How to Prevent Dry Rot in Apartments and Condos

Last Updated on May 2, 2023 by Dan Cronk

dry rot formation

Dry rot: it’s every building owner’s worst nightmare. Scientific name Serpula Lacrymans, dry rot is a destructive fungus that can move through plaster, concrete, brickwork, and wood to cause extensive damage to buildings. 

While it’s challenging to repair dry rot once it’s started, you can stop it before it begins. At Deck and Balcony Inspections, Inc., our team specializes in identifying complex issues like dry rot and making repair recommendations to resolve them as part of our SB 721 and SB 326 inspection services.

In this guide, we’ve compiled our extensive knowledge to help maintenance personnel learn to spot the signs of dry rot and treat it in its early stages. 

Let’s dive in.  

What is Dry Rot?

Dry rot is a durable fungus that thrives in damp, dark places often overlooked by maintenance personnel.

Dry rot can be caused by several species of fungi, all of which digest parts of the wood that give buildings strength and stability. 

Dry rot begins as a group of microscopic spores that float through the air until they find a damp, moist area to germinate and grow.

As they grow, they send out fine white strands known as hyphae, which consume wood. 

Left untreated, it will continue to grow until 100% of the wood it feeds upon is destroyed. 

Usually, it results in tens of thousands of dollars of unexpected structural damage and cosmetic repairs. 

how to prevent dry rot

What are the Dangers of Dry Rot?

The hazards of dry rot are many. 

Without prompt repair and treatment, dry rot can deteriorate wood structures to the point that they become unstable or even dangerous. 

Dry rot was the cause of the deadly Berkeley balcony collapse in 2015, for example.

Part of the reason that dry rot is so destructive is that it can affect various exterior elevated elements, including outdoor decks. 

The reason for this is simple: 

Horizontal deck boards and stair treads hold water. While treatments are available to make deck boards water-resistant, these treatments don’t make wood 100% waterproof.

Over time, water can begin to intrude within deck boards, causing them to rot.

The bottoms of painted balusters are another prime spot for dry rot to take hold.

This is because these balusters are usually made from untreated pine and are painted to resist the elements. 

The unpainted end, however, is vulnerable to water intrusion. 

When water becomes trapped beneath the bottom of the baluster, it can’t dry out adequately, giving fungi a chance to grow. 

In addition to the above, dry rot in homes can cause health problems. 

Since dry rot indicates high levels of condensation and dampness and involves the proliferation of fungal strains, it can cause respiratory problems and create or exacerbate conditions like asthma and respiratory distress. 

How to Prevent Dry Rot in Apartments and Condominiums

caulking deck

When it comes to dry rot, preventing it is much easier than repairing it. With that in mind, here are a few tips to keep dry rot from occurring in the first place:

  • Seal cracks. Check for gaps and cracks in balconies and decks. Seal any cracks you find with fresh, water-resistant caulk. Scrape away any old caulk from these cracks. You’ll also need to repair exterior windows and siding if the paint in these areas is chipping or peeling. 
  • Pay attention to T 1-11 siding. T 1-11 siding is above the sight line. As such, that’s where most dry rot starts – especially on the top sides of trim on top of windows and doors. These high-risk areas will experience dry rot within 3-4 years. To protect these areas, it’s important to paint and seal all exposed T 1-11 siding annually.
  • Encourage residents to do their part. While HOA board members are responsible for much of the exterior maintenance that helps prevent dry rot, residents can also do their part. Encourage residents to clean their gutters and clean up any standing water (after storms or heavy rainfall) from their decks and balconies as quickly as possible.
  • Remove standing water. After a heavy rain or storm, sweep or mop standing water from outdoor decking as soon as possible. 
  • Be mindful of building-adjacent sprinkler heads. While building-adjacent sprinkler heads can keep landscaping lush, they can also cause water damage that leads to dry rot. As such, we recommend replacing building-adjacent sprinkler heads with bubbler heads—more on this in the next section.
  • Invest in routine inspections. Investing in regular condo and apartment inspections is the best way to prevent dry rot. A skilled building inspector can detect early signs of dry rot and make maintenance or repair suggestions.

10 Dry Rot Examples & Maintenance Solutions

dry rot balcony

Dry rot can take many different forms and require many unique maintenance solutions, and it’s essential to learn to identify and navigate each of them.

Here are a few examples:

Example #1: Dry rot caused by landscape cover

We’ve often seen dry rot caused by a buildup of landscape cover retaining moisture around posts or other deck and balcony bases. 

