Choosing the Best Anchor to Fasten to Concrete

[Michael Thomas]

Came across this researching fastening methods for handrails and found it interesting - turns out these are lots of factors I had never considered:

Choosing the Best Anchor to Fasten to Concrete ~ Concrete Fastening Systems (http://www.confast.com/articles/choosing-the-best-concrete-anchor.aspx)

[Gunnar Alquist]

Great. A lot of information, but no answers.

[chris mcintyre]

For handrails I love the tapcon type fasteners, I found in the older concrete (or brick) that if you go up a 32nd or 16th of an inch in bit size it will keep the fastener from breaking and you don't lose any holding strength.

[Gunnar Alquist]

For handrails I love the tapcon type fasteners, I found in the older concrete (or brick) that if you go up a 32nd or 16th of an inch in bit size it will keep the fastener from breaking and you don't lose any holding strength.

Was this approved by the manufacturer?

[chris mcintyre]

Was this approved by the manufacturer?

Probably not :o, but it works!:D

I guess this might not be a good idea if you were hanging cabinets or your tankless water heater, but for handrails where you are relying on the fasteners shear strength, I have not had any issues (that I'm aware of :) )

[Jerry Peck]

I found in the older concrete (or brick) that if you go up a 32nd or 16th of an inch in bit size it will keep the fastener from breaking and you don't lose any holding strength.

"and you don't lose any holding strength."

And you have pull out tests to support that?

Followed by "Probably not :o, but it works!:D "?

HOW do you know "it works"?

Seems to me is that all you really know is that the masonry anchor 'goes in easier', which leads one to believe 'it comes out easier', not unlike the information Michael posted about wearing the threads down and losing holding power ... :eek: ... that's what you just accomplished by 'oversizing' the drilled hole.

[chris mcintyre]

I feel that I could make a pretty good case that they do hold. I could defend my shear strength argument, but without manufacture allowances for the increased hole size I would only dig myself a deeper hole with this crowd, so I digress :).

[Jerry Peck]

I feel that I could make a pretty good case that they do hold. I could defend my shear strength argument,


But ... ;) ... "shear" is not all there is to "anchoring" something in place, in fact, "pullout" is frequently just as important, or even more important, than shear ... and I doubt you could easily defend pull out with a larger hole. :)

[chris mcintyre]

But ... ;) ... "shear" is not all there is to "anchoring" something in place, in fact, "pullout" is frequently just as important, or even more important, than shear ... and I doubt you could easily defend pull out with a larger hole. :)

Can't argue with that, but.....



Came across this researching fastening methods for handrails



For handrails I love the tapcon type fasteners,



.....but for handrails where you are relying on the fasteners shear strength,....


The handrail is typically between a post/column and a wall, or two walls. So in the case of handrail, and only handrails, pull out should not be an issue.:)

[Jerry Peck]

The handrail is typically between a post/column and a wall, or two walls. So in the case of handrail, and only handrails, pull out should not be an issue.:)


"So in the case of handrail, and only handrails, pull out should not be an issue."

To the contrary, pull is quite an issue.

A handrail is required to resist a 200 pound load in ... ANY DIRECTION ... which includes all directions other than simply vertical, and vertical is the only direction where shear would be the determining factor, otherwise the determining factor is likely to be pull out ... especially if the holes are oversized a bit ... ;)

[H.G. Watson, Sr.]

For handrails I love the tapcon type fasteners, I found in the older concrete (or brick) that if you go up a 32nd or 16th of an inch in bit size it will keep the fastener from breaking and you don't lose any holding strength.

That is absolute bull.


http://www.icc-es.org/reports/pdf_files/ICC-ES/ESR-1671.pdf


Safe working loads for single installation under static loading should not exceed 25% of the ultimate load capacity

For example, if the ultimate shear value for a 1/4" diameter Tapcon® with a 1-1/2" embedment in 4000 psi concrete is 1380 lb., then the safe working load ...



Tapcon® Concrete Screws for Concrete, Brick and Block ~ Concrete Fastening Systems (http://www.confast.com/articles/tapcon-screw.aspx)


Even with its small size and ease of use, Tapcon® concrete screws <../products/tapcon-concretescrew.aspx> still offer considerable holding values. It is important to remember that the holding power of any anchor is always dependent upon the quality and strength of the base material, depth of embedment and proper hole size. When comparing technical data for different manufacturers, it is important to determine what values are being given – ultimate load ratings or working load ratings. Either term is acceptable, but it is important that when comparing products equivalent values are used.

Below is pull out, shear and tension data values for standard Blue Screws:
The holding values in the charts above are ultimate holding values for the list of embedments shown. A safety factor of 4:1 (or 25%) is generally accepted as a safe working load. For example, if the ultimate shear value for a 1/4" diameter Tapcon® with a 1-1/2" embedment in 4000 psi concrete is 1380 lb., then the safe working load for that screw is 345 lbs.


