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Blocking a lally column for finish and handrails

EthanB's picture

I've got a lally column at the bottom of a stair case in a basement finsihing project. Everything down there is going to be red oak. So I'm planning on boxing the column but I need it to be pretty solid as the handrail will be fixed to the column. I was thinking about putting blocking on the column which I'd then nail the red oak box to, either by using 1/4" tapcons thorough the steel and into the concrete, a powder actuated tool (although I'd have to rent this), or maybe another option. Anybody have any suggestions, or concerns about this?





Ethan (post #202276, reply #1 of 2)

While I understand the need to make a firm post for your rail, blocking may not be necessary if your box is strong enough.

Here's what I've done when faced with boxing a steel column.  While in a perfect world that post would be plumb, in reality it's often close.  So, when making up the box I've oversized it enough to be able to plumb it both ways w/o interference by the steel.

And, for fasteners I've relied alot on PL Premium const. adhesive.  Blobs on the column both sides/top bottom middle.  Lay over a 3 sided assembled  column, bedding it in the adhesive.  Fill any voids while its open, then glue up (titebond) the last pc and nail it off.  Brace if possible dead plumb and let sit overnite.  You can block the top above a drop ceiling if you wish.


Do the same with blocking if you wish.  So the size of the column isn't overpowering for the space-use 3/4 plywood-either total coverage like above, or try to line up blocks (not recommended).  If you see the need to fasten to the steel, predrill for self tapping screws (hex head and countersink) through the ply and into the steel.  The predrilling is usually necessary as the gauge of the steel is way more than normal tappers can handle.

Then make up your wood column oversized and shim plum to that post wrap.


The glue only works if you do it properly and allow to sit till cured.  That and bracing it off so what's right when you start is right when you're done.

In a series of columns, a string line up top and working to a chalk line on the concrete is a good way to keep them all together.

Bottoms are easy-up top not so.  If you can, cross block to your line on the joists, then set the finished column. 

Best of luck.

A Great Place for Information, Comraderie, and a Sucker Punch.

Remodeling Contractor just outside the Glass City.


Put a 2x4 against the column, (post #202276, reply #2 of 2)

Put a 2x4 against the column, facing the stairs.  Attach it to the column with 3-4 spiral clamps.  Fit your box (with one side open) around the column and fasten to the 2x4.  (You might need to shim a little -- tack the shims to the inside of the box.)  Have the handrail brackets fasten through the box face and into the 2x4.

Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville