Aerobic floor vibrations?
Q. Our house does not have a foundation problem, but the living room furniture used to shake when we would do our morning aerobic exercises. So we installed some steel posts under the joists to make the floor more rigid. Unfortunately, this is a problem now that we are selling the home. When the buyers' home inspector saw the posts, he reported that they need concrete footings and permanent attachment to the framing. If we had never added these posts, there would be no problem. What should we do, add footings, take the posts out, or what?
A. Removing the posts after the home inspector made his recommendations will probably raise suspicions with the buyers. Adding concrete piers may or may not be necessary, but it may be the path of least resistance for selling your home. The only other approach is to get an opinion from a structural engineer.
The home inspector, when faced with an unusual installation of this kind, had reason for concern, but he should not have drawn conclusions that exceed his professional expertise. Unless he is a licensed structural engineer, he was exceeding the scope of his inspection by prescribing specific types of structural repairs. Instead, he should have recommended further evaluation by a licensed structural engineer. That would be the proper course of action for a home inspector.
If the living room floor used to flex when you did your aerobic exercises, the joists may have been over-spanned when the house was built. In that case, the posts that you added may have been necessary, and having them secured in a proper manner may now be an appropriate upgrade.
Q. We are having new carpet installed in our home. When the carpet layers removed the old carpet, we discovered large cracks in the concrete slab, some that go all the way across the room. We're worried that this may be a major foundation problem because we have expansive soil throughout the neighborhood and because we often hear popping sounds in the attic at night. Does this sound like a serious problem?
A. Most concrete slabs have moderate stress cracks. In areas with expansive soil, cracks can be minor or major, depending on various factors, such as steel reinforcement in the slab and aggregate fill between the slab and the soil. You should also be aware that the largeness or smallness of these cracks is not determined by their length, but by the width of separation, that is, the size of the gaps. A crack that is more than one-eighth of an inch in width is considered to be large. If the separation is less than this, the cracks are usually not regarded as significant, regardless of their length. If the cracks in your slab are large according to this standard, you should have them evaluated by a licensed structural engineer.
The popping sounds in the attic are probably unrelated to the slab cracks. Expansive soil causes ground movement when there are seasonal changes in ground moisture. If the popping sounds in the attic occur at night, it is probably due to temperature changes. As the night air cools the roof and attic, framing materials contract, and this often causes popping noises to occur.
• To write to Barry Stone, visit him on the web at www.housedetective.com, or write AMG, 1776 Jami Lee Court, Suite 218, San Luis Obispo, CA 94301.
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