When it comes to mold inside walls, The Mold Twins have been on well over 1,200 calls in Los Angeles alone. We know we can provide you the best tactics to deal with the potential dangers of it, how to determine if there is and what you should do to remove it.

Five most common causes of growth

  1. Air conditioning condensation line breaks inside the wall
  2. Sewer Drain line with slow occurring leak
  3. Had a water pipe leak in a wall but you never dried down the area properly
  4. Window leaks, then water slowly drips into wall.
  5. Water intrusion from outside coming into your wall from rain or irrigation due to stucco, siding, etc that’s compromised.

Five most common signs

  1. Odor – you smell something but just can’t see anything.
  2. You don’t feel good when your home and you feel better when your away.
  3. Constantly itchy nose, red eyes and sneezing.
  4. Staining on interior wall and base molding.
  5. Wall appears to be wet and damp.

How do I detect black mold inside my walls in the first place? -Bella, Los Angeles

You can purchase a moisture reading device and check if a particular area has moisture. If there is moisture, then it’s more than likely there’s going to be mold.


When you find the wettest area, cut open 6 “ by 6 “ and then use a bright flashlight to inspect if there is growth.

Can I just open the wall & use bleach to clean it? -Rich, Santa Monica

You have to be very careful when treating mold inside the wall.

A few things to know first:

Depending on the age of the property, there could be asbestos & lead, so be cautious of opening materials, this can cause a procedure 5 clean up.

Build a contained area with plastic so you don’t spread the mold spores causing secondary damage.

Here’s a great way to capture particulates/ dust from spreading using simple shaving cream:

And finally, please do not use bleach. There is so much on the internet about using bleach, but we promise it doesn’t work.

We’ve been on hundreds of calls where they’ve used bleach, and it comes right back in a matter of days.

Your better off using a mold removal agent like RMR or contact the Twins today, you can purchase ours.

How do I remove mold from my inside my walls? -Ruben, Monrovia

There are products specifically designed for mold removal on wood like our rapid mold removal agent shown here:

Think you have mold inside your walls? Call to schedule your detection or remediation service with our team today!

Why is mold growing on my base molding and lower part of my walls only? Tere, Lawndale

These are all indications that there is moisture present such as water intrusion coming from outside. Perhaps sprinklers & outside planters, foundations, slow pipe leak in a wall – all these we have detected to be sources.

I’m a Los Angeles renter and I keep telling my landlord that I think there is mold inside my walls, what should I do? Becca, Los Angeles

Hire a Los Angeles mold inspector, especially if you know there was a leak and the property owner didn’t dry it down properly. You can certify mail the landlord for your records, and deduct it off next month rent.

Most often, most Los Angeles mold inspectors will not open walls without owner of property consent.

What is the best way to prevent mold inside walls? Jeremy, Studio City

Preventing mold in walls is maintaining your plumbing, condensation line for HVAC, home well ventilated, windows & doors waterproofed.

In a kitchen, keeping your underneath dry.

There are mold prevention paints on the market that have antimicrobial defense inside, that have a long term lasting effect.

In a bathroom, having a good exhaust fan like this Panasonic whisper is ideal.

I have mold inside my closet walls, and there is no leak? Maria, Westlake

Mold inside closet walls means there is no air flow and most likely you have a lot of content inside that is creating dew point/ sweating.

The best thing you can do is clean and place some charcoal/dehu bags at each corner.

These will not only assist in the extraction of moisture but get rid of odors that are related to mold.

How much does a Los Angeles mold removal company charge to remove mold from inside walls? Gene, West Hollywood

This truly depends on the extent of the mold growth and what caused the mold in the first place, how wet are the walls, is it a large wall area, small wall area.

All these play an important factor in cost.

The range we have charged here at the Twin Home Experts over our 37 years performing mold cleaning is a high of $12,300.00 for some extreme cases and a low of $950.00 for very light and small cases.

How much does inside wall mold testing cost? Tina, Brentwood

Testing for mold inside walls requires making a small incision to the materials of that wall.

Swab testing: $189

Air mold samples: $289

Plus $50 per sample-results to you in 24 to 48 hours.

Can I test myself or do I have to hire a Los Angeles mold testing company? Karen, Los Angeles

Yes, you certainly can. It really depends on what your intention is. Are you a renter or landlord and need it for legal, then no, we wouldn’t advise it.

But, if you’re a homeowner and just curious, then absolutely. Here is a quick video to guide you.

I found this yellowish fungus growing from inside the walls? Cindy, Simi Valley

This is not a mold. This is considered the most dangerous fungi to a home or property, its considered “the house eating fungi.”

It’s called Poria, it literally sucks the nutrients out of the wood framing inside walls and causes massive destruction.

Is mold inside walls dangerous? Patricia, Santa Monica

Here’s a customer that had severe mold inside the walls and crawl space. It affected her skin, this is how we treated it the mold: we used our dual dry decontamination fogging.

The best way is to verify by an air mold sample: this will determine if the mold inside the wall cross contaminated into the indoor breathing space.


When it comes to mold inside walls, you have to be extra cautious about how you handle it so you don’t create secondary damages from mold spores, asbestos, and lead contamination.

Contact the Mold Twins today, we’re always here to help. Thank you for visiting our site.