The Problem

I was called to inspect a prefinished ⅝-by-5-inch engineered Brazilian cherry floor due to small cracks in the veneer.

What Happened

The flooring was installed in March of 2014 in a home in the south-central U.S. It was glued over an existing concrete slab with a moisture vapor retarder underlayment and a polyurethane wood flooring adhesive. The installers tested the moisture of the slab with a moisture meter but did not take moisture readings of the wood flooring.

The customers first noticed the cracks in May 2016. The contractor looked at the issue and said it could be related to direct sunlight overheating the boards, as the cracked boards were adjacent to a wall of mostly windows. The contractor agreed to use leftover flooring to repair the affected boards, but by the time workers went to perform the repairs in December, the areas with cracks had expanded.

The Inspection

I inspected the flooring in June 2017, and the surface cracking was noticeable from a standing position throughout the installation. The cracks weren't uniform: They were at the ends of some boards, from end-to-end on others, and diagonally across some; some boards had a solitary crack.

The temperature averaged 75.9 degrees and the RH was 46.9%, which meant the wood's equilibrium MC was 8.7%. I tested the wood flooring MC in several areas; at a ¼-inch depth, it averaged 6.07%. At ¾-inch, it averaged 8.64%—within the normal EMC range.

RELATED: Engineered 101: Understand the Fundamentals of Engineered Wood Flooring

When I was there, the air conditioning was running. The customers said they did not use any humidification during the heating season. I looked up weather data to estimate what the indoor RH had been since the original installation. It showed that over the previous three years there had likely been 247 days when the RH in the home had been lower than the flooring manufacturer's recommended 35%–55% RH range, with 170 of those days at or below 25% RH. I checked the surface temperature of the wood flooring and found areas in the direct sunlight averaged 95.1 degrees while areas without direct sunlight averaged 72.3 degrees.

I determined the flooring in the home had been affected by low RH outside of the recommended range; this is considered a job-site-related issue.

How to Fix the Floor

The problem was so widespread that the entire floor had to be replaced.

In the Future

The customers in this case said that at no time did anyone advise them that they needed to keep their home within any particular humidity or temperature levels. Education of the customer is critical when selling an engineered product in an area that might experience low humidity.

Flooring made of engineered hardwood should not crack and split. 8% MC is excellent........ this is not a climate issue

Hi Raymond...I think you might not be understanding what the article is stating. It was 8%MC at the time of the analysis but the Relative Humidity would have massively dropped during heating season with a corresponding massive drop in the MC. If the house dropped to 20% RH in the winter the moisture content of the Jatoba veneer would have been well below its specification. However, the fair argument is that our engineered flooring must be able to handle a large range of humidities and resulting moisture contents. We manufactures have been creating ‘fragile flooring’ for years and that must stop. If an engineered floor cannot handle existing in humidities from 15% RH to 70% RH, then this product is unsuitable for North America.
Good comments and I’ll add part of the challenge here is it is not a
simple question that he posed. It takes knowledge and expertise to navigate through all the choices to come up with an acceptable / Best choice for each unique situation. There are significant differences with glueing over concrete versus stapling over a wood subfloor, Rotary veneer versus sawn face veneer and in this case Jatoba a specie to the informed that misbehaves in a dry environment versus say Oak. To me glueing engineered Jatoba over concrete ( that in most cases I’ve seen this occur, the concrete was never tested and there is an imbalance built into the equation add on top a dry climate = less than desirable result in the making. Any wood product solid or engineered directly glued to concrete surely can work well but takes additional investigation that sadly seems to seldom undertaken. But in the vast majority of installations be it solid or engineered, sticking with a starting point of 6-9% MC, having a substrate at the proper moisture content to begin with and staying in between 6-9% with or without added RH control, results in very little misbehavior. Go outside this especially with certain species glued over concrete and you experience misbehavior. Taking the entire set of variables and site conditions into account can and does, even in very dry climates , produce a positive result for all parties.

The issue is that over the last couple of years, there were 170 days where the relative humidity was below the manufacturer recommendations. During those days of extremely low Rh is when the veneers split. I agree that 8% MC is excellent, unfortunately it was not the case during the winter time, I would estimate that the MC got between 4-5%, causing the splits in the veneers. Thanks for reading the article, I hope that clears things up?
it can gain the moister again by sweeping the floor by damp cloth and hair crack will close
Hi Mohammad Omar,

