Ask the Architect

What’s that smell?


Q. Our house has a smell that, at times, is so bad that we can’t stay there. We’ve had plumbers look at the sewer pipes, put in special vents, and one guy put in a piping system with a fan to take methane from the ground from under the house. We have special vent fans going out the walls, but the smell hasn’t gone away. We’re so frustrated. Any ideas about what could cause this?

A. I was able to consult you on this problem, and there are many reasons for a home to have smells like this. The basic reason is biological if it isn’t chemical, so we first discussed cleaning solutions used and how often. If we can be sure the smell isn’t chemical, then we examine the ways nitrogen or sulfur is released, from bacterial sources to natural gas additives piped into your home for heating and cooking.

We walked all over the inside and outside, and I spotted many different sources. On the outside I began where I always do, at the highest point. Water and a food source are necessary for organisms to form mold communities, giving off nitrogen as they develop, so I look for water flow areas, such as the way the roof is pitched and rain gutter and downspout characteristics that allow for standing water or saturating materials.

What most people don’t generally notice is that pinholes in siding and around rain gutters and windows let rainwater soak into areas behind, holding water like a sponge. Leaky attics, through louvers and missing shingles or gaps around a roof vent, cause small drips to accumulate for months on the top side of sheetrock, until the soup that forms soaks through to reveal itself as ceiling stains. In the meantime, spores develop, which eat and defecate, giving off nitrogen.

Your home had closed exterior underside roof soffits, with no means to vent air, preventing moisture from evaporating before spores can use it to take a drink. Then there was the vent added on the waste pipe just after the sink trap inside a vanity. I didn’t smell anything there, but it was an odd solution to vent sewer gas under a sink, or anywhere inside a house, a violation that couldn’t pass a plumbing inspection.

Landscapers had piled 30 inches of earth against the foundation to create a landscaped planting bed. There didn’t appear to be waterproofing separating the soggy earth from the foundation and wood wall above, which leads to rotting materials that can also emit smells. But the No. 1 reason for smells may be the large indoor plant in a broken pot that had moss and organic matter. Keep track of when the smell appears, the weather, indoor humidity, the watering of the large plant, right after doing laundry, etc. It will be an ongoing investigation, and there may be several sources. Stay tuned.

© 2018 Monte Leeper. Readers are encouraged to send questions to, with “Herald question” in the subject line, or to Herald Homes, 2 Endo Blvd., Garden City, NY 11530, Attn: Monte Leeper, architect.