How to Avoid Cupping in Wood Flooring?

How to Avoid Cupping in Wood Flooring?

A lot of work goes into the selection of the right colour, the right width, the right grain as well as the right product when it comes to the selection of wood flooring whether it is engineered or solid. Selection of the right product and its installation are key points so that Wood Floor Cupping can be avoided; leave aside the additional costs attached to fixing and the annoying time you spend to deal with the problem. With SurfacesReporter take a look at some of the reasons for Wood Cupping and know How to Avoid Cupping in Wood Flooring.

What is Wood Floor Cupping?

Wood floor cupping refers to the defect in the wood floor where the sides of the flooring are higher than the centre of the boards thus giving it a visibly concave shape. Cupping in Solid wood flooring occurs as a result of an elevated Moisture Content (MC) at the bottom of the flooring as compared to the moisture content at face. Wood swells as the moisture content are increased and shrink when the moisture content diminishes.

Pradeep S Kampani, MD, Premier Timber and Trading Pvt. Ltd. (L) & Ar Ateet Vengulekar, Blue Arch Interiors & Architects, Mumbai (R)
Ar Ateet Vengurlekar says “Cupping becomes very obvious when looking across a floor against the light. Minor cupping could be the result of seasonal changes of relative humidity.”

Causes of Cupping

As mentioned above, the most common cause of wood floor cupping is moisture-related yet there are various conditions where the MC plays its role, let’s take a look at some of those.

  • Wet subfloor - Underlayment and/or subfloor that are too wet at the time of installation will cause wood floor cupping. A cupped floor develops moisture from the underlayment or subfloor moves upward through the hardwood as the back of the wood becomes wetter than the face of the wood.

  • Improper acclimation of wood - A wood floor that is placed in a house for acclimation may pick up moisture if wet work such as painting and plastering is being performed resulting in wood floor cupping following installation.

  • Existing or new concrete slab is too wet - Failure to properly perform testing of concrete or wood substrate prior to installation of the hardwood.

Yes, engineered flooring can cup too!

Quite like the solid wood which expands on an increase in moisture content, some engineered flooring cups too. However, the difference is, it cups on a decrease in moisture content and is known as ‘dry cupping’. It is important to note here that not all engineered flooring is the same though the common construction is the face of the desired wood species applied to plywood or any other backing material. This backer provides structural integrity and stability during changing moisture conditions. The face of an engineered floor is relatively thin as compared to the backer.

During manufacturing, the moisture content of both the face and the back should be the same and within an expected range. Often the face and the backer are of different species and the two layers may act differently during changes in MC after the flooring is manufactured. When the moisture in the face experiences a significant decrease, it can shrink and as the face pulls across the width of the backer it starts to curl up or cup. Dry cupping can be a seasonal occurrence, especially in climates that are cold and have a long heating season. Unlike solid wood flooring, extended acclimation times will not reduce the possibility of the engineered flooring cupping during periods it is experiencing low moisture content.

Steps to avoid Cupping

As per Ar Ateet Vengulekar, Blue Arch Interiors & Architects, Mumbai, “Minor problems may be caused by seasonal changes. The defects come and go with summer-winter changes. This can only be avoided by operating an HVAC all year around. For more severe moisture problems, expensive repair work or replacement may be necessary. Drying out and re-sanding may help. If the defects are so severe that the structure of the wood has been damaged or the wood is permanently distorted, there is no cure. The floor has to be replaced.” 

The issue of cupping happens only once in a while, according to Pradeep S Kampani, MD, Premier Timber and Trading Pvt. Ltd. He disclosed a few ways of handling a cupped floor. Carefully sanding the top layer of the flooring and touching up wherever it is required is one of the ways, he said. Taking out the cupped flooring and drying it out in sun to try and revive close to the original shape, is another way. Drying of the subfloor is also very important. He also shared some pre-installation steps to avoid cupping:

  • Keeping the material at a proper storage facility is of paramount importance. 
  • Fix flooring with the help of clamps put underneath. 
  • Sending the material to the installation site minimum 48 to 72 hours before installation to acclimatize with the surrounding is important (to open the vertical flaps).
  • Check the site both in terms of sub-floor level and moisture content. To ensure that moisture doesn’t affect the flooring, a barrier sheet of good quality is required to be put before the installation.
  • Must provide for enough expansion gaps on all four sides during installation. 
  • Moreover, make sure that wood has optimum moisture content taking Indian conditions into consideration. The moisture content of good wooden flooring should be in between 8 to 12 % ideally.

Also Read: Problems with Veneer? A Few Tips for Applying It Right

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