roughly centered on the 3.5" PT column.

So I took my biscuit joiner, with a couple of guide rails and routed a rounded groove in the first ledger board. The diameter of the blade is very close to the column dia. and the depth adjustable to the .5in I needed.

Here are some pictures of the job.

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(post #84184, reply #16 of 19)

Did you leave the PT in direct contact with the steel collum?

(post #84184, reply #17 of 19)

Forgot to add that point. Strip of vycor flashing between.

(post #84184, reply #18 of 19)

Good trick

(post #84184, reply #19 of 19)

great...



now keep the pics comming


Mike Hussein Smith Rhode Island : Design / Build / Repair / Restore

Mike Smith Rhode Island : Design / Build / Repair / Restore

              www.mfsmithbuilder.com

(post #84184, reply #13 of 19)

Are they concrete filled lally's ? If so, they are usually made from a very low grade  and thin wall steel. I wouldn't reccomend any mods to them. If they are steel pipe columns you could weld ledger support angles to them and bolt the ledger to them.


Rich