? on proper install of wall in area subject to freeze - base preparation?

[jim_wilson]

Hi Jim,

Interesting project - I have done similar here - got 300' of granite curbing and built a single high simple retaining wall for raised beds on a slope up to a stone wall at the front of our place. I used 3" or so 3/4 stone and tamped as the base - as I usually do build dry stack walls.

The concern I have about your project is stacking the curbing, adhesive degrading over time, and how to hold it together with the freeze/thaw cycles we have.

I would slope the blocks 10* or so back into the banking and also offset the second row maybe an 1" or so from the bottom row.

How to hold the top from pushing out may be a challenge too. Possibly a lag and an eye in each block connected to the geo grid material? That's a bit of hammer drilling in 20-25 blocks.

Just my thoughts and keep us posted with pics of course!

Carl

The stacking thing was the part that concerned me the most too.

That's why I'm asking the questions - I figured I get some more varied opinions about how to properly install this so I'm not "fixing" it at some point down the road.

One of my thoughts on how to avoid the upper stacked layer falling over was to do something like this:

Light grey = the granite blocks
brown = topsoil
red line = Geogrid
blue circle = drain pipe
dark grey = concrete
light green = waterproof sheet or membrane
dots = 3/4 stone

basically what I'd do is pour both put down a sheet of geogrid low down to tie the wall back to the soil, then I'd put poured concrete behind the granite wall blocks as a further reinforcement to the wall - to keep the pressure of the soil from pushing it over. On the side of the concrete facing the soil - I could put either a sheet of water proofing - or something like Grace Bituthene (concrete foundation waterproofing membrane) to keep the water from penetrating into the concrete from the ground behind.

I didn't show it in the picture properl - but I could lean the stacked granite curb pieces back at some angle to help hold them in place.

 

[dave1949]

To be honest, when you started this thread, I thought you intended to stack the curbing on the flat sides, not the narrow edges. I don't have a lot of faith in the stability of the two stacked on edge, they are how thick .. 6" or so? They are heavy, but over time I would be worried. I think that is why Carl (I think) suggested the 10* slant and 1" setback.

The solution with the concrete is really more like putting a stone veneer on a concrete wall, than building a stacked stone wall.

 

[Rustyiron]

Thanks for all the responses guys.

Davedj1: I was actually looking at some Allan Block products just last week for another wall I want to put up - and I plan on using some geogrid on that - so I should probably think of using the geogrid to help tie this wall in also.

.
I was also planning on sinking the first course into the ground about 4-6 inches.

Rustyiron:

I'm attaching an image I put together to see if I understand what you're saying correctly.

I've heard of using the pink rigid foam along "frost slabs" to keep them from freezing underneath - I guess I never thought of using it for a wall also.

Legend for the image:

grey blocks are the granite curbs I'll be using for the wall.

green is the grass layer

brown is the layer of topsoil

red is the geogrid tying the wall back to the soil behind it

the grey/yellow dots are 3/4 stone

pink is the 2" foam

the yellowish color is the lower soil layer(s) (under the topsoil)

This is what I meant except the foam at the lower grade being placed (to the left) of the wall, out where the cold is, under the wall is ok but I don't think it's necessary. Now this method is the extreme "fix" in poorly drained soils & conditions. Your 2nd (without the foam) drawing is fine for most situations. I also envisioned you stacking in the flat dimension, I would guess that stepping back & leaning in along with the geo fabric will be ok but place greater importance on minimizing the ground "push" by means of a generous overdig with the stone backfill. Looks like a nice job, be sure to take some pics! You might check with local contractors that do this type of work for advice on the stone "footing". You mention compacting it and that suggests a stone with dust material, a loose, stone only (3/4-1") base that will not hold water is what I would use. You are not supporting/distributing much weight, like if you were building a house on it. Your concern is drainage

 

[Soapandbacon]

http://landscaping.about.com/cs/lazylandscaping/ht/retaining_wall.htm

Drainage and dead men and solid compacted base are important things....check out the link above or any of the dyi retaining wall or dry stack stone wall sites.

