Understanding the Fortifiber Moistop Water Vapor Barrier

Importance of water vapor barrier


A true vapor barrier can protect your flooring from moisture that wicks through concrete and wood. Fortifiber Moistop is a product used by many construction companies for that purpose. It’s especially important in basement settings, but even ground-floor rooms can be subject to moisture fluctuation because of ground moisture below the building. It can not only damage the flooring and its components, it can at times seep through the concrete and corrode the steel bars over time. Repairing such corroded bars will take a considerable amount of time and labor charges. The challenge is to stop as much of the ground moisture from entering a building as possible, and a good vapor barrier do the trick.


A perfect solution from the Fortifiber Building Systems


Fortifiber Moistop is a brand name for a line of several water vapor barrier products made by the Fortifiber Building Systems Group of Reno, Nevada. Fortifiber makes products for many building insulation needs, and they are all worth a look. But in this article, we will focus on underslab water vapor barriers as protection for flooring in high moisture areas.


Fortifiber Moistop underslab water vapor barriers (or retarders) are engineered polyethylene sheets designed to provide resistance to water seepage beneath the concrete slab that forms the foundation of a house, and along the concrete walls of a house’s basement.


Types of the Fortifiber Moistop


The Moistop Ultra 15 and Ultra10 (the numbers refer to the product’s thickness in mils) are all engineered to meet or exceed ASTM E-1745-97 standards for Class “A”, “B” and “C” underslab vapor retarders. Moistop Ultra 6 meets Class B and C standards. Moistop Underslab, a paper and fiberglass composite coated on both sides with polyethylene film, is not rated.


The Moistop Ultra series products all earn a US Perms (permeability) rating of 0.02, while the Underslab product is described as “less than 0.03” Perms. The lower the Perms value the more resistant to water seepage the product is.


Comparing the strength of different manufacturers’ water vapor barrier products can be difficult because manufacturers use different strength tests. But the Moistop Ultra 15 has a tensile strength of 70 lb.-ft./in. using ASTM E-154, Section 9, testing methods. Moistop Ultra 10 has a tensile strength of 50 lb.-ft./in., while Moisto Ultra 6 has a tensile strength of 32 lb.-ft./in. Moistop Underslab has a tensile strength of 72 lb.-ft./in., perhaps thanks to its fiberglass reinforcement.


In terms of puncture resistance, Moistop Ultra 15 is tops at 4,200 grams. Moistop Ultra 10 is next at 3,200 grams. Moistop Ultra 6 is third at 2,000 grams. Moistop Underslab is not rated for puncture resistance.


Curiously, some construction experts do not consider puncture resistance to be a very big deal in water vapor barriers. They argue that punctures open up only a very small percentage of a water vapor barrier’s surface area, and that a barrier whose surface is 99 percent intact is 99 percent effective.


Another controversy involves whether a water vapor barrier should be covered by sand before a concrete slab is poured on top of it, to protect it against punctures. The same school of contrarians maintains that direct contact between concrete and water vapor barrier is beneficial. It is air flow that makes water vapor pass across the barrier, they reason, and direct contact with hardened concrete blocks any air flow through a puncture. Sand, on the other hand, is full of air pockets that will allow water vapor to cross the barrier. However, these technical debates hardly matters to the end user who just wants flooring that does not get and is free from the troubles caused by moisture content. The technology that can prevent this from happening is welcome, no matter if it is sand or concrete.


Other solutions from Fortifiber


Fortifiber also makes weather-resistive barriers for the exterior walls and roofs of homes and commercial buildings. Jumbo Tex is used behind stucco, wood, and other exterior finishes providing a barrier against rainfall and flood waters. Basically, Jumbo Tex is an asphalt-saturated Kraft paper, generally known as Grade D Building Paper. It is used in conjunction with Fortifiber’s flashing products, which seal the joints between walls and roofs.


Fortifiber’s product line is an inexpensive, reliable water vapor barrier solution and weather-proofing system. Owing to these very reasons, this brand has been able to command the loyalty of a very sizeable community in the country. Their products and designs are aimed at people who cannot afford to spend too much, but nonetheless, want to have a clean and dry basement. This is exactly what Fortifiber and its numerous products offer. Any time you plan to install flooring in a basement area, or even on the first floor of a building that’s above a high water table, applying a vapor barrier first will protect the flooring product from ground moisture. Make sure you conduct adequate research as to which vapor barrier you need to install. You can also make use of the internet for help with this.

2 thoughts on “Understanding the Fortifiber Moistop Water Vapor Barrier”

  1. Thank you for your time… i am laying a 3/4″ stone 22″sq paver on top of bitchathane water proof membrane, and I have about 2″ of height
    to work with,, what would you do as far as should i float a 1″ bed or use hardyboard it is outside on a deck and i cant use any nails.


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