Cracked Foundations, Adobe Clay Soils and Water in Silicon Valley

In Santa Clara County, as in much of California, we have adobe clay soil and it’s expansive.  That is, when the dirt gets wet, it expands, and when it dries out, it contracts. Hence it’s sometimes referred to as “shrink-swell” soils.  (Every state in the union has areas with this problem – a color-coded map on geology.com shows areas with more and less expansive soils.)

Why is expansive soil an issue for homeowners and would-be homeowners in Silicon Valley?

The trouble is that the expanding and contracting soil is far stronger than concrete and the foundations upon which a home sits. A well written and illustrated six page paper can be found online explaining the mechanics involved for those interested in more detail on the hows and whys of expansive soils. (It states that the ground can life as much as 5,500 pounds per square inch!)

What I’d like to focus on here is mitigating the risks and preventing the problems associated with expansive soils.

The trouble is not so much that the soil is wet or dry.  The problem is in the back and forth, the movement. When the soil is kept at an even amount of moisture, it does not expand and contract.

Obviously, rain is seasonal and we cannot control all moisture on or near the house. We can, though, work to move water away from the house and away from the foundation.

Keep rain away from foundations on adobe clay soil!

Winter storms can bring an enormous amount of water onto a home’s roof, and when it channels down gutters and downspouts, there can be a large amount of water exiting in just a few places.  Where does that water go?

 

downspout no extender near foundation

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How is that wood siding working out?

Damaged wood sidingWood siding is extremely common in the San Jose area and Silicon Valley as a whole, both on condominiums & townhouses and also on houses.  (We do not see a lot of vinyl siding here, as we might in other parts of the country.) Water is the #1 enemy of houses – even more than termites!  It is necessary to control water intruding into the wood, because if it gets in, fungus and rot can get a start on your home.

How do you prevent  water damage, fungus, and dry rot on wood siding?

Exterior wood needs to be painted about every five years or it can crack, peel, and otherwise allow moisture intrusion. If the wood is kept sealed, it can do very well against water. Another big cause of expensive wood repairs outdoors is earth to wood contact.  If you have ever built a fence, or had one made for you, you’ve probably seen that the best practice is to put the wooden posts into concrete rather than directly into the dirt.  The reason is simple: soil gets damp and the wood will wick up the moisture, whether it’s fence boards, posts, part of a wooden deck, or the siding on your home.  If the siding or other wood comes near the soil, the recommendation is to separate them one way or the other. In the photo I’ve included with this article, the siding of this townhome complex was allowed to touch the earth.  You can see the results: expensive repairs needed! The old saying goes that “an ounce of prevention is worth a pound of curse”.  It’s especially true with caring for wood siding and other times of wood on the outside of your home or in your yard.   If you can remember to do a walk-around every few months, at least twice a year, you are more likely to find the beginnings of issues before they become thousands of dollars.  Keep a schedule for painting and make sure you do it before it looks like it’s needed.  If you wait until there’s chipping and cracking, you may already have trouble!  Watch for earth to wood contact, and rake away the soil or take other measures to protect your siding. This is true for owners of townhomes too.  It seems like decades ago, home owner associations were often responsible for siding, but in the last few years I’ve been finding more and more HOAs make that the owner’s responsibility, even if the HOA is in charge of the painting schedule.    Make sure that you have a look at your siding regularly so that you can stop fungus and dry rot in their tracks and prevent a small headache from becoming extremely costly. Finally, it’s a good idea to have a pest inspection (termite inspection) every 3 to 5 years to nip any issues in the bud. Related reading: What Is Cellulose Debris (in a pest or termite report)?

 

 

 

Avoid earth to wood contact

Earth to Wood Contact wood losesWhether you’re looking to buy your next home or a home owner now, it’s imperative to understand how bad moisture is for wood.  So many people assume that the worst thing that can happen to a house is termites, but most of the time, it’s water – and whatever brings water to the house, fence, deck, wooden retaining wall, mailbox post, etc.

This conduit for water includes soil   Earth touching wood will conduct water up to the wood, like a wick.

Often the earth to wood contact problems come in improperly installed or maintained fences, in which the posts should be put into a concrete base.  Have a look at the image on the right – the moisture from the ground has come up to the fence, damaging the wood and likely rotting it too.

Most properties in Silicon Valley have an abundance of wood elements.  It’s smart to check them periodically to make sure that they aren’t directly touching soil.  By keeping them apart, you’ll help to extend the life of that component.