An example of proper deck flashing and water sealing.

How to properly attach a deck to the home.

plastic or Vinyl deck flashing

proper flashing technique for attaching a deck to the home.

Here we see vinyl deck flashing with a short return down the face of the ledger joist (the first board attached to the home), the siding was cut and removed and the ledger attached directly to the house framing and sheathing. adhesive flashing was also placed behind the ledger and extends down and just over the next siding board so that any possible moisture penetration is routed outside the siding again. The vinyl flashing extends up under the door and the siding adjacent to it. You can also see how a small notch was cut into the outside joist so that the 3/8″ return on the vinyl flashing can extend down through it so no water can travel across the top of the joist.

It is important that the flashing either be vinyl, stainless steel or that Vycor deck protector either covers the pressure treated wood or is used in place of traditional flashing. Standard painted or galvanized flashing will rust away in short order.

ACQ treated lumber, corrosion and it’s causes.

Several years back environmental regulation mandated the removal of arsenic from the treatment of wood products, definitely a good thing. Heavy metals were being found in the soil beneath play equipment at schools and other sites. This posed a real challenge for wood product chemists and manufacturers, how to market a pressure treated wood without the usual chemical cocktail. The way they achieved this is by adding large amounts of copper to the formula, ACQ. Here’s the battery part, batteries are made possible by the placement of dissimilar metals in an electrolyte to create a current by the corrosion of the metals. The same thing happens when steel or zinc plated hardware and nails come in contact with the high level of copper in treated woods. There are specially coated hardware and stainless steel alternatives to most products you can use on a deck. If you use a standard metal component the level and rate of corrosion is shocking. literally in a couple of weeks a regular zinc plated hanger will look like the battery post on an old car, greenish fuzz and all. One area of particular concern is deck screws. the steel used for screws is less elastic than that of nails and the ACQ treatment causes them to become very brittle and in the case of composite decks which expand and contract slightly the fasteners are highly prone to breakage. Even the ACQ rated screws are not immune to this. I almost exclusively use stainless steel fasteners on my composite or cellular PVC decks and only use stainless nails on fences. Not only is stainless more corrosion resistant but, the steel is more elastic as well resisting the shearing caused by the deck movement. Stainless will cost more on the front end but, save you big in the end.

ACQ treated lumber and non galvanized metal connectors, hinges and hardware, how to prevent corrosion.

Why is this important?

It is important to understand that the corrosive nature of ACQ treated lumber comes from electrolysis, not a low PH(acid) quality of the lumber. The contact of steel with the high level of copper in the treated wood creates this electrolysis and corrosion. It can destroy or severely damage a metal component in only a few years. Significant aesthetic damage can occur in weeks on some cases. As a Seattle deck builder and fence installer,  weather and the corrosion that comes with it is a major concern.

What can be done to protect my hangers when using ACQ treated lumber?

One of the easiest ways to use a non ACQ rated metal component is simply to insulate it from the copper in the treated lumber with an adhesive flashing barrier. This interrupts the conductivity between the steel component and the copper in the wood. This is actually a building code approved method for when a hanger or other engineered component that is unavailable in a resistant form must be used. In the photo you can see how I have bedded the post with a strip of Vycor “deck protector and then scored the outline of the hinge to remove the excess flashing around the hinge. You can learn more about ACQ and electrolysis in my related post.

Vycor backing is peeled away from around standard coated hinge.

Vycor backing is peeled away from around standard coated hinge.