Skip to Content

Can Drylok Be Used as a Vapor Barrier

When building or remodeling a home, it’s important to consider the question of moisture. Specifically, how you protect your walls and insulation from moisture damage, which could affect the integrity of the structure and cost you packets of money in repairs and future prevention.

Drylok is an excellent waterproofing agent, so it stands to reason that it would be a good vapor barrier. In this article, we examine the effectiveness of Drylok as a vapor barrier, application, pros and cons, and the best products for use as vapor protection.

Drylok has waterproofing products that can be effectively used as vapor barriers in your basement. Drylok over-performs as a vapor barrier, protecting masonry walls from vapors and up to 10-15 PSI of water. Drylok has some products specifically designed as a vapor barriers.

Differences Between Waterproofing and Vapor Barriers

The main difference between waterproofing and vapor barriers is the degree to which water can enter through the material. Both are methods to prevent moisture from damaging your walls and home.

Waterproofing may not be necessary for all areas of a basement but instead in specific areas where water is leaking through. Vapor barriers are more likely to be applied or installed throughout a room to provide an efficient barrier.

1000sqft NASATECH (6 Mil Reinforced Scrim) White/Foil (Waterproof) Vapor Barrier 4ft x 250ft Encapsulation Pier Wrap Crawlspace (White/Foil) Solid Super Strong Reinforced Scrim

It’s important to remember that while waterproofing materials can be used as vapor barriers, vapor barriers are not all waterproof. Another important thing to note on this topic is that insulation cannot substitute for a vapor barrier in the fight against humidity. You can read why in my article: Will Insulating Basement Reduce Humidity.

Drylok Is an Effective Vapor Barrier

Drylok is a well-known waterproofing agent that can keep water from entering the pores of cement, masonry, and other foundation materials. It is effective for stopping vapor penetration due to its semi-impermeable (<1 perm rated) coating.

Drylok should be applied directly to concrete or masonry walls and floors. During home construction, it can be applied to either the interior or the exterior of the masonry walls in your basement.

Applying Drylok or another vapor barrier to the exterior of the wall is ideal in a warmer climate where humidity is higher outside. Applying Drylok on the internal side makes more sense when humidity is higher inside the house, so in colder, dryer places. A humid climate is just one of many reasons why basements get humid and require vapor barriers and waterproofing.

One potential drawback of using Drylok as a vapor barrier is that it must be applied to specific materials whereas plastic vapor barrier can be placed in variable positions within your home’s walls.

How to Apply Drylok as Vapor Barrier

Drylok is recommended for concrete, stucco, cement, masonry or brick walls, cinder, or porous terra cotta. However, we have some tips for applying Drylok to wood as well.  

Make sure your walls and floor are dry or mostly dry before applying the Drylok (it is a fairly similar process for most Drylok products, but you can check out each product’s application instructions on the website.

Prep the surface by cleaning it thoroughly using a wire brush. If there is any white build-up, called efflorescence, caused by salt deposits on the walls, it will need to be treated using either muriatic acid or Drylok Etch following the manufacturers’ instructions.

Drylok UGL White - Powder concrete and masonry etch & cleaner - Prepares interior/exterior masonry and concrete for waterproofing and painting - 12 ounce
  • MASONRY ETCH & CLEANER - Highly effective in etching. It removes unsightly efflorescence (salt deposits) as well as excess mortar.
  • USE - It is perfect for treating smooth concrete and condition galvanized surfaces prior to painting.
  • COVERAGE - 300 square feet per 12 ounce container when used as a cleaner. 150 square feet per 12 ounce container when used as an etch.
  • IDEAL - For removing efflorescence and excess mortar build-up on tile, galvanized metal, stone, concrete and brick

Last update on 2024-05-29 / Affiliate links / Images from Amazon Product Advertising API

Fill any cracks and holes in the wall’s surface. Make sure to seal the crack between the floor and the walls as well.

Apply Drylok using a roller, a sprayer (only some products can be sprayed on), or a brush. Drylok should be applied until the entire surface of the wall is covered. This should take a minimum of two coats.

