Outdoors >
Garden >
How to Build a Wood Arbor for Garden or Yard
Learn how to construct a cedar garden arbor with built-in benches.
Minnesota homeowners who have "his" and "hers" gardens want to construct an arbor between the two that lets them sit and admire their flower beds. A built-in bench on each side of the structure will provide seating and a graceful open-raftered canopy which provide shade. In consideration of their Minnesota winters, they will use pressure-treated two-by-fours as the core for the support posts and set them 3 1/2 feet into the soil to place the ends below the frost line. The exterior of the two-by-fours will be encased in cedar to give them more bulk and make them match the rest of the project.
Step by Step Instructions with Video
Step
1
Choose a Site without Underground Obstacles
Start by checking with utility companies to ensure there are no electric, water, or gas lines in the vicinity. If your home has a septic tank, you should verify that you will not run into the septic tank or the septic drainage field which has gravel lined channels.
Step
2
Experiment with Orientation and Dimensions
Use two-by-fours to experiment with the orientation and dimensions of the arbor. The front and back dimensions can be wider or narrower than those of the sides--there is no preset formula for the design. Similarly, will the arbor be aligned with the house or garden or straddle a path? Lay the two-by-fours on the ground in various configurations and then step back to view it from several angles while your imagination works.
Step
3
Lay Out a Rectangle in the Correct Size and Shape
Lay out 4 two-by-fours to delineate a temporary rectangle in the desired dimensions, once you have selected the location and orientation. Traditionally, arbors are a little wider than they are deep, so we elect to build ours 6-feet wide by 5-feet deep.
Step
4
Confirm the Rectangle Has 90-Degree Corners
Use a framing square to ensure all four corners of the rectangle are perfect 90 degree angles.
Step
5
Mark the Corners with Powdered Chalk
Mark them with powdered chalk and remove the two-by-fours.
Step
6
Select a Posthole Digger or Power Auger
Decide whether to use a posthole digger to manually dig the postholes or a gasoline-powered auger. The work crew voted and unanimously chose the auger. Most home improvement or equipment rental companies have models to rent with different sizes of power units and augers. In selecting the equipment, consider both the size of the hole to be dug and the size and strength of your helpers.
Step
7
Dig the Holes 42-Inches Deep to Avoid the Frost Line
Dig post holes at the four corners, digging down 42 inches (3 1/2 feet) to get below the frost line. We don't want the Minnesota winter to freeze the ground beneath the posts and push them out of the ground with "winter heave."
Step
8
Hold the Auger in Vertical Position and Drill Slowly
Hold the auger vertical and drill slowly. An auger of this size requires two able-bodied people to hold it steady. It you drill too quickly and hit a rock beneath the soil, the auger can wrench free from your grasp abruptly or actually throw you off your feet. Lift the auger every few seconds lets it spin freely to cast off the dirt it has bored from the hole. We reach the maximum depth that can be bored with the current auger and will need to add an extension.
Step
9
Remove the Steel Pin Holding the Bit to the Engine
Remove the steel pin that holds the auger bit to the engine.
Step
10
Remove the Power Unit Leaving the Bit in the Hole
Lift the power unit off the auger bit and set it down, leaving the bit in the hole.
Step
11
Insert an Extension into the Bit
Insert an extension into the top of the bit. Align the holes on the auger and extension and slide a pin back in to secure them. The rental company that supplied the auger and extension should also supply the extra pin.
Step
12
Remount and Pin the Engine and Bore the Hole
Remount and pin the motor and finish boring the hole.
Step
13
Bore Three More Holes
Bore three more holes the same way, ensuring that all are 42 inches deep. Before moving on the each new hole, you can remove the engine and extension to lessen the weight and help extract the soil-laden auger bit.
Step
14
Add Crushed Rock to the Bottom of the Holes
Add a few inches of crushed rock to the bottom of each hole to allow for drainage.
Step
15
Set the Pressure-Treated Posts in the Holes
Set the two-by-four pressure-treated posts in their holes. The chemical treatment prevents wood rot.
