Tips for installing concrete screw anchors (Tapcons)

As a local handyman,  I work on projects where it's not uncommon that I'm following up on work someone else did before I got there.  A lot of times, I'm there because of work someone else for before I got there.

I can't tell you how many times I've gone into garages and basements with poured concrete or concrete block walls and have to work on handrails, shelves, anchor straps and posts, etc... that have concrete screws used in them and they aren't installed right.

Here's a few tips on putting in concrete screw anchors. 


First: Is it the right hardware. 

Should it be a concrete anchor screw or a plastic concrete anchor with a different type of screw?  Maybe it should be neither of those and should be using a sleeve or wedge anchor instead.  Perhaps a powder activated fastener would be the best choice.


There's a lot of different vectors that need to be taken into consideration when fastening into concrete.  For the sake of this discussion,  we're assuming the right fastener is a tapcon concrete screw.

Second: Pick the correct length of tapcon


The drill bit recommended is about an inch longer than the total thickness of the material being fastened and up to 2" deep. 

The screw should be long enough to go through the material and up to ¼" to ½" less than the hole depth. 

Third: Pick the correct diameter fastener

The shank size should be determined by the weight or pressure anticipated for the screw(s) to have to hold.  The heavier the weight or greater the pressure it has to resist or hold against, the bigger the screw you'll need.

Fourth: Install to the correct depth

This may be simultaneously both the easiest part yet one of the most common incorrectly done.  Especially where tapcons are involved.

I see so many tapcon screws installed anywhere from 3 inches or more deep into the concrete.  That is overkill.  Tapcon screws are intended to only be driven about 1¾" deep into the concrete.  When you drill the pilot hole, you add ¼" longer.  

The extra ¼" is for debris from drilling.  If there is too much debris, it can prevent the screw from fully seating into the hole.

That means in most residential use cases, any tapcon hole should only be drilled about 2 inches deep.  In the case of these concrete screws, using longer screws does not necessarily mean you will get better fastening.  In some ways, it might actually lead to a less desirable result. 

Fifth: Have a long set of drill bits handy.

I have 6" long masonry bits in my toolbox.  Two of them;  the 5/32" and the bigger 3/16".  These make the pilot holes for the 3/16" and 1/4" screws.

Why so long if the pilot holes only need to be up to 2 inches deep? To drill through at least a 2 by board, maybe 2 of them then into the concrete.  When you're doing floor sills or something like that, you don't really have time to mess around so you put your material in place and start drilling down the line.  Often you get someone to go behind you putting the screws in if it's a big job.
 
No, If you're fastening material that already has holes drilled for fastening or you can drill anchor holes before fastening, it's not necessarily a big deal.  You can use regular length masonry bits.  I do that most of the time.  Sometimes though, when you hit a certain situation and need to drill through material, those long bits will save your bacon. 

Six: Consider what you're drilling into.


Not all materials are the same.  Drilling into concrete or driving a screw directly into concrete is not the same as solid stone. Concrete, depending on the mix, can be more or less sandy and crumble when it comes into contact with a drill bit or screw and enough force behind it.  It can also produce more dust and debris than stone will potentially choking off the hole for the screw to go into.

Lastly: Use the right tools


Obviously, you need to use a hammer drill with masonry bits to drill the pilot holes.  We've covered that pretty well.  When it comes to driving the screws, often you will see on the packaging or manufacturer website to also use a drill to drive the screws in.   The difference is you DO NOT use hammer drill mode.  Use regular drill mode. 

You can however, use an impact driver to drive the screws.  In fact, you'll find it might be easier to drive the screws with the impact driver than the hammer drill.  Be advised though that the impact driver will probably have significantly more torque than the hammer drill and can actually over drive the screw and cause damage to the hole in the concrete or stone.

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