Retaining wall & concrete driveway - order of operations

[aigel]

Hi Guys!

I ripped out landscaping from my driveway to make it wider. I need more space for projects! I will need to get one driveway wide strip of concrete poured and build a retaining wall. There is only about 1.5 feet of dirt to retain against the neighbor, so I will want to build this wall myself. I think I want to use a stacking system, mortar free. Something like this:

https://www.belgard.com/products/retaining-walls/belair-wall-20

The concrete work is too much to DIY, so I will need a contractor for that.

From all I read and see in the neighborhood, the retaining wall is built first and then the concrete is poured right up against it? Is this correct?

I figured I'll contact concrete contractors now, see if they can do the leveling first, then I build the wall and then I have them back to finish?

WWPPOTD (what would PPOT do?)

Thanks!

G

[908/930]

I am not a pro, but you would likely want to get the foundation prepped and the first row of blocks in, how high are the blocks, those will be mostly below grade. the one snag I see of having the wall finished prior is getting concrete splatter on it. But they do normally use the form to gauge thickness. Don't place weight on the driveway for a couple of weeks, about 28 days to full hardness.

[look 171]

I have more questions then answers for you. WHat's this wall holding up? Soil or is it on the flat used as a fence to keep the old man next door out of your property? Have a pic?

Generally, build the wall and place the concrete after (even if flat, get some type of footing below and use rebar but you are not going to use block?). Sounds like you just want to fill in the planter area next to the existing wall?

[aigel]

Soil - and an existing wall. Soil is rock hard - well established with hedges holding it together.

I expected to dig down at least one brick deep and set it into sand, no concrete.

[dad911]

I'd build the wall first. Cover it with thin plastic when they pour to protect from splatter.

Originally Posted by aigel

......

The concrete work is too much to DIY, so I will need a contractor for that.
......

IMHO pouring concrete is easier than building retaining walls.....

[look 171]

Look like there's a bit of slope? The high side is where the hedge is? Personally, I put a concrete footing instead of just a trench with a bit of sand as base. It will be so much more stable. With the set up from your link, it will eventually creep and move due to rain or gravity. But if you must, make sure the blocks are glued or something. I am not a bug fan of those pretty stack stone type walls because you will be doing it again in 8-10 years if there's a slope.

[wilnj]

Your sequence is correct, you definitely want to build the wall first. I can’t really tell from the picture, are you saying the wall is 1.5 high or 1.5 feet from the property line?

If it’s from the property line, I’m assuming you mean to the proposed face of the wall?

I would suggest the following assuming an 8” high retaining wall block:

1. Excavate for the footing to a depth at least 16” below the proposed driveway elevation. Also excavate enough to allow for the thickness of the wall plus 6”.

2. Compact the soil with a plate tamper.

3. Put in 8” of crushed stone, compact stone with a plate tamper.

4. Set your first course of block on the compacted stone. Place high quality landscape fabric down the back of the block and up the against the soil creating a trough.

5. As you add courses of block, backfill behind the wall with stone. Also fill the cavities of the wall block with stone as you go up. If you’re not using a hollow block, look for one that has holes for pins or use adhesive as suggested above.

6. When you get to finished elevation of the wall, leave the stone in the back low about 4-6”. Fill with topsoil and seed.

Originally Posted by look 171

Look like there's a bit of slope? The high side is where the hedge is? Personally, I put a concrete footing instead of just a trench with a bit of sand as base. It will be so much more stable. With the set up from your link, it will eventually creep and move due to rain or gravity. But if you must, make sure the blocks are glued or something. I am not a bug fan of those pretty stack stone type walls because you will be doing it again in 8-10 years if there's a slope.

I’ve built walls as high as 50’ with no issues, like everything else, it’s the preparation that counts.

[look 171]

Originally Posted by wilnj

I’ve built walls as high as 50’ with no issues, like everything else, it’s the preparation that counts.

You are telling me you build 50' tall wall without concrete footing but a crush stone and compaction? a 50" wall must be holding up something from behind.

[dad911]

We have done some tall walls. 10' +-. There is a geo-mat/grid that is put in every 4th course or so, that ties the block back to the dirt/stone. Drainage behind the wall is key.

In this area anything over 4' high needs a permit and an engineering design.

[look 171]

Originally Posted by dad911

We have done some tall walls. 10' +-. There is a geo-mat/grid that is put in every 4th course or so, that ties the block back to the dirt/stone. Drainage behind the wall is key.

In this area anything over 4' high needs a permit and an engineering design.

3' out here in earthquake country.


10' and 50' is a huge difference.

[aigel]

thanks guys!

Yes there is slope to the next door neighbor which creates that step against the bushes - but also the driveway has significant slope from the garage to onto the street. On my picture you can see a milk crate for size scale reference.

We have a great landscaping material company in town. I will go by there for more advice and looking at engineering solutions. The latest looks to be interlocking walls with pins.