Step
16
Clamp on a Post level to Ensure the Posts Are Plumb
Clamp on a post level and ensure that the two-by-fours are perfectly vertical or plumb.
Step
17
Attach a Horizontal Wooden Brace
Attach a horizontal wooden brace to the first post at ground level and screw them together temporarily.
Step
18
Brace the Remaining Posts and Ensure They Are Plumb
Confirm that the adjacent post is vertical and screw the opposite end of the brace to the second two-by-four. Repeat this process until temporary braces support the posts on all four perimeters of the arbor's base.
Step
19
Brace the Four Posts at the Top
Repeat the process at the top, clamping the upper braces while you make incremental adjustments to ensure that everything it plumb, and attach the braces. Both sets of temporary braces will hold the posts vertical and properly spaced while you work.
Step
20
Fill the First Post Hole with Dry Concrete Mix
Fill the first hole with dry fast-setting concrete mix.
Step
21
Saturate the Mix with Water
Add water until the dry mix is saturated. We use a gentle flow from a garden hose. No mixing is required. If the water pools, just turn the hose off until the water sinks in and then apply more water if necessary. The manufacturers provide directions for the appropriate quantities of water on the back of the bag.
Step
22
Ensure the Post is Plumb
Use a bar level to confirm that the post remains perfectly vertical as you add water to the mix.
Step
23
Repeat the Process to Add Concrete Mix on Three More Posts
Repeat the process to add concrete to the remaining post holes. Add more mix if necessary until the level stabilizes at the top at about the same elevation for all four posts.
Step
24
Let the Concrete Set for 30 Minutes and Remove the Braces
Allow the concrete to set for about 30 minutes and then remove the braces.
Step
25
Use a Stop Block on the Miter Saw to Cut Multiple Casings
Set up a stop block on your power miter saw and worktable to cut lengths of cedar to cover the two-by-four cores of the posts. Your goal is to add bulk and make the posts more attractive.
Step
26
Cut the Cedar two-by-fours
Make the cuts. You will need four lengths of cedar for each post. In our project, we make each 70-inches long.
Step
27
Attach the Cedar Two-by-fours to the Pressure-Treated Posts
Attach the two-by-four cedar. Use rust-proof screws and cover both the wide faces of the pressure-treated two-by-fours first.
Step
28
Cut and Attach the Two-by-six Cedar Casings
Cut and screw wider two-by-six cedar casings, also 70-inches long, over the sides of the pressure treated two-by-fours and the cedar sheathing you attached in the last step. The result is a more substantial post with a little ridged detail on two of the four sides because of the slight differences in dimension.
Step
29
Mark 3 1/2-Inches on the Beam for a Scalloped End
Mark the first support beam in preparation for cutting curved ends. This is the side beams that run from front to back along each side of the arbor. Use a combination square and pencil to mark 3 1/2-inches inwards from the long edge of the beam.
Step
30
Mark 6-Inches for the Other Scallop Dimension
Readjust the combination square to mark 6 inches inwards from the end of the beam.
Step
31
Align the bottom of a 5-Gallon Bucket on the Marks
Align the bottom of a 5-gallon bucket on the two marks and trace the curve, if you use something with a smaller diameter, the curve will be too abrupt.
Step
32
Cut the Scallop with a Jigsaw
Cut out the curve piece with a jigsaw. Repeat this process to make the same curved notch on the other end of the beam and on the remaining three side beams.
Step
33
Lift the First Side Beam into Position
Lift the first side beam into position, with the scallops on the bottom, and screw it to the post, making the top edge of the beam flush with the cop of the cedar encasing the first 70 inches of the posts.
Step
34
Install the Second and Remaining Beams
Install the second side beam and then the remaining beams on the other posts. On completion, you will have installed four side beams--a pair on the left and on the right side of the arbor.
Step
35
Trim the Post Tops with a Japanese Handsaw
Trim each post to length, just above the point where the cedar casing on the posts ends, Use a Japanese handsaw for these cuts.
