Select a design
Arbors, sunscreens, patio covers or gazebos, all are designed to keep us comfortably out of the hot sun while
we relax with friends and family. Arbors are one of the most appealing and there's a multitude of designs possible.
Many of my customers have simply handed me a picture they've cut from a magazine. I'm confident you'll have no trouble
getting some ideas.
The size of your column will depend on both size of your structure and amount of weight you plan to set on them.
For example, if your going to use 6x6 beams with 2x12 joist and then lay 2x4 slats on top of that, you probably won't
be using 4x4 posts to support it. Keep in mind, if you want to enjoy using this structure, having adequate
support will not only be more secure it will appear it as well. Using columns not large enough can allow the structure
to have excess lateral movement which is not a good thing to see if you happen to be under it on a windy day.
Before setting columns
will help to determine size of framing members and number of columns needed.
Setup a batter board
and string line around the structure
1/4" out beyond the desired dimensions. This 1/4" clearance is added so columns won't interfere with the
string. When setting columns, allow for this 1/4" clearance. If possible, measure from an existing
structure or other monumental object like a street curb, fence or concrete retaining wall to setup your
first line. This will be your reference line and will not be adjusted again unless both ends are adjusted
equally. Arbors are sometimes located over a deck, concrete or right over bare ground. If your building over
existing concrete, cutouts will have to be made of a size depending on the size of your vertical columns.
16" square is nominal. A hole, 16" square and 24" deep from the finish grade should be dug into the earth
and filled with 6" of concrete to serve as a footer. The end of the column that will sit on this footer
should be coated with tar up to three inches above finished grade. Then wrap a layer of clear 4 to 6
mill polyethylene plastic around the tar. Wrap the plastic high enough above finish grade so that later
when you trim the bottom of the column with a band of 1x4 or 1x6 you can cut the excess plastic off
flush with the top of that point. Both the tar and the plastic will go a long way to give protection from decay
especially when using cedar columns. Even pressure treated products made today do not have the insect
and decay inhibiting qualities as once was and should be protected.
Drive some stakes into the ground, two at each column and about 4' away or far enough away so
you can reach the top of a 2x4x8' brace set at an angle from the stake and extending toward the top of
the column. Starting with the corners, set each column on its footer then plumb and brace remembering
to allow 1/4" between column and string. Check dimensions near top of columns for proper measurements.
Once all corners are set, run a string near the top of each side that has additional columns yet to be
set. Allow the same 1/4" clearance as before, then set, plumb and brace these columns measuring for
proper distance to center before securing. Expansion block such as cedar 1x4 should be installed next
to existing concrete if cutouts were made. A few vertical pieces of 3/8" rebar stakes doweled at an
angle into the footer will help for strength if not installed when footer was poured. Some areas may
require stirrups as well. Stirrups are a continuous strand of 1/2 rebar, usually three total, around
each column and secured to vertical stakes to prevent the concrete from breaking over time. Some rebar
suppliers can take care of this fabrication but you can cut short pieces of rebar and secure to your
vertical 3/8 rebar stakes then tie the corners if you prefer. Finally, fill the holes with concrete
and let setup overnight.
Only use galvanized or stainless steel fasteners with cedar or pressure treated materials. Other fasteners may
stain and streak cedar while the copper solution used in pressure treated material is simply not compatible with other
fasteners. Ask for compatibility before you purchase bolt, nails, brackets or screws, they are important.
Cut top of columns to desired height for head clearance from finish grade to bottom of lowest framing member,
usually the beam. Seven foot is nominal however there may be no restrictions or specific code on arbors in your area.
Set your supporting members or beams and secure with proper fasteners. Larger heavy members should rest atop columns
or set into a notch in the side of the column. Smaller lighter members may lay along the side of the column so long as
they are properly secured. Remember, the larger the lumber the more weight, the more weight the larger the supporting
members or beams. Set any members above the supporting ones and fasten with proper nails or screws.
I'm a firm believer in wood protection. It is only wood and wood after all is biodegradable. So why not make it
last as long as possible? Even if its pressure treated wood it should have one or two initial coats of preserver to
seal out water and sun. Your local paint supplier or hardware store can help you with this. As you look at the structure
to be sealed you may feel it to be too large a project with all its many edges, corners and hard to reach places. Not to
worry if you decide to use a clear or transparent sealer, simply purchase a small pump up garden sprayer. Cover all grass
and vegetation before spraying. Re-coat according to sealer manufacturer recommendations.