Retaining wall footing depth

[lennyzx11]

This is a silly question so bear with me.

I want to put a cinder/concrete block wall as a retainer in my yard between two level surfaces. One is three foot higher than the other.
The length will be around 15-20 ft.

In Vermont the frost depth for footings is 48”.

Do I have to go 48” down from the lower elevation?
That makes the wall approx 7 ft in height with 4 ft buried and 3 ft showing to the top grade.

That seems a little over excessive.
Thank you,
Lenny

 

[mbohuntr]

This is a silly question so bear with me.

I want to put a cinder/concrete block wall as a retainer in my yard between two level surfaces. One is three foot higher than the other.
The length will be around 15-20 ft.

In Vermont the frost depth for footings is 48?

Do I have to go 48 down from the lower elevation?
That makes the wall approx 7 ft in height with 4 ft buried and 3 ft showing to the top grade.

That seems a little over excessive.
Thank you,
Lenny

Well, if it heaves, how much work will it be to replace it? There is a technique using a buried piece of foam insulation in front, and under the concrete called a frost wall. My breezeway and garage were built with it and neither has heaved or cracked.

 

[Clint S]

Are you getting a permit, if no do what you wish. The frost line depth is where to go if you dont want to do it again (maybe). If you wish to take a chance and save some work it's on you to decide. We have a building here on footer that is 2 feet deep, has not moved in 50 years. We have another that is cracked in many spots due to movement

 

[LouNY]

A lot will depend on the soil you are working with and the drainage, if you are in clay or hardpan and do not have good drainage it will move if not below the frost line.
The frost line will vary considerably depending on many things, the amount of snow cover when the temps get very low, the moisture content when the ground freezes,
how compacted the ground is. A lawn area with undisturbed snow fall will have a much shallower frost depth then a plowed driveway.
Also I am not a fan of blocks I much prefer poured concrete, I have seen several instances when water saturated blocks froze and spalled materialfrom the blocks.

 

[AllDodge]

Why not use retaining wall Stones/Blocks? I installed one about 120 feet long and goes from 4 to nothing and its been there for 20 years. Set the first stone under the ground and just keep going. Put fabric next to the earth and then rock between stones and fabric. Not going over 4 feet high you don't need the larger stones, mine are the 6 inch high ones

Re-edit

 

[mikester]

This is a silly question so bear with me.

I want to put a cinder/concrete block wall as a retainer in my yard between two level surfaces. One is three foot higher than the other.
The length will be around 15-20 ft.

In Vermont the frost depth for footings is 48”.

Do I have to go 48” down from the lower elevation?
That makes the wall approx 7 ft in height with 4 ft buried and 3 ft showing to the top grade.

That seems a little over excessive.
Thank you,
Lenny

If you are happy to see retaining walls falling over or are intending to flip the property for max profit and minimal investment then go for it.

 

[lennyzx11]

If you are happy to see retaining walls falling over or are intending to flip the property for max profit and minimal investment then go for it.

No, I didn’t want to go it wrong. It just seemed to me that 4ft down for a 3ft wall seemed excessive.
I’ll do it right.

 

[RalphVa]

I've built retaining walls in La and here in Va out of those mortarless blocks bought at Lowes/Home Depot. Wouldn't matter if they heaved. They'd kinda all move as needed, but they certainly would not crack like a mortared wall would if not built deep enough. I always put the first course about a 1/2 block below grade on top of a smooth bed of something like pea gravel, about 1" deep (enough to allow you to smooth it to the contour of the soil; doesn't have to be level). Never had any problems with the quite long one in La over the 6 years there, and the one I put in here is fine going on 19 years. Both were/are about 3 ft tall. Around, here, the county/city people have built mortarless walls near 20 ft tall. Have no idea what their footings are.

I'd inquire at the place where you'd buy them (like Lowes/Home Depot) to see what they recommend or know that customers have done if you don't want to do what I've done.

Never did any yard work on our little property and house in Poultney, Vt. My FIL built a cute little well head around our well-in-a-pipe like they do now all the time for county wells. He built it out of field stone, think with no mortar. Don't recall he went very deep for the footing on it. It never fell apart or ever seemed affected by frost.

Ralph

 

[Streetcar]

I've built retaining walls in La and here in Va out of those mortarless blocks bought at Lowes/Home Depot. Wouldn't matter if they heaved. They'd kinda all move as needed, but they certainly would not crack like a mortared wall would if not built deep enough. I always put the first course about a 1/2 block below grade on top of a smooth bed of something like pea gravel, about 1" deep (enough to allow you to smooth it to the contour of the soil; doesn't have to be level). Never had any problems with the quite long one in La over the 6 years there, and the one I put in here is fine going on 19 years. Both were/are about 3 ft tall. Around, here, the county/city people have built mortarless walls near 20 ft tall. Have no idea what their footings are.

I'd inquire at the place where you'd buy them (like Lowes/Home Depot) to see what they recommend or know that customers have done if you don't want to do what I've done.

