Home & Garden Columns

About the House: On the Case of House Mold

By Matt Cantor
Friday June 02, 2006

It never ceases to amaze me what madness the media and the legal community have created out of a little thing like mold. 

It happened with asbestos about 25 years ago and, although that has calmed down a great deal, there are still companies making millions removing what is most likely not going to hurt you if you leave it where it is. 

These are, of course, hot button issues because for every 1,000 cases of not mattering very much, you can always find one that might be a real case. And so we all suffer for a lack of understanding and good shared knowledge about the subject. 

Molds are funguses. They are part of our world, they’re literally everywhere we go and on almost every surface in nature. They are part of what makes the biosphere operate. Without funguses, bacteria and insects (FBI), we would have no breakdown of organic matter and no transformation into new life (including the produce at the store, the fish in the sea, you and me). 

Molds are also part of our intimate world. They’re not just outside the door, they’re in the pizza, the brie and some less common foods like tempeh and the meat substitute quorn. 

Without mold, there’s no penicillin. In short, we eat mold, we breath it and it lives in our shower. Additionally, mold’s first cousin, the mushroom, is on the diet for most folks and, if properly chosen, proves quite safe. 

For most of us and under the majority of conditions, molds do very little harm to us. When we take a walk in the woods we are surrounded by molds which are releasing their spores (to give birth to more of the little wonders) into the air. 

The problem with mold in the home is almost (I said almost) entirely a matter of moisture. For homes that have moisture problems, mold is a real issue. But, then again, moisture would be a problem if there were no molds at all. 

If you have high humidity in your home a wide range of funguses, including those that have no interest in human beings, can do quite a bit of damage to the wooden (and wood pulp) parts of your home. 

Those oft-seen pest reports are, locally, mostly about fungal damage and usually not so much about the work of insects. Again, this is invariably about water or elevated humidity levels in the home. 

There is one fabulous exception to this that we’re not seeing too much in this area but has done some major damage to houses in Southern California. That would be poria incrassata which brings it’s own water with it (eek) and can, thereby, consume lots of wood when no leaks exist to wet the wood. We don’t have much of it up here so don’t freak. 

But back to the main point; that molds (again, a subset of the funguses) are rarely found in large growing colonies except where a good source of moisture is present. In other words, when the inside of the house is leaking. There are mold problems in houses that have competent roofs and walls but which have basements which flood or weep copiously. 

There are houses that have mold in closets because the overall humidity in the house is high. There are houses where mold is growing in lots of places because it’s either raining inside the walls or the roof. Or when there is a source of water below and very low porosity through the structure. The last case is more common in newer homes than in old ones. 

We’ve begun, in recent years, to build houses that are so tight that they’re literally pressure tested before they can pass muster. Our local housing stock is mostly very porous and so we lose lots of heat and pay high bills. But, we also don’t have the same kind of problems with fungi.  

I’ve been in a few houses that clearly had serious mold/fungus problems and they were invariably ones that had a moisture problem that would require addressing even if there were no concern about the dreaded M-word. It’s not OK to have the inside of the house be damp, is it? Well, I suppose if you’re Newt-Man it would be a good thing but I don’t have a big N on my spandex wrapped chest and so, like most folks I will call for help if the inside of the house gets wet. 

Here are a few things you can do if you believe you have mold in your home. First, if you’re getting sick, talk to a doctor. If you have good reason to believe it has to do with where you’re living, get out. This will do two things. 

First, it may help you get better, and second, it will act as a control in an experiment, helping you to understand what may be making you ill. You’ll have eliminated one variable from the equation and can run the experiment again (i.e. stay alive). 

Second thing. Find and address sources of wetness. Molds and funguses are found in homes as a result of leaks or of elevated humidity due to inadequate isolation or ventilation of moisture sources, such as wet crawlspaces, basement or gas appliances (gas appliances give off huge amount of water vapor).  

Some of the simple things that CAN but do not always work to address the latter include: the use of vapor barriers (plastic sheeting over damp soil), sump pumps, drainage systems, diverting gutter downspout water away from the house and increased crawlspace ventilation (which allows moisture to reach equilibrium with the outdoors through evaporation). 

For many houses I see, a vapor barrier combined with a small amount of ventilation (1 square foot per 1,500 square feet) should be sufficient, although I prefer to see 5-10 times this amount of ventilation. One square foot per 150 square feet of crawlspace is the basic code requirement and I virtually never see it met. I also see quite a few houses that clearly have elevated moisture levels. 

A hygrometer can be bought from any cigar store (I’ve gotten them on ebay) and can be hung inside the house to monitor moisture levels. The only problem with this method is that various molds and fungi propagate at a wide range of moisture levels (some only grow at 100 percent!) so once again, we’re back to basics. 

Keep the house as dry as possible and if you have allergies, try to keep it bone dry. If you have significant allergies to mold, my person feeling is that you should never try to live in an environment that has any significant moisture level and that will exclude many places. 

I, for example, don’t eat any dairy. Life’s throws us all curve balls but I’m a happier guy when I don’t eat cheese. So I’d suggest that you grin and bear it and stay away from clammy housing if you know you react poorly to mold. 

If your landlord has a damp house and you have good reason to believe you’re getting sick from it, move out. If you’re child seems to be getting sick from your damp rental, move out and if it’s your house, well, it’s time to find the window leak, the roof leak or the moisture in the basement.  

The important thing is to keep everything as dry as possible, starting with your sense of humor. 



Got a question about home repairs and inspections? Send them to Matt Cantor, in care of East Bay Real Estate, at realestate@berkeleydailyplanet.com.