subject: Problems With Poured Concrete [print this page] Several rules of thumb apply when evaluating cracks in concrete. The first rule says simply: The bigger the crack, the more serious the problem. Small shrinkage cracks are normal in many concrete constructions. But any crack that extends all the way through a concrete wall or slab should be repaired, since it provides a pathway for water, pests and hazardous radon gas.
Another rule of thumb is that cracks are more serious when the surfaces on either side of the crack shift out of alignment. When such shifting and/or settling occur, other structural elements (floor and wall framing, for example) are often affected. Finally, an "active" crack (one that becomes larger or smaller) is more serious than a stable crack (one that doesn't change size). If you're unsure about how serious a crack might be, contact a concrete repair contractor or a building inspector for a professional evaluation.
Spalling
When a concrete surface deteriorates with material flaking or crumbling away, this is called spalling. On a floor or wall, spalling is more of a visual problem than a structural one, and can be repaired using different epoxy or mortar-based patching compounds. If spalling occurs in concrete steps, this can pose a safety hazard, so repairs should be done right away.
Voids
A void is an air space that is created when the concrete is placed or poured. Some voids are intentional - like the hollow cores found in concrete blocks, for example. Unintentional voids that form on the surface of poured concrete (sometimes referred to as pitting or bug holes) don't look good, but they're easy to spot and fill.
Hidden internal voids can compromise the structural integrity of a concrete footing, wall or slab, creating weak points where the concrete can crack. When unintentional internal voids occur, it's often because of air pockets that form during a pour, or because the concrete mix had too much aggregate and not enough mortar.
Staining
Concrete is a porous material that can stain easily. Stained concrete isn't a problem in a space that isn't used frequently (like a crawl space or unfinished basement, for example). But a stained garage or patio floor can be an eyesore. Fortunately, there are cleaning preparations designed specifically for removing stains in concrete, and most of these can be purchased and used by homeowners. To prevent stains from taking hold, concrete should be finished with a sealer or paint designed specifically for concrete.
Leaks and excessive moisture
When a poured concrete foundation leaks, it's often because water is coming in through cracks that have formed after construction. But water can also enter through holes around the metal form ties used to hold the foundation forms together. These ties remain in place after the forms are stripped away, and if there's enough water in the soil outside the house, leaks can occur around the form ties.
Even when a concrete wall or floor has no cracks or holes, moisture can make its way through the material because concrete absorbs water easily. If water leaks or excessive moisture are problems in your basement or crawl space, it's wise to contact a foundation repair specialist or a basement waterproofing contractor.
