How to remove black mold from drywall

How to remove black mold from drywall

Apart from being an obvious health hazard, black mold sitting on drywall is unsightly and can indicate a water leak or indoor humidity problem. Here we will discuss methods for removing black mold from both finished and unfinished drywall. However, before taking any such steps, the cause of the problem first needs to be addressed.

Topics covered
  • What causes mold on drywall
  • Safety measures
  • Remove black mold from finished drywall
  • Remove black mold from unfinished drywall
  • Preventive measures

What causes mold on drywall

Before removing mold from drywall, it would be best first to find out what caused it. The most common culprits are excessive indoor humidity levels, which is an easy fix or a leak/unseen water damage, most often originating from behind the wall or from above in the ceiling. If you suspect a water leak use a moisture meter to check behind the wall of the affected area.

Only after first taking care of the cause can you safely start the cleaning process without having to worry about whether or not the problem will return.


Safety measures

Before we remove mold from drywall, we will first have to make sure that we have the correct safety gear and know the proper safety protocols. Also, if the problem covers a large area then it would be better to get a mold remediation company to come do the removal for you.

Respirator: Mold spores are likely to be released into the air when handling the drywall, so wear an N-95 respirator mask to prevent breathing them in.

Windows: Open some windows in the room to get some fresh, clean air circulating.

Clothes: Wear clothes you can immediately throw into the wash once you are done cleaning because spores can easily stick to clothing.

Rubber gloves: Mold spores can cause rashes when landing onto your skin, so be sure to wear a pair of protective rubber gloves.


How to remove black mold from finished drywall

Remove mold from finished drywall

The process behind removing mold from finished (painted) drywall is quick and easy compared to steps required for unfinished drywall. The coat of paint seals off all pores; therefore, any mold growth on your wall is merely sitting on the surface and can easily come off. The only choice you have to make in this regard is what type of cleaning agent to use. Here you will find a list of effective cleaning solutions, but for this example, we will use baking soda.

What you will need: A spray bottle, baking soda, white vinegar (optional), a soft brush, a dry towel and a vacuum cleaner (preferably a HEPA filtered vacuum).

1: Prepare the cleaning solution

As mentioned, we will be using baking soda in this example. Simply mix one part baking soda with five parts of water in a spray bottle. And although this cleaning solution works great on its own, you can also add some white vinegar to the mix for extra effectiveness.

2: Spray onto the problem area

Lightly spray the baking soda solution directly onto the affected areas and let it soak in for 10 to 15 minutes.

3: Gently scrub

Gently scrub the mold off from the drywall with a soft brush. You will notice it coming off easily.

4: Thoroughly dry

Since water or humidity caused the problem in the first place, it would be wise not to leave the wall wet. Dry the cleaned area off with a towel or cloth. You could also let an electrical fan blow onto it for a few minutes.

5: Vacuum

As an extra precautionary step, vacuum the surrounding areas to get rid of any potential spores. A HEPA filtered vacuum cleaner would be ideal in this situation.


How to remove black mold from unfinished drywall

Remove mold from unfinished drywall

Fixing a mold problem on unpainted drywall will take considerably longer and is more labor intensive. There will be no actual cleaning involved – instead, the moldy section will be cut out and replaced. If you are unable to do this, then its recommended you employ the services of a contractor.

What you will need: Plastic sheets, a pencil, a utility knife, some sandpaper, a new piece of drywall, some drywall compound, and a vacuum cleaner (preferably a HEPA filtered vacuum).

1: Cover the area

Since we will be disturbing mold during the removal process, we have to use plastic sheets to cover the surrounding areas. This is important since disturbing it could potentially release countless numbers of spores into the air. Also, ensure the room is well ventilated and wear a respirator mask.

2: Cut the drywall out

Carefully mark straight line squares with a pencil around the part you want removed. Once done, take a utility knife and carefully cut straight along the lines and remove the drywall section. Be careful where you place the cut-out piece as it does contain mold.

3: Vacuum

After safely disposing of the old wall section, throw the plastic sheets away and vacuum the entire area. It’s recommended you use a HEPA vacuum system, but if you do not have one, a regular vacuum is your next best bet.

4: Insert new section of drywall

Measure the square hole you made and cut a new piece according to the measurement. If you like, you could paint the backside of the new part with antimicrobial paint as an extra safety precaution because nothing is worse than mold that sits behind walls. Insert the new piece into the opening, but be sure it fits nice and tight with no gaps. Secure it into position with screws to the wood beam behind the wall.

5: Finishing touches

Apply some drywall compound around the edges of the new piece. This secures it into position and closes off any gaps and cracks. Allow 24 hours for the compound to dry before using sandpaper to carefully even off the edges. Done!


Preventive measures

Mold resistant drywall: Use mold-resistant drywall wherever possible. It costs a little bit more than the regular type and is not 100% foolproof, but it does drastically reduce the risk and can save you from a lot of problems later. They are available at most good hardware stores and even your local Home Depot.

Paint wall surfaces: Drywall has a porous surface, and this allows fungal roots to dig their way down. This is the reason why unpainted drywall has to be cut out and replaced whenever mold appears on it. To reduce the amount of work required, make sure it’s painted. That way, the pores are sealed, and whatever mold grows it can simply be washed off. You can even take it a step further and use a mold-resistant paint.

Indoor humidity: Consider investing in a good dehumidifier system to keep indoor humidity levels in check. This won’t only spare your walls from fungal growth but just about everything else too.

Moisture levels behind walls: In a lot of cases, the problem is a leak behind walls where it’s out of sight. Periodically check the moisture levels behind your walls with the help of a quality moisture detector.


More Information

The best moisture meters reviewed

How to remove mold from ceilings

How to protect drywall with mold resistant paint

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