Frequently Asked Questions
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 a 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 allow enough moisture vapor to pass through, it can become trapped in the subfloor, such as plywood or OSB. This may eventually cause the subfloor to rot and develop mold or mildew, leading to additional problems. A vapor “retarder” helps control the moisture passing through without completely blocking it.
Q. What can excess moisture do to flooring?
Excess moisture in a wood subfloor can lead to cupping or buckling of the wood flooring. Similarly, excessive moisture in a concrete subfloor may prevent the adhesive bond from curing properly or cause it to break down completely.
Q. What causes moisture vapor?
Moisture vapor rising through a wood subfloor is often the result of moisture from a crawl space. The NWFA Installation Instructions provide specific guidelines for crawl spaces, and if these guidelines are not followed, they could permit excess moisture vapor to enter the wood flooring. Moisture vapor in concrete can arise from a slab that has not fully cured, the lack of a vapor barrier beneath the concrete slab, or water from the water table pushing up through the slab. By consulting the NWFA Installation Guidelines, you can find helpful tips for assessing job site conditions to help you identify potential moisture hazards.
Q. How do I prevent moisture vapor?
We don’t want moisture to disappear; we want to manage it properly. The first thing to determine is the amount of moisture vapor. Concrete testing is becoming more scientific. For many years, calcium chloride tests were the standard. Now, we have added relative humidity testing on slabs. Each test has protocols to follow, and it’s best to have a copy of the ASTM test guidelines. Most flooring covering distributors will have a copy available.
Testing wood subfloors requires a moisture meter correctly calibrated for the type of material and species of wood flooring. Follow the instructions of the wood flooring and adhesive manufacturers regarding the approved moisture levels 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, meaning a layer of high melt-point asphalt is situated between two kraft paper sheets. It is rated as a premium vapor retarder because its perm rating is less than one perm. It has higher moisture resistance than many products currently offered for this application. Additionally, it allows the installer to work on a clean surface and is highly resistant to tearing.
ASU-15 is an excellent product. It is an asphalt-saturated paper; in other words, it consists of one layer of kraft paper saturated with asphalt. ASU-15 is ideal for moderate vapor. Additionally, it provides the installer with a clean work surface. This product endures wear and tear more effectively than roofing felt paper.
Q. I use red rosin paper all the time under my floors, why should I change?
Red rosin is an excellent paper product for use as a clean work surface. It does not act as a vapor retarder, as it allows excessive moisture to pass through to the wood flooring. Red rosin paper will break down when exposed to excessive moisture. Jackson Building Products offers red rosin paper, but it is not intended to function as a vapor retarder.
Q. Tell me again, why I need to LSU 30-30-30 and LSU-15?
Our papers provide an affordable solution to various subfloor moisture vapor problems. Our products hold NWFA approval.
Glossary of Terms
Perm: This measures the rate at which moisture vapor passes through a material. The lower the perm rating, the less moisture can pass through.
Ambient Conditions: Our products cannot control a house’s indoor environment. Wood’s comfort zone is a relative humidity range of 30% to 50% and a temperature range of 60 to 70 degrees. Excess humidity in a room or a closed room may cause the wood to cup and possibly buckle. The customer needs to understand how to maintain the appearance of the wood flooring.
Concrete is a combination of binding materials and coarse and fine aggregates. Because of the varying availability of aggregates, the concrete in each location will differ. Some aggregates absorb and retain moisture longer than others, which is an important reason for testing concrete.
Acclimation: The time it takes for a wood floor to adjust to its environment. Typically, the wood flooring manufacturer will provide this information; however, there isn’t a one-size-fits-all answer to the question.
Cupping: Wood flooring twists, creating higher edges than the center.
Moisture Content: The amount of water or humidity that has soaked into the wood.
Contact us about Jackson Building Products Underlayment Products
919-896-7395
