Water damage

Severe wood rot has decimated the roof rafter and the plywood roof sheathing. You can see the white wood fungus growing on the underside of the plywood. (Tribune Media Services)

Q. I was at a party this weekend and, of all the crazy things to talk about, a discussion started about what is the biggest danger to a house falling down. Wind, poor soil, bad foundation, poor construction, etc., were all debated heavily. I so wish you would have been there to settle the debate. What, in your opinion, is the biggest danger to a house? --Mike C., Bar Harbor, Me.

A. The answer was right there in front of all of you! After all, you live immediately adjacent to the ocean there in Bar Harbor! Had I been invited to the party, I would have done my best to convince the crowd that the greatest danger to any dwelling is water. If houses could talk -- and in a way they do when they finally collapse -- they'd be screeching like the Wicked Witch of the West did when doused with water at the end of "The Wonderful Wizard of Oz."

What is the common feature of almost all the great buildings that are still standing after thousands of years? They are built of stone. Granite is perhaps the most durable of all. Perhaps the wise builders of these structures knew that water quickly causes wood to rot. They realized that if they wanted to build something that would last for the ages, they had to use stone.

Yet even stone is not immune to destruction by both wind and water. All you have to do is visit the Grand Canyon to see what water can do when combined with gravity. Look at how wind and water are eroding the great Sphinx.

Here in the USA, we still build primarily with wood because it's very cheap compared to other options. However, the wood we use today in no way resembles the wood harvested from the forests 200 years ago. Many of the old-growth trees our ancestors felled had much tighter growth rings. Compared to the framing lumber you and I can buy today, the old-growth lumber of yore contained a much higher percentage of dense summer wood, which is much more resistant to rot than spring wood.

Water is the fuel of wood rot. If it is allowed to saturate a wood structure, as you see happen in abandoned homes or even in occupied but neglected ones, the structure, or parts of it, will collapse. Water will also blast apart masonry chimneys over time, and it will do the same with rock foundations and poured concrete, given enough time. Freezing weather only accelerates the destruction of brick, concrete and stone structures, thanks to the expansion of the water that seeps into micro cracks and then freezes.

Water will attack and corrode steel or iron in a house. Think of how steel is used to support primary structural elements in a home and how thousands of uncoated steel nails are used to connect critical pieces of wood framing. Water laughs at the thin electro-galvanized coating on certain nails used in residential construction. Within just decades, it can wear through this and attack the steel core. This is why double hot-dipped galvanized nails are better, and stainless steel fasteners are the best.

Look back at the builders of old and you'll discover they knew all of this. They used simple felt paper to cover the wood framing of houses to keep them dry. The masons of old knew to use mortars that contained lots of hydrated lime in them, as this material would work over time to actually heal tiny hairline cracks in the mortar where water would try to enter.

The roofers of old knew to use 40-pound tin-coated steel or copper for roof flashings. These materials could last well over 100 years and could be soldered to prevent water from touching the wood. These same roofers knew that using stone as a roofing material (i.e., slate) would help slow down water's relentless attacks.

The sad thing is that much of the hard-earned knowledge of the older builders is being lost. All of their knowledge can be found in many older homes. You just have to look for it.

You'll see they knew all about stone, slate, copper flashings, heavy felt paper and so forth. They also figured out that generous roof overhangs would help keep water away from houses just as we use an umbrella in a rain shower.

The older builders also knew all about the surface tension of water. Who would think that would be something you'd have to worry about? But that's why masonry and wood window sills had a kerf channel cut into them on the front edge of the underside of the sill. This channel causes the water to stop and turn into a droplet that falls to the ground instead of clawing its way under the sill toward the wall face.

There is abundant evidence that water is the primary foe of a house and that the long lost builders knew it and tried their best to educate us.