![]() The plaster droops on the backside of the laths and dries, forming “keys.” These keys keep the plaster tight to the wall. The plasterer forces the first coat of plaster - the brown coat - through the grooves between the laths. Plaster is applied in three coats and built up to a thickness of 3/4-inch to make the finished wall. The lath is installed with 1/4-inch spaces between each piece. The 1 1/4-by-1-inch-thick wood, called lath, is nailed horizontally to the 2-by-4-inch wall studs. To understand how, it helps to understand the guts of lath-and-plaster walls. You’re on the right track when you ask if you can simply reglue the detached plaster. With the stud bays open, it is an opportune time to reconfigure lighting and electrical outlets to our liking and to add insulation to exterior walls.īut tearing out the plaster and drywalling a room is a ton of work, and we can appreciate your wanting to avoid it. Most often when we’ve been presented with old plaster walls we’ve opted to strip them and apply drywall rather than engage in the seemingly constant battle of repairing them. I can handle small holes and cracks pretty well.Ī: Old plaster is the bane of old houses. My questions are: Can this be glued back into place, or must we remove all the loose stuff and replaster? How does one handle the bubbles (like an air pocket) that occur in the plaster? Any suggestions for a proper repair would be greatly appreciated. ![]() You can press it and it moves closer to the wall. In two areas there is a large “plate” of plaster that is loose. We had the roof redone last summer, and the banging and hammering seriously re-cracked the plaster. The walls and ceiling were cracked during an earthquake and poorly patched before we moved in. This completely isolates the stucco from the wall surface but supports its weight so it doesn’t fall off.Q: We are getting ready to repaint our home office. If bond can’t be attained by cleaning or bonding agents, you will have to use paper-backed lath to assure mechanical anchoring to the wall. Alternately, you might apply a dash-bond coat or a bonding agent to allow for direct application of stucco. These include sandblasting or acid etching. With worse conditions, you need more aggressive techniques. Depending on the contamination, you might only need to wash with water. If water sprinkled on the wall is not readily absorbed, then the surface must be handled differently. Generally, stucco that is applied directly to solid surfaces is placed in two coats that together total 5/8 inch of thickness. Unless it’s very hot, dry and/or windy, moisture on the wall together with that in the plaster is usually sufficient for curing. It dampens the unit, reducing its water demand and the potential of premature dryout. This prepares the unit surface to absorb paste from plaster. Immediately prior to plastering, the wall should be pre-wetted. If it is readily absorbed, then the surface is expected to bond well with stucco. Potential for bond can be quickly checked by a simple test: sprinkle the wall with some water to see how it absorbs. Partial bond will create undesirable stresses and can lead to delamination and cracking of the stucco layer. The entire surface must have uniform bonding potential or you can run into problems. Older walls may have bond-inhibiting characteristics, in the form of paint, sealer, or some other coating or dirt on the surface. This is generally not a concern with new walls. If contamination is present on the substrate surface, good bond is inhibited. Concrete masonry surfaces are both absorbent and textured, two things necessary for bond. ![]() ASTM Standard C 926, Specification for Application of Portland Cement-Based Plaster, permits direct application of stucco to solid surfaces like concrete and masonry as long as bond is sufficient. Portland cement adheres well to lots of materials, especially to other materials made from the same type of ingredients. As such, they have a great affinity for each other. Stucco is made from the same materials as concrete and concrete masonry. With a substrate of concrete or concrete masonry, is it necessary to use lath? Metal lath is regularly used over stud wall construction with or without sheathing materials. This question probably arises because plaster is often attached to wall surfaces that have metal lath affixed to them. ![]()
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