Anchoring the Ledger

Anchoring The Ledger

Most decks are attached to the house with a ledger because it easily adds strength to the structure. In some areas with unstable soil, however, a deck must be unattached to prevent damage to the house and deck if it shifts.

Make it level and strong
The ledger will act as the reference point for laying out the entire deck, so take time to position it precisely and level. If the siding or door is not level, you may be tempted to install the ledger out of level for appearance's sake. Resist the temptation: An angled ledger greatly complicates the rest of the construction process.

Attach the ledger with lag screws driven into framing members -- not just into the sheathing. Most homes will have an exterior joist (sometimes called a band joist) just below the door sill. That's where the ledger goes. Drill test holes to make sure the screws will have a hefty 2x board to grab.

Prestart Checklist

Time
Four to five hours to cut and install a 16-foot ledger board on a frame house; longer to attach to masonry

Tools
Layout square, tape measure, level, circular saw, hammer, drill, socket wrench

Skills
Measuring and cutting boards, testing for level, driving lag screws

Prep
Draw the exact location of the ledger on the house

Materials
Ledger board(s), lag screws with washers, shims if necessary

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Setting a ledger into siding

In many areas it is common to cut and remove a section of siding and then set the ledger inside the cutout. The potential problem with this method is that it exposes the house sheathing, which is not pressure-treated and can rot if it gets wet, even it it's covered with builder's felt. If your inspector requires this method, follow these steps:

-- Cut vinyl or wood siding using a circular saw with the blade set to cut just through the siding and no deeper. (For aluminum siding turn the saw blade backward.)
-- Finish the cuts at the corners using a knife, a chisel, or tin snips.
-- Staple on a layer of 30-pound felt to protect the sheathing.
-- Cut drip-cap metal flashing to fit and slide it up under the siding. The flashing must cover the top edge of the ledger.

Step 1

To mark the top of the ledger, measure down from the bottom of the door sill the thickness of the decking plus 1 inch. This small step-down will keep most rain and melted snow out of the house.

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Step 2

Using a carpenter's level or a water level and a straightedge, draw a level line on the house siding to indicate where the top of the ledger should be positioned.

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Step 3

Mark the outside edges of the ledger on the siding.You may be able to remove siding. If you are cutting the siding, extend this mark 1-1/2 inches (the thickness of the rim joists) past the actual length of the ledger on each side. This will allow you to fasten the rim joists to the ends of the ledger.

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Remove Siding: Unlock the siding

If you're cutting a ledger recess into vinyl siding, you may be able to save some time by unlocking the siding with a zip tool (available from your home center or siding distributor).

If the width of the ledger is the same as a full siding panel (or close to it), unlock the panel, install the ledger, and reinstall siding pieces cut to fit around it.

If the ledger is a different size and you cut the siding, you may be left with corners that you have to remove.

To unlock the siding push the zip tool up between the locking flanges of the siding and slide it along the length of the panel. The tool will push the edges of the flanges apart, allowing you to remove the siding.

Step 4

If you have beveled siding you can cut out a recess for the ledger or if your codes allow it, install beveled cedar siding as a flat backing. Rip-cut the cedar so its thickness matches the thickness of the siding. Attach each piece with a nail every few feet.

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Step 5

If there is an existing concrete stairway, your inspector may want you to remove it. If you do not remove it, you'll need to cut the ledger to fit around it. Hold the ledger in place and mark for a cutout so that the ledger will rest on top of the concrete.

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Step 6

Cut the ledger board and the header to length. The header is usually 3 inches longer than the ledger because it's fastened to the ends of the rim joists. If you need to notch the ledger for an obstruction, use a circular saw, stopping just short of the corners. Finish the cuts with a handsaw.

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Step 7

Lay the ledger and header next to each other with their crowns facing outward and the header overhanging the ledger by 1-1/2 inches on each end. Mark both boards for joists, in this case every 16 inches. Mark a large X on the side of the line where the joist will go.

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Step 8

Push a flashing up beneath the siding about an inch. Have a helper or two hold the ledger in place while you drive 3-inch screws to hold it in place temporarily. Make sure the ledger has its crown side up. Test the ledger for level and adjust if necessary.

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What If... Your ledger is on masonry?

Ledgers installed on masonry surfaces need protection from water. There's no siding on masonry to hold the flashing, so cut a slot for it. Install the ledger and mark the wall about an inch above it (or the width of the flashing less about 1/8 inch).

Tack a level guide board on the ledger so the saw blade will cut on your mark. Using a circular saw equipped with a masonry blade, cut a kerf from one end of the ledger to the other -- as deep as the top lip of the flashing. Blow the dust out of the kerf with a shop vacuum and push the lip of the flashing into the kerf until it's seated firmly. Then caulk the top of the flashing with silicone caulk.

Step 9

Check indoors to make sure lag screws will not hit any gas or water lines or electric cable. Counterbore pilot holes if you want recessed lag screw heads. If possible, avoid your joist marks. Then drill through the ledger only, with a bit slightly smaller than the diameter of the lag screw threads.

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Step 10

Use a long bit to bore a smaller hole through the house framing. Slip a washer onto a lag screw and tap the screw partway into the hole. Tighten the screw with a socket wrench, keeping it perpendicular to the ledger.

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Step 11

Every few feet along its length, check the ledger's face to see that it is close to plumb. To make adjustments, try tightening one screw. If that doesn't work, loosen both screws, insert a shim at the bottom or top, and retighten.

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