Devastating Rot Damage from Cap Flashing Details

Cap Flashing  Details

Sometimes we come across decks that have been leaking for a long time with no signs from the inside or out. When we come to your house we always give the exterior a review and look for any possible problems/weak spots in the deck design. Cap flashing is one of the usual suspectsCap Flashing

At this particular job the customer called us to look into a deck on the other side of the house. I noticed a few improper waterproofing details and gave the customer a price for the repairs. After talking for awhile with the client I asked about the other deck and was told that they were not experiencing any problems. We looked at the deck and rightly so there were no issues with the actual deck, I did however notice a area of concern. If you look at the picture you will notice that the cap flashing was stopped at the post and caulked. This is a typical detail that I run across that can have devastating results.


Cap Flashing membraneFlashing Membranes

The majority of buildings in that where built in the 80’s to mid 90’s it seems that everyone (building inspectors included) all seemed to forget a very important part of waterproofing a parapet wall. The B.C. Building code has always stated that all up-stand walls require a flashing membrane. It seems that everyone used the flashing part and capped all of the walls with metal, but the most important part of the membrane was forgotten. This has caused extreme rot problem, when any water penetrates past the joints and details of the metal flashing it comes in direct contact with the wood framing. As most of us know it doesn’t take a lot of trapped water to start a devastating mold and rot situation. The picture on the left show a type of self adhesive membrane that acts as a proper flashing membrane.


The Damage from Improper Cap Flashing

Cap Flashing Damage


The amount of damage was substantial, fortunately we discovered it at this stage. With the damage not being apparent initially, usually by the time signs are showing in the house it is beyond belief. Typically we hear of respiratory problems, severe allergies and a musty smell. To repair the damage it is like anything else the longer it is delayed the more problematic it becomes.

Fell free to call us to get your free assessment.

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