 

[BuilderML]

This is what i would do. Sorry for the poor picture but i think you'll get my point.
1) Remove all organic material under wall
2) Provide for 6" of 3/4" process compacted base , Do not use stone only. The reason you do not use stone only is because stone is meant to collect the water.
3) I would set first stone at least 6" below finish grade.
4)Tilt stone back alittle
5) Set second stone
6) Install 4" perf. pipe draining to daylight. "black circle in picture"
7)Backfill with stone 3/4" or like size "what ever is cheapest" Red area in picture
8)Install landscape fabric "yellow line in picture"
9) Backfill wall
Just a few notes. In my book you can or can not use the geo-grid thats your choice.
The only time you would use stone only under the wall is if you have a perf. pipe draining to daylight to collect and remove the water otherwise using process is the way to go as it will not collect the water like stone will. If you plan on bonding your top and bottom stone together with whatever product you select make sure it is flexible otherwise it won't work. The main problem i see with the way you are building the wall is the way i think your are thinking of laying the stone. As with retaining wall blocks when they are dry-stacked they have a way of locking the backs of the stone so they won't slide forward. If you layed the blocks flat i would say no problem at all but laying them on edge will make them top heavy and thats not what you want.
Again this is what i would do and as with everything else everyone has there own way of doing things. One more thing i would like to add and it would be alot of work. With the way you are stacking your stone the only way i would do it is if you had a hammer drill and pinned your top stone to the bottom stone then i would say have at it your good to go."Green Pin in Picture

 

[jim_wilson]

This is what I meant except the foam at the lower grade being placed (to the left) of the wall, out where the cold is, under the wall is ok but I don't think it's necessary. Now this method is the extreme "fix" in poorly drained soils & conditions. Your 2nd (without the foam) drawing is fine for most situations. I also envisioned you stacking in the flat dimension, I would guess that stepping back & leaning in along with the geo fabric will be ok but place greater importance on minimizing the ground "push" by means of a generous overdig with the stone backfill. Looks like a nice job, be sure to take some pics! You might check with local contractors that do this type of work for advice on the stone "footing". You mention compacting it and that suggests a stone with dust material, a loose, stone only (3/4-1") base that will not hold water is what I would use. You are not supporting/distributing much weight, like if you were building a house on it. Your concern is drainage

The pieces of granite I using are from a quarry that closed and had bargain basement pricing on pieces of curbstone and other processed granite pieces. The pieces are roughly 3 feet long, 16-20 inches high (they're not all the same) - and 6-7 inches thick. I know what you mean about laying them down - that would be the "easy" way to build the wall - the mass of the wall itself would probably hold it in place if I was to build like that. This probably compounds matters some but what would the top and bottom faces of these blocks are very smooth - the "face" that I want to show is rough hewn and I think will make a nice looking wall once the blocks are stacked. My thought was that the fact that I've got some smooth faces means that if I can lay these right - I can get a wall with a look of some nicely fitted granite blocks.

I'm looking for the best way to make it all hold together if I can.

I'll see if I can get some pics of the granite blocks I'm going to be using - that might help give a clearer picture.

I took a quick look at the frost protected shallow footing guide that dstig1 posted a link to in a previous response just to refresh my memory on what I thought I recalled about that subject. I understand what you're saying about placing the foam out to the left - extending out to where the frost is, my problem with that in this particular installation - is that the wall is going to be right along a property line - so extending the foam out to the left would entail either A) setting wall a few feet back from the property line , - or - B) asking the neighbor for permission to dig up his lawn.

I don't really want to do A , and I don't think the neighbor would go for B.

