This Old San Carlos House, Part III: Drainage.

April 29, 2011


Water: The Ultimate Irony.

Water is THE most essential compound when it comes to supporting life as we know it — but it's “Public Enemy #1” when it comes your home.  Whether it's from a leaky roof, faulty plumbing, or poor site drainage, I believe that water causes more damage to homes than fire, or any other naturally occurring event.  And what's most amazing about water damage in this area is that it's seldom catastrophic in nature — more often, it's gradual, chronic, and often goes undetected.

In this edition of This Old San Carlos House, we'll talk about one particular water-related problem that plagues many old San Carlos homes — poor drainage.

Water Under the House.

The most common manifestation of poor site drainage is the presence of water under the house.    Now, of all places to have water on your property, this is absolutely the last place you want it to be.   Why?  Persistent moisture in the crawl space of a home is a recipe for disaster — and the more moisture there is, the bigger your problem is going to be.    Some of the problems that arise from excessive moisture under your house are:

  • Wood Destroying Organisms.   Subterranean termites absolutely love moist ground.  They are able to live and reproduce with ease in wet soil.  And wood that's exposed to constant moisture will start to grow fungus, which is another organism that feasts on wood.  Both of these bad boys are troublesome to a home if left unchecked.
  • Oxidation.  Moist environments are even tough on anything metal under the house — joist hangers, plumbing, ductwork, etc..   Even if they are made to resist moisture, chronic exposure to water will oxidize just about any metal.
  • Mold.  In some cases where there's copious amounts of standing water, mold can take hold and spread not only under the house, but into the living area as well.
  • Structural Weakness.   Dry, solid soil supports a home much better than wet, squishy soil.    When a foundation is surrounded by water, it starts to settle into the wet soil.  This settlement creates uneven stresses on the house, which usually show up in the form of sloping floors, cracked walls, and fractured foundations.    Even the concrete in the foundation will deteriorate over time if it's constantly wet.

So, how does water get under the house in the first place?  There are many ways, and they generally fall under one of three categories:

Poor Design.

When homes were built in San Carlos back in the 30's and 40's, there was very little thought given to drainage.  Heck, many homes didn't even have gutters or downspouts back then.  And those that did have downspouts usually terminated them right next to the foundation — which kinda defeats the whole purpose of them in the first place.   Even the yards in some places aren't sloped away from the home like they're supposed to be.   So when the rains came, the water had a clear path under the foundation.

In most new construction today, it's common to tie the downspouts together and then terminate them away from the foundation, thus eliminating most of the roof water away from the underside of the home.


If a home is located on a hill or at the base of a hillside, then it may be squarely in the path of the ground water that drains only one way — downhill.   I recently saw the result of this in one house where there were several inches of standing water under the house.  Ugh… The likely culprit?  Continuous water draining down the hill.

Mother Nature.

If outdated home design or location doesn't do you in, then nature just might.  Much of the land on the peninsula sits atop a network of underground springs and aquifers.  Sometimes that water just finds a way upward  to the ground level and ultimately under your house.   The closer your home is located to the bay, the more that tides can come into play, too.  That's one reason why you may encounter an old home way down in the flats that has a sopping wet crawl space.


The good news is that most, if not all, drainage problems can be resolved.  The bad news is that it the remediation can be as cheap as a quick Home Depot run, or as much as $25,000-$30,000 for a complete transformation of the underside of your home.  It really depends on how severe your problem is.   If you suspect that you're getting water under your home,  try the easiest solutions first:

  • Extend downspouts away from the foundation, or install splash plates to keep that water from draining back toward the house.
  • If possible, make sure the ground around your home is graded away from the foundation.

If that's not getting you where you need to be, it's time to call in a drainage specialist.  They can diagnose the source of the water and design a solution that works for your particular home, such as a french drain (see below).

Diagram of a French Drain

It's important to note that every home is different, and how and where your home is situated will have a big impact on the solution that's best for your drainage problems.

CleanSpace – The “Cadillac” of Solutions.

Technology for drainage remediation has come a long way since the old San Carlos homes were built back in the last century.    Nowhere is this more evident than in a solution known as CleanSpace.   This is basically a total hermetic encapsulation of the underside of your home, and keeps out not only moisture and it's related problems, but also those pesky rodents and insects.   Since a picture is worth at least a few thousand words, take a look at this video about CleanSpace:



None of the drainage remediation techniques that you see today (sump pumps, french drains) were readily available or even invented back when your old San Carlos home was originally built.  So it shouldn't be a surprise when you're leafing through a property inspection report and you see that there's evidence of moisture under your crawl space (wet soil, water marks on the foundation, fungus damage, efflorescence, etc.. )   If you're considering buying a home that has obvious drainage issues, be sure to budget enough funds to solve the problem in a reasonable time (preferably the first year.)   If you already live in a home that has drainage issues, it's critical to get these resolved, not only for the well being of the house and for the safety of those who live in it, but also the resale value down the road.

This Old San Carlos House is an occasional series on the White Oaks Blog.

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  1. Double Glazing Tamworth on July 22, 2011 at 4:03 pm

    The gutter is the part of a building’s roofing structure that is responsible for collecting rain water, and disposing of such water is a way that does not lead to a damage of the building. Without gutters, buildings would have shorter lives, as rain water falling effect of induced structural weakness.

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