Company History

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Lightweight Concrete

Lightweight Concrete is a generic term that covers many types of concrete that are light by nature or manmade and typically range in density from 20 pcf to 120 pcf. The two most common ways to make a concrete mix lighter are by the introduction of lightweight aggregates such as shale, volcanic rock or pumice in place of standard solid rock aggregate and by introducing air into the concrete mix, commonly referred to as “air entrainment”. The most common type used in residential construction is air-entrained meaning air is introduced into cement slurry and agitated resulting in a honey-comb matrix of concrete and air voids. These Lightweight Concrete mixes typically produce approximately 1000 psi and were used extensively in the 1960s,70s and well into the 80s for fire and sound control in wood frame multi-family apartment homes, offices, medical facilities, and many other types of structures. This generic product was made using a foaming agent (soap type surfactant material) which is injected under pressure through a nozzle to create “foam” (microscopic air cells). The foam is introduced into a cement mixer and displaces aggregates and increases the volume of the concrete without adding weight, which creates lightweight concrete.

Although Lightweight Concrete was the standby product for floor underlayments 30 years ago, it also came with a host of issues. Building paper is stapled to the subfloor and expansion joints are installed off of the outside corners of framed walls to help control the direction of cracking as the product is pumped into place and finished. As the concrete cures it shrinks and cracks appear. The building paper helps to plug small holes and acts as a bond breaker between the concrete and the plywood to reduce cracking when shrinkage occurs. Slab curling is also expected at the expansion joints as the top dries quicker than the bottom. Although there were many drawbacks, overall Lightweight Concrete was a great new innovation for wood frame construction sound and fire control in the 1960s. Lightweight Concrete never was developed or intended for use as a thermal mass for radiant heating systems. Imagine ¾” tubing with only ¾” lightweight concrete cover over the tubes - as the lightweight shrinks the tubes act as the expansion joints and cracking develops. The air or honey comb matrix within the Lightweight Concrete has insulating properties which result in higher operating costs, less efficient heating systems and potentially a non warrantable substrate for finish floor goods.

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Gypsum Concrete

In 1972 Gypcrete Corporation started producing the first gypsum floor underlayment. Years later with an expanding line of products they changed their name to Maxxon Corporation and Gypsum Concrete was introduced to the Seattle market in 1980 faced with some tough competition by the Janes Brothers (yours truly) which had established a strong lightweight concrete business, and the battle soon began. The Janes name has been synonymous with floor underlayments for over 50 years. Originally starting with my father installing swimming pools and lightweight concrete in the early 1960s, by the 70s my brothers and I had the market share of lightweight concrete with several million square feet poured. We weren’t about to give up ground to some new product! The battle ensued for two years until Gyp-Crete Corporation asked us to represent their product. We agreed, recognizing the future of residential floors would be a superior product called Gypsum Concrete. Today 95% of multi-family residential floors are Gypsum Concrete. Today there are three major producers who manufacture Gypsum Concrete products, United States Gypsum, Maxxon Corporation and Hacker Industries. Over the years we have installed material from all three manufacturers and our product selection is based on the highest material quality from the producer and manufacturer support of the product.


The acceptance of Gypsum Concrete by the architectural community and General Contractors has been extraordinary because they recognize the benefits of no shrink-cracking, high strength, and flatter floors with less floor preparation. The popularity of Gypsum Concrete is ever increasing, from Bellevue’s twin 43 story towers to a dog house with radiant heat on Mercer Island to Seattle’s Four Seasons Hotel/Residences, Kenny G’s residence, and the Gate’s residence. Although my father and brothers no longer have involvement, Janes Gypsum Floors continues to provide the quality services of the past and we look forward to working with you.


Regards,
Kurt Janes
President