Retaining Walls

[StoneHeartFarm]

MarkV

I know exactly the stuff you're talking about. The local dealer here has about 30 different styles that you can get. The woodstove shop uses it for building fireplaces. The advantage it has is that the sizes are relatively uniform, so it makes it easy to lay. And you're right, it's very realistic. When I fist started seeing it, about the only way I could tell was to tap it and listen to the sound. Now, I've seen enough that I can sometimes tell by the color. Natural stone usually has a little more color variety, unless you get a REAL expensive job and somebody does a lot of sorting.

When you applied your stone. What process did you use? Did you hang any metal lath (diamond lath) first, or did you just add mortar and push the stone into it?

SHF

 

[StoneHeartFarm]

You're going to have to follow the rule of thumb for earth contact homes. "The best way to keep them from leaking is to keep the water away from them." In other words, the run off has to be channeled away from the walls. If you get your drive crowned so the water will go somewhere else, it will probably save your wall.

In my case, I had considered a bottom or mid level sock tube. But, I don't think I'm going to need it. There's always a small amount of residual heat loss with earth contact. I help a buddy build his earth home aout 7 years ago. His wife planted petunias and strawberrys in the berm. She has the only petunias I have seen around here that "over winter", she never has to replant them, I've even seen them stay green in January. I've added a little bit more insulation in my walls (3x as much), so I don't anticipate that much loss. But I also have about 6' of my wall that I didn't put a footing under just as a test. No problems last winter, the solar gain was enough to keep the inside temps above freezing many days and I didn't get any frost heaving. When I get the balance of the insulation in there and the retaining wall finished, things might change. But, there will also be more heat inside the envelope then, so the residual loss will be greater. Guess I'll find out. /w3tcompact/icons/smile.gif Good thing I like working with stone. /w3tcompact/icons/laugh.gif I'm gonna look like that Arnold Schwatsenegger guy by the time I'm done. /w3tcompact/icons/laugh.gif /w3tcompact/icons/laugh.gif. Kidding aside, it must be working. Last year I was running around without a shirt and the wife pops up and says "You got Pecks!". I said "Yeah, I had a six pack too, burp, but I drank it." /w3tcompact/icons/laugh.gif /w3tcompact/icons/laugh.gif /w3tcompact/icons/laugh.gif.

SHF

 

[mlmartin]

Isn't it the truth. I've noticed a significant increase in flexibility and upper body strength since I started building (and rebuilding) stone walls.

Matthew

 

[MarkV]

SHF,
I ended up using both methods for putting the stone up. On the poured walls we put up a skim coat of mortar that we scored, let dry, back buttered the stone and stuck. Behind the woodstove we ran 1/2 ply, 15lb roof felt, metal lath and applied with mortar. Leaving a 1/2 gap between stones (depending on stone style) leaves room to grout between the stones. Finishing the joints with a wet brush even made me look like a mason.

MarkV

 

[StoneHeartFarm]

Which do you think gave you the best adhesion? Scratch coat or metal lath? I'll be putting natural stone on a poured wall (inside the house) and I'm tempted to use the metal lath with scratch coat to ensure the scratch coat stays put.

SHF

 

[MarkV]

SHF,
I have not had any problem with either system after the first 2 years, anyway. On a poured wall, I would just use the scratch coat. I would dampen the wall to keep the scratch coat from drying to fast.

MarkV

 

[GlueGuy]

Biggest issue with a poured wall is dealing with the hydraulic action w/o enough drainage. I like the open-faced drainage offered by rock or retaining wall brick. Lots of places to let the water out. Also, consider using a geo-textile to keep drainage pipes from clogging up with silt.

I am starting to think toward a combination wall. Use the engineered retaining wall brick to construct the "wall", and face it with the cultured stone to make it look nice...

Just a thought. Might be a bit expensive to do it that way.

The GlueGuy

 

[StoneHeartFarm]

GlueGuy,

Wouldn't you lose the drainage benefit by adding cultured stone over top? Usually you have to apply a pretty good base of mortar underneath.

SHF

 

[MarkV]

GlueGuy,
I would have to agree with SHF and don't see how the combination of materials would work to well. The cultured stone I used just would not look right without the joints filled with mortar. As you are pointing out, the key to any retaining wall (of any size) is the drainage to avoid hydraulic action. Another option I have seen with poured walls is to wire sections of pvc pipe to the rebar which leaves weep holes when the forms are pulled. Drain tile, silt cloth and gravel backfill has always worked for me, so I have never built in weep holes.

