Retaining Wall - Recommendations Sought

[Richard]

Due to council regulations in my area I needed to bring soil into my block of land which created a hight difference of 1.2 meters between the back of my block and the rear boundary of the block. That is, on the raised soil we put a brick house; from the back of the house there is about 2 meters of soil in level with the house and then it slopes till it reaches approximately 5 meters from the rear boundary (the rear boundary is where the neighbour's block starts).

I now want to build a retaining wall at the rear boundary and fill my back yard with soil so that the hight difference between the house and the rear boundary is much reduced.

Measurements for my retaining wall - Required length: 15 meters at the back and approximately 5-6 meters of each side (right and left sides) Required hight: say, 80cm

I read about those interlocking bricks marketed as 'd-i-y' products. I am wondering if this is really a work for an absolute beginner (using those interlocking bricks) or should I call the professionals? A rough estimate from a landscaper was $AU25,000 (for a 1 meter high wall) which does not leave me much for landscaping.

Thanks in advance Richard

[BobK207]

I'd get a quote from a masonry contractor. IMO (unless there are some really diffcult local conditions) that quote is about a factor of 3 high.

Unless I messed up the exchnage rate ~6k US should be about right

cheers Bob

[RicodJour]

Not up on the exchange rate and how your local pricing works, but that seems like an awful lot of money. A retaining wall of that height is no problem for a DIYer, as long as you have a strong back and/or strong beer for your friends and neighbors. It's a lot of work, but very straightforward. You might want to investigate hiring some day laborers because the work will go very quickly with two or three guys helping you, particularly if they're used to working with shovels and wheelbarrows.

Call a local masonry distributor and find out what sort of interlocking block they carry and how much they get for it. Then go to the manufacturer's web site and check it out in detail. For a low wall like that, they'll probably just instruct you to bury the first course of block to keep the wall from sliding. Then it's just stacking the block and backfilling.

You should have very few cuts required. So few that you have a couple of choices of how to do it. You could leave the corners unfinished, stepping the block back as you go up, then hire someone to cut the corner pieces and finish the installation (half day of work), or rent/buy a saw with a diamond blade and have at it.

R

[buffalobill]

lots of discussions on this, searched and:

[Bill Kearney]

Depending on what size blocks you might be able to just split them with a masonry chisel.

[hallerb]

If at all possible just slope the land and use NO wall. Walls ALWAYS fall down and will be a lifetime maintence headache:(

[Stubby]

The Great Wall of China is still there. What do you mean ALWAYS????

[RicodJour]

The guy apparently wants a flat lawn - it's sloping now. If the slope was okay with him he wouldn't have posted.

The OP is talking about a 30" high wall of interlocking block. How is that going to fall down? If it moves, move a little dirt, reset the block and backfill.

But the low wall won't move, there's not much pressure behind such a low wall, and if it did move it would probably be such a miniscule amount that it wouldn't matter.

What's the big deal?

R

[Art]

We just had Anchor block retaining wall put up in the US. They are nice because they don't rely on fiberglass pins but instead have a lip on the back bottom of each block. We had a pro do it. Height varies up to 6 feet high. Overall the job was a bitch just watching them work. I would not want to do it.

[Mys Terry]

A good retaining wall that will hold up needs a bit of engineering. It needs substantial anchoring back into the hillside and proper drainage. Otherwise, tons of hydrostaic pressure can build up behind it and push it over. It's not just a simple stack of blocks.

[RicodJour]

On a 30" wall, there's no engineering needed unless it's built on a substantial slope or if there's a structure nearby whose foundation might exert loads on the wall.

The interlocking block rely on their weight to hold back the wall and they're usually lipped so they step back as the wall goes up. There's no need to tie in a 30" high wall, there's no need to have it engineered and in every jurisdiction I've ever heard of, there's not even a need to get a permit for such a low wall.

If the soil is clay and the OP is nervous about hydrostatic pressure, he can just install some drainage behind the wall and run the pipe to daylight. it's probably overkill, but it's still easy and inexpensive to do.

This is about as simple as it gets in retaining walls.

R

[Mys Terry]

My wall will outlast your wall by many decades.

[hallerb]

The Great Wall of China is still there. What do you mean ALWAYS????

