Attaching sheet metal to concrete block

Stan in Oly, WA

Well-known Member
I have to strengthen a very short section of concrete block wall in a situation where I can't increase the thickness of it by even a quarter of an inch. That's the amount of clearance I have with a steel security door I'm trying to install. More than a quarter inch of additional thickness will cause the door to bump into a garden window, and removing that would entail what would essentially be (or soon become) a kitchen remodel.

One way I thought of attaching the sheet metal to the concrete block would be to drill and insert steel fasteners in the block, grind them flush, and plug weld the sheet metal to them. Would this work? I know that exposing concrete to welding temperatures can result in popping and spalling. I suspect that heating metal to similar temperatures in a hole in concrete would do even more damage. I have all the materials I need to do a practice run, but it would save time to get the information here.

Thanks, Stan
 
Before I tried welding, Stan, I'd try pan-head Tap-cons. Mark the hole locations by drilling through the sheet metal with a regular metal drill enough to mark the concrete behind it, drill the hole in the concrete with a masonry drill, countersink it slightly with a larger drill (head angles might not match but it shouldn't be off enough to bother), install your sheet metal and then send home your Tap-con through both layers. Should draw up pretty much flush.
 
http://images2.mcmaster.com/Contents/gfx/large/92403a803p1l.png?ver=15861864

I've heard them called "threshold anchors". They're a flat head version of a sleeve anchor.
 
Thanks, Tim. That's a perfect step-by-step description of how to do it. I have to admit, there's a certain beauty to having a plan for doing something in a way that will actually work.

Stan
 
Thanks, Steve. I'm going to take that as two votes (yours and Tim V's) for doing it with mechanical fasteners rather than trying to do it in an interesting, but untested and potentially failure-prone way. Only about one out of three of my unorthodox schemes ever comes off without a hitch.

Stan
 
Yes, I did, Mark--thanks for noting that before poor Stan buys pan-heads and says "wait--this ain't gonna work"!
 
If the block is hollow cells and is not filled, not high strength, be careful with the size and depth of the fastener, you don't get much pull out or shear value in hollow block, with that in mind, care is needed in fastener diameter here. If that flush mount sleeve anchor is available, its going to be better than grinding and plug welding for sure, heat that fastener shank enough, you could pop the adjacent material in the hole, or fracture it. I'd use a minimal size fastener here.
 
Have you considered using glue , there are plenty of structural adhesives that will set hard and give enormous strength over a large area .
 
I like the idea of glue, Charles, but I'm leery of it due to a bad experience I had a couple of years ago. I couldn't find the information I needed regarding the proper adhesive to use for the specific material and substrate I was working with. I took my best guess (and put too much faith in the advice of someone I should have realized didn't know enough to be offering advice) and wound up having to spend a lot of time repairing the damage and doing the job again---differently the second time. I'll look into it, though.

Thanks, Stan
 
Thanks, Billy. That confirms my worst suspicions. So, no welding.

What do you think of the idea of Tapcons? They thread directly into pre-drilled pilot holes in the concrete, which seems to me would cause the least amount of compromise to the integrity of the (unfilled) block of any mechanical fastening method. Sheer is not going to be a problem. What I need to do is strengthen the location for a door jamb where the framing is inadequate for the installation of a security door.

This started as a project to replace an aluminum screen door with a steel security door---a job that I hoped I would be able to do in a couple of hours. When I got the screen door and the brick molding out of the way, I could see that the condition of the framing would prevent the security door from actually being secure (it would still look secure, which I hate to count on as being enough) unless I could figure out a way to beef up the framing. Now I'm trying to come up with a way to do it without having to tear into the walls inside the house. It's a location where doing that would involve just about every problem you can run into except for plumbing. Of course, to balance that out, I'd probably find rotted lumber, and/or insect damage.

Stan
 
Tapcons are a worthy candidate, thin enough and thread in, not expand like a sleeve or wedge anchor. One of the things with concrete masonry construction, C.M.U. or concrete block, is to coordinate reinforcing, filling or fully grouting cells where fasteners are needed, in addition to using high strength C.M.U. with 75% filled cells, which means to the layman, the cell webs/walls are thicker and the C.M.U. should be able to be certified to 5000 p.s.i. I had a mid rise building call for 6000 p.s.i. C.M.U. and was told by a major supplier that 5000 was the threshold at that time, meaning they would provide masonry certifications for that C.M.U. I presented it to the engineer of record as a request for information and or change to the design, still demanded 6000 psi, it was built with 5000 psi with fully grouted cells. Anyways, the reason I recollect it, those allow for stronger connections, fasteners, harder to drill too, but, when filled, its just about like concrete.

That door will only be as strong as what its fastened to, it would be ideal to reinforce the surrounding structure, to obtain stronger connections.

I know what you mean by opening a can of worms, had one this weekend, basement/garage center door, one side post/jack rotted at the bottom, but the inner members to replace, (and could have been done without too much trouble) but would have taken hours longer for the same effect, so I jammed a new pressure treated stud in there between the footing and the framing above, stiffened it as if it all was good,filled the voids below with concrete, and set the door onto a bed of concrete, making a curb for the water and supporting the threshold without shims or voids where vermin could hide, live etc., saved me hours of work, and got the same result, favor for a friend, he was real happy and the darned thing fit perfect, operated as it should, wish they were all that easy LOL !
 

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