Thursday, March 29, 2012

The Water Table Myth and Tornado Protection

In several different contexts of late, the continuing myth of the local water table being too high (or too variable) for certain types of construction has come up.  My colleague Dr. Matt Biddle has brought to my attention that this is essentially balderdash!  His father was in the concrete business, and Matt's opinion certainly seems well-founded.  Concrete can be poured and will set up just fine completely underwater!  The home construction industry has been selling the idea that a high water table somehow precludes having basements across a great deal of the southern US.  It seems that the reality is that no such problem exists!  In the past, homes used to be constructed with basements here (in OK, and elsewhere in the south) all the time.  But it's cheaper and faster to build homes on a slab than it is to dig out for a foundation at the homesite and build that foundation before commencing home construction.  This added cost would have to be passed on to customers.  But if people can't afford that cost, then perhaps building on a concrete slab is a viable economic alternative.  Be nice to have the choice!

The home construction industry also opposes needed changes to building codes to reflect the actual threat from tornadoes and strong winds here in the plains - for similar reasons:  it adds to the cost and to the time needed to construct a home.  The latter is critical - builders make their profits by speed of construction.  Get it built quickly so it can be sold quickly!  Builders often seek exemptions from building codes in order to reduce construction time, while sacrificing structural integrity - the use of powder-driven nails to "secure" walls to the sill plate is a classic example.  Building codes generally specify the use of J-bolts for securing the walls to the foundation/slab but the builders circumvent this by obtaining an "exemption" to use the much less secure nailing method (much faster!).  So the bottom line is that if the builders had to increase the price because of their additional costs and time, they wouldn't be able to build so many homes.  Fewer people could afford them.  Profits go down.  The opposition from home builders to change is understood, but it's not necessarily in the best interests of the home buyers!

The tired "water table" excuse has been used for so long now, it's passed into "common wisdom" and so isn't even questioned - Ooops, the water table is too high here!  No basements are possible!  Everyone knows that, so don't bother to ask about it!  This is a classic case where someone raises a somewhat esoteric objection to a proposal, and the proposer is not aware of the reality of the situation, thereby feeling compelled to accept a completely specious argument mostly out of innocent ignorance.  I encounter this sort of thing from time to time - I can think of folks who are masters at pulling such objections out of thin air in a conversation, where further investigation after the argument shows that the objection is in fact without any substantial basis.  I hate it when that happens during an argument, but I admit that I have fallen victim to such, even recently.  The water table objection has been accepted as valid, despite its evident lack of validity, for so long, no one now even contemplates mentioning the issue to their home builder.  If I wanted a basement for a new home I was building, could I even find a contractor willing and able to do it here in central Oklahoma?  I wonder.

What's really bothersome is that builders use the false claim that basements are precluded by the water table as an excuse for not building homes with basements.  This has a direct impact on the availability of in-home tornado sheltering places, of course. That's actually why I'm writing this essay.  If more homes had basements that people could use for below-ground shelters, then we could reduce tornado fatalities as a result.  Just being below ground is not enough, however - there should be something sturdy (like a staircase or a workbench) under which to shelter while in the basement, as debris can fall into the basement!

I recently heard the same incorrect "water table" argument from someone as an excuse why a subway system couldn't be built in a southern state.  I've seen examples where railroad tunnels have been built on the bottom of bays and rivers, surrounded on three sides by water!  The idea that the water table is an impenetrable barrier to the construction of underground rail transportation is just plain false.  A high water table may complicate matters some, and perhaps extra costs will be incurred, but the water table excuse simply doesn't wash (pun intended!).  People may not like the proposal of using rail as a means for public transport, but the water table is not a valid reason to reject such proposals.

When you hear the "water table" argument come up in conversation, feel free to ask the person using it to show evidence that it's a valid argument!  Yes, high water tables can cause leak problems for basements, but there are ways to minimize/prevent that leakage.  It's just not a valid excuse for not building basements in the southern states of the USA!


Eric Weaver said...

Around here (central NC) the deal is that the local builders are comfortable with building homes without basements as much as it is anything. Production builders build on slabs for the ease of mass-production, and the local builders just don't think about it, since daddy and grandaddy did just fine building homes over a crawl space.

You will see some homes with basements in this market.With a few exceptions, these are typically available on some of the higher-end homes. It is definitely not the same here as when I was a boy in Ohio! We grew up in a nice enough but very modest home, and it sure has a basement with a workbench to hide under.

David R. Legates said...

Back in 1981, I worked for a mechanical contractor. We were tasked to install a fuel tank for the boiler and it was to be submerged at a location just outside the school to be renovated. This was in Stevensville MD which is located at the eastern terminus of the Chesapeake Bay Bridge (US Rt. 50/301). The fuel tank was about 8 feet tall and we were at an elevation of five feet above Mean Low Lower Water (MLLW). If we could sink an 8' tank at 5' MLLW, putting in a basement to protect lives should be a piece of cake!