Saw a show about the great wall in under copnstant repair, and its not really a retaining wall.

if building a wall make certain its well drained behind it, using perforated drain pipes covered with anti clog sleeves, and tons of gravel. a good foundation below the frost line also helps too. otherwise it need rebuilt every 5 years, done right it might last 15 or more.

when you ignpore my advice and build a wall anyway, just remember my advice the next time your rebuilding it

[hallerb]

I have lived in this home since 1972, and have rebuilt one wall 3 times:( Its about 3 feet high.

On the other side of my driveway I removed nearly all of the wall and sloped the hill about 20 years ago. It hasnt done a thing!

Next time the offending wall becomes a problem its a goner!

I have a short set of walls over 6 feet high, rebuilt 3 times. The drop there is too big to slope:(

Remember even a low wall can be a fall danger for a kid, might not matter to you, but perhaps to the next buyer of your home:(

Kids just roll or slide down a slope:)

groundcover on a steep slope is beautiful, rebuilding walls is hard work...........

[Harry K]

For normal ground water, there is no need for drain tile using engineered blocks. There is plenty of space between each block for seepage. Now if the upper level gets swamp like, that would be a different proposition.

Harry K

[RicodJour]

This is an intelocking block wall you've rebuilt? Are there tree roots pushing on it? Soil type? Drainage?

After rebuilding it the first time and having it fail, why wouldn't you have built it correctly the second time so there wouldn't have been a need for a third time rebuild?

Well, in that case, you shouldn't be rebuilding so much as replacing the wall. If the original design is inadequate there's no point in rebuilding it to the same design.

A fall danger...? C'mon. With that logic you should be advising against two story homes, bathrooms and cars. If a kid falls off of a

30" high wall onto grass, he'll get a grass stain and probably not much else. If that same kid takes a stumble down the stairs, slips in the tub or gets hit by a car while riding a bicycle, it's a different story.

The OP's looking to build it up 30" in about 15 or 20 feet. That's not exactly the hill a kid would pick to roll down.

Invoking the "magic word" safety doesn't validate your argument when the danger is minimal to start.

It's not a steep slope. It's less than a 2/12 pitch.

I also don't automatically assume that a lawn is more attractive than a lawn with a nicely designed retaining wall. Ddi you ever see someone just plunk a table and chairs down in the middle of a lawn? No one does that. They gravitate to the edges - it's just human nature. Having a terraced lawn creates spaces that are more natural for their intended function.

I'm not sure why you'd want to talk the OP out of his esthetic choice. It's his house.

R

[hallerb]

The Great Wall of China is still there. What do you mean ALWAYS????

Saw a show about the great wall in under copnstant repair, and its not really a retaining wall.

if building a wall make certain its well drained behind it, using perforated drain pipes covered with anti clog sleeves, and tons of gravel. a good foundation below the frost line also helps too. otherwise it need rebuilt every 5 years, done right it might last 15 or more.

when you ignpore my advice and build a wall anyway, just remember my advice the next time your rebuilding it

[hallerb]

The Great Wall of China is still there. What do you mean ALWAYS????

Saw a show about the great wall in under copnstant repair, and its not really a retaining wall.

if building a wall make certain its well drained behind it, using perforated drain pipes covered with anti clog sleeves, and tons of gravel. a good foundation below the frost line also helps too. otherwise it need rebuilt every 5 years, done right it might last 15 or more.

when you ignpore my advice and build a wall anyway, just remember my advice the next time your rebuilding it

[RicodJour]

My Dad can beat up your Dad. Great argument.

Tons of hydrostatic pressure...okay, sure, spread over the entire length of that 30" high wall there would be tons of pressure, but the design load per SF of wall is orders of magnitude lower.

I have no idea what you do, but the design load for a retaining wall that is supporting a structure, which is _not_ the OP's case, is, depending on the soils, somewhere around 30 - 60 PSF/Fdepth. The block weighs more than that. That's why, pay attention, it's called a gravity retaining wall. If there's adequate drainage (stick in a perf pipe with a sock, gravel > adequate drainage) there's not going to be any problem with hydrostatic pressure or frost heaving. So where's the engineering necessary in a 30" high wall?

You're making a big deal out of nothing. If you want to design these things, or learn more about them, the manufacturers have tons of literature and often have free software to help you.

R

[Mys Terry]

My Dad wrote a book on how to design and build retaining walls back in the

1950's. It's long out of print, but the laws of physics haven't changed much.

I've seen plenty of "your" walls, and they were bowed and crumbling.

Mys Terry