Retaining wall

[OneStaple]

Hey all,

I'm getting close to the point where I'm going to need to redo my retaining wall. I had a structural engineer look at it about 6 years ago, and he told me that it was in mediocre shape and was fine at the time, but would need replacing in 5 years or so. Well, I think that time has come.

This is what I have. It's built out of pressure treated 6x6's. It's about 5' tall and 48' long. It's parallel to the back of the house and about 20' away. There is a deck (also pressure treated wood) on the flat area created by the retaining wall that we will probably replace at the same time.

As you can see in the pictures, the wall is bulging out and pulling away from the sinkers. The sinkers are also rotting out, with many of them essentially dirt at the ends. I included two pictures of the ends of sinkers, one mostly rotted out and the other half way (one of the better ones). The corners are no longer lined up, as you can see.

I'm sure some of you have done retaining walls before, so I'd love to get your thoughts/ideas on what to do. I'm not super eager to just put new pressure treated wood in (on both the wall and deck), as I'm sure it'll become a problem again in 10-15 years, but I also realize that any other method is apt to be way more expensive. And our budget isn't unlimited, of course. While I do most home projects myself, I think this is one that I'll have to have hired out. I believe the height requires an architectural plan.

We're also open to changing designs to better make use of the space behind our house. The first 20' to the retaining wall is nice and flat, but we have another 40' or so beyond the retaining wall that is essentially just overgrown. We could move the wall further out to give more flat space and make it taller to compensate. Or we could build a "deck" from the edge of the retaining wall outward to accomplish a similar feeling. Doing a multi-tiered wall isn't as appealing, since it would make the flat area closest to the house smaller.

Thanks,
Tyler

[daveferg]

I can relate---I have several PT timber-type retaining walls I installed about 24 years ago and they look very similar to yours as far as condition.

If mine ever get to the final point of needing replacing, I'd go with either mortared stone or dry-fit concrete block retaining wall blocks (likely the cheapest).

First off---at least around here 4 ft. is the tallest permissible wall without being designed by an engineer. From what you describe, you could avoid the single wall 5 ft. high, by terracing or stair-steping the walls-----I believe they have to be parallel and have 4-6 feet separating them. This is pretty easy to do.

Don't forget to install proper drainage tiles/gravel, etc. behind the walls to allow for water drainage.

[Lynden]

Do some research on mortarless retaining wall systems. Allan Block and Keystone are two to consider. Both have many different block designs to choose from.

http://www.allanblock.com/products/retaining-walls.aspx

http://www.allanblock.com/retaining-wall...ering.aspx

http://www.keystonewalls.com/pages/produ...ndard.html -- click on "wall products" and "structural wall products"

[daveferg]

Here's another source for blocks---


[url=http://www.basalite.com
]web page[/url]

Do some shopping around and save your back by finding a vendor who will deliver to your home. For DIY----you'll need a yard or two of 3/4" or so gravel---both for the base for the first course, and then to add behind the rows of block as they are laid---this helps lock them together.

All the fine work comes in laying the first course level. After that---invite a bunch of friends over to help build the courses. About the only skill needed at that point is someone to cut some blocks in half so you can run a staggered stacking pattern----just have some beer and pizza ready to go at the end of the day.

If you want belt and suspenders for bonding the block----I'd suggest using masonry adhesive applied just before setting one block on top of another. You're going to want this adhesive for attaching the cap row anyway---I just find it cheap insurance.

[2beast]

We do this for a living...............

I would build the wall with retaining wall block.
Not the cheap little ones from the box store

Compacted gravel base below the first row which should be below ground level.

A foot of clean gravel behind the wall for drainage with a layer of fabric between the soil and rock to keep it clean.
Install drain pipe behind wall to supply drainage.

With this height I would reinforce it with geogrid




Build and finish wall and live happily ever after

[daveferg]

I'd certainly listen to 2 Beast---he does some beautiful work.

My only word of advice is look at the dyed ones with a faux type front of adobe blocks, stacked, etc. I had the plan front concrete done and it's not very attractive, whereas in another spot, found one that looked like irregular adobe blocks which really is cool.

[geek2me]

2beast said:

---

We do this for a living...............

I would build the wall with retaining wall block.

---

Do you have recommendations on vendors for the blocks?

Thinking about doing a small (about 3' high tapering to grade) along the driveway.

[2beast]

It depends on where you are located and what is available.

I would stay away from block from the big box stores.
There is a reason that they are cheaper.

There are quality manufacturers out there who specialize in wall block and pavers.

We have recently had to replace full walls and patios due to cheap block or pavers crumbling.

A recent patio repair on cheap pavers (which I hate doing but it was part of a larger project) the pavers crumbled when we tried to compact them into place

[Gui]

2beast said:

---

I would build the wall with retaining wall block.
Not the cheap little ones from the box store

---

What if the wall blocks blow the budget? Would you then go to PT wood or stick with blocks but go to the box store?

[Curlycherry]

Beware the live of man made blocks. There have been a lot of them used around me over the last ~20 years. We have places where the walls are 30-50' tall. Something I am noticing is that in many places the blocks are crumbling from the face side. Not every block, just a few to up to ~15-20%. That means of course that the entire wall will need to be torn down and rebuilt which is big bucks.

One suggestion would be to use natural stone. Cost is higher by a little in the install, but they will last forever. It is what I used in 1993 and my walls are still perfect and fine. My friend that I am helping build his house we used local stone. His wall is two level and ~20' tall at its highest point and his average stone is ~4' wide, 12" tall and 3' deep. That wall will never go anywhere. Another friend used the same big stones to hold up an area for a swimming pool and they went up 10' in a single wall of stone. The pool fence at the top made it meet code.

Funny thing is Google Earth caught us making the wall for my friend's house build. They took the shot right after we finished back filling. For scale the shop in the right of the photo is 32' by 80', so as you can see at the top of the trees in clearing, the retaining wall is big.