digest
Short Summary
Main recommendation: Attach a deck ledger board to the house by first removing the siding behind it, then keeping the connection dry with house wrap, drip edge, and J-trim, rather than fastening it straight over the siding. Jeff's central warning is that bolting a ledger over siding traps water behind it, which rots the wood around the lag bolts and invites pests, while a properly flashed connection should last roughly 50 years.
Key Points
- Ledger boards fastened over siding cause compression and water intrusion, so the siding must be cut out first; brick is the exception because it is already a structural component and can be drilled directly.
- The house wrap (Tyvek or Type-R) is a water barrier and vapor-resistant layer, not an air barrier, so it diverts liquid water down past the ledger and hardware while letting vapor escape.
- A preformed metal drip edge is installed behind the flashing to create a water diversion system; Jeff stresses this manages water rather than waterproofing the exterior.
- Jeff says about 90 percent of house damage occurs around ledger boards and rim joists, which is why he adds extra protection.
- Siding should be installed before the floorboards so the siding runs continuously down, with J-trim used because a clean starting strip is unlikely after cutting.
Details Worth Noting
- Concrete instructions:
- Clean up the original house wall, and if it is siding, use a grinder to cut out the area where the ledger will sit, accounting for the siding size needed to reinstate it.
- If the wall is brick, pre-drill holes through the brick all the way to the rim joist; no removal is needed.
- After mounting the ledger, retape the house wrap over it, fixing any tears or rips first.
- Install the preformed metal drip edge (Jeff bought it at Home Depot) behind the flange so it sits at the top of the ledger.
- Staple the house wrap, or use plastic cap nails designed for house wrap if the work will be left unattended.
- Install J-trim for the siding, adding drip holes with a screw if the trim lacks them so water can escape at the corners.
- Attach all hardware, such as joist hangers, using structural screws or nails.
- Leave a small gap between the decking and the siding so water can drain, and blow out debris a couple of times a year, for example with a pressure washer.
- Seal the joint with electrical tape where needed.
- Jeff notes that a deck installed correctly should last at least 50 years, and that he is working on a house he bought and reattached the ledger two years earlier, with the connection still dry.
- The siding is described as a hundred-year product that does not need attention once installed correctly.
- Jeff recommends spending about $20 on materials and half an hour on the cut-out, arguing it prevents the deck from failing after only 20 years due to rot and insects.
- He suggests replacing old siding during deck work as a home value investment.
Bottom Line
A ledger board is only as durable as the water management behind it, so cutting out siding and layering house wrap, drip edge, and J-trim is the difference between a deck that lasts decades and one that rots within years.
