Lime In Crawl Space

Lime In Crawl Space

Lime In Crawl Space

I have noticed many websites recommending to utilize lime in crawl space. Then, I speak with a vapor barrier manufacturer that recommends in his customer instructions to spray lime powder to facilitate the absorption of humidity and bad odors coming from holes inside the foundation, animals burrowing, or simply the bad smell o mold.  

When you introduce lime in crawl space, then it is quite a problem to actually go down and crawl inside the crawl space having your hands and nose covered. You have to always cover your face and protect your hands after you apply lime in crawl space.

A solution can be to have a good encapsulation, even without external vents. Moisture will drop below the average range I recommend here. Install a dehumidifier, a sump pump and an antimicrobial poly barrier with a temperature gauge and a humidity gauge as well. Also, I would spray Boracare (ethylene glycol, known as uncolored anti-freeze) on the underside of your floorboards to prevent termites and other bugs: this procedure is called termite-bondand is sometimes included in termite control service contracts.

However, about termites and encapsulation, using encapsulation instead of lime in crawl space, let me tell you the following.

If you have termite insurance or a warranty as a part of termite control service contract, you should check the insurance policy or the aforementioned service contract because encapsulation process does not enable a physical termite inspection, thus voiding the warranty or extinguish the insurance policy terms. For this reason, encapsulation can only cover the ground and the blocks. All wood floor should remain exposed in order to supress humidity.

After the lime layer absorbs a certain quantity of moisture, it will saturate and will not absorb the excess quantities thereof.


The lime cuts the odor and helps to break down the organic matter in the soil. It is a recommended fix to a sewage leak.

One significant application of calcium hydroxide is as a flocculant, in water and sewage treatment. It forms a fluffy charged solid that aids in the removal of smaller particles from water, resulting in a clearer product. This application is enabled by the low cost and non-toxicity of calcium hydroxide. It is also used in fresh water treatment for raising the pH of the water so that the pipes won’t corrode where the base water is acidic. The reason is that it’s self regulating and does not raise the pH too much.

I see lime in crawlspaces all the time: usually under old rural farmhouses. Owners seem to think that the lime will absorb any water that gets in the crawlspace. All the lime does instead, is make a pasty mess. Of course the homeowner would be better off correcting the numerous grading and drainage issues I usually find at these homes. People also think that planting trees in a wet area of the yard will absorb all the water. It absorbs some water, but once again it is usually a grading and drainage problem. I suggest to plant some trees in areas of your garden or landscape whan I discuss solutions to deal with the hydrostatic pressure in the basement.

Lime dust, lime powder, hydrated lime- these are all names for the chemical compound calcium hydroxide.  

Calcium hydroxide is used in a wide range of industrial applications: removing impurities from steel during manufacturing, producing mortar and cement, and treating sewage and petroleum waste.  It is, in fact, an extremely useful chemical product- just not for residential use.


On paper, lime seems like a logical option.  It can absorb moisture, which is why it’s used for treating waste and spilled chemicals.  And it could be used for pest control, because it’s fatal if ingested.  However, there are significant downsides to using it for either of these purposes.

1. Lime Can Only Absorb a Limited Amount of Moisture

You can’t expect a one-time application of powder to cope with ongoing water seepage.  It’s a “one-time” application because it will only work for one instance, like a spill or sewage leak that is being repaired.  Once the lime has done its job, it needs to be removed and disposed of in an environmentally safe manner.

If you have water getting into your crawl space, you need to determine the source and take the appropriate action.  A crack in your foundation should be repaired, not only to stop water but to preserve your foundation’s stability. 

If the gutters discharge close to the property, what is usually the case I see, perform downspout extensions. Extending the downspouts is something simple that you can do yourself.

Furthermore, when the waterflow comes through the soil of the crawlspace, you should be installing water drainage like we have explained when discussing flooded crawlspaces right here or what we have studied here when you see stagnant water after a heavy rain.

(Downspout extensions are a DIY we fully endorse!)  And if the water is coming up through the dirt “floor” of your crawl space?  It’s time to consider installing water drainage.  

2. Lime is Hazardous to the Touch

I mentioned earlier that lime could be used as pest control; that does not mean it should be.  Lime can be fatal if ingested, and that means to any animal- including pets and people.  While it isn’t particularly likely that you or Fido will eat lime powder, it doesn’t have to be ingested to harm you.

Skin exposure to lime can cause severe burns and skin corrosion.  If particles of calcium hydroxide get into your eyes, you can suffer tissue damage and blindness.  Anyone who is going to work with the lime substance should be properly outfitted with the appropriate PPE (personal protective equipment).  This PPE includes chemically resistant clothing, gloves, boots, and safety goggles. 

