April 5, 2006
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Too Much Wetness!
Kathryn's trip to Bremerton last week must have upset the cosmic weather destiny somehow. She had a beautiful "sunny" time in the Northwest, and now LA's perpetually sun-smoggy skies look like Seattle's. Northwest-style weather is supposed to carry on all this week and NEXT week as well.
This is worse than a mere inconvenience for Bob Sawyer's crew, or a continued delay in the steel delivery (which ought to come "soon" whatever that means). In the 24-to-36-hour gaps between downpours, we are seeing "efflorescence" in our block walls.
This means two things: possibly too much salt in the mortar mix (??), and the concrete walls, all 20 feet of them, are waterlogged. This might become a big problem. Big enough to delay the completion of the house... by months.
Sneak peek at a future construction detail:
The whole concept of high-thermal-mass construction is to even out the temperature swings between midday and midnight, and even from week to week and month to month, to eliminate as much as possible the need for air conditioning or heating. More on that later when we are actually hanging the styro and stucco.The concrete block is our high-mass layer. The insulation-layer is OUTSIDE the exterior wall, protecting it from summer heat and winter chill. This means condensation (which is inevitable) forms on the backside of the insulation, and the Tyvek wrap is there to keep the moisture out of the block wall. The inner moisture barrier (painted onto the block) is redundant, to really ensure against mold etc. inside the house.
Mold is bad. Kathryn is allergic to mold, so even "normal" levels of mold are not acceptable for us.
Here's the problem: we are almost to the Tyvek-wrapping stage of construction (which ought to coincide with installing the windows and exterior doorframes). We have already done the inner moisture-barrier bit. But the concrete walls are holding water nearly equal to their own weight!
Concrete block, it turns out, is like a very rigid slow wick, drawing water up into its structure but evaporating it out the same way. The mortar with which we filled it behaves similarly. The sort of efflorescence we're seeing is a symptom that the concrete walls are so saturated with water it is seeping out from the inside, not running down the outside. And leaching out the mineral salts from the concrete at the same time.
If we wrap this soggy sponge in Tyvek and moisture-barrier-paint, it may take decades to dry out properly... in the meantime, the inner paint layer is the least impermeable barrier (though the slab-on-plastic beneath the walls will eventually become more water-permeable over time). That means serious interior mold problems for many many years.
Unless we let the walls dry out.
It took weeks of soaking to get the block so waterlogged.
It will take months of low-humidity wind and warm sunshine to dry them out.
Hmmm.