Solution: Posts should be checked annually for dry rot. Posts that are affected by dry rot should be replaced, and the landscape cover should be regraded so that moisture is no longer trapped at the base of the post. 

Example #2: Dry rot caused by spray sprinkler heads next to wood-sided buildings

Another common cause of dry rot is the placement of spray-type sprinkler heads next to wood-sided buildings.

During their daily watering cycles, these spray-type sprinkler heads can force spray upward beneath the protective covers of a building, creating the perfect environment for dry rot. 

Solution: Instead of spray-type sprinkler heads, switch them out for drip or bubbler sprinkler heads. 

Example #3: Dry rot caused by termite damage

Over time, dirt and debris can accumulate around the base of the deck and balcony posts, creating the perfect environment for termites and dry rot to take hold.

Solution: Check posts for dry rot annually. Make sure to leave at least 2” vertically between the posts’ bottom and surrounding landscaping material or dirt cover. 

Example #4: Dry rot caused by dissimilar materials

Different materials, like stucco and wood siding, contract and expand at different rates. This means they’re likely to crack at the seam where they meet, creating a perfect opportunity for water to intrude. 

Solution: Check the crack annually to ensure dry rot has not developed. Caulk and paint the cracks annually. 

Example #5: Dry rot caused where trim boards meet around doors and windows

While today’s pre-primed “engineered” trim is convenient, it’s made of finger-jointed pine, which has a very low dry rot resistance.

What’s more, factory-installed protective prime coatings are durable and designed to withstand various weather conditions, but cutting the boards to fit doors and windows often exposes unprotected pine at joints.

Solution: If you notice gaps around these joints, caulk and seal them as soon as you identify them. 

Example #6: Dry rot at the tops of window trim

Over time, rainwater runs down the exterior siding and gathers on horizontal trim surfaces. Since these areas are usually above the line of sight, they’re seldom checked by maintenance personnel.

Solution: Using a small screwdriver, check the top of the building’s trim for signs of dry rot. If no dry rot is found, paint and caulk these areas annually. 

Example #7: Dry rot on horizontal deck rails where they meet vertical columns or posts

The areas where horizontal deck boards meet vertical columns are very likely places for dry rot to develop since water gathers in these places. 

Solution: Use a screwdriver to prod these areas and test for dry rot. If the wood is sound, caulk and paint the areas annually.

Example #8: Dry rot in unpainted trim

Unpainted trim is highly susceptible to dry rot wherever it occurs. Even if work is new, dry rot can occur. If cracks appear between the siding and trim, they must be sealed immediately.

Solution: Check the sides of all your building’s trim for gaps, cracks, and spaces. Apply durable caulking and paint to close them as quickly as possible. 

Example #9: Dry rot in the tops of beams

The tops of beams are exposed to the weather all the time and are prime areas for dry rot development. Unfortunately, they’re also very seldom checked for dry rot. 

Solution: Inspect the tops of all beams annually, using a small screwdriver to test the durability of the wood. Spray a fungicide into the area on top of the beam, allowing it to penetrate deep into all cracks. Seal cracks with durable caulking and apply at least two coats of paint. Recheck, seal, and paint annually. 

Example #10: Raised nail heads

Raised nail heads on surface deck boards signify that nails have lost some of their holding power. This could indicate the beginning stages of dry rot. 

Solution: Remove the nail, get a 50 ml syringe, fill it with fungicide, and inject it into the nail hole. Replace the nail with a larger screw. Repeat the process for all raised nail beds. Reinspect and replace annually. 

The Best Way to Prevent Dry Rot: Get a Professional Building Inspection

While you can learn to recognize the signs of dry rot and even replace boards affected by the early stages of dry rot, the only REAL way to know if you have dry rot is with a professional inspection. 

In California, HOA Board Members are required to comply with SB-326, which requires routine building inspections. Apartment buildings, meanwhile, must comply with SB-721, which requires building inspections every six years.

At Deck and Balcony Inspections, Inc., our team specializes in providing comprehensive, thorough building inspections to identify and protect against dry rot. 

Our team helps apartment owners, HOA Board Members, and building managers comply with California’s building inspection laws and keep all elevated elements safe and sturdy. 

Ready to learn more about our services or claim a spot for your upcoming SB-326 or SB 721 inspection? Contact us today.



Dan Cronk is the Founder & President of Deck and Balcony Inspections, Inc. Dan has 40+ years of experience in the construction industry. As a certified structural inspector and general contractor, Dan has extensive knowledge about California’s deck and balcony laws and enjoys sharing his expertise with the community.




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