A few thoughts on crawl spaces

Don’t you just love your crawl space? Those dangling cobwebs,

looking pipes and wires, inexplicable puddles, and that wonderful

smell? And that is just the kind of crawl space you can get a look

into or (heaven forbid) actually enter! Maybe you’re lucky enough to have

one that has little or no access, and you can let your imagination eagerly

fill in all those cobwebby details.

Dave has a re-occurring dream about the perfect crawl space (sad, but true).

The air is dry and there is no falling insulation. There are plenty of lights and the smooth, dry floor is covered with impermeable plastic or concrete, making movement easy. All the wires, pipes and ducts are well fastened and out of the way. There’s no mold, insects, critters, puddles, cobwebs, dead cats, snakes, escaped convicts, or Jimmy Hoffa.

Alas, it’s just a dream.

Very few crawl spaces are dreamlike — more are like nightmares —and most are downright nasty. You will often see the terms “healthy” and “unhealthy” connected to crawl space information, and this is apt, because both the building’s health and yours can be affected by the conditions in a crawl space.

Trapped moisture

Trapped moisture is a key issue when it comes to

building health. It causes rot, the growth of mold

and bacteria, rust, failing finishes and equipment.

One way to eliminate much of the moisture in your

home is by not breathing, cooking, bathing, or

washing and drying your clothes. But then that kind

of ruins the point of having a home.

Since the building is already working to get rid of

the moisture being created by you and your family,

it doesn’t need the extra load of moisture that often

rises out of an unhealthy crawl space. The attic

becomes the final destination for all of this moisture, and Harley will often find moldy, deteriorated roof sheathing as a result.

To prevent mold, rust and other damages, the walls and floor of a crawl space should be insulated so that moisture can’t get inside. Gutters and foundation drains should direct water away from the outside walls, and a moisture barrier should cover the entire floor and walls of the crawl space. If the water table rises, or regular seepage occurs, a sump pump should drain the entire crawl space if possible, not just one corner.


Ventilation of the crawl space is an issue of some debate these days. The original thinking was that air should be allowed to change out with natural cross-ventilation through code-required openings or vents, and the moisture in the air would get removed in the process. It’s now argued that the passive vents don’t vent, but merely let in warm moist air in the summer —which condenses, contributing to problems — and freezing air in the winter — which puts plumbing at risk.

One corrective strategy involves humidity-controlled power vents that come on only when conditions are dryer outside than inside. Another alternative strategy is to completely seal off the crawl space from air movement and moisture, and moderately heat the space.


Insulation in a crawl space is another area in which you can use several strategies.

What we often see is the floor above insulated with incorrectly installed (paper facing down) fiberglass overhead, between the joists, with nothing but rusting staples and spit to hold it up.

                                                                    Imagine the job of installing this insulation: you are on

                                                                    your back in a cold, damp, tight, dark space, working

                                                                    overhead with dust and debris falling into your eyes.

                                                                    It’s rare that the thorough work of a craftsman is

                                                                    observed. As fasteners, we’ve seen everything from

                                                                    chicken wire, Tyvek, plastic sheet, to the metal

                                                                    lithography sheets from a 1954 Ithaca Journal. Most of

                                                                    the time, there are no fasteners, and the insulation is

                                                                    falling down, often damp, and at times becoming a

                                                                    home to mice and rats.

                                                                    The other less common, but more modern method is to

                                                                    insulate the walls if possible, leaving the joists open

                                                                    and clear, involving much less material. The space

                                                                    require minimal heat and would not have vents

                                                                    to let in cold air.

Like so many things, if you research the subject of crawl space science, you will undoubtedly come up with conflicting information about how to deal with the conditions in crawl spaces, their maintenance and improvement. Every house is different, with its own array of strategies and solutions.

There are companies who specialize in crawl space improvement and troubleshooting. If your crawl space environment is relatively dry, with no damaged framing, and insulation is in good shape, there’s no need to make any drastic changes. But if there is degrading wood, mold in the crawl space or attic, cold floors, rapidly deteriorating equipment, moist soil or standing water anywhere, you may want to consider taking steps to improve the environment in your crawl space.

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Campbell and Davies LLC    201 Dey St Suite 211 Ithaca, NY 14850   

607 216 0036    fax 607 216 0402   campbellanddavies@yahoo.com   


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