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.