MarkV

 

[GlueGuy]

Actually, I already thought about that. I doubt that "all" the open slots on the retaining wall brick are needed to properly drain. To deal with that, I would either leave gaps between every 3rd or 4th brick, or else embed small tubes every so often to allow water to drain out.

I guess the desire is to try and pretty them up a little bit...

The GlueGuy

 

[StoneHeartFarm]

Tubes through should work for you. Would be a bit of a problem here since any moisture in the tube would freeze in the winter. It's probably better to leave the moisture behind the wall than in the wall. But, you don't get that cold, so drain tubes should work. The problem would be having enough of them to allow the water to run off. I would also think you would need a run of drain tile to feed your tubes, so the water would basically get into the tile and then run into the tubes and through the walls.

Just to throw out yet another idea and I have no idea if its good, bad or would even work-- have you seen the new styrofoam blocks they are using to build basements? Basically a big styrofoam block with channels in it. You wire the blocks together run some rebar and fill with concrete.

If you used a product like that and then removed the foam, you would have a grid-type wall with vertical and horizontal bars that would leave good drainage. How do you get rid of the foam? I bet that firebug RPM could help ya. /w3tcompact/icons/laugh.gif

SHF

 

[GlueGuy]

I think the drain tiles behind the wall are still a good idea. In fact, I'd think they were required. If you look at the web site I listed earlier, they give installation information elsewhere on their site showing just that. I'd also throw in a geo textile to keep silt out of the tiles.

My understanding of the foam conrete forms is that the foam stays in there for insulation purposes. I think I saw them used on the Bob Villa web site somewhere.

The GlueGuy

 

[GlueGuy]

SHF,

Dug around on the net a little bit and found these links:

Foam panel foundation forms

Smartblocks

American Foam Products

General Information

The GlueGuy

 

[StoneHeartFarm]

You're right. Normally the foam stays. What I'm suggesting is the basic grid shape, and the foam was the easiest way I could think of to make it. Think of a retaining wall that looks like a big window screen, with holes say 6"x6". (Hence the blocks and then remove the foam). Plenty of space for planting something. Strawberries, flowers, etc. Excellent drainage. It WOULD need landscape cloth (the good quality stuff) to keep the soil from washing out during rain storms. But it should eliminate drainage problems and most probably frost heaving. Only problem would is I don't know how strong such a net would be. Probably strong enough though if they are building house foundations that way.

SHF

 

[mlmartin]

Thanks for posting those links.

Sometime in the future (when I get most of my _other_ projects done) I'll be building a greenhouse. I'm would like to store excess heat without taking up floorspace. I'm thinking of using the foam forms to build an insulated concrete foundation. I'd put perforated pipe on the bottom with some risers and cover the pipes with 1 1/2 inch stone. The risers would go to the roof peak at either end where thermostatically controlled blowers would move the hot air under and through the stone.

I'd set the blower thermostat a few degrees cooler than the thermostat controlling the power vents. I would think that a system like that could reduce the cost of heating dramatically.

Matthew

 

[StoneHeartFarm]

Matthew,

My upper body gets a good work out. Its the lower body that gets torn to pieces. This has blown my knees right out. I don't know how the old timers did it. Must have limped alot /w3tcompact/icons/laugh.gif.

I think I know what you want to do with your greenhouse. The gravel in the floor would basically act as thermal mass, getting warmed up during the day and slowly releasing the heat at night. Basically, you want to grab the hot air from near the roof and push it down into the gravel. This warms the gravel, which warms the greenhouse when the sun goes down. Is that about right?

I saw plans once for a greenhouse that was built out of old 2 liter pop bottles, filled with salt water and cemented together to form the exterior walls. The idea being that the sun would warm the wall during the day and it would radiate out at night.

I think your idea would work. I'm concerned about being able to blow the hot air down, though. If you can situate the greenhouse on a south facing slope, you might be able to scrap together a solar water heater, and use that to transfer heat from the outside into the gravel.

