Don’t Sweat the Small Cracks in Slab


QUESTION: When we bought our home, the inspector reported no problems with the foundation. After moving in, we installed new carpet, and when the old carpet was removed, we found several cracks in the concrete slab floor.

The carpet layer said this is normal, but cracks in our house don’t seem very normal to us. We’re wondering if something could be wrong with our foundation. Do your think our home inspector made a mistake?

ANSWER: Every concrete slab has cracks. Even when you don’t see them, slabs are laced with networks of micro-cracks resulting from common shrinkage.

When new concrete hardens, shrinkage always occurs. And because concrete is not an elastic material, cracks are inevitable and rarely a cause for concern.


Unless the cracks in your floor are an eighth of an inch or wider, they are probably the result of normal stress, as the carpet layer said.

In some localities, cracks in slabs may also result from expansive clay soil. When this happens, the floor elevation will usually be higher toward the center of the house and slope downward toward the outside walls.

But again, if the cracks appear narrow and even, serious concern is usually unwarranted.

If the adverse effects of expansive soil are significant, other symptoms, such as cracks in walls and ceilings or ill-fitting doors and windows, are likely to be observed. When such damage becomes apparent, or when the slab cracks are unusually wide, a licensed engineer should be consulted.

Cracks in slab floors can also result from tree roots. If large trees are growing too near your home, removal of some roots, or possibly even the trees, may be warranted.

Chimney Cap Can End Slow Water Seepage

Q: A home inspector noticed a white, fuzzy substance on the inside walls of my fireplace and advised installing a chimney cap. This stuff is kind of powdery and appears on the bricks from time to time.

I just clean it off whenever it occurs and haven’t noticed any other problems. How can a cap on the chimney possibly affect the inside of the fireplace?


A: The white chalky substance in your fireplace consists of mineral salts known as efflorescence. These typically form on brick and concrete surfaces when moderate moisture penetration occurs.

Slow water seepage is the most common way that mineral salts get on masonry surfaces. When the water dries, these salts crystallize. This typically occurs with brick fireplaces because rain caps are not required on masonry chimneys. Consequently, rainwater entering a chimney can penetrate through the smoke shelf into the firebrick lining.

Fortunately, a small amount of efflorescence is not likely to have a significant effect on the general strength and integrity of the masonry lining of the firebox. But if continuous moisture seepage is left unchecked for many years, the bricks and mortar can gradually weaken and disintegrate.

The home inspector was correct in his recommendation. Have a certified chimney sweep install a metal cap on the flue top. In so doing, you can prevent continued moisture intrusion. In the process, you can also ensure that an approved spark arrester is in place and that no significant deterioration of the masonry has occurred.


Commercial Building Needs an Inspection

Q: I am involved in my first commercial real estate transaction. When I requested that the property be reviewed by an inspector, my agent said that this is an uncommon practice, typically reserved for residential property.

I’m afraid to buy any kind of real estate without a professional inspection and am surprised that anyone would take such a risk. What do you advise?

A: During recent years, the real estate market has gradually adopted the custom of home inspections for most residential purchases. The process began in the mid-1970s and by the 1990s had become a standard practice for most home buyers.


But with commercial real estate, an awareness of inspection services has barely awakened in the minds of many investors. In fact, in some areas, the very topic of building inspection rarely enters the discussion when commercial property purchases are negotiated.

The reason for this disparity is a mystery. From the standpoint of structural integrity, general safety and financial liability, the need for a detailed physical inspection is just as vital with commercial real estate as with residential property.

Roofs are just as prone to deterioration and leakage, foundations and wall construction is equally subject to damage and settlement, plumbing fixtures and piping are no less likely to incur leakage, and the risks of fire and shock hazards in electrical systems are equally probable regardless of the type of building being purchased.

Furthermore, the price of most commercial buildings exceeds that of most residential properties.


With purchase figures ranging in the hundreds of thousands of dollars, sometimes in the millions, the price of an inspection is a bargain when you measure the consumer protection it provides. What’s more, the inspection fee can often be recouped in the form of repairs contracted by the seller.

When you tally the pros and cons, commercial property should be purchased with both eyes open, and those eyes should belong to a qualified property inspector.


Got a question about any aspect of the home inspection? Send it to Barry Stone, Los Angeles Times, 540 Atascadero Road, Morro Bay, CA 93442. Queries can also be sent via e-mail to:


All questions will be considered for use in “Ask the Inspector” but cannot be answered individually.