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Stupid footer question Bill 04-09-2008
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Posted by Pierre Levesque on April 10, 2008, 11:27 am

>
>
>
>>
>>> Ok, here comes the stupid footer question of the month. I've been
>>> researching info on constructing a garage and know that I have to have a
>>> footer below the frost line, which in my neck of the woods is 32 inches,
>>> my
>>> question is exactly WHAT has to be below that line. Does the entire
>>> footer
>>> need to be below as in a 8 inch thick footer has the top of the footer
>>> at
>>> 32 inches or does the footer just have to sit or have its bottom at the
>>> frost line.
>>>
>>> I originally thought it was the first way but have since seen some
>>> inferences that it might be the second way. I want to do this correctly
>>> but
>>> if I can start the footer 8 inches higher I save on hand digging 16 x 8
>>> inches of dirt and save on 8 x 8 inches of concrete for the stem wall
>>> thus
>>> lightening the load on my wallet and back.
>>>
>>> Bill
>>
>> Top of the footing.
>>
> Around here it is a 48" frost line and to the BOTTOM of the footing. Why
> the top? What if the footing is 2' thick?
> EDS

Since the footing supports the foundation wall or basement slab isn't it
logical that the footing should be below the frost line so as to not be
subject to the freeze/thaw cycles that occur above the said frost line?

That's the main reason...




Posted by RicodJour on April 10, 2008, 1:07 pm
On Apr 10, 11:27 am, "Pierre Levesque"
>
>
>
>
>
>
>
> >>> Ok, here comes the stupid footer question of the month. I've been
> >>> researching info on constructing a garage and know that I have to have a
> >>> footer below the frost line, which in my neck of the woods is 32 inches,
> >>> my
> >>> question is exactly WHAT has to be below that line. Does the entire
> >>> footer
> >>> need to be below as in a 8 inch thick footer has the top of the footer
> >>> at
> >>> 32 inches or does the footer just have to sit or have its bottom at the
> >>> frost line.
>
> >>> I originally thought it was the first way but have since seen some
> >>> inferences that it might be the second way. I want to do this correctly
> >>> but
> >>> if I can start the footer 8 inches higher I save on hand digging 16 x 8
> >>> inches of dirt and save on 8 x 8 inches of concrete for the stem wall
> >>> thus
> >>> lightening the load on my wallet and back.
>
> >>> Bill
>
> >> Top of the footing.
>
> > Around here it is a 48" frost line and to the BOTTOM of the footing. Why
> > the top? What if the footing is 2' thick?
> > EDS
>
> Since the footing supports the foundation wall or basement slab isn't it
> logical that the footing should be below the frost line so as to not be
> subject to the freeze/thaw cycles that occur above the said frost line?
>
> That's the main reason...

The frost line is a design criteria, and, as with all design criteria,
incorporates a factor of safety. If you want to pay more to build in
an additional factor of safety by excavating deeper, well it's your
money. The primary problem is the moisture in the soil, so if you
have poorly draining soils, don't have foundation drains, and your
gutters dump water next to the foundation then I would agree that
going deeper is a good idea. Otherwise it's wasted money.

R

Posted by EDS on April 10, 2008, 2:13 pm



>
>>
>>>
>>>
>>>
>>>>
>>>>> Ok, here comes the stupid footer question of the month. I've been
>>>>> researching info on constructing a garage and know that I have to have
>>>>> a
>>>>> footer below the frost line, which in my neck of the woods is 32
>>>>> inches, my
>>>>> question is exactly WHAT has to be below that line. Does the entire
>>>>> footer
>>>>> need to be below as in a 8 inch thick footer has the top of the footer
>>>>> at
>>>>> 32 inches or does the footer just have to sit or have its bottom at
>>>>> the
>>>>> frost line.
>>>>>
>>>>> I originally thought it was the first way but have since seen some
>>>>> inferences that it might be the second way. I want to do this
>>>>> correctly but
>>>>> if I can start the footer 8 inches higher I save on hand digging 16 x
>>>>> 8
>>>>> inches of dirt and save on 8 x 8 inches of concrete for the stem wall
>>>>> thus
>>>>> lightening the load on my wallet and back.
>>>>>
>>>>> Bill
>>>>
>>>> Top of the footing.
>>>>
>>> Around here it is a 48" frost line and to the BOTTOM of the footing. Why
>>> the top? What if the footing is 2' thick?
>>> EDS
>>
>> Since the footing supports the foundation wall or basement slab isn't it
>> logical that the footing should be below the frost line so as to not be
>> subject to the freeze/thaw cycles that occur above the said frost line?
>>
>> That's the main reason...
>
> That was my thinking, and thus that the entire footer should be below the
> frost line.
> If not, then whats the point of the frostline?


Backfilling should be done with a structural fill not susceptible to
freezing. A damp backfill with many fines just tossed back in will heave a
foundation just by being frozen to it. I always backfill with gravel to
within 8" of the surface, place a geofabric or tarpaper sloped strongly away
from the building for several feet, and complete with topsoil. The geofabric
or tarpaper keeps the fines from infiltrating the gravel and directs them
(and some moisture) away from the building. Any basement in our climate (New
England) should have drainage tiles set at the bottom of the excavation on a
substantial bed of gravel, sloped to an outlet. In some cases I've used 2
sets of drainage tiles, one half way down.
EDS



Posted by Bill on April 10, 2008, 2:35 pm

<snip>
>
> Backfilling should be done with a structural fill not susceptible to
> freezing. A damp backfill with many fines just tossed back in will
> heave a foundation just by being frozen to it. I always backfill with
> gravel to within 8" of the surface, place a geofabric or tarpaper
> sloped strongly away from the building for several feet, and complete
> with topsoil. The geofabric or tarpaper keeps the fines from
> infiltrating the gravel and directs them (and some moisture) away from
> the building. Any basement in our climate (New England) should have
> drainage tiles set at the bottom of the excavation on a substantial
> bed of gravel, sloped to an outlet. In some cases I've used 2 sets of
> drainage tiles, one half way down. EDS
>
>
>

How do you guys handle a non-basement foundation?

Bill

Posted by EDS on April 10, 2008, 5:10 pm


>
> <snip>
>>
>> Backfilling should be done with a structural fill not susceptible to
>> freezing. A damp backfill with many fines just tossed back in will
>> heave a foundation just by being frozen to it. I always backfill with
>> gravel to within 8" of the surface, place a geofabric or tarpaper
>> sloped strongly away from the building for several feet, and complete
>> with topsoil. The geofabric or tarpaper keeps the fines from
>> infiltrating the gravel and directs them (and some moisture) away from
>> the building. Any basement in our climate (New England) should have
>> drainage tiles set at the bottom of the excavation on a substantial
>> bed of gravel, sloped to an outlet. In some cases I've used 2 sets of
>> drainage tiles, one half way down. EDS
>>
>>
>>
>
> How do you guys handle a non-basement foundation?
>
> Bill
Just go down 4' and backfill same way. Usually no drainage tile needed. Most
of my work is commercial work, so houses may be a bit lighter. The 4' is a
given and I've done 6' in the Northeast Kingdom area of Vermont.
Slabs-on-grade make for cold feet.
EDS



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