# I can't get tapcon screws to tap into the concrete slab!?



## Monty (May 21, 2007)

*I can't get tapcon screws to tap into the concrete slab!?*

My husband and I are installing a 5/8" plywood subfloor plus 1" foam over our concrete slab. We are using 3/16 tapcon screws that are 2 3/4" long. We have rented a hammer drill, and are using a 5/32 bit to drill into the concrete. We are drilling down 1/4" longer than the screw, but the screws don't seem to be tapping into the concrete. Our screws will go in so far, but then the head of the screw gets stripped, despite brand new bits. Maybe our regular drill does not have enough power to get the screws to go down?? Do we need a drill with more torque to get the screws to go in?? Does anyone know why we might be having trouble? What can I do to fix this? It states on the tapcon box that for a 3/16 screw to use a 5/32 drill bit, which is what came with the box...and is what we have tried and is not working. We have tried using a 3/16 hammer drill bit as well, but this proved too big.


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## Zel1 (Mar 21, 2007)

Maybe try the lowest speed setting on the drill? I know sometimes the higher speeds tend to strip the heads. Also, maybe try a square drive, or even a hex head?


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## RippySkippy (Feb 9, 2007)

Are you using the hammer drill to drive the screws? If not...I would HIGHLY recommend it or an impact driver. When I drove a couple hundred screws for a project last summer with a standard 18V cordless...those babies would just torque and snap in a heart beat...with the hammer drill...piece of cake. You might try the tapcon driver, it's ok...I have it. If you use the same hammer drill for drilling and driving...it'll be quicker than chucking and re-chucking all the time.

You might want to check out the split anchors for this application, WAY faster to install...and I've had excellent results from them in a "no load" application. (look around on this site, there's a ton of information on different connectors and applications, no affiliation)

Another option are the GRK concrete screws...but you'll find them similar to the tapcons.

Good luck.


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## NateHanson (Apr 15, 2007)

Are you using the right size philips bit? You might need a #3 for that screw.


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## Clutchcargo (Mar 31, 2007)

You need the socket bit to drive those in. The screwbits just strip the screwhead out..


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## handy man88 (Jan 23, 2007)

Make sure you use a shop vac and remove all the dust in the hole. Try predrilling even deeper. Also, if they were using the wrong size screw bit, the screw would strip before the head breaks off.


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## Monty (May 21, 2007)

*thanks everyone*

we've ended up going with redheads and simply predrilling, then hammering those into the concrete slab. thanks for your advice!


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## NateHanson (Apr 15, 2007)

handy man88 said:


> Also, if they were using the wrong size screw bit, the screw would strip before the head breaks off.





Monty said:


> Our screws will go in so far, but then the head of the screw gets stripped, despite brand new bits.


I think they're saying that the screw heads are getting stripped, not breaking off. 

Sounds like they need a hex-socket drive. 

(If you have a hex-to-square 1/4" adapter, you can use a regular socket in your hammer drill.)


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## wingman77 (Jun 15, 2009)

Monty I am having the same problem installing floor can you give more detail on how you did it using redheads (what is a redhead)

Thanks


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## wingman77 (Jun 15, 2009)

Having the same problem as Monty I am using 1/4 tapcon x 2 3/4 as well as 1/4 x 3 1/4. Material thickness is 5/8 plywood and 1 inch foam board. I drill the correct hole depth but tapcon does not go all the way down it stops about 3/8 from the plywood .I have tried driving with the hammer drill either breaks the screw or strips the head torque gun just stops driving it is only a 12 volt .I clean the hole properly so I know that is not the problem. Using countersunk hexhead tapcons because must be flush with plywood.


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## Zel1 (Mar 21, 2007)

I recently used some 1/4" tapcons and had some minor issues. My advice would be to drill the hole slightly deeper, maybe a 1/4" and use compressed air to clean out the holes. If the drill dust has nowhere to go when the screws get there, its like not having the hole predrilled. Just my .02


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## RippySkippy (Feb 9, 2007)

Have you thought about using the split drive anchor?


