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Frost Line and retaining wall


bandeg's Avatar
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06-20-11, 07:08 AM   #1 (permalink)  
Frost Line and retaining wall

In an earlier post, it was recommended that my field stone retaining wall's footing be built below the frost line. In Massachusetts isn't the frost line 48 inches?

Does this mean that my 2.5 foot retaining wall needs have a footing 48" deep and my wall will need to be 6.5 feet with four feet underground? This structure does not have to hold up a house or deck, but it will hold in or 'retain' one side of a patio.

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Regards,
--B

 
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stickshift's Avatar
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06-20-11, 07:43 AM   #2 (permalink)  
Rigid walls need a footer below the frost line, segmental block walls do not

I would think you would want the latter

 
bandeg's Avatar
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06-20-11, 10:17 AM   #3 (permalink)  
Thanks. Many of the segmental block walls look industrial. We have a fieldstone wall bordering our property. Can you suggest a block wall that would compliment this?

Would a dry-stacked stone wall also be a footer-less option to consider to retain one side of a patio?

 
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07-01-11, 03:55 AM   #4 (permalink)  
To frost or not to frost.

The first thing you need is to understand what a frost footing is and why it is neccesary. When the ground freezes it heaves up, how much depends on the moisture content. When it thaw's it goes back down. During this process, a wall that rests on top, has no choice but to go with it, up & down. This movement is not consistent from one end to the other, resulting in cracking and eventually crumbling of the structure.

A poured concrete wall suffers from this. A mortared block wall, I assume this is the segmented wall spoke of here, will suffer also over time. The joints become loosened.

A dry stack wall does not matter. The joints have enough space to allow this heaving movement. The large spacious joints in a dry stack wall are like expansion joints in other strucures, they will take movement.

These senerios are what an engineer will tell you and I will tell you this much.

I am from the midwest, frost depth is to be 36" deep.

I have been in the structural "poured" concrete wall and footing feild for 19 yrs. I have not seen it freeze below 16" nor have I saw real considerable damage to a wall from frost heaving. I have seen hydraulic (water) up-heave that damaged strucures, but I have saw walls with no frost protection have NO damage.

If a wall is poured or built right, it creates a beam in its entire length. This beam withstands some movement. It is usually the structure on top of the wall that is at risk.

For your little 2 and 1/2 ft. tall wall for a patio, you could probably do whatever you desired and be alright. Depends on who you talk to.

 
Concretemasonry's Avatar
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07-01-11, 04:40 AM   #5 (permalink)  
98charles -

A segmental retaining wall (SRW) does not need a footing and it does not incorporate any steel reinforcement. It easily be curved (inside and outside corner), so tthat is the reason for huge amounts built around the world.

Heights range up to 44'+, all without footings. The engineering precludes all rigid footings

Dick

 
doc's Avatar
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07-27-11, 03:47 PM   #6 (permalink)  
I am far from an expert on this sort of thing, but two years ago I built a round raised planter using retaining wall block. I buried the first course 1/2 deep on top of 3 or 4 inches of crushed base stone. I went 5 courses above the first one. We live in mid-Indiana and so far I've seen no problems with the blocks.

 
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