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bolt anchors in cinder block

brucet9's picture

I have to install a gate across a 4'10" space between stucco house wall and concrete block wall. I expect to bolt 4x4 posts on each side for hinges and for latch, thus giving me a 52 1/2" gate.

I'm looking for the best bolt anchors for the posts. If I can't screw one side into a stud behind the stucco, I'm thinking of 3/8" Hilti toggler bolts.

To attach the other side to cinder blocks, what is the preferred fastener? Will lag shields break the blocks? Should I use some sort of expanding anchor bolt in the mortar joint or in the block itself? I can't choose the alignment to be sure of hitting a web or a hollow of the blocks, since the house side dictates where the gate goes.

Thanks,

BruceT
BruceT

(post #107479, reply #1 of 38)

Tapcon's...........someone else probably knows better, with const. adhesive.

(post #107479, reply #3 of 38)

I would disagree with tapcons in cinder blocks.  Cinder block isn't dense enough to prevent the inevitable pull out forces the gate will create on the tapcons.   For cinder block usage, tapcons work a lot better in shear than in pull-out. 


I would use the hilti toggle bolt if it will be in an open web, a lead shield if it is in a web and an expanding anchor if it is in a solid, poured cell. 


The gate will act as a huge lever trying to pull out any fastener you will use, so use plenty and use something beefier than you think you will need


Edited 11/28/2008 9:39 pm ET by MikeRyan

(post #107479, reply #2 of 38)

bust a hole in the block, add the bolt and then fill that cell with concrete

(post #107479, reply #13 of 38)

If the cells weren't grouted when the wall was built, it seems to me I would have to fill 5feet of cell all the way to the ground to fill behind my top bolt wouldn't I?

BruceT
BruceT

(post #107479, reply #16 of 38)

If you were going to go that route, you would stuff the bottom of the cell with heavy paper (such as a grocery bag or portland mix bag).  That way, you are only filling the cell that you need. 


This way would actually work if you are going to mount a 2x4 over the hole, so you don't have any repair work, but it is tedious to fill that hole with a small cup, or stuffing it by hand. 


I used this method to secure an eyebolt to the wall to lock up a kayak outside.  Punched a hole lower for the eyebolt and another higher to fill, reached down through the top hole and put a 2" washer and nut and then filled the cell with a bag of quikcrete.  Kayak hasn't walked away yet.

(post #107479, reply #21 of 38)

yes, about two five gallon buckets full

(post #107479, reply #4 of 38)

I'd go with some sort of expanding anchor. I agree there is not enough density in the cinder block for tapcons.

 


Family.....They're always there when they need you.

 

Family.....They're always there when they need you.

(post #107479, reply #5 of 38)

Mike Ryan's concern about the leverage exerted by the gate is well founded. It might be worth considering a crosspiece above (and below?) the gate if aesthetics and budget permit.


 What is under the stucco?

(post #107479, reply #6 of 38)

Which side will carry the weight of the gate? How heavy is the gate?

I'd try to use toggle bolts if possible, in the CMU. If not, either an expanding anchor of some sort or Simpson 2-part anchor adhesive.


The mark of the immature man is that he wants to die nobly for a cause, while the mark of a mature man is that he wants to live humbly for one. --Wilhelm Stekel


Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

(post #107479, reply #7 of 38)

Bruce,

Lag shields and other expanding anchors are quite likely to either work loose or break the blocks. Your best bet is some sort of adhesive anchor. Brownbagg's idea has merit, and is a type of adhesive anchor. All-thread in epoxy is what I was thinking. Hilti sells stainless screens shaped like a condom that are used with epoxy when you have to drill into the void of the block.

The screen goes in the hole, then the epoxy, then the threaded rod. The epoxy comes out evenly through the fine mesh and bonds the rod to the block without having to fill the whole cavity with $$$ epoxy.

Epoxy anchoring won't work loose with vibration and does not wedge the substrate apart like an expanding anchor does.

Toggle bolts plus PL Premium will work okay on the stucco house side if you can't reach a stud.

Bill


Edited 11/29/2008 3:25 am by BillBrennen

(post #107479, reply #14 of 38)

Thanks for the suggestion. I was a little concerned about possibly breaking a block with a redhead or lag shield, especially since it is the neighbor's wall; I'd get both myself and the HO in hot water.

BruceT
BruceT

(post #107479, reply #35 of 38)

What Hudson & JTC1 say makes a lot of sense, so if it were me I'd try the tapcons through a 2x4 (then you can double the 2x if you want) I'd try for one tapcon in each block the 2x covers ..AS LONG AS :1)the block is in good shape, (good morter joints & not those  crumbly old kind of blocks) 2) The gate doesnt weigh an excessive amount.


