The short answer
What Rotting Means for Lath and Plaster
Lath and plaster walls consist of wooden strips called lath covered with layers of plaster. The plaster is a hardened mineral material, so it does not rot like organic matter. However, the wood lath behind the plaster can decay if it stays wet for a long time. This decay is what people often describe as rotting.
When moisture soaks through the plaster, the wood lath absorbs it. Over weeks or months, the wood can break down, lose strength, and even grow mold. The plaster may crack, sag, or crumble as its support weakens. You might notice a musty smell or see dark stains spreading on the surface.
- Soft or spongy areas when you press on the wall
- Dark water stains or yellow-brown discoloration
- Cracks that widen or plaster chunks falling off
- A musty or earthy odor near the wall
- Visible mold growth on the plaster surface
- Bubbling or peeling paint that never dries
Signs Your Wall Has Water Damage
You can often spot moisture problems before the wood lath rots. Look for stains that grow larger after rain or after running water. Touch the wall gently to find soft spots. A damp, cool feeling can indicate trapped moisture inside the layers.
Check the baseboards and corners for swelling or warping. Water often travels down the wall and collects at the bottom. If you see efflorescence, a white powdery residue, that means water has evaporated and left minerals behind. These clues point to an active leak or high humidity.
Mold is another warning sign. Black or green patches on the plaster mean moisture has been present for a while. Mold can also spread to furniture and belongings. If you or anyone in your home feels unwell, see a doctor. For mold removal, consult a mold professional.
How to Check the Wall Yourself
Start with a simple visual inspection. Use a bright flashlight to examine the wall surface from different angles. Look for uneven areas, bulges, or discoloration. Run your hand slowly over the plaster to feel for soft or damp patches.
Press gently with your fingertips on suspected problem areas. If the plaster gives way slightly, that indicates moisture damage underneath. You can also use a moisture meter, available at hardware stores, to measure the dampness. Insert the pins carefully and compare readings across the wall.
For a closer look, you might need to expose the lath. A small hole in an inconspicant spot can reveal the wood's condition. If the lath is dark, crumbly, or has a rotten smell, the damage is advanced. This is where a professional inspection becomes useful.
What to Do If You Find Rotting Lath
First, stop the moisture source. Turn off the water supply if a pipe is leaking. Fix roof or window leaks as soon as possible. Dry the area with fans and dehumidifiers to reduce humidity. The faster you remove moisture, the less damage the wood will suffer.
For minor damage, you might dry the wall and let it stabilize. However, if the lath is soft or crumbling, that section likely needs replacement. The pros can remove the damaged plaster and lath, then rebuild the wall with modern materials. They can also check for hidden mold and structural issues.
The cost depends on the extent of the damage, the size of the affected area, and the materials needed. A small patch might be manageable, while a large section could require significant work. Local water damage pros can assess the situation and explain the options.
- Shut off the water source if a pipe is the cause
- Dry the wall with fans and open windows
- Remove wet furniture and belongings from the area
- Take photos for your records before any repairs
- Contact your insurance company to discuss coverage. Policies vary, and your insurer decides what is covered.
When to Call in the Pros
If the damage covers a large area or you cannot find the leak, professional help is wise. The pros use specialized equipment to detect moisture behind walls and map the extent of the damage. They can also dry the structure thoroughly to prevent mold growth.
A water damage inspection can determine if the lath is truly rotting or just damp. Moisture mapping shows exactly where water has traveled. This information guides the repair plan. The pros can then remove damaged sections and rebuild the wall properly.
Water damage does not wait
Water keeps spreading into floors and walls, so it is worth acting early. Calls are answered 24/7.
Call Now (801) 383-0232Frequently asked questions
Can I repair rotting lath myself?
Small patches might be doable if the damage is limited and you have some skill. You would cut out the bad lath, add new wood, and apply plaster or drywall. But large areas or hidden moisture problems are better left to the pros to avoid future issues.
Will the plaster need to be completely removed?
Not always. If only a small section is damaged, the pros can patch it. But if the lath is rotten over a wide area, they may need to remove the plaster to access and replace the wood. The repair approach depends on the extent of the damage.
How do I prevent this from happening again?
Fix leaks promptly and keep gutters and roofs in good shape. Reduce indoor humidity with exhaust fans in bathrooms and kitchens. Check pipes and seals regularly. If you notice any water stains, investigate the source right away to stop moisture from reaching the lath.