Here is the honest answer up front. You can do DIY crawl space encapsulation if your crawl space is dry, has room to move, and has no mold or rotten wood. If it has standing water, mold, or soft joists, those need fixing first, and usually by a pro.
That second group is bigger than most people think, especially here. North Georgia summers are hot and sticky, and our red clay holds water against the foundation for weeks after a storm. A lot of the crawl spaces we open in Gainesville and Woodstock need drainage work before any liner goes down.
If yours passes the check below, DIY crawl space encapsulation work is very doable. It is hard on the knees, but doable. This guide walks you through it.
Can You Encapsulate Your Own Crawl Space?
“Can I encapsulate my own crawl space?” We hear that question a lot. Grab a flashlight and look. You want a yes on all four of these:
- Dry floor: No standing water, no mud, no wet patches days after rain.
- No mold: No fuzzy white, green, or black growth on the joists or subfloor.
- Solid wood: Push a screwdriver into a few joists near the outside walls. It should not sink in. Floors upstairs should not sag or bounce.
- Room to work: At least 18 inches between the dirt and the bottom of the joists. Less than that and you will be lying flat for days.
Any “no” means stop here. Sealing a crawl space with one of these problems locks the problem in. Get an inspection first, then decide.
Still not sure encapsulation is even the right move for your house? Our guide on crawl space encapsulation worth it covers that decision. This post is about doing the work.
Crawl Space Encapsulation Materials You Need
Here are the DIY crawl space encapsulation materials for a full job. Buy a little extra liner and tape. You will use it.
| Material | What it does | What to look for |
|---|---|---|
| Floor and wall liner | Covers the dirt and the walls so ground moisture stays out | Reinforced polyethylene, 12 to 20 mil. Thicker holds up better if you crawl on it. |
| Seam tape | Seals the overlaps between liner sheets | Tape made for crawl space liners, not duct tape. |
| Mechanical fasteners | Hold the liner to the walls and piers | Plastic pins or termination strips made for masonry. |
| Sealant | Seals the top edge of the liner and small gaps | Butyl or polyurethane sealant that sticks to concrete and plastic. |
| Foam board | Insulates the foundation walls and rim joists | Rigid foam board rated for crawl spaces. |
| Vent covers | Closes off the foundation vents | Covers that seal airtight; foam board cut to fit also works. |
| Dehumidifier | Removes moisture once the space is sealed | A unit built for crawl spaces, not a household model. |
For how each piece fits into the full system, see encapsulated vs sealed crawl space.
Is a Crawl Space Encapsulation Kit Worth Using?
A crawl space encapsulation kit is one package that has the liner, tape, and fasteners. This will come in handy if you do not wish to do any shopping yourself. However, take time to look at the packaging.
Kits normally have the liner, tape, and fasteners. However, kits may not have a dehumidifier, wall insulation, vent covers, or sealant. Also, some kits may have liners that are not thick enough for your crawl space.
Therefore, a kit is only the beginning, not the end. You need to first measure your crawl space – both floor and walls.
How to Encapsulate a Crawl Space (Step by Step)
This is the correct process to follow when encapsulating a crawl space. You should not hop from one step to another. Each step is dependent on the previous step.
Before starting: Put on a respirator or dust mask, gloves, kneepads, and long-sleeve shirts. Old insulation and dust are very dirty. You need a light and should be extra careful around wires and pipes.
Plan your project: Calculate the floor area and how much height there is at the walls before adding it to the liner size. Draw out your crawl space, taking note of all piers, pipes, and the access door.
Do it in parts, house by house, and do not crawl over your own job. Also, make sure that the people at home know where you are headed.
- Fix water and drainage first: Gutters, downspouts, grading, and any leaks come before any liner. If water still gets in, the liner just traps it. See how to fix water before encapsulating.
- Clear debris and old insulation: Remove any loose debris such as rocks, wood bits, and junk. Any sharp items left lying around on the dirt floor will puncture the liner later. Remove any previous insulation, typically old fiberglass, between the joists and dispose of it in bags. Typically it’s wet anyway.
- Cover all the foundation vents and the rim joist area: First, ensure that every single foundation vent is sealed off from any leaks, then seal off the rim joist (which is the wooden area surrounding the top of the foundation walls) with the use of foam board.
- Insulate the walls: Fasten foam board to the inside of the foundation walls. Our post on crawl space wall insulation explains which materials hold up best.
- Liner flooring and walls: Place the liner across the entire floor and the wall foundation. All seams must be overlapped by a minimum of 6 inches and taped together. The liner should then be pinned against the wall foundation and sealed from the top side. Start from the most remote corner and work your way out to the door.