Do I Still Need to Drylok the Walls?

If you use Drylok as a vapor barrier behind your masonry walls, you likely still have to apply Drylok to the masonry itself to prevent water absorption.

Drylok on exterior walls prevents moisture from entering from the outside. You will still need to Drylok the internal side of the masonry in order to prevent inside moisture from absorbing into and deteriorating the concrete.

The necessity of this depends on the type of room and the amount of moisture present inside and outside. In colder climates, inside waterproofing is more important because moisture will want to permeate outwards.

Vapor Barriers Cannot Substitute for Drylok

Vapor barriers do not have the ability to keep out walls of water and prevent leaking. Traditional vapor barriers are going to have edges where water can seep through since their job is controlling water vapor.

Similarly, if you need to Drylok your masonry, you cannot forgo this and just install a vapor barrier (non-Drylok).

XFasten White Vapor Barrier Tape, 9 mil, 3.78-Inch x 60-Yards, Waterproof Moisture Barrier Tape for Crawlspace Encapsulation, Construction Sheathing Seal Film, Housewrap Seaming and Underlayment Seal

Is Using Drylok as a Vapor Barrier Worth It?

Drylok can be more expensive (even up to 5 times more expensive!) than other vapor barrier options because it provides more protection.

A cheaper vapor barrier option is polyethylene plastic sheathing, such as Norkan Poly Sheeting, which is installed inside a house’s frame between the studs and drywall.

Norkan Poly Sheeting 10' x 100' 3mil White/Semi-Transparent - Top Visqueen
  • Plastic poly sheeting
  • Landscaping
  • Tarps
  • Size can vary +/- 10%

Last update on 2024-05-29 / Affiliate links / Images from Amazon Product Advertising API

Pros and Cons of Using Drylok as a Vapor Barrier

All-in-one – provides waterproofing and vapor barrier all-in-oneCost – may cost more than other vapor barriers
Versatility – can be applied to floors, exterior or interior wallsLifespan – may need reapplication in the future
Durability – while other vapor barriers may be more flimsy, Drylok does not risk rips or tearsApplication – must be applied to concrete/masonry (at least for the warranty to be valid)
Degree of water protection – up to 10-15 PSI of water (depending on which product you buy)Time – takes 2-3 hours to dry between coats and at least 2 coats to cover

Best Drylok Product for Vapor Barriers

There are several Drylok products that can be effectively used as vapor barriers. Both Drylok Original Masonry Waterproofer and Drylok Extreme Masonry Waterproofer can be used as vapor barriers.

While both products are effective vapor barriers, they differ in cost, warranty length, and water resistance. An extensive comparison of these products can be found here.

Drylok 27512 Latex Water Proofer, 1 Quart, White
  • GUARANTEED to stop water - withstands 10 pounds of hydrostatic pressure (PSI), equivalent to a wall of water 22 feet high
  • Fully transferable 10 Year Warranty
  • Helps protect against radon gas penetration by reducing vapor transfer
  • Low-odor formula complies with all current VOC requirements

Last update on 2024-05-29 / Affiliate links / Images from Amazon Product Advertising API

Drylok Drylok-28613 28613 Extreme Latex Masonry Waterproofer Interior/Exterior Smooth Finish, White, 1 Gallon (Pack of 1)
  • GUARANTEED to stop water – withstands 15 pounds of hydrostatic pressure (PSI), equivalent to a wall of water 33 feet high
  • Fully transferable 15 Year Warranty
  • Helps protect against radon gas penetration by reducing vapor transfer
  • Green Wise Certified

Last update on 2024-05-29 / Affiliate links / Images from Amazon Product Advertising API

Drylok Makes a Vapor Barrier Product

Drylok actually sells vapor barriers:

You can see and compare their range of vapor barrier products here. They are not waterproofers, so their protection against leaks and walls of water is much lower, but you will probably find their prices to be more affordable.


Amazon and the Amazon logo are trademarks of, Inc, or its affiliates.