How to install Fence Posts
“The
most common flaw in all deck and fence projects is poor footings”
Here in
Ontario we use footings 4-5’ in depth. A good rule of thumb is to bury
1/3 of the final height of the fence. This will usually give sufficient
lateral strength.
·
If you are contemplating a solid fence (sound barrier), or a fence
higher than 6’-0” consider increasing the post size to 4” x 6” or 6” x
6” posts due to possible wind damage. If working
with cedar, consider using treated lumber which is about 25%
stronger than red cedar. You can always face with Cedar
after. Again for solid or oversized fences increase the size
of the posts or decrease the size of sections or both.
*“Call
your local building department first and obtain their specifications
before initiating any project”
Our
standard footing shown utilizes a post set in concrete 4’
deep.
The
upper 2’ of the footing is backfilled with limestone screenings or fine
crushed
stone.
The
corner posts are set first and a string line is cast ½ “ from the side
of the
post to allow the in line posts to be set accurately.
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Why a Two Part Footing Works
*Illustration
shows how compression over time locks the concrete in place1)
Screenings compact or settle- allowing the surrounding soil to expand.
The concrete will not compact. Over time the soil will encroach over
the concrete thus locking the footing in place.
2)
When pressure caused by the expansion of freezing soil or swelling clay
based soil (as it absorbs moisture), is transferred to the screenings
they will give way allowing the ground to rise and fall independently
of the footing.
3)
Screenings will drain effectively and also allow for evaporation
keeping the footing relatively dry.
4)
Limestone screenings will prevent growth of vegetation, which retains
moisture and causes wood rot.
5)
A footing is only as solid as the ground around it. The screenings will
conform to the contour of the ground and adapt to seasonal changes or
those caused by extreme winds etc. The post will be noticeably more
stable than traditional concrete to grade footings.
Caution:
Deck blocks are a floating footing,
They are free to rise and fall with the effects of frost. They are suitable on stable
ground. Where the
ground has been excavated i.e.: within
3’ of a foundation or where grade has been elevated by adding soil they
are not
recommended. (If you are intent on using these add a round patio stone
beneath
it for additional stability. Never connect a floating deck to a
foundation.
Fence spikes are never recommended. A
seriously inferior product. They will not withstand the pressure
exerted by
wind on a fence and have shown to be inadequate under the pressure of a
deck.
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Why do footings lift ?
The
source of the problem—concrete to ground level. Since the top of the
hole is
larger than the base, a lip for frost to catch is formed.
As
the concrete is lifted by frost, soil falls into the base which causes
the
footing to remain—A little higher every year.
Concrete
retains moisture—If using cedar or untreated lumber consider sealing or
treating with preservative the portion of the post that comes in
contact with
the ground or concrete.
*
Always call for utility locates prior to digging.