Cork Underlayment Installation
Cork is commonly used for sound control in high rise condominiums or apartments. Often it is glued down to concrete with the use of adhesives. However, with today's wood flooring adhesives it becomes imperative one knows what they're getting into when using cork with any type of glue down type wood floor. Why? Today's urethane adhesives are extremely strong and will pull the underlayment from its glued position if a standard latex adhesive is used.
Avoid Expensive Mistakes
Often problems are associated with companies that handle ceramic tile and know very little about hardwood flooring. They have for example, a 4,000 square foot job that calls for 50% tile and the remainder engineered hardwood. The ceramic tile installers go in first and cover all the areas because they know their company will be doing the wood floor as well. What many don't realize is the same adhesive used for traditional cork underlayment and tile cannot be used for hardwoods that are glued with urethane adhesives.
Often they learn by expensive mistakes. I've heard some say it depends on the type being used. Frankly I say hogwash; "Why take chances, sure costs are much higher, but do you want to come back six months later and have to redo the whole job?" There are no easy fixit methods for cork that releases from concrete.
Like any type of glue down installation, the concrete has to be clean and dry which typically includes scraping the slab free of paint and other contaminants. The ideal tool of today is a product named Diamabrush that can be used with a standard rotary buffing machine.
For high-rise subfloors, moisture is generally not an issue, but cork is also used for comfort with on grade level slabs. If you're planning a project that calls for cork make sure the contractors don't cut corners. Sometimes they may get lucky, but once you start hearing strange sounds when walking on your new hardwood floor, chances are very good the wrong adhesive was used.
Underlayment Types and Costs
For years the most common type of sound control was 1/4" acoustical available in 4 foot by six foot sheets or rolls of 200 or 400 square feet. Other thicknesses are available ranging from 1/8 inch in thickness up to 1/2 inch. While this type of sound control is still the most widely used, other forms have come on stream with improved underlayment properties created by the popularity of floating floor systems. Before you go off seeking pricing on any of these, always check what your association requires.
Costs for 1/4" material will vary widely from one region to another but a good guesstimate is $1.30 per square foot(SF). Adhesive costs¹ will run in the .50 to .75 SF range with labor adding on another $1.25 per square foot. All costs should be used as a general guide
Gluedown Type Installation
Procedures for installation, call not only for proper adhesives and preparation, but using a roller as pictured on the right. Once the material is laid into the adhesive, proper adhesive transfer should take place. The use of a 100 or 150 pound flooring roller insures a proper bond, providing the right amount of adhesive was used.
For installation of glue down hardwood over this type of sound control, a good rule of thumb is to wait until the next day to begin the wood floor installation. This allows plenty of time for proper bonding between the sub floor and underlyament.
In addition, once the cork is laid there are recommendations to tape all seams tightly. This insures no gaps open keeping a continuous sound barrier.
As a substitute for more common cushioned synthetic underlayments, cork does not requiring gluing to the subfloor with floating floors. The product can simply be laid out and taped together at the seams so as to keep it intact during the installation process. One word of caution with this method; any loose laid material can become a trip hazard if corners should happen to curl before floors are installed over. Additionally, cork can rip and tear easily with simple foot traffic when using this method.
Solid Hardwood Floors
Using cork with a nail down application over common wood sub floors is something that can be addressed with any knowledgeable professional. However, do not expect this application to provide the benefits as they do with floating or glued floors. Reasons being, once fasteners penetrate the cork and into the actual sub floor, the benefit is lost at approximately 25 to 50% ²
Thicker underlayments have also been known to reduce the holding capacity of the fastener being used. For those seeking solid hardwoods on concrete over a plywood underlayment, cork can be glued or loose laid.³
Other Types Of Sound Control
Only very recently have these systems being approved by condominium associations. In fact their uses are could replace cork in the not too distant future because of several factors.
• Other Sound Control - Proflex and Mapei have sound deadening properties as do multipurpose adhesives for glue down floors.
• Quicker Application- Unlike cork that has to be glued to the subfloor by way of a trowled on adhesive, the two systems mentioned have a sticky tape residue on the backing. Once subfloors are properly prepared and free of any contaminates, a primer is applied usually with a paint roller. After application of the underlayment glue down hardwood installations can take place immediately.
• Thinner Construction
Follow Installation Specs
In recent years more emphasis has taken place in the performance of any sound control system. Of particular note is the actual installation of both hardwood and sound control. Neither can be butted against any structural support of the building. This would include walls, columns and the like. Essentially any sound transfer to these objects reduces the benefits desired.
How About Those Confusing Acronyms? ASTM Testing
I’m simple guy and yet I have problems separating the difference when looking at the wide array of testing numbers. How do they test for this stuff? With a tapping machine shown in the video below. For those that want to satisfy the condo association and don’t mind too much about the noise that will stay in you own area, you want to look at IIC which stands for impact insulation class.
More On IIC
¹ Based on urethane hardwood adhesives and not latex.
² Bob Gende, AcoustiCorkUSA. National Wood Flooring Association education April 2015
³ Loose laying can sometimes rely on the direct plywood fastening method to concrete which has in recent years become more scrutinized.