Plywood Rot

By Robert Robillard on Home Repairs And Remodeling

Hi Robert,

Plywood Rot and Copper Flashing Question

I saw your deck flashing “how to” on your blog. Thanks for the tutorial, it has been very helpful. I’m in the process of doing something similar on the deck of 1920 cedar shingled four square in Dorchester. I have two questions for you: 1) Where did you get your copper flashing from? 2) Do you handle small jobs?

I’ve laid down Grace Vycor over the ledger and am getting ready to put down 3oz. copper flashing. I bought an 8″ roll and bent a right angle so 6″ goes up against the side of the house and the 2″ sits atop of the ledger. Do you consider 3 oz. heavy enough considering the weather we get here? If not, any recommendations on where to pick up flashing?

In pulling the rotting shingling off the house I’ve found that the sheathing directly under the threshold is damp to the touch. My guess is that the the corner weaving is tired and compromised and/or the head flashing over the door no longer works. I’m not sure I have the time or the expertise to handle the door job at this time. Are you interested in taking a look at it?

Will Allen

Hi Will,

Thanks for your questions.

The copper you’re describing sounds like ledger flashing that my lumberyard sells to cover the new pressure treated lumber. I don’t like using it and feel it’s too thin.

I buy my copper in Waltham at Harvey Industries. I buy their 10 ounce 3’x 8′ sheets. 16 Ounce Copper Sheets or 24 gauge is a heavy weight copper sheet often referred to as “roofing copper” or “roofing flashing.” It weighs approximately 1 pound per square foot. It’s often used for roofing and flashing, various art and craft projects, DIY projects such as back splashes, counter tops and range hoods.

The problem with you using the gauge copper is that you will need a metal brake to bend it.

Once option is to by 1- 1/2″ copper drip edge from your local roofing distributor. I use these three: Harvey’s, Beacon Sales or Bradco. the drip edge is preformed and will fit over your ledger board, if you need higher coverage you can overlap flat copper over the drip edge. For the flat copper you can buy 6″ or 8″ roll copper which is sold by the foot and is easy to work woth and cut with snips.

You mention that the plywood is damp. If you take a nail punch or screw driver and jab it into the plywood does it go through?

If it does you have a problem. If it doesn’t and your plywood is structurally sound I recommend letting it dry out a bit, cover it with house wrap or tar paper, install you r shingles according to manufacturers recommendations and properly deal with the suspected flashing issues that caused the dampness.

I also recommend using the Vycor on the corners under your shingle weave as a redundancy weather layer.

Unfortunately I do not travel out your way but I know several reliable contractors who do. Email me for their names.

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About the author

Robert Robillard

Carpenter / Remodeler / Editor

Rob Robillard is “The Concord Carpenter” Rob is a builder, general contractor, carpenter, woodworker, and editor of Concord Carpenter and ToolBoxBuzz As a General Contractor and carpenter, Rob owns and operates Concord Carpenter LLC. A full-service remodeling and construction company. Rob is a recognized leader in home building best practices and a source for how-to information for building professionals. On this website, Rob covers all aspects of home construction, building science, home improvement, woodworking, remodeling, and some of the best product and tool reviews. Rob is in charge of our Tool and Product Review series - Concord Carpenter Videos where we post all of our tool reviews and video tutorials. Rob approaches remodeling and building construction with a pragmatic and problem-solving approach. He enjoys using his knowledge and experience to help and educate building professionals as well as DIYers on best practices in the construction and remodeling industry. He's a strong advocate for "raising the bar" in the construction trades and promoting the trades to youth. #BeAMentor #Green2Great Craftsmanship, quality, and pride guide his journey on this channel The Concord Carpenter's motto: "Well done is better than well said!" : Read more about Rob

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