# Brick and Mortar versus Brick and Construction Adhesive



## rsmproductions (Jan 5, 2008)

I'm hoping to get some thoughts from you regarding using mortar or landscape block adhesive when building retaining wall, etc. I need to build a foundation for a small waterfall 4 feet high at the most and am thinking of using the gray concrete block that places like Home Depot or Lowes sells. I'm have no experience with mortar and am looking at the adhesives to glue the block together. Is this strong enough to do the job? Also, in looking to the future I am going to need to replace the exisiting treated lumber retaining wall on the back of my raised bed and considering using the concrete block to do this. The height wouldn't be more than 18-20 inches but the length would span the width of the backyard - 75' or so. Would the adhesive be strong enough for this as well? If so is there one product over another you recommend.

Thanks,
Richard


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## ralphbrades (Jan 3, 2008)

Richard, 

To be honest I don't think that you would ever get it to work... I have some experience using epoxy based "Needle Piling" to hold a foundation together but that was in a geologically "suspect" area of the world (Corinth). I think that you are back to two loads of sand to one of cement. It is the weight of the bricks that hold the structure together rather than the mortar -which is used to stop the bricks moving. Here in the Peak District we are famous for our "Dry Stone Walls" made by local farmers and builders due a tax on Lime in the 18th century -hence they have no mortar. Although I do know the basics of brick laying -the technique is simply slop some mortar down and squish a brick on top then knock around a bit until it is "square". The concrete mix that works for foundations for me is four loads of ballast to one of cement. 

I don't know what the prices are in your part of the world but yesterday a 25Kg bag of Portland Cement cost me £6.29p and the four 25kg bags of ballast were £4.57p each. So I had 125Kg of "adhesive" for £24.57p 

regards 

ralph


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## Jerry Barnes (Jan 2, 2008)

You might be better off with those landscape blocks, they have a lip on the back that grabs the back of the block below it, you can stack them pretty high, just alternate them some, not right on top of each other. No mortar/adhesive needed.


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## docwatsonva (Jan 2, 2008)

Richard,

I have used adhesive successfully in building concrete walls. The product I use is PL Polyurethane Construction Adhesive that can be found at Lowes. I built a 3 ft. high wall using this product and it is still in great shape after 5 years. Here are a couple of photos:




















This adhesive IS waterproof.

Here are some tips:

Build on a flat level surface that doesn't have to be concrete. I used tamped stone dust.

Offset each subsequent layer about 1/8" - 1/4" to force the wall to lean in a bit.

Backfill behing the wall with 1/2" stone for good drainage.

The wall really doesn't need weepholes since the whole wall actually weeps.

My wall has shown no movement at all.

Doc


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## astrayelmgod (Jan 2, 2008)

They're called mortarless blocks for a reason. Weight alone keeps them in place very nicely. You can't go up very far; how far depends on which size you get, and Lowes at least has a sign that tells you how high for each size. But two feet or less is no problem for any size. 

I tried polyurethane outdoors here (Southern Calif), and it turned to powder after a few years. I was told that the chemical reaction that causes it to set up never really stops, it just slows down, but continues until nothing is left.


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## John J (Dec 29, 2007)

I had to build a retaining wall I used Cinder-block. 


I put the blocks in proper order like I was building a wall with out mortar.

Iused the ladder thingies that you are suppose to use every so many layers. 

I then filled the voids in the blocks with Concrete with a couple of pieces rebar down in the concrete.


JJ


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## rsmproductions (Jan 5, 2008)

When building my tunnel last week I decided to use the gray concrete block glued together with Loctite Landscape Block adhesive. (see my thread "The Redwood Creek and Tallulah Ridge Expansion Project" under Tracks, Trestles and Roadbed. It was extremely easy to use and made building the tunnel a quick job. At one point I forgot to keep a "window" opening in the back just in case of a needed train rescue. So I decided to knock out one of the blocks. The block crumbled with little work but the part that was glued didn't come out as easily. After I did all this I realized that the tunnel is not that long and getting a stuck train would be easily to get. So I put a new block back in the place I just took out (silly me). I used a chisel to get the remainder of old glue and block off. It looks like a sturdy process...but I'm sure time will tell. I don't expect this area to get much in the way of moisture except what Mother Nature decides to give (if ever) so am not completely sure how it will survive over time.

Richard


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## docwatsonva (Jan 2, 2008)

Richard,

I am confident that glued blocks will hold up to weather. How many years, I'm can't tell you. As I mentioned above, my wall is still very strong after over 5 years. The wall serves as one large weep hole. This summer we have had over 35 inches of rain with no impact on the wall.

Doc


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## fyrekop (Sep 20, 2011)

Richard,

I used the concrete decorative blocks from H.D. that have a 1/4 inch ? lip on the back edge. The wall is 20" (5 blocks) high and encloses an area 75' x 35' and the only issue I've had is the fill dirt washing out through around the edges of the block. This was fixed by backing the wall with landscape cloth so water can seep out but the dirt doesn't. No adhesive used. A landscaper I spoke with said he has gone as high as 6' without adhesive as long as it is back filled. Free standing wall he uses adhesive for anything over 2'. 

Alan


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## docwatsonva (Jan 2, 2008)

I chose not to use the blocks with the lip on the back because I wanted to have my train yard on that side and determined that there would be too much lean-in by the time the wall reach 3 ft..

You would have to lean over quite a bit to load cars on to the track. As I mentioned before, I set back each row about 1/8 - 1/4 of an inch so that, at the top of my wall, there is only about 2 - in. of setback.

The blocks with a lip do build a stronger wall that is less likely to fall above 3 ft.. I've seen them as high as 20 ft..

The important thing with the blocks I used is to backfill behind the blocks with stone as you add layers.

Doc


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## rsmproductions (Jan 5, 2008)

The area I'm planning to replace in future is the sides and back. When I originally built the raised bed I built about 12" away from the fence so future fence replacement wouldn't harm the bed. I used pressure treated 4x6 for the posts with 2x6 attached to make the wall. I attached tar paper to the wood so the dirt and any moisture wouldn't touch the wood. The issue I have now is some of the 2x6 pieces are bowing and coming detached. I may have to "patch" those spots temporarily as purchasing the amount of landscape block will hit the pocket book big time. I need to replace a fence at my rental property first.

I appreciate everyones suggestions and thoughts.

Richard


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## FlagstaffLGB (Jul 15, 2012)

All good suggestions...so part of it becomes personal taste and what can be viewed. I often have used CMU with maybe a coating of parging (latex and stucco mix) to cover the outside if you can see it. The "castle block" or dry stacked blocks (like Home Depot sells) is usually more decorative. As long as it doesn't have a surcharge (pressure from an inclined embankment or water behind the wall), it does very well up to about four feet. Both methods require a good foundation. You can place blocks in a sand or gravel bed, but over time....say 5-10 years, the soil will shift and you can have portions of the wall sink or move and not look like it was originally placed. I prefer to dig below frost line, pour a concrete trench (8"x16" cross-section) and place one or two #4 rebar in the middle. Makes for a very stable wall. 

As far as the bowing of the 2x6s that are either rails or backer support for fencing slats, if they aren't put together in a "T" or "L" section (meaning you need to use two pieces per rail), then you are correct that they are going to bow over time. Depending upon the temperature swings and the humidity in your area, this can be a continuous maintenance problem...hence many folks eventually go for the PVC fencing...pricey but doesn't warp. 

Good luck.


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