Dog Pee Corrosion

Structural Issues


A nice couple from Ballard called you the other day with a question concerning the structure of their home. You were kind enough to give them my name and I did respond and I'd like to thank you very much for this referral. This gives me an opportunity to tell you about something that may be a bit off the beaten path of the typical home inspection problem but one day you might make use of the following information.

[ for full effect, read with sense of great drama ]

My discovery comes roundabout not from the couple above but from my own home. A while back we remodeled parts of our home including replacing the posts and brackets supporting the carport which had taken on quite a sag at one end. There had been some earth settlement at that corner but I was also concerned about one particular 4x4 carport bracket (steel tube type) which had rusted so deeply as to be almost cut in half. The rust was at midpoint of the exposed column, not right atop the slab. Oddly, the other post supports were in fine shape. The roof overhangs were the same. The slab looked the same. What had caused this one bracket to fail?

While watching a bit of UW TV during a lunch break, I found my answer. The program was a live feed from a mechanical engineering class and the discussion was on causes of corrosion. The prof. was discussing a case he was familiar with in which an elderly couple, while sitting outside drinking their morning tea, had the deck collapse from under them. According to the professor, the cause of the deck collapse was "DPC." Seems the couple had a dog which would urinate on this one particular post repeatedly throughout the day. Apparently, urine is quite corrosive when splashed on mild steel. This was my answer! My carport bracket failure was caused by Dog Pee Corrosion or DPC.

Have a great day.


Thanks Tom! Now I can tell people that you are a great designer and a DPC Expert!


By the way, Tom can be contacted re. design services (or DPC) at: Greggs Building Design, email: or (206) 524 2808