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How To Guide - Flashing Installation / Repair

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Flashing the ledger board

Flashing the ledger board. Proper flashing is one of the most important precautions in deck construction. Water entry causes rot and the moisture often results in wood-destroying insect damage. It may rust the attachment fasteners and cause structural failure. There have been many stories over the past years of decks falling off a house under a party of people. Water penetration is one major reasons.

In the past, when pressure treated lumber was treated with CCA preservative you could use aluminum or lower grade galvanization (zinc-coated) flashing. But today, because the new chemical ACQ contains a much higher concentration of copper, this causes corrosion between dissimilar metals. When flashing a deck constructed with ACQ preservative, it's recommended that you use heavily galvanized steel or copper sheet metal.

Because of snow and ice, you may want to line the house wall behind your deck attachment with a layer of bituminous membrane before you begin your metal flashing. Flashing exists to divert water from behind the ledger. You can accomplish this in a couple of ways. Most builders have their own methods of proper flashing. We recommend the following steps when flashing to a surface with siding: Use a 14" wide roll of flashing tucked 2" underneath the top cut and let that roll hang down and over your bottom cut. We recommend having a kick out bend to cause the the water to drip off the bottom of the metal, below the ledger. A second flashing strip should tuck underneath the top cut siding and bend out over the ledger and down one inch in front of it. This will prevent water from getting behind the ledger, and penetrating the house frame. At a junction of two layers of flashing such as inside and outside corners, just overlap them by 12 inches and seal the lap with silicone. If you plan to use copper sheet flashing, be sure to use copper nails to secure it in place



Ledger Board Bolt Size & Spacing

We have calculated the spacing between ½" carriage bolts for 2"x8", 2"x10" and 2"x12" pressure/preservative treated southern yellow pine framing. Your local building codes may determine a different spacing all together, so be sure to contact them to verify building requirements. These charts are calculated to determine the widest spacing your carriage bolts should be with different ledger sizes. test



2"x8" Ledger
Joist Span From Ledger To Beam (feet) 6 8 10 12 14 16
On-Center Spacing Of Bolts (inches) 36" 36" 34" 29" 24" 21"


2"x10" Ledger
Joist Span From Ledger To Beam (feet) 6 8 10 12 14 16
On-Center Spacing Of Bolts (inches) 36" 36" 35" 31" 26" 23"


2"x12" Ledger
Joist Span From Ledger To Beam (feet) 6 8 10 12 14 16
On-Center Spacing Of Bolts (inches) 36" 36" 36" 31" 29" 26"


Removing the siding for flashing

Some builders prefer to not remove the siding barrier between the house and the deck frame. We feel it is important for a properly secure ledger to always be touching flat to the frame of the house for its strongest hold. You can only achieve this by removing the siding.

Vinyl or Aluminum siding can simply be removed from an area one foot around the deck frame. You then just cut it to fit back around the frame and flashing when the deck is completed. Be sure to purchase a "J Channel" to make a clean transition from the siding to the deck frame.

Wood or concrete-composite siding can be cut carefully with a circular saw leaving an extra inch around the finished measurement for flashing. Be sure to cut your wood siding ½" off the finished deck floor height so it doesn't wick water off the floor and cause rot.



Attaching the ledger board to the house band

Attaching your new deck to your house is the best support you can offer your deck. Since your house is already constructed, it doesn't cost you any additional support foundations and beams.

We cannot stress enough that when attaching your deck to the house band that you drill through the house band and use ½" carriage bolts to secure the ledger to the wall. We believe that the ledger should be flat against the wall for its greatest strength.

When drilling holes into the house band, you may damage a utility, plumbing or wiring. Be sure to measure off inside the house obstacles that will be behind where the deck will be located and transfer the measurements to the outside before drilling.

You can attach your ledger to the house sill plate but your bolts will have to be longer to go all the way through. Below is a diagram to show proper attachment of the ledger to the house band.



Attaching the ledger board to brick siding

Brick may look like a sturdy wall to attach a deck to but that is not the case. Brick is only a siding and should never support much of the load if any at all. You should never attach a deck to just the brick. You should always go through the house band joist or house foundation wall and carriage bolt the deck to the home.

The brick isn't attached to the home well enough to prevent a load shift and keep the deck from pulling way from the house all together. The deck may fall and take down the entire wall of bricks. When bolting on the ledger with any bolts you choose, do not tighten the bolt enough to crush the air space behind the brick wall. If the bolts are too tight, the wall can buckle, and the bricks above may fall down on top of you. If you are attaching the deck to a brick wall, most of the load should be resting on a beam set close to the home.

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