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## Bronx (Apr 11, 2008)

*Tapcons*

There are many reasons that tapcons fail. You have 1 5/8 of material being fastened to the concrete and the mininum embedment of a 1/4 tapcon is 1" into the concrete. A 1/4 x 2 3/4 tapcon is the correct size.
The hole to be drilled is 3/16. The hole must be cleaned out with a shop vac and driven with a #3 phillip tip driver. When driving the screw use a corded drill that is not a hammer drill.


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## Willie T (Jan 29, 2009)

Zel1 hit on a very important point..... compressed air. Very often a shop vac will not get all the dust out. And as you are drilling, it pays to pull the bit upward, yanking out as much of that dust as you can about every three or four seconds.

Don't forget your eye protection when blowing out the holes... that crap will come straight back toward your eyes.


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## HABSFAN2006 (Feb 25, 2009)

Bronx said:


> There are many reasons that tapcons fail. You have 1 5/8 of material being fastened to the concrete and the mininum embedment of a 1/4 tapcon is 1" into the concrete. A 1/4 x 2 3/4 tapcon is the correct size.
> The hole to be drilled is 3/16. The hole must be cleaned out with a shop vac and driven with a #3 phillip tip driver. When driving the screw use a corded drill that is not a hammer drill.


Above is the proper procedure that has worked for me everytime.
Ensure the hole is deep enough...Another secret, is to ensure you are perfectly straight, with some downforce on the drill. Also, do not stop for any reason mid way.
Once you get the hang of it, none of them will strip.


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## wingman77 (Jun 15, 2009)

Thanks all great advice.Blowing hole with compressed air as well as yanking drill bit up while drilling helps clear the hole. Bought a Ryobi impact 18volt gun great tool it drives those screws without a problem.:thumbup:


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## windowguy (Jan 27, 2009)

Tapcons are wonderful, you shouldnt need an electric device to screw them in, just a socket.

dust left in the hole is the #1 reason i've found that stops the screw from going in and thus breaking the head off.. compressed air with the "straw" on the end is best for clearing them out.

another tip for extending the life of your drill bit is to blow out the dust in the hole about halfway down through your drilling. Mashing the dust on the tip for 30 seconds wears it down faster. Do this extra step while it seems like adding time to the project actually will save time in the long run by conserving your bit.


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## Flt_Simulation (Feb 14, 2009)

For you folks that are considering installing plywood over a concrete slab, here is how they do it here in the Philippines:

1. First, a thin poly foam moisture barrier is installed directly over the exsisting concrete floor. I don't have a photo of the poly foam sheeting actually on the floor, but here is a photo of a roll of the stuff:




2. Next, a layer of 10 mm Marine grade plywood will be installed over the poly foam sheeting and secured with screws into the concrete floor.

Here is a worker using a large hand drill with a masonary bit to drill through the plywood and into the concrete floor below:




3. A plastic anchor is then inserted into each hole, and the end of the plastic anchor that extends slightly above the plywood is cut off with a sharp chisel:




4. Then, scews that resemble drywall screws (I think they are actually drywall screws) are pounded into the plastic anchor with a hammer (quick and easy) ... This holds the plywood very tight to the concrete below:


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## HABSFAN2006 (Feb 25, 2009)

#1, omg
#2, wow, slitely different practices here in north america, specially northern states / canada
#3 he might not be wearing shoes, but i hope he wearing eye protection if hes "pounding" in those screws.

thanks for sharing


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## Quickdraw (Nov 18, 2008)

If Im not mistaken the Tapcon people recommend dilling the hole 1" deeper than the screw penetration.