This means you are risking your safety if you work with lime powder.  And any service technician or contractor who needs to access your crawl space is also at risk.  These could be plumbers, electricians, or contractors (like our project manager).  This could easily become a legal issue- especially if you don’t disclose it to the technician in advance.   And if you do disclose it, they may refuse to do the work or charge you additional fees for acquiring the necessary PPE. 


If lime dust can cause burns and tissue damage on contact, imagine what happens if it’s inhaled!  Inhalation of calcium hydroxide can cause burns in the throat and esophagus, swelling and irritated tissue, and difficulty breathing.  

The air quality of the crawl space influences the air quality of the living quarters as the airflow will always be moving upwards.

The lime dust you’ve spread on the ground under your house could be stirred up by a number of things: the HVAC unit kicking on, wind gusts getting through cracks, even animals or contractors accessing the crawl space.  

Once those lime particles are airborne, what’s keeping them from getting into your ventilation system? Your HVAC pulls air in, heats/cools it, and blows it into your home.  Maybe it’s not letting a large amount of lime dust in, but how much does it take to irritate your eyes? Or cause lung irritation in someone with asthma?  Given how many other pollutants and allergens are already in our environment, do you really want to add a harmful substance to the mix?  


Question: Is there any benefit to using lime in a crawlspace other than for odors? Is it a deterrent for spiders, snakes, mice, etc.? What type of lime is used? If it goes under the vapor barrier, won’t the moisture from the ground mix with it and produce heat that will ruin the vapor barrier’s effectiveness?

Answer: Crawlspace odors are usually caused by a leaky sewer pipe, damp fiberglass insulation, dead animals, mold, cardboard and debris, to name a few possibilities.

Lime powder, found at home stores, garden centers and some pet stores, can be used to absorb strong odors that might be coming from a crawlspace. An additional benefit of lime powder is that it dehydrates and suffocates insects that come into contact with the powdered form of lime.

Calcium hypochlorite can also be used as a disinfectant, but this form of lime, found at pool dealers, can become unstable when exposed to air and moisture. Calcium hypochlorite lime creates heat as it off-gases chlorine gas, which may not be suitable when confined to a crawlspace.

Spread the powdered lime on top of the existing vapor barrier, adding more powder after a few days if the odors persist. Once the odors have dissipated, remove all the old vapor barrier and lime. Remove all debris and vegetation and then install a new 6-mil-or-thicker black or clear vapor barrier, securing it to the crawl floor with bricks, stones or vapor-barrier pins.

You should also consider a product called CleanSpace, which is a 20-mil-thick white liner that encapsulates the floors and walls of a crawlspace foundation, eliminating virtually all possibilities of ground moisture reaching the floor system of the home.

Where there is no moisture, you have essentially eliminated all possibilities of decay and odors. It is imperative that a crawlspace have a secure, insulated access door to prevent pest entry and to conserve energy.


Lime In Crawl Space For Raw Sewage

I have explained how to use lime for raw sewage in this article. It would be one of the few exceptions where lime in crawl space could be uutilized, as the controlled risks are very low in comparison with the benefits of the treatment proposed.

The sewage and contaminated soils under the home should be removed by professionals who have the experience and proper equipment to work in such hazardous conditions.

Once the area has been decontaminated, a layer of 6-mil plastic vapor barrier can be installed.

If you are a determined DIYer, though, make sure you wear a long-sleeved shirt, rubber gloves, eye protection and a half-facemask respirator.

Use a sled or piece of plywood as a skid with a rope attached so that a helper can pull the buckets of soil out and a second rope attached so that you can retrieve the empty buckets without having to go in and out with each load.

Once the area has been cleaned, spread hydrated lime to reduce the odors and to dry the soils. Cover the entire dirt floor with a 6-mil vapor barrier. Discard the rubber gloves, clean your tools with a mild bleach-and-water solution and launder your work clothes immediately.

In a basement, use a wet/dry vacuum to clean the spill, emptying the canister into a toilet. Any contaminated material including carpeting and wall coverings should be discarded. Place smaller items in plastic garbage bags and set outside for proper disposal.

Woodwork and wood furniture can be washed using 1 cup household bleach to 1 gallon of warm water. Venting the basement using fans will help to remove odors and speed the drying process.

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BY M. Kogan

Hello, I am Marcio. I am an architect and designer, alma mater is Mackenzie. Retired in theory, but an architect never retires completely. Along with architectural projects, I am a filmmaker and have completed some short documentaries. Filmmaking and design are my passions. In HomeQN I write about home decoration and foundations. The goal is to teach homeowners to DYI as much as possible, and when this is not possible, enable them through knowledge, to evaluate service quotations and choose the best service technicians.

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