I Finally Filled the Basement Crawlspace with Sand

Did you know that basement crawlspaces were a “thing”? They are. There are people around this world who deal exclusively with them and there are websites dedicated completely to them. I should know. I just ordered some specialized tape from one of these websites. Crawlspaces are a hot topic on Youtube as well because they go hand in hand with the ever-popular subject of home insulation and to a lesser degree, the semi-popular structure of the home.

Okay, here’s the deal – crawlspaces are disgusting areas of a house that no one ever wants to spend any significant length of time in. Because of this, they’re often neglected and aren’t set up properly. This is especially true for older houses that aren’t up to modern coding standards. Many basement crawlspaces are damp or downright wet places that are breeding grounds for mold and rot. If you don’t attend to an area in this type of condition, your house can collapse. It’s true. Forget about the mold for a minute – your house can actually collapse. It can rot away right under your feet.

So, what’s the primary cause of mold and rot in a crawlspace? Many people think it’s water that accumulates under a home in the winter and spring. Since water tables are usually elevated during these times of the year, houses that were built in locations that are prone to either flooding or lack of drainage can have more than a foot of water sitting down in the basement for months. The truth of the matter is, most of the damage is actually caused by condensation during the humid summer months. Crawlspaces are notoriously cool and when the humid air from outside flows into these cooler spaces, the humidity condenses on anything it can and simply soaks what it touches. Think about taking a cold can of soda from your refrigerator and leaving it on your countertop at noon in July. Within an hour, you’ll have a puddle of water surrounding that soda. Now think about humid air flowing into your cool crawlspace 24 hours a day all summer long, via a vent of some other sort of air gap. All that wood down there is getting soaked to the core. And the insidious thing is, you can’t even tell it’s happening because the wood looks and feels dry. You have to use a special tool to measure the moisture content of the wood.

Our house had two issues. First, because it sits low in a high water table location, the basement would fill with about a foot of water during the months of April and May. This was just a given and I let it happen. When we first moved here, I freaked out when I saw this and I tried to pump the water out with a sump pump. That stupid thing ran all day and all night for weeks until I realized that the effort was futile. The basement kept filling up to that level, so I unplugged the pump and let it sit. It’s been that way for years. When the ground thawed, the water disappeared until the next year.

The second issue we had down there was general condensation and moisture. Apparently, there were quite a few gaps in areas that there shouldn’t have been and those gaps were letting air in. I mentioned in a previous post that we have two areas of the cement block foundation that had missing cement blocks. One of these openings was under ground and the other had the dryer vent sticking through it. Neither were sealed and when I went into the crawlspace to inspect the area, I found sitting water directly surrounding both of these spots. Also, any copper pipes above those areas had water dripping from them. Condensation is real and it works fast. It can create a four inch deep puddle overnight.

Another area of condensation was the concrete walls of the foundation. Those are generally cooler than the outside temperature, so they’re always wet. The condensation combined with groundwater leaking through the porous concrete can do a lot of damage. And finally, the dirt floor of the crawlspace itself is just plain terrible. It’s wet when it seems dry. Water incessantly evaporates from it. The problem is, covering it with plastic to stop the evaporation does little if the other issues I discussed are still allowing groundwater and condensation to infiltrate the area under a house. It’s a real mess that needs to be tackled aggressively.

I knew a sump pump didn’t work. I actually had two of them down under and they both didn’t work. The only alternative I had was to fill the crawlspace in with some sort of medium to raise the floor above the top of the outside water table. Essentially, to fill in the pond. The problem with that was, I didn’t have the greatest entry points. I considered filling five gallon buckets with sand or gravel and walking them down into the basement for about a year. Then I thought better of it. If I had tried that, none of you would have ever heard from me again. I would have jumped off a cliff half way through.

After cutting that concrete from the back pool deck (read about that here), I decided the best way to go would be to fill the basement with sand by shoveling that sand through both of those missing cement block holes I mentioned above. It was a thought, but I had no idea what type of effort would be needed until I started doing it. So I ordered some sand.

I first ordered ten yards and when the guy delivered it to me, he said that he gave me 12. It was a lot of sand and it took me about a week and a half to shovel it into a wheelbarrow, walk it around to the back of the house, dump it next to that small opening and then shovel it into the hole. Then, when I couldn’t fit anymore in, which usually took about five wheelbarrow loads, I’d have to go down into the basement to spread it around. I have no idea how many loads I had to walk around to the back of the house, but it was a horrible experience. I felt weak, it was hot outside and it was backbreaking labor.