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## slydevil (Jan 13, 2010)

wingman77 said:


> Thanks all great advice.Blowing hole with compressed air as well as yanking drill bit up while drilling helps clear the hole. Bought a Ryobi impact 18volt gun great tool it drives those screws without a problem.:thumbup:


+1

after sucking the hole out and yanking out dust w/ the bit, the same drill that couldn't do the job earlier worked just fine. oh and also use the 'hammer' setting.

thx to the above posters for the solution!!! :thumbup:


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## jlhaslip (Dec 31, 2009)

Tapcons can be replaced by drilling a hole slightly larger in diameter than a framing spike.
Insert a doubled over piece of rebar tie wire into the hole as far as the depth of the hole.
Insert framing spike and hammer it home.
Would only suggest this for down nailing, not vertical material.

Properly sizing the hole/nail/wire combination will create a very solid connection. Ideally suited to the subfloor application.


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## rustyjames (Jul 20, 2008)

I've never had any problems with Philip head tapcons, never blew out/sucked out the holes or needed an impact driver. I think the OP's problem is not using the right bit, or not "laying into it" when driving the screw. Using hex heads isn't the answer because for this application you'd want the heads to be flush.


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## Wino (Dec 28, 2009)

http://www.confast.com/products/technical-info/tapcon-concretescrew.aspx

The above link is from the manufacturer. They recommend drilling the hole 1/2 inch deeper than required, as well as fully cleaning the hole. It also recommends using a hammer drill in hammer drill mode.


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## sabrinaofmn (Aug 7, 2010)

*How we did it*

My husband and I are installing 3/4 inch plywood sub floor over terrazzo, which is apparently stronger than plain concrete. We too had difficulty getting the screws to go in. Here's how we did it. 

First, we were using the smaller Tapcons (which have red on the box). We were using 2 1/4" skinny Tapcons. The concrete bit just wasn't strong enough. It would break. And we weren't using the Tapcon bit. We were using a higher-grade Bosch bit. The bit was just too skinny. It didn't have enough strength, so it would break. The solution was to move to the larger diameter Tapcons (with green on the box). We wound up using 1/4 x 1 3/4 Tapcons with the phillips head. I also recommend the 1 3/4 depth because it heats up your drill less than the longer screws, and Tapcon themselves said that one inch over the depth of the material is sufficient. With these screws we used a 3/16 inch Bosch SDS plus rotary hammer drill bit. This bit is doing the job, cutting through the terrazzo with no trouble. We do break a bit occasionally, so buy one half dozen before you start. But the system is working. 

Next you need a #3 phillips bit to drive in your screws. We tried doing this with a regular drill, but it wasn't powerful enough. You need an impact driver. We bought a Hitachi impact driver at Lowes for $189, and it's turned out to be a great little tool -- very well made. The batteries charge super fast, and that little tool drives in the screws with no problems. You need the #3 phillips bit that is made for an impact driver, not a standard drill. 

You also need a separate drill with a 3/16 inch wood bit for predrilling the holes in the plywood. So it goes like this:

1. Drill holes with your 3/16 inch wood bit using a standard drill in the corners of the first sheet. After the corners are done you will drill the rest of the sheet.
2. Use a rotary hammer drill with a 3/16 inch bit to drill into the concrete. Don't drill too far lest you overheat your drill or bust a pipe or something. I tried using tape as a guide, but it didn't work. Just use your eyesight. Don't drill too many holes or it heats up the drill bit too much. Don't drill more than ten holes at a time, for example. 
3. Drive in a 1/4 x 1 3/4 Tapcon with an impact driver using a #3 phillips bit made for impact drivers. 

This system works. The screws sink below the surface of the board (but not too low), and we are really moving along at a fast clip. You need good tools, though. We have a Bosch rotary hammer drill. If you are having trouble drilling through the concrete, your drill isn't powerful enough. 

Buy a half dozen of each -- #3 bits, 3/16 wood bits, and 3/16 concrete bits. We are doing 1,000 square feet, and we have already gone through that many and aren't yet done. 

Best of luck.


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