The foam box idea is solid. I've got 3" on the outside of my foundation. Use either pink or blue foam, but not Tuff-R or a similar product. Pink and blue foam hate water and will not absorb if. Tuff-R (according to what I've found on the net), actually LIKES water and that's why those products have foil and plastic vapor barriers on them. One warning about foam on foundations, though, cover it on the outside, even below grade. Two reasons, 1. mice love to tunnel down and nest in it. (I've heard of a fix for that), 2. Grass and weeds send out underground runners that will bore right through the stuff. Any little openings lets water get through and that makes a channel for your heat to follow on the way out.

I've come, through all of this, to view heat a lot like water. It will move from a place of high pressure (hot) to a place of low pressure (cold). Water flows downhill, heat flows uphill. Water will leak through any little crack and so will heat.

Let me know how this works out for you. There may be a greenhouse in my future too.

SHF

 

[mlmartin]

I don't think my wife would like a soda bottle greenhouse. I don't think I'd like the looks of it, either.

You understood what I'm trying to do with the greenhouse and stone thermal mass. Getting the warm air under the stone is the important part. I can start storing heat in October and have the whole mass warm by December, when we typically start getting freezing daytime temperatures. If I have to run electric heat in January and February, I will. I'm not trying to maintain 68 degrees, since most of my tropicals will survive 45. It shouldn't be too expensive.

Thanks for the pointers on foam. I'm inclined to use the foam concrete forms and then following the manufacturers guidelines on interior and exterior protection. From what I've read, I should be able to get close to R-20 through the foundation walls. I'll probably pour a concrete floor at the bottom of the foundation. It will be easier to insulate a level slab than compacted fill.

Having a five sided concrete box will also help keep water out of the stone. I'm going to put a sump pump in, just in case. I'll end up with about 3 cubic feet of storage for every square foot of greenhouse.

Matthew

 

[StoneHeartFarm]

Matthew,

I had some problems with the pop bottle job, too. You really can't see the bottles, because they're covered over with cement. But, just knowing 1/2 of my wall is hollow plastic filled with cement eating salt water was enough to turn me off.

The foam blocks would be the easiest method to build with. They make a much neater poured wall that what you or I could probably get by building forms. The only advantage a straight poured wall would have is that all of the cement could be used as additional thermal mass. With the foam blocks, you pretty much lose the cement as mass.

Will the back wall (North facing) be cement or frame? If you use cement you can paint it black and use that as additional mass. Basically, I'm thinking the more mass you have that can store heat, the longer it will radiate when no heat is being gained.

The slab is a two edged sword. It will keep water out, but also keep it in. The sump pump is a good addition. What sized pipe are you planning to run through the gravel bed?

SHF

 

[mlmartin]

Easy is good. In the time it takes to make a set of concrete forms, grease them up, use them, tear them down and _then_ attach foam to the concrete you could have erected the whole greenhouse/w3tcompact/icons/smile.gif As far as losing the concrete as part of the thermal mass, I'm planning on a 12' X 18' greenhouse. The percentage decrease in thermal mass (under 10%) is probably a fair trade for the extra R-10 on the insulation.

I'm planning to use R-3 twin-wall polycarbonate for all of the skin, even the north side. It will be in a protected area (in front of the new barn) with full southern exposure all winter long. It's really and ideal location, with water and power. The only problem is that I have to tear down the old horse shed that is currently on the site.

I haven't done all of the calculations, yet. I suspect that I will be using two six inch risers and a six inch manifold on each end. I'll use four inch perforated pipe as runners spaced as closely as possible. The runners will be interleaved to cover as much area as I can.

The guy in the next cube is a thermal engineer. He'll be helping me to size the pipes and blowers.

I'm planning to use aluminium flashing as a UV/root protector for the exposed foam. It should start behind the twin-wall, cover the foam and extend 10 inches into the soil. That should take care of any grass roots.

Matthew

 

[GlueGuy]

Well, you can use gasoline... /w3tcompact/icons/crazy.gif

When I wanted to make a "thing" (like an intake plenum, or other odd shape), I would carve out some styrofoam in the shape that I wanted, then cover it with fiberglass/epoxy (NOT polyester resin!!). I would remove the foam by pouring in gasoline; which melts the foam.

It was then easy to clean up the part with a little sandpaper/dremel whatever.

Not sure that would be practical on a retaining wall...

The GlueGuy