Admixtures for the acceleration or retardation of stucco set and curing times should only be used after laboratory testing under conditions that closely approximate the job site conditions for the time and location of the project. In general, it is not a good practice to modify the cement for convenience or without a specific need.
There are two primary types of cracks that occur in stucco: shrinkage and movement. Both are easily identifiable by the pattern in which they crack. The “alligator-back” pattern is indicative of shrinkage cracks.
Uses and rules for bonding agents are frequently misunderstood.
The use of Portland cement/lime mortars for unit masonry and/or stucco was the standard of the industry for nearly a century. Since the introduction of specialized masonry cements, the use of cement/lime mortars has declined, particularly in the sun-belt states.
Tips for choosing a consulting expert to work with stucco.
Stucco over expanded metal lath. Most common errors.
We used to require a delay of at least 24 hours for curing of the scratch coat prior to application of the brown coat. With the technological improvements to plasters made from masonry (stucco) cements, this is no longer the case. Updated 9.20.13
The term “ghosting” in stucco refers to the visibility of the mortar joints in the concrete masonry wall substrate. Where stucco has been properly placed and cured, this should not be evident. Ghosting is caused by several factors but is preventable with care and precautions.
Residential - lath and plaster inspection checklist.
Though frequently suspected, stucco does not leak. It is the lack of sealant around penetrations through walls (windows, doors, hose bibs, dryer vents and others) that have caused the greatest majority of these leaks.
There is no “rule of thumb” as to the amount of time that should pass prior to painting as conditions change daily and regionally. The important factor is the extent of curing and that can be measured in pH levels.
The lime in fresh plaster, concrete and masonry can cause what we know as lime burn, a condition that results as an allergic reaction to chromium, which is naturally occurring in the limestone used to produce cement.
From time to time you may experience a spotting of the stucco through the paint in the form of rust. There can be several causes for this phenomenon including the sand source, shipping, the water source or an external debris source on the plastered wall prior to painting.
Weather has a significant effect on the application requirements of stucco in both a macro (seasonal) and micro (daily) basis. Factors contributing to these effects are: temperature, humidity, wind speed, solar exposure.
Stucco Code Approval
There have recently been several instances in which Building Officials have asked for the Florida Building Code Approval number for stucco cement. The Product Approval Program Oversight Committee determined that approval numbers are not necessary or possible for this product for a number of reasons.
Placing Portland Cement Plaster on concrete structures is a fairly simple process and successful application provided a few preliminary steps are taken to ensure bond.
ASTM developed standards for stucco (Portland Cement-Based Plaster) in the manufacturing, testing and installation of stucco cement, lath and accessories, and aggregates to be applied.