What Are the Signs of Damaged Lath and Plaster in Older San Jose Homes?

1. What Are the Signs of Damaged Lath and Plaster in Older San Jose Homes? If your home was built before the 1950s, there’s a good chance it features original lath and plaster walls. These materials were standard in historic home construction, offering superior insulation and a classic finish. However, over time, this system can deteriorate due to age, moisture, or structural shifts. Recognizing the early signs of deterioration is key to timely lath and plaster repair in San Jose, CA, and can help preserve both the integrity and charm of your home. Cracks That Keep Coming Back Hairline cracks are normal in older plaster walls, but cracks that reappear after patching or that widen over time are a red flag. These may signal underlying movement or separation between the lath and the plaster. In homes around San Jose, common causes include settling foundations or past seismic activity. Horizontal or stair-step cracks, in particular, could suggest that the lath has pulled away from wall studs, which requires professional attention. Bulging or Sagging Wall Sections If you notice areas of your wall or ceiling that appear to bulge outward or sag slightly, this could mean the plaster has detached from the wooden lath behind it. Over time, the keys — the hardened plaster that seeps between the wooden slats — can break due to gravity or water intrusion. Left untreated, these sections can collapse entirely. Homeowners should avoid poking or pressing on these areas, as weakened plaster can crumble or fall suddenly. Hollow Sounds or Soft Spots One simple way to check for damage is to gently knock on different areas of your plaster walls. Solid areas will produce a consistent sound, while damaged or detached sections may sound hollow. In some cases, the plaster may even feel soft to the touch. This kind of damage often signals a larger underlying issue and should be assessed quickly to prevent further deterioration. Water Stains and Mold Growth Water damage is a common enemy of old plaster. Discoloration, peeling paint, or brown stains on ceilings and upper walls often indicate a leak above the surface — from

2. plumbing, the roof, or condensation in the attic. Moisture weakens the bond between the lath and plaster and can lead to mold growth, which poses additional health risks. San Jose homes that experience seasonal rains or are located near older infrastructure should be routinely inspected for these issues. Crumbling Around Fixtures or Openings Another subtle sign is crumbling plaster around windows, doors, light switches, or electrical outlets. These are points of stress where movement is common, and they can become early indicators of plaster failure. While it might seem cosmetic at first, continued crumbling can spread and eventually require a full panel or wall section replacement. Paint That Won’t Stick or Peels Rapidly If you're repainting and notice that new paint refuses to adhere or peels quickly, it may be due to deteriorated plaster underneath. Old plaster that has absorbed moisture or has started breaking down will not hold paint properly. In some cases, homeowners will find that entire layers of paint and plaster lift off together — another clear indicator that repairs are overdue. Time to Consult a Professional While some minor repairs can be handled with patch kits or plaster compound, persistent or large-scale issues should be handled by skilled professionals. Lath and plaster is a delicate and labor-intensive system, and poorly executed repairs can lead to more damage later. For accurate diagnosis and long-term restoration, it's often best to bring in experienced plastering contractors in San Jose who understand the materials and architectural style of older homes. Resource: What Are the Signs of Damaged Lath and Plaster in Older San Jose Homes?