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Steam and wood

Steam and wood

Steam and wood

(OP)
I have a damage investigation I am investigating and part of the damage was due to a broken water line, part due to a broken water heater. The water heater put steam throughout the whole three story house over a 6 to 8 hour period before the leak was discovered. Apparently, condensed water was dripping off the exposed beams and walls, and the temperature in the house reached somewhere between 100 to 130 degrees F due to the steam.

My question is how long would you expect wood members to have to be exposed to the steam to induce significant swelling in the sections. Obvious damage was done to some members with additional spaces between the cardecking on the ceiling after it dried. Just trying to justify the physics here.

I am thinking that the cardeck expanded, closing most of any existing gaps, but when it dried, it did not reposition itself either back to the original position, or uniformly, opening up intermittent gaps between the members.

Anybody seen anything like this before?

Mike McCann, PE, SE (WA)


RE: Steam and wood

130 degrees F, no applied pressure, for 8 hours is not enough to affect wood any more than hot water / high humidity for the same time. I would evaluate that way.

Back in the day when aircraft were made of wood (World War I or Howard Hughes' 1947 "Spruce Goose" - actually Birch) wood had to be steamed under pressure to raise the boiling point. Conditions such as 212+ degrees F, 20 PSI, for 12 or more hours were typical.

Even today the manufacture of plywood may use steam under similar conditions.

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RE: Steam and wood

I haven't seen the exact condition before, but have seen irregular gaps open in t&g decking.
Gaps will tend to open up due to drying. Most probably between installation and equilibrium some time after.
As-manufactured decking may be up to 19% MC, surfaced dry. In a dry environment maybe down to 5-10%.

Gaps may be non-uniform due to warping of the boards or restraint by the fasteners.

I don't think a short term air moisture would have time to penetrate the wood and cause volumetric change in the time stated.

I had gaps in my workbench open up to 1/4". I built it of cedar decking salvaged from a paper mill roof, where the moisture content could have been in excess of 30%!

RE: Steam and wood

I've bent wood "skis" by boiling for about an hour. These 3/4" ash boards easily took significant bending at that time.

RE: Steam and wood

(OP)
I tend to think the gaps were always there. Put up too much of this material over the years. Hard to get all the gaps uniform. Plus, you may be dealing with some initial shrinkage after they were installed back in the 60's, let alone what has happened in the ensuing years.

Mike McCann, PE, SE (WA)


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