To test, I might put one in up high, put my hammer claws on it and see if my own weight would pull it out

(post #107479, reply #8 of 38)

For commercial projects I have specified the Hilti HIT HY 20 system.  It's designed for hollow block wall.


http://www.us.hilti.com/data/techlib/docs/Product_Technical_Guide/Anchoring_Systems/4.2.8_HIT_HY_20_(278-287).pdf

(post #107479, reply #9 of 38)

(post #107479, reply #12 of 38)

Thanks for the link to Simpson. Their pictures show very well how their epoxy anchor screens work.

Not sure that that system would be any more effective than Hilti Toggler bolts, though. Seems like togglers would spread the load over a greater area of the wall of the block.

BruceT
BruceT

(post #107479, reply #10 of 38)

Bruce,  You are talking about concrete (cement) blocks, right?  Not the very ancient cinder blocks? 


The attached photo is of the redwood back gate/door I designed and built at this house.  I used tapcons to fasten the 2Xs to the cement (concrete) blocks.  It's been in service for more than ten years, even survived the North Ridge earthquake, without problem.


Edit: Couldn't get the photo to load properly.  Anyhow, tapcons are a very good answer for attaching 2X to cement blocks.  I've used them for that purpose for years and never had a problem with them.  I would advise that you use 2X material rather than 4X.  If you want the extra width, fasten another 2X to the one which is anchored. 


On the subject of fastening through stucco into an open framed wall, like in a garage: I'd suggest that you fit several 2X blocks between the studs, against the inside of the stucco. fastening them with wood screws at an angle, the same as toe nails.  With three or four blocks spaced evenly, you'll have the option of using lag bolts or carriage bolts, to fasten the 4X4 or 2X4.


Edited 11/29/2008 6:00 pm by Hudson Valley Carpenter

(post #107479, reply #11 of 38)

Thanks for the suggestions.

I do mean concrete block - didn't know there was a difference.

I've used Tapcons for low stress shear applications, like the latch side of a gate, but my new gate will have to hinge on the block wall side and that will stress the fasteners constantly and mostly in tension.

I need to use thicker than 2x4 because there is a wainscot of siding with a 2" cap on the house wall, ending right where the out-swinging gate will be mounted, so I need greater clearance. Why would 2x4 mounted on another 2x4 be better than a 4x4?

BruceT
BruceT

(post #107479, reply #15 of 38)

Why would 2x4 mounted on another 2x4 be better than a 4x4?


If you use tapcons, as I did, the length works better that way.  Less stress on the tapcon too. 


I used tapcons into the cement blocks on both the hinge and strike side of a 36" wide gate/door.  As I said, there have been no problems. 


One thing I'd advise is using longer screws to mount the hinges.  That's where the stress shows up, not the tapcons.


 

(post #107479, reply #17 of 38)

I'm with you on this one.  Sounds like some over engineering going on.


1/4" diameter Tapcons Pullout in hollow block, 1" embedment (about what you would have in a "hollow") = 406 lbs. - that is per fastener.


Deeper embedment like you could obtain if lucky enough to hit a web: 1-1/4" = 615 lbs; 1-1/2" = 851 lbs; 1-3/4" = 984 lbs.


Shear strength in "lightweight Hollow Block", 1-1/4" embedment = 1058 lbs.


Source: Tapcon data sheet packed in the screw boxes; based on results from Pittsburgh Testing Laboratories Test #CH3748 for Pullout; Test #CH3932 for Shear.


Be advised the data above only applies to Tapcon Fasteners manufactured by Buildex - not the generic, knock-off, blue, concrete screw fasteners found at some big box stores.


Yes, they are approved for use in ACQ treated lumber, if that is a consideration.


Just how much does this gate weigh?


Jim


 


Never underestimate the value of a sharp pencil or good light.
Never underestimate the value of a sharp pencil or good light.

(post #107479, reply #18 of 38)

Some people haven't gotten the message yet about the holding power of tapcons. 


The specs you've provided should back up what you, I and others have been saying about them. 


The first time I used them I started with a test.   Drilled the proper sized hole in a cement block, cranked a tapcon in, then tried using a crowbar to pull it out.  I couldn't budge it.  


Nearly fifteen years later, all the tapcons I used on that job are still holding strong. Needless to say, I'm convinced.