For minimum edge distance and spacing distance, please refer to the ICC-ES Evaluation Report: ESR-1671 <http://www.icc-es.org/reports/pdf_files/ICC-ES/ESR-1671.pdf> or Miami-Dade #07-0315.03 <http://www.miamidade.gov/buildingcode/library/productcontrol/noa/07031503.pdf> report for this product. Lightweight and medium-weight Concrete Masonry Units (CMU) were defined by ASTM C90


Indicated tension and shear values were obtained in tests conducted at CEL Consulting. Designated holding power depends on the quality of the masonry material, depth of embedment and proper hole size. These figures are offered only as a guide and are not guaranteed in any way by Illinois Tool Works, Inc. The figures indicate average ultimate tension and shear failure values. A safety factor of 4:1 or 25% of ultimate value is generally accepted as a safe working load. However reference should always be made to applicable codes for the specific safe working ratio. All values are based on close tolerance holes drilled with Buildex Tapcon® carbide drill bits. Performance of the Tapcon anchor may vary in extremely hard concrete aggregates.


As in the case with all applications, the connection design is the sole responsibility of the Building Design Engineer, Architect or otherwise responsible person charged with the design connection.



Tapcon® is a brand name of high quality concrete screws (http://www.confast.com/products/tapcon-concretescrew.aspx). The name was derived from its own definition — an anchor that "TAPs its own threads/grooves into CONcrete." The Tapcon® was patented in 1976 by ITW Buildex as the first masonry screw. Tapcon® concrete screws are self-tapping screws that are used to anchor a fixture into solid concrete, brick or block. This screw has alternating raised and lowered threads with diamond cut notches (sometimes referred to as Hi-Lo® threads). This Advanced Threadform Technology™ offers superior pull-out resistance and stability. These Hi-Lo® threads also allow for fast and complete dust removal, which permits the Tapcon® to consistently tap its own high quality threads. Concrete screws that are not Tapcon® brand work in a similar manner but are undeniably different from the original Tapcon®. No other screw performs as well as original Tapcons.

Tapcons can be used in solid concrete as well as in brick and block base material. Tapcon® concrete screws (http://www.confast.com/products/tapcon-concretescrew.aspx) can be used in a variety of applications ranging from light duty to medium duty. Some common applications for Tapcons are attaching furring strips, wood headers or plywood to concrete; mounting a flat TV above a brick fireplace; fastening conduit straps and electrical boxes to a brick or block wall; installing sub-flooring to masonry floor…there is a seemingly endless list of uses for this versatile screw!

You have to KNOW the STRENGTH of the masonry/concrete FIRST. You have to KNOW how to calculate the FORCES and LOADS. You then have to INSTALL CORRECTLY and to SPEC!

Wrong hole size is a MAJOR NO-NO!

[H.G. Watson, Sr.]

Can't argue with that, but.....





The handrail is typically between a post/column and a wall, or two walls. So in the case of handrail, and only handrails, pull out should not be an issue.:)

Apparently your "grasp" of forces & handrails (and/or guardrails?) is a bit "off".;):D :eek:

[Markus Keller]

I love tapcons and have used thousands. However, you MUST use the specified tapcon drill bit for each screw size. Otherwise it's just BS, it may hold it may not. As much as I love tapcons, they have very limited use in my experience. If the material is too soft or too hard and brittle, they are not a good option. In many situations the sleeve/expansion anchors hold better. As much as I hate plastic anchors, they work really great in brick, Totally worthless in drywall though, unlike what many suppliers would like consumers to believe.

[H.G. Watson, Sr.]

Is it obvious I indulged in some (Doc's have tabooed for me) regular COFFEE this morning?:eek: :)

[chris mcintyre]

I would only dig myself a deeper hole with this crowd,

I knew I should have ended it there.


H.G.- I really wish you would let me know where you stand on this issue, as best I can tell from reading through your post several times, I have concluded that you disagree with my statements. :D

[H.G. Watson, Sr.]

I would only dig myself a deeper hole with this crowd


I knew I should have ended it there.


H.G.- I really wish you would let me know where you stand on this issue, as best I can tell from reading through your post several times, I have concluded that you disagree with my statements. :D

Now if you stuck with just digging yourself a deeper hole, and not a larger diameter one, I wouldn't have disagreed so strongly.

[chris mcintyre]

Now if you stuck with just digging yourself a deeper hole, and not a larger diameter one, I wouldn't have disagreed so strongly.

:D Well said :D

This is my final post of 2009, wishing all of you a Happy and Prosperous 2010!

Now I'm off to finish off my Christmas scotch, smoke a cigar, and shoot some fireworks....in that order :eek: