A decade or so ago when I still made my living as a carpenter, in
part as a deck-building carpenter, I dreaded footings. The frost
depth where I worked in northern New Jersey was 36 inches, and my
home county was where the last glacier had stopped, depositing most
of the rocks it had stripped from the land on its way down from
I tried all sorts of tacks to avoid digging footing holes. I'd cut
my price if the homeowner dug them. That didn't work so well,
because homeowners rarely appreciated the importance of digging the
holes exactly where I laid them out.
Once, I pulled $100 out of my wallet to entice a guy running a
backhoe next door to drive on over. That didn't work so well
either, because the machine's overdig was so large that I spent
nearly as much time backfilling by hand as neatly digging the holes
with a shovel would have taken in the first place. And I had to
fill in the tire tracks in the lawn, and reseed the damaged areas.
I was just lucky I didn't have to come back and water the new grass
Footings continue to be a fact of life, and I recently spent some
hours interviewing deck builders from around the country about
them. Geography makes a huge difference in how footings are built,
but a lot of tricks apply across broad areas — I wish I'd
known about some of them in my deck-building days.
Paul Mantoni, Connecticut
Rather than laying out footings the typical way — measuring
out from the house, driving stakes, and stretching a string —
Paul Mantoni, a deck builder in Terryville, Conn., came up with a
different method: "I put the ledger on the house, and attach the
two side joists and the rim joist, propping them up level; I check
for square by measuring the diagonals. I usually build decks with
the joists cantilevered a foot or two past the main beam. I stretch
a string between the side joists where the beam will go, and lay
out the footings from that. Because of the cantilever, there's
plenty of room to work digging the holes."
"Our frost depth is 42 inches," says Mantoni, "but I usually go
down to 48 inches. It doesn't take a lot longer, and it makes the
building inspector happy. I charge about $200 per footing, more
where I know the ground is rocky."
Like most other Connecticut builders, Mantoni doesn't enlarge the
base of the footing beyond the size of a 12-inch-diameter Sonotube.
He slides the Sonotube into the hole, and has a helper hold it
plumb while he carefully backfills. After filling the form with
concrete mix, Mantoni uses galvanized column bases and 6x6 posts to
support the beam.
Jack Hanson, Idaho
When I asked Jack Hanson of Woodpile Products in Boise, Idaho, what
his biggest consideration with footings was, he replied, "To put
them under the beam." Humor aside, compared with those of us in the
Northeast, Hanson has it pretty easy with footings. Because it's so
dry in Boise, the frostline is only 12 inches deep despite the cold
For low-level decks, Hanson uses precast concrete piers he buys
locally. To level them easily, Hanson fills the bottom of the
footing hole with 2 to 3 inches of pea gravel.
One big advantage of the piers that Hanson uses is the integral
Simpson EPB44T post base (Figure 1), which can be adjusted in
height over a range of 2 1/2 inches. On very low decks, it's
possible to skip the posts entirely by resting the beam directly in
the saddles of these post bases.
Figure 1. Footings incorporating a Simpson
EPB44T post base can be adjusted up to 21/2 inches in height by
turning the nut below the post base.
Kim Katwijk, Washington
Like Hanson, Kim Katwijk of Olympia, Wash., uses precast footing
piers, but he sets them on several inches of dry concrete mix, and
then backfills around the pier with more dry concrete mix (Figure
2). "The soil is so consistently wet in coastal Washington," he
explains, "that the concrete has usually set by the next
Figure 2. Washington's damp climate ensures
that dry concrete mix placed below and around a footing pier has
sufficient moisture to set up within one day.
A less desirable consequence of Washington's wetness is an
accelerated rate of wood decay, particularly where fastener
penetration invites water into the untreated center of framing
lumber. To combat this problem, Katwijk uses a turkey baster to
inject wood preservative into the holes he drills for the lags that
hold the hardware to the post.
Katwijk does occasionally need to dig deep footings — for
example, when he's building on a steep slope. Washington's clay
soils tend to creep downhill, and some engineered designs require
footings and piers that extend 3 feet below where the pier hits the
slope on the low side, and extend at least 6 inches above grade on
the high side. In these cases, Katwijk reinforces the spread
footing at the bottom with a mat of #4 rebar, and places vertical
#4 bars in the pier to within 2 inches of its top (Figure 3).
Figure 3. Framing lumber holds a footing-form
tube above the bottom of the hole, allowing for a thickened spread
footing. Backfilling is done after placing the concrete.
Another strategy Katwijk offers has to do with cantilevers. He
points out that deck joists can usually cantilever farther past
their support beam than the tables in code books prescribe, because
those tables apply to houses — where the cantilever picks up
dead loads from walls, ceilings, and roofs that just aren't a
factor with decks.
Of course, varying from the code necessitates engineering, so
Katwijk keeps on his Palm Pilot a spreadsheet his engineer created
to show allowable cantilevers for various joist materials and deck
configurations. Having this information to hand allows for field
adjustments to the location of beams when there's a problem placing
John Wilder, Florida
Hillsides and frostlines are no longer concerns for John Wilder,
who started out in Minnesota — about whose long and woebegone
winters Garrison Keillor waxes eloquent. I imagined that by moving
to Jacksonville, Fla., Wilder had also escaped the curse of digging
deep footings. Not so, he says. "Florida's soils can be shifty
sand, and I often have to dig down 3 feet to find good, solid
Digging 3 feet down in sand could be pretty tedious, but Wilder
doesn't do it by hand. He rents a walk-behind skid steer with a
2-foot-diameter auger (Figure 4).
Figure 4. A walk-behind skid steer with an
auger attachment makes quick work of footing holes, and can be
rented on a daily basis.
Now, 2 feet may seem kind of large, but that's the diameter of the
spread footings that Wilder uses. He fills the bottom of the hole
with concrete, and wet-sets a Sonotube in that. After backfilling
around the Sonotube, Wilder fills it with concrete.
William Bolton, California
Bill Bolton starts with an onsite review before bidding any job
— a practice that can be applied anywhere in the
As in Florida, frost isn't an issue in Santa Barbara, Calif.;
Bolton's footings, which he pours in place, are shallow and easily
dug. Hence, he uses more of them and lighter framing — 4x6
beams and 2x6 joists in most cases.
The most common problem Bolton encounters is having to place
footings close to the house. The first floor of many Santa Barbara
houses consists of a slab — a troublesome place to hang a
deck ledger — so Bolton frequently ends up building a
freestanding deck with a line of footings near the house. To avoid
drainage systems and questionable soils right next to the
foundation, he installs a beam and cantilevers the joists the last
couple of feet to the house.
Sometimes Bolton, who works alone, subs out the footing work for
larger decks. (Frankly, I'm jealous. Not only does he live
somewhere without a frostline, it's possible to find a sub who'll
do deck footings there!)
Bobby Parks, Georgia
Bobby Parks runs an Archadeck franchise in metro Atlanta, where he
faces challenges not from the frost depth or rocks, but rather from
slopes and poor soils.
On slopes, Parks digs the footings to his geotechnical engineer's
depth and width specifications. Then he takes an extra step and
digs out a keyway along the uphill side of the footing. Perhaps 6
inches wide and deep, once filled with concrete the key helps the
footing to resist forces pushing downhill.
Other times, Parks finds poorly compacted soils with a limited
bearing capacity. One solution would be to engineer a wide,
steel-reinforced footing to spread out the loads. But bringing yard
after yard of concrete into the backyard of most subdivision homes
is a logistical nightmare.
Parks' geotechnical engineer, John Stanhope, has an easier
solution. He has Parks dig the hole substantially wider and deeper
than normal, and fill it with ASTM 57 crushed stone, which is a
blend ranging from 1 1/2 inches down to 1/4 inch. Poured concrete
footings rest on the "57 stone."
Most deck builders use fairly conventional concrete footings,
whether poured in place or precast, but some other options are
worth taking a look at, as well.
One engineered solution that works anywhere that's not terribly
rocky, and might be a good choice for problem soils is the Diamond
Pier (Pin Foundations, 253/858-8809, www.pinfoundations.com). Holes
through a reinforced concrete block guide pins — made from
galvanized-iron pipe — that are driven into the ground by a
demolition hammer (Figure 5). To determine the size and length of
pipe, a soil report is necessary.
Figure 5. Pin footings are an alternative to
conventional footings in most soils, and can sometimes provide a
solution in problem soils or environmentally sensitive areas.
Designing the loading requires a knowledge of the underlying
Because no excavation is needed, Diamond Piers seem a good choice
for environmentally sensitive areas. According to the manufacturer,
Diamond Piers will in most cases resist uplift from both frost and
expansive clay soils.
At the International Builders' Show earlier this year, John Wilder
discovered the Magnum Piering system (800/822-7437,
www.magnumpiering.com), which consists of a 6-foot-long galvanized
pipe with auger blades attached to the bottom (Figure 6). It's
driven by a skid steer, excavator, or tractor with an auger drive.
As with the Diamond Pier, one advantage is there's no excavation,
so there's minimal disturbance to the ground. If you use a tracked
skid steer, the weight of the machine is distributed over a broad
area, and the native soils will hardly be disturbed.
Figure 6. Like pin footings, helical footings
are made from galvanized steel. No signifi-cant excavation is
required for their installation, which can be done with a variety
of machines with auger-driving capability.
Another product is the Redi-Footing (866/586-6082,
www.redifooting.com), a combination base and cap that work with
schedule 40 PVC pipe to form a footing (Figure 7). If your back is
anything like mine, the light weight alone might tempt you to try
it. According to the manufacturer, each Redi-Footing can support
10,500 pounds, when used with suitable soils. An ICC Evaluation
Service report is still pending, but the manufacturer claims the
Redi-Footing is accepted in Rhode Island and in various other
Figure 7. Combined with a length of schedule
40 4-inch PVC pipe, plastic Redi-Footings are lightweight
alternatives to conventional footings and are said to be capable of
supporting over 5 tons each.
Finally, there are a couple of commercial forms — the Square
Foot (Sound Footings, 877/924-2323, www.sqfoot.com) and the Bigfoot
(Bigfoot Systems, 800/934-0393, www.bigfootsystems.com) —
that affix to the bottom of a Sonotube to create a larger footing
base (Figure 8). The advantage of these is that once the tube is
attached, the entire assembly can be backfilled and
Figure 8. Footing forms attach to round form
tubes to create a spread footing that can be backfilled and
inspected prior to placing concrete.