What lies beneath: choosing the right underlayment or subflooring

Remodeling & Your Flooring

When it comes to your flooring, the subflooring and underlayment are just as important as the flooring itself.

There are different types of flooring underlayment products available and it's crucial the correct ones are applied to the right situation. Using the wrong underlayment, or neglecting to use any at all, can result in squeaky floors, cracks in tiles, and other easily avoidable mishaps.

Before we jump into the different types of flooring and their underlayment requirements, the first thing to consider is the initial subfloor. This is generally a 3/4" plywood which ties directly into the floor joists beneath. Here are a couple of subflooring techniques to keep in mind;

floor joists
  1. There should be a layer of adhesive under the subflooring, which is then also nailed down with 'ring' nails. The combination of adhesive and ring nails plays a large role in preventing squeaky floors. Forget one of these two steps and you're asking for trouble.
  2. Should you be remodeling an older home with squeaky floors, one way to tackle the problem is to screw down the existing subflooring wherever needed. You may also need to add more supports to the floor joists underneath if they are sagging substantially. 
  3. If you're adding a new addition to your home, the floor joists should be able to withstand the intended weight which will be placed above them. For example, if the floor joists have a long span (which means slight deflection or sagging in the middle) it's worth considering the function of the room. If it is a kitchen or bathroom with heavy appliances or cabinets, you should consider beefing up the joists to be a bit more than what code asks for. This is especially true if the finished floor will be tile work.

Now that we've covered some subflooring basics, the next step for flooring is the underlayment. Here's a quick breakdown of different underlayment products and application procedures for various types of flooring.

1. Hardwood flooring

remodeling with hardwood flooring

When it comes to hardwood flooring, it is recommended to use whats called white silicone vapor paper as an underlayment. As the name implies, this paper works as a vapor barrier. Wood expands and shrinks due to moisture and/or temperature, and so this paper minimizes these effects on the hardwood flooring. The silicone paper can be rolled out right onto the subflooring. The last thing to keep in mind before installing the hardwood flooring is to ensure the paper surface is clean and smooth. It's a good idea to keep a broom handy during installation to periodically remove saw dust, broken nails or staples, etc. 


2. Tile

There are different underlayment products available for tile floors, with tile size, joist span and floor dimensions playing a part in choosing the correct one. Firstly, there is whats called fiber cement board. This is generally a 3' x 5' board about a 1/4" thick, heavy duty and sturdy. It helps provide a durable, water-resistant surface for the tile. For large tiles, ceramic tiles and surfaces above long joist spans, there is also what's called Ditra underlayment. Ditra is a polyethylene uncoupling underlayment with a grid structure. The bottom of this product is attached to the subfloor with a thin-set mortar. Ditra also provides whats called uncoupling, which allows for in-plane movement between the subfloor and the tile, helping to eliminate a major cause of cracking.

3. Laminate flooring

For laminate floors, the recommended underlayment is a foam or pad which can be rolled out during installation. Some laminate flooring products are even produced with a pad built into them, allowing for a quick installation. The benefits of this underlayment for laminate floors include adding a bit more insulation value, hiding any imperfections which may be in the subflooring beneath and making the floor a little softer to walk on (extra padding makes a big difference). The manufacturer of the laminate flooring will suggest an underlayment thickness and may also provide their own underlayment.

4. Vinyl or Linoleum

1/8 " or 1/4" multiply is the recommended underlayment for most vinyl or laminate flooring surfaces. The multiply will help to hide any imperfections in the subfloor, and will help keep the surface smooth. Without the multiply, you risk seeing little bumps, seams from the subfloor, etc. These thin sheets come in 4' x 8' sizes, sometimes smaller.

Using the right products in the right situations makes all the difference for any remodeling project. The prep work going into any installation is just as important as the finished look. If you're ever unsure of which underlayment to use for a particular floor, it's recommended to ask a professional or the manufacturer of the flooring product you intend on installing.

Remodeling your bathroom or kitchen? Visit these sections of our website for more information and inspirational photos.

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