Moisture and Your Home

Well, gee, guys.  I thought this particular blog had been forgotten about.  I know I'd forgot about it.  There is a particular little point about slab foundations and and water that I purposely left off here, but it somehow failed to stir the pot.  I feel like the guy who's been lost in the wilderness for 6 months, and finally the search committee recognizes he's gone.  Well, I ain't dead, just been busy restructuring my whole marketing plan.

Speaking of footings, Donald has given me an idea.  Why not require 42 inch footings everywhere?  Heck, let's go on and require them to be 24" wide also, and slabs 6".  What's a little extra concrete?  I'm not thinking frost, because we don't have that issue down here.  I'm thinking expansive clay soils, and all the damage they do.  I think a monlithic slab with the above dimensions would withstand anything frost, clay, or all but the nastiest earthquake could do.  The whole place may move, but the foundation would stay intact.  What do you guys think?

Uh, I'd like to clarify for everyone not familiar with the tree rat controversy that it was Carl the Instigator who started all that.  My new-found realtor friend Judi, who unfortunately lives among the Texicans, was suckered into involvement. 

I do like to stir up the pot, admittedly, and anything having to do with crawl spaces and moisture will do it every time.  Hey, it's the best method of teaching and learning for inspectors---stir up their natural competiveness.  You'd better be dang competitive if you plan to remain in the business of home inspections.  When this particular blog was sorta hot, opinions and observations came out of the woodwork like termites on a slow roast.  And it was all good.  Many, heretofore considering themselves well informed, discovered that region, subtleties in climate, and differing soil conditions are all considerations when it comes to crawl space venting methods.

To vent, or not to vent, that is the question;

Whether 'tis nobler to install open vents and vapor retarders,

or to apply foam or rigid insulation with

6 mil plastic and a supply duct, and, thereby, dry it.

Then, there is the question of pure economics.  Some clients will need inexpensive alternatives to the latest building science.  They won't be able to afford the new heating and air system, and the cost of labor and materials to seal a crawl space which may be problematic on the home they want to buy.  That's when the "old" methods come into play.

In the Mississippi Delta, nearly every home with a crawl space has a vapro barrier.  Very often, the surface of the vapor barrier will be wet.  Although atmospheric humidity is a problem, most of the moisture actually comes from the ground up.  Delta soil is an almost perfect ancient mixture of silt from upstream and the myriad small rivers and tributaries which criss-cross the Delta, loess soil blown in from Texas millenia ago, assorted clays, and humus.  It's been turned over, gully-washed and re-mixed into some of the richest natural soils in the world.  It sucks up water like a sponge until it's saturated, then gives up that moisture slowly and steadily in the dryer months.  It is very difficult to seal off with a vapor barrier, and drainage away from a home is an on-going battle in the region because the soil moves.  Generally, two choices are evident.  The first, sealing the crawl space, is rarely even considered, even in new construction.  There are particular problems to overcome anyway, since much water vapor move up from the soil.  The second is a more conventional approach, with a twist.  This isn't done much, either, but it definitely works.

Along with vapor barrier and venting, install a continuous duty fan in the access, with a simple switch control so you can turn it off during heavy rains.  That keeps the air moving, and prevents most condensation since it also keeps the temperatures in the crawl space relatively even with outside temps.  Notice I used the word "relative."  Furthermore, despite what Mr. Happyrock (sorry, Stephen, in case you read this. The Devil made me do it) thinks, adding some heat in the winter will definitely affect relative humidity...but don't close off the vents, because, remember, that water vapor is actually coming up from the soil.  My Dad used old kerosene lamps, two to be exact, under our 1200 square foot home.  Carbon monoxide?  Not with a well-built home, and that fan continuously exchanging the air.  After all, I am still here to relate the story.  These days, a couple of electric forced air fan heaters of 1500 watts or so will do it.  Heck, about a dozen naked 100 watt bulbs strung out on a dedicated circuit and properly installed will do it.  They will produce enough heat to lower the relative humidity just enough.  The whole thing can easily be rigged to a humidistat.  Voila! A cheap and effective system for crawl space moisture control.

Observations?  Arguments? Counterpoints? Bring 'em on!

Carl, I'd like to know what you think.

Over in the flatlands, keeping water away from the foundation is a tough chore on a city lot, especially in a neighborhood with a lot of mature trees.  Drainage is slow at best.  When I say flatlands, I do mean FLAT.  Often, tree growth creates negative slope that was not there in the beginning, and in many cases, there simply is no place to drain the water to, except onto your neighbor's lot.  Ditches and swales on either side of streets often stay full of water after a good thundershower for days, or until it evaporates.  Lots and lots of mosquitoes reside in the Delta, and they're big and mean.  You can see the steam rising from the ground from 75 feet.  Most people out in the countryside have the good sense to haul in fill dirt and actually create a mound to build on.  The nearest natural high ground is the 90 foot row of hills that define the eastern rim of the Delta.  Some people actually pump water off their lots to the nearest and lowest point that will not simply allow the water to drain right back on them.  It's a problem.  There is lots of mold, and many bowed floor joists on older, and some not so older homes.  Managing moisture is no easy task.