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Rain Shower,70°
Saturday, August 2, 2014
A sinking support post?

Q. We built a second-story addition two years ago, and one corner hangs over a porch with a post going down to the ground. I recently noticed that the ground around the post is sinking. It’s now about a foot deep, and I’m worried about the post sinking, too. There are small cracks in the wall and ceiling of the second floor bath above the post. What causes this, and what can I do to stop the sinking?

A. You have a sinking feeling about your sinking post and are concerned about sinking more money into your home. I looked at your problem, and I saw that the ground and patio around your post and footing are sloping right to them. In other words, the area is bowl-shaped, with your column right in the middle. I checked the soil with a rod, and it’s soft. Then I looked at the under-hanging porch roof above. There were no signs of movement. But then I looked at the roof slope, rain gutters and downspout. The rain washes over the full gutters, which were stained, and drops right to the spot where water collects at the base of the column.

So, basically, the accumulating water is drawing the soil downward for two reasons: the soil is loose and not tamped, and the water is seeking a low point, forcing it to drag the soil downward. What should have happened, by code, is that the ground must always slope away from any building part, and your yard clearly doesn’t slope away from the house or the post.

The cracks in the wall and ceiling are potentially a problem related to a sinking post, although that would need to be monitored. The post is supposed to be sitting on firm, undisturbed soil. If the cracking upstairs gets worse, you may have a soil problem under the post, which is much more serious and expensive to solve. On the other hand, new construction uses lumber that’s not always completely dry, and as the wall studs and roof rafters acclimate, they shrink and enlarge, depending on seasonal humidity. It’s best to make observations with a ruler or tape measure and even photos for a few seasons to see what happens.

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