Crawl Space Vapor Barriers

Vapor barriers: a complete guide for Alabama homeowners


crawl space vapor barrier installed in crawl space on floors and walls with dehumidfier

Basement or crawl space encapsulation almost always involves the installation of vapor barrier materials designed to protect the interior of your home from unwanted moisture. These are most commonly made of wide sheets of polyethylene (plastic) film.

The film can me made in single or multiple layers and usually comes in industry standard thicknesses ranging from 6 mil, which is the entry-level minimum, to 90+ mil on the excessive end. For reference, a “mil” equals one-thousandth of an inch in thickness and material cost can run anywhere from fifteen cents to $1.50 per square foot.

When it comes to Vapor Barriers, how many mil is right for me?

Usually, the thicker the pricier, but not necessarily better. What some companies wont tell you is that maximum thickness isn’t necessarily the best value depending on your need for vapor and puncture resistance.

crawl space sheeting on rollWhile 90mil might sound appealing, there is often a point of diminishing return and value. We find that 12mil usually offers the best performance and value. Ultimately, this is a choice you’ll want to discuss with your installation expert.

Vapor barriers are basically ordinary sheet plastic that can keep most ground moisture out of your basement or crawl space, but even the most expensive varieties are not 100% effective.

Small amounts of moisture are bound to get through depending on weather and seasonal conditions, but the idea is to keep seepage to a safe minimum that can be managed. Some multi-layer vapor barriers may come with anti-microbial agents embedded between layers to help slow the development of rot and mold.

How vapor barriers work

crawl space moisture barrier under house installed on floors and columns

When warmer air in or under your home contacts colder air or surfaces, condensation can form, leading to accumulation of unwanted moisture. If it isn’t blocked or doesn’t have somewhere to go, this moisture can lead to the formation of mold or deterioration of wood structures and may also attract destructive pests to vulnerable parts of your home.

When installed correctly, engineered polyethylene provides a physical barrier that prevents unwanted moisture from entering your crawl space or basement. Vapor barriers (also known as crawl space moisture barriers) work best in combination with other preventive measures that may include proper interior and exterior drainage, up to date seals around doors, windows, and utility penetrations, or supplemental equipment like sump pumps and dehumidifiers.

After careful surface preparation, vapor barriers are installed on floors and walls with professional sealing materials to provide tight, even, and continuous encapsulation.

Why do I need a vapor barrier?

Nobody wants a moldy, dirty, nasty crawl space – right?

We’ve already touched on the three biggest threats to your home and your health that vapor barriers can help prevent – mold, rot, and pests that thrive in damp environments. You might think that these kinds of risks are confined to your basement or crawl space, but nearly half of the air on the ground floor of your house can come from your crawl space. It only takes a small amount of mold to aggravate respiratory issues and related health problems.

This kind of natural air circulation (referred to by engineers as the “stack effect” which works on the same principle as a chimney) can also cost you money. Vapor barriers, especially when supported by other water removal methods, can reduce the temperature difference between your floors and the crawl space or basement area. This can help to improve the stability and efficiency of your heating and cooling systems and lead to lower energy bills, which add up over time.

For smaller spaces where you don’t see signs of moisture damage, vapor barrier installation is a preventive maintenance job that can be handled by an ambitious do-it-yourselfer. The tools and materials are relatively easy to come by at consumer home improvement stores and the instructions you can find online are simple enough for a novice to follow. For larger or older homes, especially where any signs of moisture damage are present, you will want to work with a trustworthy basement or crawl space encapsulation expert who is knowledgeable about the preparation and remediation work that needs to be done before the barrier materials go in.

crawl space vapor barrier installed on floor and posts with sump pump

How to find the right basement and crawl space encapsulation partner

Crawl space encapsulation and general foundation restoration companies come in all shapes and sizes from solo contractors to huge regional companies. The best ones are experts in both structural issues and moisture, guarantee their work, provide detailed no-pressure estimates, and get consistently good reviews in the local area where they operate.

SouthernDry is a local family-owned business with a reputation for high quality, affordable work. In the unlikely event that you’re unhappy with a SouthernDry job, we’ll stick with you until the work is done to your satisfaction. We understand that your home is your most precious investment, and as we do with our own homes, our job is to help you protect it. We provide the most reliable foundation repair and restoration services anywhere in Alabama.

Unlike the typical experience with big box companies, you’re more than just a number to us. Our qualified Project Planner will talk you through the condition of your home and make sure you understand all of your restoration options. Our goal is to help you make a confident decision about the solution that is best for your home and budget. You’ll know your point of contact by name and will never get passed around by impersonal “customer service” reps.

If you’d like to know more about basement or crawl space encapsulation, we would be delighted to meet with you at no cost and provide you with a complete evaluation.

At SoDry – we love what we do and we have fun doing it

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