Step
36
Review the Plans for Canopy to Note the Dimensions
Review the plans for the canopy before proceeding. Note that each canopy beam incorporates several distinct design shapes when viewed from end to center. Each end has a scallop that matches the side beams and then a flat area where the canopy supports will rest on the side beams once installed. In the middle, there is one long arch. Using two-by-ten or two-by-twelve beams will allow room to cut a nicely curved arch--the wider the beam the greater the possible curve. We use two-by-tens, but once they are shaped, the face of the curved beam will be no more than 6-inches wide and will match the side beams we made earlier.
Step
37
Lay Out, Scallop, and Mark the Canopy Beams
Lay out the cedar two-by-tens for the canopy beams that will span the front and the rear of the arbor. Cut scalloped ends to match those on the side beams. Start at the inner end of each scallop and measure/mark about 12 inches toward the center of the beam. Place these marks on the bottom edge of the beam--they denote the two flat areas on the bottom of the canopy beams that must rest squarely on top of the side beams. In the next step, you will use these marks as references for making the center arch.
Step
38
Tap in Small Nails to Mark the Top and Bottom of the Arch
Tap a small nail into the wide face of the beam as close to each of these two reference marks as you can get without splitting the edge of the wood. Tap another nail at the exact center of the beam?s length about 4-inches upwards from the bottom edge. Drive these three nails in securely, but leave most of the nail protruding. Repeat this process to mark the top of the arch, but place the center nail at the top center of the canopy beam. Drop down about 4-inches from the top edge of the beam and drive the two outer nails aligned exactly with the outer nails on the bottom edge of the beam. Note: These measurements will differ if you are not using a two-by-ten beam.
Step
39
Position a Thin, Flexible Strip of Wood
Center a uniformly thin, flexible strip of wood on the top row of nails. Rest the strip above the top center nail, bending it gently so that its ends are under the two outer nails. Let any extra length protrude evenly at the ends. The strip is of a uniform thickness, so it bends consistently and describes a graceful arch.
Step
40
Trace the Arch Top along the Curved Strip
Trace along the strip with a pencil to mark the top of the arch on the beam. The remaining length of the top will be flat all the way to the ends.
Step
41
Reposition the Strip and Trace the Bottom of the Arch
Reposition the strip on the bottom row of nails and trace the bottom of the arch. On completion of this step, you have cut lines marked that leave a 6-inch wide face on the beam along the arch, the flat areas at each end, and the scallops already cut. Confirm these dimensions and adjust if necessary.
Step
42
Cut the Arch with a Jigsaw
Cut the top and bottom of the arch with a jigsaw. Use this beam (only) for a template for the arches on the other canopy beam.
Step
43
Connect the Arches with a Stringer at Each End
Connect the two arches with a stringer at both sides. Pre-drill clearance holes through the arches and into the ends of the stringers. Attach them with screws.
Step
44
Center and Attach the First Two-by-two Slat
Position a two-by-two slat midway along the top edge. Attach the slat with screws, starting at the center and working outwards.
Step
45
Use Temporary Spaces on the Slats
Use temporary spacers to maintain a uniform distance between each slat.
Step
46
Lift the Canopy onto the Beams
Lift the canopy, once assembled, up to the beams.
Step
47
Center It on the First Layer of Beams
Position it, centering it on the first layer of beams and relative to the rest of the arbor.
Step
48
Angle a Pair of Rust-proof Screws into Each Corner
Secure it by angling a pair of rust-proof screws into each corner.
Step
49
Cut and Pre-drill Four Brackets for the Benches
Cut and pre-drill 4 screw holes in two pairs of brackets to support the benches. Scallop the ends of the brackets in the same manner as the ends of the support beams.
Step
50
Secure Each with 4 Screws
Secure them to the posts with four screws each.
Step
51
Cut 2 Two-by-six Lengths for Each Bench Seat
Cut two lengths of two-by-six for each bench seat. Secure them to the brackets. The inner board will be longer, since it is entirely clear of the posts, but the outer board must fit between the two posts with a little room for clearance.
Step
52
Coat the Arbor with Wood Preservative
Coat the entire arbor with wood preservative.
