This is one subject that I find impossible to understand. Although the
theory about having a firm foundation to a point just below the frost line
is clear, everywhere I look I see construction of steps and sidewalks that I
know is not built on a foundation or other support rested at a point below
the local frost line.

I live in an area where the frost line is commonly known as two feet, but
has been known to go down to three feet.

My first case in point is sidewalks and walkways. I see many sidewalks
made either of concrete, flagstone, etc that I know for sure have not been
built by first digging two or three down to get below the frost line. I
see walkways made of flagstone placed in mortor, where I know for sure that
the entire structure of the walkway is no more than five or six inches
thick. How do they avoid frost heave ?

I would like to build some steps up a fairly steep slope. This would be
about 14 steps over a span of about 25 feet (I am just estimating here).
I would like to have flagstone steps, set in mortor. If I follow what I
have read in prior posts here, I would have to build 14 separate footings,
all 2 or 3 feet deep , upon which to place each steps. That would be a
**major** project !!

At one time, I thought that the frost heave problem was a consideration in
structures that would carry a lot of weight, such as the foundation for a
home (traditional footings) or a deck post to support a deck. But then I
read that even steps, sidewalks, and walkways must also be built so as to
avoid frost heave.

I must be missing something here, or somehow totally misunderstanding of how
to deal with frost heave in constuction projects such as these discussed.

Can someone please clear this up for me ???

Thanks !!

James

James wrote:
This is one subject that I find impossible to understand. Although the
theory about having a firm foundation to a point just below the frost line
is clear, everywhere I look I see construction of steps and sidewalks that I
know is not built on a foundation or other support rested at a point below
the local frost line.

I live in an area where the frost line is commonly known as two feet, but
has been known to go down to three feet.

My first case in point is sidewalks and walkways. I see many sidewalks
made either of concrete, flagstone, etc that I know for sure have not been
built by first digging two or three down to get below the frost line. I
see walkways made of flagstone placed in mortor, where I know for sure that
the entire structure of the walkway is no more than five or six inches
thick. How do they avoid frost heave ?

I would like to build some steps up a fairly steep slope. This would be
about 14 steps over a span of about 25 feet (I am just estimating here).
I would like to have flagstone steps, set in mortor. If I follow what I
have read in prior posts here, I would have to build 14 separate footings,
all 2 or 3 feet deep , upon which to place each steps. That would be a
**major** project !!

At one time, I thought that the frost heave problem was a consideration in
structures that would carry a lot of weight, such as the foundation for a
home (traditional footings) or a deck post to support a deck. But then I
read that even steps, sidewalks, and walkways must also be built so as to
avoid frost heave.

I must be missing something here, or somehow totally misunderstanding of how
to deal with frost heave in constuction projects such as these discussed.

Can someone please clear this up for me ???

Thanks !!

James


The key with making flatwork like sidewalks and such survive frost
heave, is good substrate and drainage. Well tamped dirt and good layer
of gravel or whatever. Any water that runs under the concrete needs a
place to go before it freezes. On something large, like a patio that is
trapped up against a house foundation, you do sort of need footers.
Heaved and cracked patios are dirt-common up north here, and often
contribute to basement flooding. (If the concrete is thick enough and
well reinforced, it tilts as a unit, raising up on the side away from
the warm foundation, and you get a pond against the foundation.)

You can tell when a non-pro laid a sidewalk- squares lift and settle
with the seasons, even if no tree roots are nearby. I've seen sidewalks
less than 10 years old self-destruct, and I've also seen sidewalks 100
years old still in fine shape, other than the pitting from the salt
splash from the street. Experience and not cutting corners makes the
difference.

(Disclaimer- I ain't an expert, so this is one of the categories where I
am willing to pay somebody who is....)

--
aem sends...

James wrote:
This is one subject that I find impossible to understand. Although the
theory about having a firm foundation to a point just below the frost line
is clear, everywhere I look I see construction of steps and sidewalks that I
know is not built on a foundation or other support rested at a point below
the local frost line.

