Retaining Wall questions

[EddieWalker]

I need to build a retaining wall in my backyard so I can change my fencing around for my dogs. Phase one is about 3 feet tall, and probably 20 feet long. Nothing huge. Then Phase two will probably be about the same height, but closer to 50 feet long to create a flower bed.

I have some experience with retaining wall blocks with a lip on them, but I'm considering the type of blocks that are flat and require construction adhesive to hold them together.

As of right now, this is our top choice.

https://www.lowes.com/pd/Belgard-Quarry-Goldrush-Retaining-wall-block-Common-12-inx-12-in-Actual-12-0-in-x-12-0-in/5001527669?store=1965

Does anybody have any experience with a brand that worked out well when doing this? I prefer PL over Liquid Nails, but I'd love to learn about another brand that is better for this.

I do a lot of tile work and I'm wondering is something like Thinset Mortar would be better then Construction Adhesive?

On the walls that I've built before, I've always used about 6 inches of Road Base Gravel under the first block. I'm not really sure what this accomplishes, but it seems like the universal agreed upon way of doing it. Would concrete be better? I've also seen where they bury the first row and build up from there. Any thoughts on what works best?

I'm leaning towards just putting landscape fabric against the inside of the blocks and not using any gravel. For 3 feet, and with gaps in every block, I don't see how gravel will help with drainage. Each blocks is designed to drain water when stacked together. The landscape fabric will be more to keep the dirt behind the blocks, then dealing with water.

Thank you

 

[ChiefBodie]

The gravel underneath is necessary for drainage. Compact it well in 2 inch increments or your wall will suffer.

The fabric, as you describe it, will cause the wall to fail. It will slowly but surely fill with fine sediment until it no longer passes water. You want gravel as backfill.

 

[2manyrocks]

I thought gravel under the first course was to create a level base and allow some drainage. Similarly, gravel behind the wall with drain outlets prevents heavy waterlogged soil from pushing the wall over.

 

[chim]

Not a lot of experience with block walls. We did have a subcontractor build a concrete retaining wall years ago following a professional engineer's design. It was maybe 10' high and shaped like an inverted T. Behind the wall they first placed a plastic egg crate looking material followed by Mirafi fabric and clean stone - then earth. At the base of the back side there was perforated plastic pipe to drain.

 

[Captain Dirty]

A good way to view a retaining wall is that it is a dam holding back a pool of muddy water. In rocky New England where fieldstone is readily available, a rule of thumb is that the thickness of the wall at the base be at least 2/3 of the finished height. This gives sufficient mass to resist the forces of the mud and water which is greatest at the bottom of the dam. The walls are also laid with a "batter" or leaning back so that movement of the stones will tend to make the wall vertical rather than overhung. If the stone is laid up "dry" the cracks and crevices between the stones provide an escape route for water that accumulates behind the dam.

If the wall is veneered by mortaring stones in place on the face, or as you propose, gluing up 4 x 6 x 12 concrete blocks, you will have put an impenetrable membrane against the downstream side of the dam. It is necessary to provide some relief of the building pressure that traditionally was done with "weepers", lengths of 1-1/2" or larger pipes set into the wall near the bottom. I suppose one could provide relief with a suitably sized washed stone footing or with spillways around the ends of the dam.

It may be that the 3' height will be low enough that the 5-1/2" thickness will suffice, at least for a while. I am Calvinist enough to believe that mass and drainage as 2manyrocks suggested is desirable.

 

[beeforty]

I've used a Keystone product that can stack up to 3'. Country Manor® | Keystone Retaining Wall Systems
The gravel base that they typically say to put in is for stability, but I had a hard time compacting it evenly inside a trench! The first time I did the gravel for about 50 feet but later just poured a 3" concrete footing slightly wider than the blocks and everything is holding up fine. There is enough gaps in the blocks that water can come through but a a layer of fabric keep out the silt. This type uses a pin to keep the blocks inline and they have a cap that covers the top. Not being glued together you can alter or remove more easily in the future, I modified one area when I wanted to add steps in one section of a long run of a wall.

 

[Streetcar]

The aggregate base provides uniform bearing surface and provides resistance to sliding. The concrete does not provide the slide resistance.

Burying the first block is for slide resistance.
Gravel behind wall is for drainage and reduce lateral forces on the wall.
Mortar will change the forces on wall and it may be under designed for those forces. I typically use pl for adhesive

 

[cj7]

You may want to check into local building code. Based on relative height there can be anchorage or drainage requirements and railing or fence requirments.

Perhaps others will comment.

 

[Streetcar]

Typically building codes start with four foot tall wall

 

[Streetcar]

Eddie
Reading rock and Reddy rock are two large wall material suppliers in my area