Stucco near you

Stucco is applied as a multiple-layer process, sometimes in two coats but more commonly three, whether it goes directly onto masonry or onto wood or metal lath. The first is the scratch or pricking-up coat, followed by a second scratch coat, often called the floating or brown coat, and finally the finishing coat. Each layer has a job: the first bonds and is scratched or cross-hatched to key the next, the second levels, and the third carries the texture and the colour.

Thicknesses and timing are specific. Federal preservation guidance describes a scratch coat of roughly a quarter to three-eighths of an inch, a second coat of about the same thickness with the first two together generally not exceeding about five-eighths of an inch, and a finish coat of about a quarter of an inch applied after the previous coat has initially set. Each coat usually needs 24 to 72 hours to dry before the next goes on, and longer in cold weather, which is why a proper stucco repair takes days rather than an afternoon.

Bond comes from wetting and from keying, not from products. Both masonry and wood lath must be kept wet or damp to ensure a good bond, because dry substrates pull moisture out of the stucco too rapidly and cause cracking, loss of bond and generally poor quality work. A mechanical bond is always preferable to reliance on bonding agents, which should not be used on walls likely to stay damp or where large amounts of salts are present.

The federal guidance is categorical about the primary cause: most stucco deterioration is the result of water infiltration into the building structure, either through the roof, around chimneys, window and door openings, or from excessive ground water or moisture penetrating through or splashing up from the foundation. The listed culprits are unglamorous and fixable: ground settlement, lintel and door frame settlement, inadequate or leaking gutters and downspouts, intrusive vegetation, moisture migration inside walls from interior condensation and humidity, vapour drive from furnace, bathroom and kitchen vents, and rising damp from poor drainage around the foundation.

Water infiltration causes wood lath to rot and metal lath and nails to rust, which eventually makes the stucco lose its bond and pull away from its substrate. That is why the sequence matters: after the cause of deterioration has been identified, any necessary repairs to the building should be made first, before repairing the stucco. Roof, gutter, downspout and flashing repairs, better drainage and redirected runoff come first; the plaster comes second.

The second common cause of failure is a previous repair. Inexpert patching, particularly in portland cement, which tends to be very rigid and is therefore incompatible with early, mostly soft lime-based stucco, causes additional deterioration rather than curing it. A wall that has been patched several times in unsympathetic material can reach the point where patching is no longer viable at all.

Assessment comes first, and it is done by hand. Testing should be carried out systematically on all elevations to determine the overall condition of the stucco: unsound, punky or soft areas that have lost their key will echo with a hollow sound when tapped gently with a wooden or acrylic mallet. That survey, not a glance from the street, decides how much of the wall is actually coming off.

How the patch is shaped affects how it reads afterwards. Repair is best carried out in a contained or well-defined area, and where the stucco is scored in imitation of masonry, the patch should be squared off to follow the existing scoring rather than left as an irregular blob. The number and thickness of the coats used in the repair should match the original, and the finish coat should be worked to match the original texture.

Curing is where hot-weather repairs are lost. Freshly stuccoed areas should be shaded or even covered, particularly in hot weather, and in hot weather it is also good practice to keep the new work damp, at approximately 90 percent humidity, for 48 to 72 hours. A patch left to flash off in direct sun in July will craze and let go, no matter how good the mix was.

Patching is the default, and the sounding survey tells you whether it is still realistic. The federal benchmark for going further is specific: complete replacement of historic stucco with new stucco of either a traditional or a modern mix will probably be necessary only in cases of extreme deterioration, that is, a loss of bond over more than 40 to 50 percent of the stucco surface. The other trigger is accumulated bad repairs, where the physical and visual integrity of the original has been so compromised by prior incompatible work that patching would not be successful.

Colour and texture usually decide how far a patch extends. A hand-mixed match is generally close enough to cover a whole wall or an area distinct from the rest of the building, but it may not work for a small patch in a conspicuous spot on a primary elevation, where it may be necessary to conceal repairs by painting the entire patched elevation or even the whole building. That is a reason to plan repairs by elevation rather than by square foot.

Where the house is modern rather than historic, the questions are the same but the answers are easier: the mix can be a contemporary one, matching is simpler, and the decision turns on how much of the wall has lost bond and what caused the water to get in.

Stucco repairs, like most other exterior masonry work, should not be undertaken in cold weather, meaning below 40 degrees Fahrenheit and preferably warmer, or if there is any danger of frost. Water in the mix that freezes before the material has set destroys the bond, and no amount of surface finishing recovers it.

Heat is the opposite hazard and just as real. The recommended practice is to shade or even cover newly stuccoed areas in hot weather and to keep the work damp for two to three days so it cures rather than dries. On southern and southwestern exposures in summer, that can mean working early, hanging shade cloth and coming back to mist the wall.

Because each coat needs a day to three days before the next can go on, and longer in cold weather, a full three-coat repair occupies a working week of site time even when the area is modest. Schedule it in a stretch of mild, settled weather rather than squeezing it in before a cold snap.

California is the clearest example of a state that licenses this trade by name. Its C-35 lathing and plastering classification covers a contractor who coats surfaces with a mixture of sand, gypsum plaster, quick-lime or hydrated lime and water, or sand and cement and water, or a combination of such other materials that create a permanent surface coating, applied with a plasterer's trowel or sprayed over any surface that offers a mechanical means of support, and who installs the lath, metal studs and other bases that provide the key or suction for those coatings. Virginia licenses contractors in classes according to the value of their contracts and attaches specialty designations to them. Florida's statutory contractor categories do not include plastering, so there the relevant checks are local registration, insurance and references.

Permits are a building department matter and vary widely; a patch is almost never permitted work, while re-cladding an elevation, replacing lath and sheathing or altering openings often is. If the house was built before 1978 and painted stucco will be disturbed, the federal lead rule applies: the firm must be lead-safe certified with trained workers, and the exemption for exterior work disturbing 20 square feet or less of painted surface does not cover window replacement, demolition of painted surfaces or prohibited work practices. Cutting or grinding stucco and masonry also brings the federal silica standard into play, with its 50 microgram per cubic metre exposure limit and its requirement for dust controls and a written exposure control plan.

LokalMatch is where you start looking, not where the plastering happens. Describe the stucco job once, say how old the house is and which elevations are affected, add photos, and stucco and plastering pros serving your ZIP code get in touch; they pay for the requests they receive. LokalMatch does not mix stucco, does not price work and does not vet, rank or recommend any contractor, so confirming the licence where your state issues one, the lead certification and the insurance is up to you.