Never did any yard work on our little property and house in Poultney, Vt. My FIL built a cute little well head around our well-in-a-pipe like they do now all the time for county wells. He built it out of field stone, think with no mortar. Don't recall he went very deep for the footing on it. It never fell apart or ever seemed affected by frost.

Ralph

over 4ft height usually requires design by engineer for precast block walls. The blocks are designed to be installed level with gravel as foundation

 

[Diggin It]

I want to put a cinder/concrete block wall as a retainer in my yard between two level surfaces. One is three foot higher than the other.

What is your purpose? If it's just decorative/landscaping, it probably doesn't matter. In that case, I'd probably drive longer rebar into the higher ground at an angle and attach the block to that rather than go deeper under the lower surface.

 

[oosik]

I have one short - 50' long - retaining wall. I dug down about 2 1/2 feet - put down a half foot of gravel - came up with loose cement blocks. No mortar. I'm sure the wall moves with the season but it's still where I installed it 30 years ago. Local codes call for four foot burial for footers.

 

[Diggin It]

Use of the lower side matters too. If it's a patio/seating/play area where people could get hurt, construction needs to be more substantial that if it's for landscaping/flower bed/garden/lawn.

 

[KennyG]

As noted above, it all depends on the soil composition and drainage. If you dig a trench a few feet deep and backfill with gravel, it will probably be stable. I lived in a house with a foundation that was brick laid in a shallow trench in the sand. It was in fine shape after 50 years. However, if you area in heavy clay, it's more of a concern. You could do a ground beam. This would be a poured reinforced concrete foundation (perhaps 8 to 12 inches square) with some deep holes to get down near the frost line. This is how we used to pour foundations for outdoor equipment like large A/C units. We would pour a 4 inch thick pad with a few "postholes" deep below it.

 

[PA hayseed]

Just to add to the myriad of advice offered here, I would suggest you go with a dry stone wall. They have been used for hundreds of years and don't require a footer. Some are rebuilt every 50-75 years or so. If you do dry stone, just remember the length of the stone sits into the wall, not along the wall. People do this wrong all the time, because it uses less material to build and it is quicker.

Here is a link to a place that knows a little something about dry stone Dry Stone Conservancy

The only problem with the dry stone people is that they are located in Kentucky

 

[PILOON]

30 years ago I built a dry stone wall about waist high and it still has not moved.
We are in a 4 foot deep frost zone.
Largest ones are at the base getting smaller as they near the top.
One trick is to make sure the surfaces mate as well as possible and if not seat them in a clay like soil.
Stuffing moss between the spaces also helps.
Don't lay perfectly vertical but tilt the wall back slightly as you build it, like perhaps 5 degrees or so, that way if frost does heave the stones can flop back come spring thaw.

In fact as I think it over all three of my properties have their fair share of stone walls and that in varied soils.
Being lakeside we wanted flattish areas rather than hills hence retaining walls to create terraces.
LOL, they have been there so long that I have actually forgotten about them.
I'll add that I have never needed to do any repairs.

Another trick is (if so equipped) is to pressure wash the faces once the wall is completed for that look of perfection.
Milk or cream will help propagate that mossy aged look.

 

[LouNY]

I don't care for the old style dry stacked stone walls, after a great many years they do shift about and need rebuilding to look good.
I would not consider a loose stacked stone wall for a retaining wall at all.
I have been involved in burying many miles of stone walls to enlarge fields and merge some fields into one to make them easier to work.
I don't like stones doesn't matter if they are stacked in a wall, loose in a field or piles in the corner of a field.

 

[MikeInEburg]

Another very forgiving wall medium are gabion baskets. You can generally just put them on the ground surface. With clay soil, I'd probably still add drainage stone behind.

 

[PA hayseed]

I don't care for the old style dry stacked stone walls, after a great many years they do shift about and need rebuilding to look good.
I would not consider a loose stacked stone wall for a retaining wall at all.
I have been involved in burying many miles of stone walls to enlarge fields and merge some fields into one to make them easier to work.
I don't like stones doesn't matter if they are stacked in a wall, loose in a field or piles in the corner of a field.

You may like them you will see
You may like them in a tree
Sorry, your response had me thinking green eggs and ham. I wish I could have taken some pictures of those stone walls you took down. There are a lot of varieties of stone walls.

For the OP, I have 4 retaining walls made of dry stack stone around my house (big stones). The one set of walls are used to retain about 4' of ground (tapering out) around my basement door so I can walk out. 10 years so far with no issues. The other two are around my driveway.

 

[lennyzx11]

I actually have did dry stack and mortar field stones. Used to be a hobby. I haven’t did any since moving from Oklahoma to Vermont last year. I may do that but thinking that blocks would go quicker. Especially at the pace I work!

 

[AllByteNoBark]

I would use the large retaining stone blocks. Bury the first one and make sure it is level and build up from there. Make sure and put the fabric behind them as AllDodge mentioned so they can drain but dirt will not wash out. They work really well and hold well. I have used them for some pretty substantial walls and never had an issue. The key is to get the first row that is buried on good solid ground and make sure it is level both direction, front to back, and side to side.