- Leave a termite inspection gap: Leave about 3 inches of wall and floor space uncovered near the wood sill plate. The termite inspector needs this gap in order to detect mud tunnels on this wood. Otherwise, this could void the termite bond.
- Seal piers and penetrations: Wrap each pier with liner and tape it to the floor sheet, as well as cutting slits in the liner for any pipes, posts, and electrical lines and taping the slit edges shut. Even small holes add up quickly.
- Install and drain the dehumidifier: Once the vents are closed, a sealed crawl space needs a dehumidifier or conditioned air, or moisture builds up fast. Set the unit on the liner and run its drain line to a sump or outside. Our crawl space dehumidifier post covers sizing and humidity levels.
After You Finish: What to Check
The job is not done the day you crawl out. A new liner shows its weak spots over the first few months.
- After the next big rain: Look for water sitting on top of the liner. Water on top means it is getting in from somewhere, usually a wall, a vent, or a pier.
- Seams and edges: Run your hand along a few taped seams and the top edge on the walls. Tape that is lifted in the heat needs pressing down or replacing.
- The dehumidifier: Make sure it runs, and the drain line is not clogged or kinked.
- After any plumber or HVAC visit: Workers crawl across the liner and sometimes cut it. Check for tears and tape them.
- The termite gap: Keep that bare strip clear. Do not let stored boxes or new foam cover it.
Small fixes now keep a DIY job working for years.
DIY Vapor Barrier vs Full Encapsulation
Not every crawl space needs the full system. Sometimes a floor barrier is enough.
DIY Crawl Space Vapor Barrier: When the Floor Alone Is Enough
The DIY solution includes installing a vapor barrier only in the dirt area. The vents stay open, there’s no wall insulation installed, and there’s no dehumidifier used either. It’s easier to install, requiring less time, often just a weekend.
It will work if the crawl space doesn’t get humid in the summertime, there is no HVAC system or ducts located under the floor, and your drainage system works properly, diverting the moisture from the foundation area. If there is moisture inside the crawl space in July and there is condensation on pipes, the floor vapor barrier won’t be enough.
For more on what a floor barrier does for your home, see our post on crawl space vapor barrier installation.
Common DIY Encapsulation Mistakes
The vast majority of the DIY crawl space encapsulation issues we fix occur because of:
- Sealing over water or active mold: The barrier covers the problem, while moisture is damaging the wood beneath.
- Closing vents without a dehumidifier: Once the vents are sealed, the humidity level increases until August hits.
- Using thin liners: Cheap plastic may tear on first use, allowing moisture to enter.
- Termite inspection loophole: Liners are installed directly against the sill plate, preventing termite tubes from being seen and invalidating your termite bond.
- Lack of permits: Installation of electrical circuits for your dehumidifier or drainage systems requires permits. This is not consistent throughout all counties, so consult with your local authorities.
When to Call a Professional?
If you see any of the following issues, call a pro rather than doing it yourself:
- Standing water or damp soil even when it rains
- Mold in the joists or subfloor
- Rotten or soft wood, or sagging floors upstairs
- Fewer than 18 inches of clearance
- HVAC systems or ducts in your crawl space
- Any water and mold issues must be fixed before the liner can be installed.
Rotten wood and sagging floors are structural issues that plastic cannot fix. The ducts will change the layout requirements of the area. You may want to read our blog post about crawl space repairs vs encapsulation.
DIY Crawl Space Encapsulation FAQs
Can I encapsulate my own crawl space?
Yes, provided that it is dry, clean of mold or decay, and there is 18 inches or more of space. Expect a few long weekends for your task. If you have water, mold, or rotten wood, address this first.
What thickness vapor barrier should I use for encapsulation?
Choose a reinforced vapor barrier liner between 12 and 20 mil thick. Anything thinner will easily tear when walked on or moved around by knees or equipment. For storing things down in the crawlspace and moving around, go for a 20 mil liner.
Do I need a permit to encapsulate a crawl space in Georgia?
This depends on your county and the changes you make. Putting the vapor barrier liner alone will not require any permit, but installation of an electrical circuit or new drainage system may require one. Check with your county building office.
What is the hardest part of DIY encapsulation?
Proper sealing of the vapor barrier around the piers, pipes, and walls. A flat surface will go quickly. The cutting and taping around the piers and pipes take up to 80 percent of the time.
Get a Free Crawl Space Inspection Before You Start
Not sure your crawl space passes the check? Let us take a look first. Tri-State Waterproofing has worked under homes across Gainesville, Woodstock, and North Georgia for over 20 years. We will tell you if it is a good DIY job, what to fix first, and what to leave to a pro. Sometimes the answer is “you’ve got this, just fix that downspout first.”
Book a free crawl space inspection or call (770) 869-7888.
