Frequently Asked Questions

The following are questions frequently asked by customers. If you have an additional question, please contact us.

Q. What is the difference between vapor retarder and a vapor barrier?

Products that have perm rating of 0.1 or less are categorized as vapor barriers (impermeable). Products that have a perm rating greater than 0.1 are semi-permeable and classified as vapor retarders.

Q. So, isn't a vapor barrier better than a vapor retarder?

If you don't let enough moisture vapor pass through it then moisture can be trapped in the subfloor, let's say in plywood or OSB. This will eventually cause the subfloor to rot, mold or mildew causing another set of problems. Using vapor "retarder" helps manage the amount of moisture coming through it, not block it off completely.

Q. What can excess moisture do to flooring?

Too much moisture through a wood subfloor will cause cupping or buckling of the wood flooring. Too much moisture through concrete subfloor might cause the adhesives bond to either not cure properly or breakdown the adhesive bond completely.

Q. What causes moisture vapor?

Moisture vapor coming through a wood subfloor is often caused by moisture from a crawl space. The NWFA Installation Instructions has specific guidelines for crawl spaces and if not followed, could allow excess moisture vapor to go into the wood flooring. Moisture vapor in concrete comes from a slab not fully cured, the lack of vapor barrier under the concrete slab or water from the water table pushing up through the slab. Referring to the NWFA Installation Guidelines there are useful tips for looking over job site conditions to help make you aware of potential moisture hazards.

Q. How do I prevent moisture vapor?

We don't want moisture to go away. We just want to manage it properly. The first thing to determine is how much moisture vapor. Concrete testing is becoming more scientific. Calcium chloride tests were the standard for many years. Now we have the addition of relative humidity testing slabs. Each test has protocols to follow and it's best to have a copy of the ASTM test to follow. Most of your flooring covering distributors will have a copy.

Testing wood subfloors requires a moisture meter calibrated properly for the type of material the subfloor is made from and the species of wood flooring. Follow the wood flooring and adhesive manufacturers instructions on what moisture levels are approved for their products.

Q. What products does Jackson supply for moisture retarders?

LSU 30-30-30 is our premium product. It is an asphalt laminated paper which means a layer of high melt-point asphalt is layered between 2 sheets of kraft paper. It is rated as a premium vapor retarder because it's perm rating is less than 1 perm. It has high moisture resistance than many products currently offered for this application. It also allows the installer to work on a clean surface and is very resistant to tearing.

ASU-15 is an excellent product. It is an asphalt saturated paper, in other words, it is one layer of kraft paper saturated with asphalt. ASU-15 is a great product for moderate vapor. It also lets the installer have a clean work surface. The product will handle the wear and tear better than a roofing felt paper.

Q. I use red rosin paper all the time under my floors, why should I change?

Red rosin is a great paper product to use as a clean work surface. It isn't a vapor retarder, because it allows too much moisture to pass through it into the wood flooring. Red rosin paper will breakdown when exposed to too much moisture. Jackson Building Products offers red rosin paper, but not as a vapor retarder.

Q. Tell me again, why I need to LSU 30-30-30 and LSU-15?

Our papers are an inexpensive solution to many subfloor moisture vapor issues. Our products are NWFA approved.


Glossary of Terms

Perm: Is a measurement of what rate moisture vapor passes through a material. The lower the perm, the less moisture is passing through.

Ambient Conditions: Our products can't control the environment inside a house. Wood's comfort zone is a relative humidity range of 30% to 50% and a temperature range of 60 to 70. A lot of humidity in a room or a room that's closed up will cause wood to cup and possibly buckle. It is important the customer knows how to make the wood flooring look good.

Concrete: This is a mixture of binding materials, coarse and fine aggregates. Every location is going to have a different concrete due to the availability of the aggregates. Some absorb moisture and hold it longer than others. That is an important reason for testing concrete.

Acclimation: How long it takes a wood floor to grow accustomed to its environment. The wood flooring manufacturer normally will give you this information, there isn't a one size answer to the question.

Cupping: Wood flooring becomes warped where the sides are higher than the center.

Moisture Content: How much water or humidity has soaked into the wood.


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