2 feet tall wall will do the job so I do not think it needs to be highly reinforced. my reading also tells me that too much concrete can be detrimental because it does not move rather than crack.

[dad911]

Consider the slope, you typically set the block level, so there will be steps. More corner /end blocks.


(not my pic, from the internet)

I've seen guys try to follow the slope, and IMHO it doesn't look right.

[Baz]

It wouldn't hurt to ask the concrete contractor you intend to use for his opinion added as a data point to the input here.

There could be something you/we don't know about or haven't thought of. And since he will be doing the work, it's important to get his input beforehand - as in before any plans are made.

[javadog]

Grade it first. Compact it.
Install a proper footing for the wall system you want to use. Spend a lot of time on this. Consider drainage on the back side of the wall before you finalize the design.
Install the wall.
Pour the driveway. If you use the right kind of mix, you can drive on it in a day or two. Most concrete suppliers will have a mix designed for the DOT to use for road repairs.
Cure the concrete properly. Keep it wet or use a sealer/cure compound.
Make sure you use tons of rebar in the concrete.

[Zeke]

Originally Posted by aigel

thanks guys!

Yes there is slope to the next door neighbor which creates that step against the bushes - but also the driveway has significant slope from the garage to onto the street. On my picture you can see a milk crate for size scale reference.

We have a great landscaping material company in town. I will go by there for more advice and looking at engineering solutions. The latest looks to be interlocking walls with pins.

2 feet tall wall will do the job so I do not think it needs to be highly reinforced. my reading also tells me that too much concrete can be detrimental because it does not move rather than crack.

One more option to consider. The driveway itself will brace the side of the short retaining wall. Now since all those bushes are going to try and tip the wall back onto your drive, you might want to talk about a monolithic pour sort of how many garage floor and stem walls are done all at once.

This makes for a "L" shape laid on its side with the short leg being the wall. The rebar would be continuous from horizontal and bent up 90º up into the wall with a pair of horizontals high and low in the wall itself.

The drive can be a grid of rebar on 24" centers both ways with a little extra over by the wall.

How many yards of concrete are you estimating at this point? if you're just over one truck you will actually save money on materials filling out the 2nd truck and pouring the wall at the same time. A crew of 5 can handle this in spades.

If the drive alone is one truck or less, forget my idea and build the wall out of block or whatever first and let the drive help with stability. At least dowel the wall to the drive.

[smadsen]

I have a concrete drive along side of the house that's nominally level (drains to the front about 1%). I had a retaining wall of 2 x 14 cedar (I think) that finally rotted out. I pulled it down and used stacking blocks with about a 1" "hook" on the back of the block. I laid the "hook" on the first course behind the concrete drive. Then stacked the remaining 4 courses & backfilled native as I went. The wall has remained dead straight & level for 10 years.

[drcoastline]

Originally Posted by aigel

Soil - and an existing wall. Soil is rock hard - well established with hedges holding it together.

I expected to dig down at least one brick deep and set it into sand, no concrete.

I assume the 1.5; wall you refer to is the wall at the sidewalk on the left side of the photo below the hedge by the cone? I also assume the wall will not go across the front but directly down the property line? This also appears to slope up? Will you be removing the wood ties out-front or building along side the ties? You are going to want to need to dig more than one course below grade out front. At a minimum one course plus 6" for the base layer. As the grade slopes up you will be going down several feet so the base remains level.

I do not know the frost line (if one even exists) in SF? But here in NJ you would want to go down 24" to get below the frost line. I would caution against setting your wall directly on the sand. That sand alone can shift causing the wall to fail. You will want some sort of base layer, typically crushed stone, concrete or a combination. It also appears the majority of the wall will be below grade except the small portion out front? I don't think you will have any pressure issues from the yard on the other side? Build the wall, lay in a fiber expansion joint along the wall pour your concrete to the joint.

[wilnj]

Originally Posted by drcoastline

I assume the 1.5; wall you refer to is the wall at the sidewalk on the left side of the photo below the hedge by the cone? I also assume the wall will not go across the front but directly down the property line?

I do not know the frost line (if one even exists) in SF? But here in NJ you would want to go down 24" to get below the frost line. I would caution against setting your wall directly on the sand. That sand alone can shift causing the wall to fail. You will want some sort of base layer, typically crushed stone, concrete or a combination. It also appears the majority of the wall will be below grade except the small portion out front? I don't think you will have any pressure issues from the yard on the other side? Build the wall, lay in a fiber expansion joint along the wall pour your concrete to the joint.

If it is a modular block wall, there is no concern about damage from frost heave and it does not need a deep footing. As I stated above, 1 buried course is the typical detail.

[Zeke]

I think it's taller that I thought. I see sections that might approach 3 feet. A stepped wall always looks nice.

[look 171]

That's a very simple wall there. I think the biggest headache is deciding on finish texture of the wall face itself.