Q: Can you recommend a waterproof no-VOC paint or coating for a bathroom? I am looking for a waterproof paint to use instead of using greenboard in the bath/shower room.
Asked by Rick
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Answered by Rick Goyette, Emerald Dream Builders
Bath-shower specifications that mitigate moisture issues such as rot and mold are extremely important to maintaining durability and indoor air quality.
I have a solution that will work as an alternative to greenboard for your bathroom project. First, the most important consideration for a green bathroom project is to address ventilation. There are four necessary conditions for mold to grow:
- A mold spore
- Mold food
Of these conditions the easiest one to control is moisture. Ironically enough, the best method for controlling moisture is to ensure the space is ventilated to the exterior of your home.
- I recommend a bathroom fan with a humidity sensor to ensure it runs at proper intervals to abate moisture.
- I've had good luck with the Broan QTRE100S. Some fans do not maintain the listed cfm rating but this one has always passed inspection on my projects.
Now that ventilation has been addressed, let's review some specifications that provide durability and reduce the opportunity for mold growth.
Removing mold food
Assuming your bathroom is gutted to the studs or is in the process of being constructed, you can select a cement wallboard to cover the walls and ceiling of the room.
- This can be considerably more expensive than drywall (greenboard or other). However, by choosing a cement board you eliminate the food source on the walls and ceiling.
- At a minimum, you should use cement board on the wet areas of the shower and tub surround. I have used cement board for the entire bath with great success.
- Some popular wall board brands are Durock, Hardiebacker, and Wonderboard.
If you choose to cover the walls and ceiling with a cement board, I would recommend using fiberglass tape and a pure (not modified) thin-set to smooth the joints. The shower and bath areas should be tiled over a water mitigation system such as the Schluter system.
At this point, you will be left with fewer finishing options for the remainder of the bathroom. The key to this specification addresses the heart of your question -- when you inquire about a no-VOC paint or coating.
American Clay plaster is a natural coating of clay plaster that can be used in lieu of paint over your cement wallboard for the remaining areas of your bathroom (not to be used in the shower where it comes in direct contact with water).
- It is a distinct look that provides an alternative to paint, can be used on the walls and ceiling, and can accommodate any look and style in your home.
- There are several benefits to this product; for more information, have a look at their website.
(Image: The Wren's Nest Blog)