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nateshirk 12-16-2013 04:09 PM

Tapcons not grabbing cinder block
I'm using 3/16"x 2-3/4" tapcons through a 2x3 and into cinder block. I'm using the bit that came with them (which seems a tad too big). They don't even start to grab. They just spin. Could the bit be too big? Would a bigger tapcon help, or would that crumble the block too?

joecaption 12-16-2013 04:40 PM

May want to share what it is your trying to do.
Any wood in contact with a block wall needed to be pressure treated.

I try to hit the mortar not the block and mostly use the 1/4 screws and always predrill the wood for a clearance hole in the wood.
If there's no predrilled hole the screw tries to push the wood away from the wall.

stadry 12-16-2013 04:41 PM

tapcons are for conc, not ' cinder block ',,, don't expect much pullout strength & expect reduced shear strength,,, those blocks have little strength other'n compressive strength ( holding up weight such as a house ! )

depending on your task, you may wish to attach a 2x4 supported by the conc floor using lead shield lags just to stabilize the 2x4

concretemasonry 12-16-2013 04:50 PM

There is a falicy about not having untreated wood in contact.

The actual requirement only applies to concrete that is in contact with the soil or actual water. It is allowed in masonry cavity walls above grade and is used on many high rise concrete structures.

It just takes a little common sense and not a blanket standard.


joed 12-16-2013 05:18 PM

Definitely sounds like the holes are too big.I have successfully used tapcons into concrete blocks many times. The blocks are harder than the mortar and give better results in my experience.

ben's plumbing 12-16-2013 05:24 PM

you will be disapointed when using tapcons on cinder block....won't hold ..ben sr

concretemasonry 12-16-2013 05:30 PM

The strength of block can vary widely since the standards (ASTM, etc.) are so low. For a good manufacturer, the strength is not a problem and they usually about 30% to 50% over the minimums because it actually is more costly to make a weak block. Water (not cement) is cheapest way to make a stronger block, but a good contractor will not accept that because dimension uniformity is the way to get economical walls.

Usually, the aggregate gradation will control the ability to hold a threaded anchor. Some aggregate types are better than others, but few block are made for nailing into.


danpik 12-16-2013 05:45 PM


nateshirk 12-16-2013 10:44 PM

Why do threads go so far off track? Can I just get some good, solid ideas on how to secure some lumber to a block wall?

Oso954 12-17-2013 12:48 AM

You might want to mention why you are trying to attach them. Hanging tools, putting up dry wall, building shelves for heavy weights, etc.

It might make a difference.

Red Squirrel 12-17-2013 01:55 AM

I gave up trying to use tapcons, I find they're too hit and miss. Some will grab but most wont.

Look at powder actuated tools, or even construction adhesive like PL premium. That stuff holds VERY well. Downside is it takes a while to cure so you can't exactly afix something and put weight on it right away, and as much as it does hold well I would not trust it for anything that has to hold people. (ex: if you have a very tall cinder block wall I would not make a second floor with only adhesive!) Then again I would not trust tapcons for that either...

For solid concrete I like to use wedge anchors. More expensive per unit than tapcons but they go in faster and hold much better.

stadry 12-17-2013 04:12 AM

you're from philly, right ?,,, ' threads go so far off track? ,,,some good, solid ideas on how to secure some lumber to a block wall? ' gosh, thought we had list'd some good stuff :yes: lead shield lags, pl const adhesive,,, we forgot conc nails ( hardened steel ) & boogers :laughing: then again, you never said what you were trying to accomplish :huh:

danpik 12-17-2013 05:44 AM


Originally Posted by nateshirk (Post 1279371)
Why do threads go so far off track? Can I just get some good, solid ideas on how to secure some lumber to a block wall?

It is called thread drift. Happens sometimes. I deleted the drift that I made. Sorry.

danpik 12-17-2013 05:49 AM

something to understand about tapcons. The method and tools used to drill the hole are important. If you have a slow drill or a dull bit the extra time the bit stays in the hole actually can make it bigger from the erosion of the dust working its way out of the hole. Also, you need to make sure you are drilling straight into the hole and not moving the bit around as you drill. Setting the screw is equally important when it comes to the proper tool. I can never get a screw to hold properly if I use a slow speed driver. I found my Makita Screw gun to work best. If you use a slow speed drill or cordless, it can cause the screw to act as a drill bit and ream out the hole as it goes in.

nateshirk 12-18-2013 06:05 AM

I will be securing drywall to the 2x3's. I need something that will sit flush or below the wood. I know.....the moisture is already taken care of. I just figured if I mentioned that I need something to do the job that a tapcon should be doing, that would be all the info needed.

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