After I finished moving the first pile, I called the sand people back and had them deliver another one. In all, I had 24 yards of sand delivered and I shoveled it all into the wheelbarrow and then shoveled it through those holes in the foundation. It was hundreds of wheelbarrow loads and I got it all done in less than three weeks. There were times when I was out there in the dark, leaning against my shovel, wondering when I would fall over. I didn’t though and as I sit here today and write, the crawlspace is chock full of all that sand. I still can’t believe it. By the way, the reason I ordered sand was because it was cheap at $11 per yard and because it shoveled easily. It also packs well.

I think I raised the floor above the water table. Take a look.

I used to be able to squat down there. Now I have to crawl and my back scrapes up against the ceiling. That’s what I wanted. For a before-view of the area, check out these photos.

Filling In a Basement Crawl Space

I still can’t believe I fit 24 yards of material down in that basement. My initial estimate was for about eight yards. It’s always more than I think.

Now that the basement has been filled and the water table issue has been dealt with, I’m tackling the condensation problem. To do this, I’m going to, what they call, “encapsulate” the area. That means that I’m going to fill in any air gaps that exist in the entire basement and then line the walls with rigid foam insulation and the floor with plastic. I already sealed the two fill holes with four inches of insulation and some very messy looking spray foam. It may be messy looking, but it’s good and solid and no air is leaking through. I’ll trim that later.

Again, that’s four inches of foam, which will give me an r-value of 20.

As I was sealing these two openings, I noticed that I could see daylight coming through from under the sill plate all around the house. All of these small leaks combined would probably equal a decent amount of humid air leaking into the basement. Since I had some of that foam sealer left over and since I have an itchy trigger finger, I decided to use up the rest of the can, sealing some of these leaks. If you ever have to use that foam for any reason, I suggest that you wear some arm and hand protection. I got a little on my arm yesterday and the foam dried. I had to shave part of my arm last night to get it off. Don’t tell anyone. It’s embarrassing.

Here’s what an unsealed sill plate looks like.

And this is what a sill plate looks like after it’s been sealed with the foam sealer.

Since I ran out of foam, I went back down today with four tubes of siliconized caulk and finished the job. I went through everything with a fine toothed comb, so I know it’s solid and there are no air infiltrations. The next step is to purchase about ten sheets of 2-inch thick rigid foam to attach to the walls using construction adhesive. This will make for a warmer basement in the winter and will create a vapor barrier to block all that moisture that comes through the walls from outside. It will also hide that cool cement surface so if any humid air does manage to get in, it won’t condense on it. I’ll tape any seams so the insulated surface is solid. After that, I’ll cover the floor with 6-mil plastic sheeting (on top of the existing plastic) and then tape that plastic to the insulation on the walls. Doing this will seal the area and no moisture from the floor or walls will be able to permeate the airspace. As a matter of fact, just by sealing the sill plate and the missing cement block areas, I can feel it drying out a bit down there. It’s incredible.

I’ll have to go to the store to get the insulation. That will cost about $30 per sheet. I ordered 12 10-ounce tubes of construction adhesive for about $56 two days ago. I also ordered a 10’x100′ sheet of 6-mil plastic for about $52, as well as a 4″x180′ foot roll of special “crawlspace” tape for about $80. Actually, it’s a 3-roll pack and it allegedly sticks to anything.

As for moving the sand around the crawlspace, most of it was straightforward. I threw each shovel full and eventually most of the basement was even. For the areas I couldn’t reach with my throwing, I built a sled to help out. I purchased a hard plastic tub from Tractor Supply as well as a pulley and some rope. I tied the rope to the tub and then snaked it through the pulley. I attached the pulley to the wall where I wanted to dump the sand. Then, I’d fill the tub, pull the rope and watch as the tub slide across the floor. Again, this was an awful experience that went on for far too long, but I got it done. I also feel a bit like a genius for coming up with the whole pulley idea.

After I encapsulate the basement, I’ll take some photos and post them here. If you have a crawlspace that’s wet, this is what you have to do to fix the situation. There’s no other alternative out there. Sump pumps can only do so much. Eventually, you’ll have to engage in some hard labor to get dry again.

Thanks for reading!