 

[jim_wilson]

This is what i would do. Sorry for the poor picture but i think you'll get my point.
1) Remove all organic material under wall
2) Provide for 6" of 3/4" process compacted base , Do not use stone only. The reason you do not use stone only is because stone is meant to collect the water.
3) I would set first stone at least 6" below finish grade.
4)Tilt stone back alittle
5) Set second stone
6) Install 4" perf. pipe draining to daylight. "black circle in picture"
7)Backfill with stone 3/4" or like size "what ever is cheapest" Red area in picture
8)Install landscape fabric "yellow line in picture"
9) Backfill wall
Just a few notes. In my book you can or can not use the geo-grid thats your choice.
The only time you would use stone only under the wall is if you have a perf. pipe draining to daylight to collect and remove the water otherwise using process is the way to go as it will not collect the water like stone will. If you plan on bonding your top and bottom stone together with whatever product you select make sure it is flexible otherwise it won't work. The main problem i see with the way you are building the wall is the way i think your are thinking of laying the stone. As with retaining wall blocks when they are dry-stacked they have a way of locking the backs of the stone so they won't slide forward. If you layed the blocks flat i would say no problem at all but laying them on edge will make them top heavy and thats not what you want.
Again this is what i would do and as with everything else everyone has there own way of doing things. One more thing i would like to add and it would be alot of work. With the way you are stacking your stone the only way i would do it is if you had a hammer drill and pinned your top stone to the bottom stone then i would say have at it your good to go."Green Pin in Picture
View attachment 317543

The picture is fine - it's clear enough to get the point across.

So - for the compacted base you show in your picture - are you saying to NOT use just 3/4" stone? I used a product the Co. I got it from called "graded base" as the top layer on my driveway. The stuff is basically a rock dust 3/4 stone mix. It compacts GREAT. I've had it down for about 5 years now and I can have cement trucks drive across it and barely leave a tire track.

Do you think that would be a better base for the wall?

 

[BuilderML]

So - for the compacted base you show in your picture - are you saying to NOT use just 3/4" stone? I used a product the Co. I got it from called "graded base" as the top layer on my driveway. The stuff is basically a rock dust 3/4 stone mix. It compacts GREAT. I've had it down for about 5 years now and I can have cement trucks drive across it and barely leave a tire track.

Do you think that would be a better base for the wall?[/QUOTE]

Correct you do not want to use just stone as that will collect water. You want to use something that will compact, size of material really doesn't matter but in your case i wouldn't go with anything that is over 1 1/2". Your process will consist of material from stone dust up to what ever size you request lets say 3/4". That should work fine as your wall base. If 1 1/4" process is cheaper go with that. They don't use large stone process under an asphalt driveway but for your wall you could use something larger. Like i said whatever is cheaper.

 

[Carl_NH]

Jim,

BuilderML diagram is what I was referring setback the top block and slope 10* or so. Just some other thoughts on the pinning of the block.

Lay your first course, then run a line from one end to the other if its not straight put a pin between the blocks to guide the line, then drill 1/4"or 3/8" holes 1-2" back along the tops of the first row say two or three holes/block. Then insert SST pins so they stick up a 1/2" or so.

Then maybe some galvanized fence sections on top of the pins 18" or so back into the grade to act as the dead man. Some stone dust/concrete mortar mix on this and some concrete behind the wall and let it set up. Then set the second course blocks up against the SST pins and on top of the fencing. I suggest SST otherwise you will have rusty wall stains in a few years.

These blocks are heavy and unwieldy at 3' long and I find it easiest to get them close with the BH and thumb, then final positioning with pry bars.

 

[jim_wilson]

Jim,

BuilderML diagram is what I was referring setback the top block and slope 10* or so. Just some other thoughts on the pinning of the block.

Lay your first course, then run a line from one end to the other if its not straight put a pin between the blocks to guide the line, then drill 1/4"or 3/8" holes 1-2" back along the tops of the first row say two or three holes/block. Then insert SST pins so they stick up a 1/2" or so.

Then maybe some galvanized fence sections on top of the pins 18" or so back into the grade to act as the dead man. Some stone dust/concrete mortar mix on this and some concrete behind the wall and let it set up. Then set the second course blocks up against the SST pins and on top of the fencing. I suggest SST otherwise you will have rusty wall stains in a few years.

These blocks are heavy and unwieldy at 3' long and I find it easiest to get them close with the BH and thumb, then final positioning with pry bars.

I'm having a hard time visualizing what you're describing. Are you saying the pins are there to give the galvanized fencing something to grab onto?