How to Install a Ledger Board for a Garden Arbor

How to Install the Ledger Board for Your Own Garden Arbor

1) Determine the height of your structure.  Assuming you know that you want your structure to be attached at one side to an existing structure (your house, for example), therefore begging the need for a ledger board, you now need to decide how tall you’d like your structure to be.  The height of your structure will drive the placement of the ledger board.  If you’ve proceeded correctly with the planning of your structure, you will at this point be referencing a construction drawing specifying the height of your structure and the location of the ledger board.

2) Get your materials together.  You’re going to need:

• Pressure treated, 2×6 board(s).
• Shim material.
• 3/8″ diameter by 5″ long galvanized, hex head lag screws.
• 3/8″ x 1″ galvanized fender washers.
• Waterproof plastic wood filler.
• Clear silicone exterior caulk.

3) Get your tools and equipment ready.  I recommend the following:

• Sturdy ladders, scaffolding, or stages.
• Stud sensor.
• Cordless drill.
• Chop (miter) saw.
• Worm drive saw or circular saw.
• 3/16″ x 12″ wood drill bit.
• 1″ spade/paddle drill bit.
• 9/16″ socket/wrench.
• 9/16″ hex drive.
• Carpenter’s square.
• Speed square.
• 48″ or 72″ box level.
• Torpedo level.
• Claw hammer.
• Carpentry pencils.
• Tape measure.
• Utility knife.
• Putty knife.
• Caulk gun.

4) Locate the structural framing members of the building to which the ledger board will be fastened.  This step assumes that the host structure is indeed of frame construction (wood 2x4s clad in wood, vinyl, or aluminum siding).  Let’s further assume that the host structure is your house or garage.  (If your house or garage is brick, you won’t be looking for studs.  The ledger board can be fastened directly into the masonry – the brick, block, or stone itself, NOT the mortar joints – using large diameter masonry screws.)  My house is a wood frame structure, so I’ll proceed with the installation methodology predicated upon this fact.

So, you’ve gotta find the studs that your house is constructed with.  A typically efficient way to locate studs is with an electronic stud sensor.  These devices can detect the presence and location of framing members very effectively through drywall, and even plaster.  But they’ll never be able to find the studs through a layer of exterior siding and corresponding sheathing.  You’ll have to find the studs from the inside of your house, establish a measuring benchmark, and mark the stud locations on the siding outside.  Use a long, small diameter drill bit to drill a test hole to confirm that your marks are in the right spots and that you’re hitting studs.  (You can always caulk the test hole later.)  If your house was built correctly, the framing members will be set on 16″ centers.  The center of each stud will be 16″ away from the centers of those studs on either side of it.  This fact should help you zero in on those stud locations.  When you find the centers of all of the studs in the relevant area, clearly mark them either just above or below where the ledger board will be installed.

The million dollar question: Why is it so important to find the studs?  Because the ledger board is going to be supporting a very large percentage of the weight of your entire structure, plus the weight of all of the vines which will eventually be growing on it.  The ledger board is probably the most critical structural element of your arbor/trellis system.  It has to be completely immobile and totally solid.  It has got to be screwed directly into the structural framework of your house or garage.  It’s got to be screwed directly to those studs.

5) Get a helper.  You’re going to need a second pair of hands to put your ledger board up.  No doubt.  Find someone you can trust.

6) Select and prep the board(s).  If your arbor/trellis system is comparatively short, you may be able to use one single board as the ledger board.  Note, however, that longer boards tend to twist and warp more acutely than shorter boards.  The overall length of my ledger board component is approximately 27′.  I used three 10′ long, 2×6 treated pine boards to accommodate this length.  And rather than square-butt them end-to-end, I cut a complimentary rabetted end profile and “interlocked” them together (see Figure “B” below).  The 2×6 dimension (actual dimension 1.5″x5.5″ was perfect.  It was more than stout enough to handle its structural, load bearing duties, and it fit beautifully over the wood siding. 

7) Start installing.  Have your helper hold the first length of board in place, keeping it perfectly level the whole time, and mark a spot on the board that corresponds to one of the stud location marks you made on the siding of your house/garage.  Make sure that the mark you made on the board EXACTLY lines up with the mark on the siding.  And place this mark within the top 1/3 of the ledger board.  Now place another mark in exactly the same spot on the ledger board as the first mark you just made, but below it, within the bottom 1/3 of the board.

•  Shim the back of the ledger board to make it plumb.  Because the individual profiles of exterior siding often recesses back from bottom to top, you’ll need to shim the back of your ledger board near the top to keep it perfectly plumb (you don’t want your ledger board sloping back from bottom to top with the profile of the siding).  Shim it out with wood shim material until it’s plumb.  Cut off any protruding shim material with a utility knife.  Hold the shimmed board in place.
• Drill a pilot hole.  While holding the board in place, pre-drill the top mark on the ledger board using the 12″ long x 3/16″ diameter drill bit.  Drill through the 2×6, the shim material, the siding and backing, and into the underlying stud.  Don’t drill too far or your bit will poke through the back of the stud, the interior drywall, and out into your house.
• Countersink the pilot hole.  While continuing to keep the board in place, drill a countersink hole with the 1″ spade bit to a depth of approximately 3/8″ to 1/2″.  This will accommodate the soon-to-be inserted fender washer and the head of the soon-to-be-inserted lag bolt, and will keep them recessed from the surface of the ledger board.  Once the board is completely lag-screwed into place, the countersunk holes can be filled with wood filler.
• Set the washer and drive the lag screws in.  After placing one of the 3/8″ x 1″ fender washers in the countersunk hole, guide one of the lag screws through the washer’s center into the pre-drilled pilot hole.  With the 9/16″ hex drive inserted in your drill’s chuck, slowly drive the lag screw into the pilot hole.  When the screw is substantially driven in, but before the drill sinks it too tightly, switch to the 9/16″ socket and tighten the lag screw by hand until it is almost immovable.  Don’t snap the screw by cranking downt too tightly!
• Repeat these last three steps for the mark within the bottom 1/3 of the ledger board.  And, while maintaining the board in perfectly level position, and shimming the board plumb as you go, repeat these steps for every stud location along the ledger board’s entire length.