Everything You Should Know About Your Crawl Space but Are Afraid to Ask

Adulting is not easy, but if you feel like you have no idea what you’re doing, don’t worry — you’re not alone. Literally no one feels like a real adult. We’re all out here pretending as hard as we can, secretly convinced that everyone else is just effortlessly adulting all over the place while we’re at home Googling things like “what is escrow” and “how replace ceiling fan not kill self.”

One thing is for sure: If your sense of adulthood and maturity is fragile, do not under any circumstances purchase a house. It will be a massive learning experience, some of which will be very unpleasant and/or extremely expensive. And there’s one aspect of some houses that confounds and alarms just about everybody: the crawl space.

If you don’t know what a crawl space is, rest easy: That means you probably don’t have one. Because if you do, you will be painfully aware of the fact that there’s a dark, damp alien landscape under your house. If you do have a crawl space and you’ve been pretending otherwise because you’re afraid of what you’ll learn, here’s everything you always wanted to know but were afraid to ask.

What is a crawl space?

First of all: What is that hellgate under your house? It’s not just a short basement. While basements can be pretty shallow and claustrophobic, the main thing that distinguishes a basement from a crawl space is usability. If the space under your house is heated and insulated, it’s a basement. If not, it’s a crawl space. In other words, the key question is: Could you finish it so that a normal, well-adjusted person live in this space? If yes, it’s a basement.

Crawl spaces are called that for the obvious reason — they are typically only a few feet tall, and so anyone who enters must do two things: Abandon all hope, and also crawl everywhere. They often have dirt floors, and typically water and sewer lines and electrical wiring will run through them. Crawl spaces exist so your home’s first floor doesn’t sit directly on top of the dirt or concrete slab, which can cause moisture issues and make it harder to heat your home. One other major reason you might have a crawl space instead of a basement: Crawl spaces are cheaper to build.

How to maintain your crawl space

You might be tempted to assume that since you can’t do much with a thousand square feet of dirt floor, you don’t need to worry about your crawl space. Unfortunately, if you own that house you should absolutely worry about your crawl space. Here are a few things to consider.

Access

Getting into your crawl space isn’t important until you have a burst water pipe or a dead animal down there violently reminding you of its existence. It’s absolutely amazing how often people buy homes without realising there’s a crawl space under their feet — or how to access it. When my wife and I bought our home, it was two years before I discovered a trap door in the floor of one of our closets — a trap door that led down into a terrifying sort of anti-Narnia filled with debris and signs that something had been there recently.

So, make sure you know how you can get down there in case repairs are necessary (or an adventurous child goes spelunking and vanishes into some other dimension). Not all crawl spaces have a trap door — sometimes you literally have to crawl under your house from the outside. Which will definitely make you regret all those chilli cheeseburgers.

Moisture control

Crawl spaces exist to keep your house off the dirt, but if that dirt is damp, then the air is damp, too. And if the air is damp all the time, mould is going to start to grow down there. So you’re going to want to take steps.

Step one is to find out if your crawl space is ventilated or unventilated. A ventilated crawl space will literally have some openings to the outside that let in air. The idea is that moisture will evaporate instead of being trapped. An unventilated crawlspace will typically be insulated to some extent. Crawlspaces used to be routinely ventilated, but at some point, someone realised that all this really did was let in the weather — if it was damp outside, it was damp in your crawlspace. Some people have chosen to close up their crawl space vents as a result, as they arguably do more harm than good.

Look for problems

If this is your first time in your crawl space, look for the danger signs: Standing water is absolutely a problem you’re going to have to deal with. If it’s not a plumbing problem but seems like groundwater, call a plumber and install a sump pump. Look at your foundation — cracks should have you running to a foundation repair expert immediately.

Examine the floor joists above you — if they look like they’re sagging, or if you can easily penetrate them with a fingernail, you may have a rot problem. Visible mould (black speckles or white and fibrous) should be dealt with, as well. And if you see tiny piles of sawdust, you might have termites. Are we enjoying our crawl space experience yet?

Vapour barriers

If the floor of the crawl space is dirt, you’ll want a vapour barrier. A vapour barrier sits on top of the floor and blocks moisture rising from the dirt, trapping it beneath before it can feed all those mould spores. A vapour barrier can be as simple as a thick sheet of plastic draped over the dirt or it can be an entire encapsulation, which typically uses a drainage mat and a thick plastic sheeting that wraps up onto the walls. Having some sort of vapour barrier is essential to keeping your crawl space relatively dry — the level of expense and effort needed is determined by how damp and humid your crawl space actually is. If the answer is “pretty humid” (you can buy monitors to keep track) you might also consider installing a dehumidifier down there.

You can also encapsulate using something like Neutocrete, which seals the dirt floor into something resembling a concrete slab. It can take some time to cure, but when it does, you can more easily and safely use your crawl space for storage.

Flooding

Your crawl space is, of course, the lowest part of your house. If the water table in your area rises, the first place it’s going to enter is your crawl space. Installing a sump pump is always a good idea if there’s any chance of that happening (and a simple water alarm can act as a warning in case that happens). You should also consider how you’ll pump out your crawl space if the power goes out since disastrous flooding and blackouts are often connected. Battery-powered backup pumps exist, as do hydropumps, which run off of your water pressure and thus need no electricity.

How to make a crawl space functional

If you’re thinking, gosh, I don’t have enough dark, damp space under my house, good news! You can often transform your crawl space into a usable basement. It’s not cheap, and it’s pretty disruptive, but if you absolutely need a man cave or space for your collection of Beanie Babies, it can be done. But proceed carefully: Digging out a crawl space might expose the footings of your home’s foundation, which can lead to huge problems, so consult with a wide variety of experts before even thinking about it.

If you get a handle on your crawl space’s moisture and humidity — and you’re reasonably sure there is no threat of flooding — you could also use your crawl space for storage. Measure how deep the space is, then look for sealable plastic containers that will fit down there (and will fit through whatever access you have). Think of it like the storage boxes you have under your bed or sofa, except under your house.

Depending on how much clearance you have, you might be able to install shelving suspended from the floor joists in a crawl space. Again, access will be a concern, but this has the advantage of keeping everything off the damp floor.

One thing to consider is that access is never easy in a crawl space, and retrieving your precious things might be a pain. Your best bet is to store the stuff you need to access only very, very rarely. Also, install some kind of light source — it could just be a simple clamp bulb that you attach to a joist, but trust me: Being able to see is essential, especially if you discover that your crawl space is some sort of House of Leaves situation and is actually much larger than is physically possible and you’ve been down there for six days and can’t find your way back.

Every house is a system of interconnected spaces, and your crawl space is an essential component. Better to get familiar with it now rather than during an emergency.