Rebuilding a retaining wall

[John Fitzgerald]

I have an old rock faced masonry retaining wall that holds back about four feet of dirt. It is leaning, and will soon have to be replaced. About 36 feet long. Does anyone on here have experience with the prefab dry stack blocks that lock together like Legos? Or something similar. I don't want to have to hire a contractor to do a concrete wall, if I can help it. This holds back dirt from the edge of my driveway for a small distance.

 

[marchanna]

Key thing is a good base. Secondly, the thickness of the wall should be appropriate to the amount and type of soil it’s holding back.

I’ve put a few in over the years.

 

[jfh28]

check the manufacturers instructions for installation and limitations of their product and then match it to your specific situation........an important thing for a retaining wall is drainage.....wet dirt weighs a lot and a high clay content can be problematic so follow their recommendations......in general once you have a solid level base the blocks themselves are not difficult to work with........Jack

 

[davrow]

Can you be more specific on the types of blocks you mean? Concrete lego blocks I'm familiar with weigh 2,000-5,000 lbs. Do you mean normal retaining wall blocks with a lip? Or some other kind of block.
I agree with John... proper foundation is key to stability and long life for the wall.
4 ft is about the max for a non-reinforced retaining block wall, lower if there will be pressure behind it (like driving tractor on the terrace it can form).

 

[flingwing1969]

You will want to ensure that the hillside the wall is holding back drains well. Often, a wall is fine for holding the dirt back but can't take the hydro-static pressure when the soil behind the wall gets saturated. Also, I like these blocks for a natural look, good drainage, and easy build. I got a great buy on a lot of them that were bought and never used before the buyer died. They are not inexpensive but they really do the job and become part of the landscape as opposed to hardscape - if you want that look.

Why Living Retaining Walls? - YouTube

 

[Streetcar]

Drainage is very important for long lasting wall. The precast blocks require a level compacted base

 

[RNeumann]

Proper footing/base as mentioned above. Some of the nicer and or higher rated walls have a fabric/grid mesh that ties back into the hill. Chevron has a station near us that has a dry stack type wall that has to be 20’ high and has a building on 100% fill.
The other two keys are to export 3-4’ behind the wall and bring in good crushed stone/engineered fill. The other key that goes along with that is to add landscape fabric and a 4” perf drain to prevent any hydraulic pressure on the wall.


Your local brick maker will have the options for you. Bricks don’t ship too far so trying to find a specific brand or look is a waste of time. Your local yard’s choices is the only practical options.

 

[Redlands Okie]

Good base and proper drainage with material to protect the drainage from clogging up.
The actual blocks and wall its self is almost a minor part of the job for a long term productive wall.

 

[John Fitzgerald]

The old wall has been there about 50 years, and I think it started failing when the former owner replaced the sewer line about 25 years ago and had a back hoe working only a few feet from the wall. The sewer line is deep and goes under the far end of the wall. I have had the place four years, and the wall has leaned about two inches more since then. It's along one side of the approach to my walkout garage-basement. The dirt level is from 8 to 12 inches below the top of the wall. The part within ten feet of the concrete garage wall is thicker and barely leaning at all. The new wall will need to be 48-50 inches tall. The old one is 58". Here's a picture.

 

[DrRod]

You need to get a copy of Stone Work by John Jerome. It is the month by month thoughts of a guy rebuilding a stone wall in New England. I'm sure you will find that it speaks to you as you undertake this project.

 

[John Fitzgerald]

You need to get a copy of Stone Work by John Jerome. It is the month by month thoughts of a guy rebuilding a stone wall in New England. I'm sure you will find that it speaks to you as you undertake this project.

He built a property line wall that took a year. I don't expect mine will take much more than a couple of weeks, once I form a plan of attack and get started, during a dry spell.

 

[jfh28]

its hard to tell from that picture but it looks like the wall is ending under the deck and you may have a problem with the post there that is holding up the end of the deck.......I'd guess that the footing for that post does not go down to the bottom of the wall so when you remove the wall theres a good chance you will undermine the soil that the footing is bearing on.......general rule of thumb is if the soil within a 45 degree angle from the bottom of the footing is disturbed it has compromised its bearing capacity......if that is the case it's not a big deal you would just have to remove the footing thats there and install a new sonotube down to the level of the bottom of the wall and fill with concrete up to the post.......Jack

 

[John Fitzgerald]

That post does not have a footing. It's a 4x4 in a hole in the ground that a contractor for the previous owner installed. I have already dealt with the other supports for that deck a couple of times and have fixed the problems there. I am planning to temporarily support it with a post on a spanner from the top of the wall to hard ground until I replace that support with a 4x6 ground contact treated support that goes onto a footing at the base level of the wall. The wall is barely leaning within 10 feet of the house, is thicker there, and in no danger of toppling at that point.

 

[Redlands Okie]

Are there no drain lines coming out the end ? Or at least indications of drain hole every so often in the rock wall ?

50 years is not that long. It’s a sad situation to see all of that rock, effort, and money wasted. Not to mention you getting to tear it out and haul it off and repeating the material, effort, and cost to replace it. A bit of gravel and drain pipe would have made a large difference.

Keep in mind in many areas a very large drop off requires handrails. No idea if its a issue for your situation.

 

[John Fitzgerald]

There are a couple of 4" pipes coming through on the inside, but they are stopped up with dirt. The previous owner likely compromised the wall by re-doing the sewer line that passes under it, (backhoe pads right by the wall) and by allowing a 6" holly tree (I removed stump four years ago) to grow about two feet from the wall along the middle of the span. Handrails are not an issue. I'll put a 36 inch welded wire fence above it if necessary. I think it will be one of those walls that steps backward with each tier.

Yes, It's a shame. The wall on the other side of the walk out is still almost perfect, and it's taller, with a fence to prevent falls.

The one that is failing is actually a concrete block wall with a rock veneer face.

 

[Redlands Okie]

Just in case its been overlooked. There are various cloths and materials used to allow water into the gravel and drainage pipes but they keep the water out.

 

[RedNeckRacin]

What ever you do, don't try and do it cheaply. Invest the time and money to do it right. Soil pressure is a funny thing and unless you are going to place a moment slab and tie into a wall, pure mass and back batter are neccessary. 2nd is proper drainage. Over excavate about a foot behind the back of the wall and plan for geo fabric and stone as we as perforated pipe to handle the water. Water not only adds weight but it lubricates and reduces the shear strength of the soils. If you want to try and do it cheaper you can over excavate more and use geofabric to tie back into the slope and use geo cells/cellular confinement to create either a clean stone wall or filling the outside cells with topsoil and make a living wall. The sky is the limit really.

 

[John Fitzgerald]

The first ten feet or so out from the house is more substantial and only barely leaning, not in any danger at all. I am hoping to somehow tie into that and not have to mess with that part, which is the trickiest, since it involves a deck support. Maybe take the veneer off that part and match it with a new wall on out from there. It's a concrete block wall with native rock veneer about six inches thick.

 

[/pine]

Have you considered just excavating, straightening and then reinforcing the wall and adding some "tie backs"

retaining wall tiebacks - Google Search

 

[goeduck]

Have you considered just excavating, straightening and then reinforcing the wall and adding some "tie backs"

I learned about tie backs at an early age. My dad told me to go get an old truck axle by the barn and dig a hole in the upper yard to match the outline of the axle and to put the axle in the hole. I thought he was crazy but the way I grew up I did not have any choice but to comply. Later I learned that he (I) was replacing the retaining wall between the upper and lower lawn and that axle was the tie back.