I live in an area where the frost line is commonly known as two feet, but
has been known to go down to three feet.

My first case in point is sidewalks and walkways. I see many sidewalks
made either of concrete, flagstone, etc that I know for sure have not been
built by first digging two or three down to get below the frost line. I
see walkways made of flagstone placed in mortor, where I know for sure that
the entire structure of the walkway is no more than five or six inches
thick. How do they avoid frost heave ?
....

To see the effects of frost heave there has sufficient moisture and a
susceptible soil type to cause the expansion of sufficient magnitude to
cause noticeable problems. Generally those surface areas that don't
show damage drain well enough or are stable enough soils to have small
movements that don't cause real damage.

Cause drainage problems in one of those areas that has previously been
ok and may well suddenly have a problem where none existed before.

--

A series of signs I saw driving from a ski area in New Hampshire back to Bostom
years ago.

Caution - frost heave 1000 feet

Caution frost heave 500 feet

Welcome to Massachusetts



Followed by several cars stopped to change tires.

It seem Massachusetts didn't build their roads as well as New Hampshire.

James;

Frost heave occurs only when there is a change in volume of the underlying
soil when it freezes. As dry soil doesn't expand or contract when it
freezes the problem occurs in the presence of water. If you can keep the
supporting soil dry it won't heave in the winter. Thus you can prevent
frost heave by constructing a good under-drainage system for your steps.
Use a deep gravel base, 6 to 12 inches deep, to allow water on the slope to
drain downwards out of the soil. Also use a good method to drain water out
of the soil at the bottom of the steps. Since your frost penetration goes
down 2 ft you need to keep the top 2 ft of soil dry so it won't heave.

Frost penetrates a lot deeper in dry soil than in wet soil. Thus it can
become a vicious circle - the dryer you make it the deeper the frost goes,
the deeper you have to keep it dry, etc. You can address this by good
surface drainage. If water doesn't sit around near the steps the underlying
soils will be dry and won't heave. The shallow gravel addresses the short
term rainfalls and snowmelts and the surface drainage addresses the long-
term wetness of the area and thus the deeper soils.

Good explanation Reno, many thanks !!

James

On May 9, 8:38�pm, "James" wrote:
Good explanation Reno, many thanks !!

James

well if a walk heaves its not a biggie repair or replace failrly
cheap.

but imagine a homes structure heaving due to lack of footer.

could cost more than the price to build the home originally.

On Sun, 9 May 2010 13:41:05 -0400, "James"
wrote:

This is one subject that I find impossible to understand. Although the
theory about having a firm foundation to a point just below the frost line
is clear, everywhere I look I see construction of steps and sidewalks that I
know is not built on a foundation or other support rested at a point below
the local frost line.

I live in an area where the frost line is commonly known as two feet, but
has been known to go down to three feet.

My first case in point is sidewalks and walkways. I see many sidewalks
made either of concrete, flagstone, etc that I know for sure have not been
built by first digging two or three down to get below the frost line. I
see walkways made of flagstone placed in mortor, where I know for sure that
the entire structure of the walkway is no more than five or six inches
thick. How do they avoid frost heave ?

They dont. If water can seep underneath and freeze, you got heaving.
When the same number of liquid molecules solidify they need more space
while forming ice (a lattice structure).


I would like to build some steps up a fairly steep slope. This would be
about 14 steps over a span of about 25 feet (I am just estimating here).
I would like to have flagstone steps, set in mortor. If I follow what I
have read in prior posts here, I would have to build 14 separate footings,
all 2 or 3 feet deep , upon which to place each steps. That would be a
**major** project !!

At one time, I thought that the frost heave problem was a consideration in
structures that would carry a lot of weight, such as the foundation for a
home (traditional footings) or a deck post to support a deck. But then I
read that even steps, sidewalks, and walkways must also be built so as to
avoid frost heave.

I must be missing something here, or somehow totally misunderstanding of how
to deal with frost heave in constuction projects such as these discussed.

Can someone please clear this up for me ???

Thanks !!

James


If your steps drain quickly they are more likely to resist heaving.