 


 


Edited 11/30/2008 8:46 pm by Hudson Valley Carpenter

(post #107479, reply #19 of 38)

1/4" diameter Tapcons Pullout in hollow block, 1" embedment (about what you would have in a "hollow") = 406 lbs. - that is per fastener


out of curiosity, where'd you get that stat?


k

(post #107479, reply #22 of 38)

"1/4" diameter Tapcons Pullout in hollow block, 1" embedment (about what you would have in a "hollow") = 406 lbs. - that is per fastener

out of curiosity, where'd you get that stat?"

I don't know about the above stat, but I found this chart on the Tapcon website:

http://www.itwbuildex.com/tapcon.htm

BruceT
BruceT

(post #107479, reply #25 of 38)

>>out of curiosity, where'd you get that stat?<<


Just like it says in my OP:


"Source: Tapcon data sheet packed in the screw boxes; based on results from Pittsburgh Testing Laboratories Test #CH3748 for Pullout; Test #CH3932 for Shear."


Curiosity struck and I fished the data sheet for a box which was purchased Saturday out of the trash - data / criteria has been changed somewhat from my "old data" in OP. Shallower embedment, pull out higher, shear lower. No independent testing laboratory was identified for the data source.


New vs old data sheet specs:


New                 vs    Old


1/4" fastener      =     same


hollow block       =      same


1" embedment    vs     1-1/4"


Pullout - 500lb   vs     406 lb


Shear - 1000 lb  vs    1058 lb


1/4" x 5" fasteners are available for fastening 4x4.


As others have mentioned a clearance hole in the wood is advisable. I would probably bore a 7/32" or 15/64" hole through the wood, run the fastener into the wood and strip the wood hole then attach to the wall.


As for the question of over torquing - there is no threaded fastener in existence which responds well to the over application of force.........


Jim


Never underestimate the value of a sharp pencil or good light.


Edited 12/1/2008 7:52 am ET by JTC1

Never underestimate the value of a sharp pencil or good light.

(post #107479, reply #26 of 38)

d'oh!  didn't see that when i first read it. 


thanks


k

(post #107479, reply #20 of 38)

Overtorque the fastener and you destroy any holding power.  This is easy to do, especially if your threads are bridging the block and the 2x4.  If you are going to use tapcons, I would drill an oversized pilot hole in the 2x4. 


I would also caution that when the 2x4 dries because one side is getting sun/heat while the otherside that is up against the wall will remain moist, so you will have some stress on the fastener from twisting/warping of the PT 2x4.


That being said, I would still use another means of fastening.

(post #107479, reply #23 of 38)

I would also caution that when the 2x4 dries because one side is getting sun/heat while the otherside that is up against the wall will remain moist, so you will have some stress on the fastener from twisting/warping of the PT 2x4.


In Southern California, where the OP lives, PT isn't needed for gates.  Construction grade redwood is more commonly used.  One of it's better qualities is it's stability.


 


 


Edited 12/1/2008 2:55 am by Hudson Valley Carpenter

(post #107479, reply #24 of 38)

I'm using 4x4's, not 2x4's and not PT. The only place PT lumber is used around here is for sill plates on slab, maybe some deck framing and where there is direct contact with the ground.

Tapcon holding power looks good on paper, but, like you, I am aware that it is very easy to over-torque a tapcon in block and strip out the hole.

BruceT
BruceT

(post #107479, reply #27 of 38)

Thanks for the data.


Like I said, a tapcon is what I'd start with.  It probably takes 30 minutes of messing around to get a more specialized fastener, which makes a half dozen tapcons pretty cheap.


 


Beer was created so carpenters wouldn't rule the world.

 

Beer was created so carpenters wouldn't rule the world.

(post #107479, reply #28 of 38)

I recommend using two 2x4s instead of one 4x4.  I would tapcon two screws at every mortar joint through the first 2x4 and then lay the other 2x4 on top and attach it with a good deck screw.  the rason for two boards is to give a better bite with the shorter distance trhough lumber and to improve the asthetics of it by having a cleaner 2x4 on top instead of crazy bolt holes or tapcon heads everywhere.


Actually, if you can, I would rather use 2x6 or 2x8 instead of 2x4 because they will hold better.  maybe incrase screws to 3 per joint line.


You can also set bolts and then grout the blocks solid and I would still recomment the two piece of lumber process to cover ugly bolt heads.




 


I refuse to accept that there are limitations to what we can accomplish.        Pete Draganic


 


Take life as a test and shoot for a better score each day.          Matt Garcia

<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" /> 

I refuse to accept that there are limitations to what we can accomplish.        Pete Draganic

 

(post #107479, reply #29 of 38)

Pete,


Just curious...why would you trust the mortar to be stronger than the block?