I agree that introducing moisture will help with the appearance of the splits, but the damage is to the finish layer as well. During my inspection the splits were tight and flush in there appearance but were still visible from a standing position. Also, the need to regulate the relative humidity during the winter with a humidifier to keep the wood flooring stable is needed. Part of the issue is that the homeowner was not informed of the manufacturer requirements for the relative humidity by the flooring company, otherwise they would have add a humidifier.
Tim is correct, 90% of my inspections revolve around problems with the lack of moisture. As a apprentice in 1971 my mentor Jens Wilslev always told me that wood will tell you a story and it NEVER lies, you just need to listen. Tim's conclusion is correct and humidification is the responsibility of the homeowner. However over the past 20+ years the retailers has increased where the wood flooring contractors who specializes only in wood flooring has decreased dramatically. This is where the lack of wood knowledge of the retailer doesn't discuss important issues such as supplemental humidification, then the blame game begins after the failure.
Retailers need to further educate their sales team about ALL wood flooring requirements so we minimize problems such as this one.
I continue to be amazed that we blame poor products on a homeowner's normal, expected use of their house. To say that an engineered flooring cracked/split/checked due to low humidity is probably a very accurate statement, but to say that its because the homeowner failed to maintain high enough humidity is 100% bull. I am sitting in a room with 24-inch wide wood veneered furniture, with wider veneered tables, doors, cabinets and even engineered flooring throughout, and I know the RH has gotten down to the teens on multiple occasions, but none of these other wood products show any distress. Its a product issue, not a homeowner issue.

Tim, what level of RH would have prevented this issue? How do you know that? How did you calculate 170 days with low RH? Where did the manufacturer recommendations come from: wood science or an accountant or an attorney?

I agree with Ray, with a slight modification: Properly made engineered flooring should not crack or split when used as flooring in an indoor environment. Just because flooring is "chopped, pressed and fused" ( from an old commercial) doesn't make it "engineered." Engineering requires some determination and use of properties and construction techniques to make a better product. That includes finishes that can handle stresses in the veneers without tearing itself apart.

I'll even agree with Roy and Jens: Wood never lies. It will tell you when its a piece of junk.
Hi Craig,
I don’t dispute your analysis. As a NWFA Inspector, I have the manufactures instructions and recommended to follow for the wood flooring. A manufacturer warranty their product to perform within their recommendations. Part of my job as an inspector is to evaluate the conditions that can contribute to the stated issue. Understanding the outside temperature and humidity during the winter and when that air is then heated to 70 degrees, the relative humidity can and will drop well below what the manufacturer recommends. The conditions at this jobsite, show that the heated air being introduced into the home ranged from 6% to 25% for 170 days over the past few years. I agree that other product will do better under those conditions, unfortunately this Brazilian Cherry flooring is not one of them.
I thought NWFA Certified Inspectors were unbiased. Here's two alternative conclusions for this situation: 1) The flooring is defective; 2) The flooring should not have been installed in that house because it was incompatible with the environment in the house. Instead of making either of those valid conclusions, the innocent homeowner was blamed. This is not unbiased. In case 1, the manufacturer is to blame, not the homeowner. In case 2, the retailer/installer/distributor is to blame, not the homeowner.

Someone sells me flooring to go in my house and it fails (when no other wood in the house fails, my house like most others does not have humidity control, and no one mentions that I need what would be very expensive, potentially harmful humidity control). Then the failure is blamed on me? Amazing.

Psychometrics can be a useful tool since it relates temperature and humidity. Heating air does lower its relative humidity, IF the moisture content is constant. In a house though, lots of other moisture sources exist. Did you account for any of them? Did you account for the slow response of wood to a RH change? Did you look at the elasticity of the finish? Did you look to see if any of the checks existed at the time of manufacturing?

You stated above "the relative humidity can and will drop well below what the manufacturer recommends." Sounds like normal, expected environmental conditions to me. Yet we blame the homeowner. Sounds like a biased conclusion to me.
In my conclusion, I stated, that the homeowner stated that the retailer did not inform them of the manufactures recommendations for relative humidity. I checked with the retailer, who could not confirm whether they informed the homeowner of the recommendation and defiantly did not do it in any written form. The homeowner will need to address the relative humidity issue with the retailer, which they did, the two parties are working out a solution. I believe that the retailer has taken responsibility for the issue.
I bought plants that are not for full sun exposure. I planted them in full sun exposure and they of course died. My fault correct? Of course it is my fault unless I was told differently at time of sale yet bothy shade and full sun are " expected use" normality's?. So like with a product where the Mfg says x% humidity needs to be maintained, their directive and a consumers choice to follow or not follow? So unless someone held a gun to the consumers head and forced them to take it, do they not have a responsibility as a consumer to read the warranty and follow it? Craig makes very valid points as does Roy, but simply blaming product is what's BS here,sorry Craig please no offense to your wisdom. Wood sciences PROVES wood expands and contracts, and even checks when MC changes enough and maybe, just maybe the product isn't garbage BUT needs the range of Humidity specified and people need to learn to read? If I decide to change my motor oil every year, not 3,000 miles, bad car when it fails to preform properly or bad maintenance by the owner? Last I checked, humidification is cheap, and actually good for people and the house when it actually does fall below 30% Look there ARE Mfg's that use the RH to blame poor products, but that doesn't mean always citing it is BS, especially with Brazilian Cherry! When a red head goes to the beach ( Jatoba) without sun screen, they get sunburned for sure, but when the Olive skinned person does ( Oak ) they don't so much. Understand the characteristics of the specie or be ignorant, that's a "choice" and being properly educated from ALL sides including the HO is the key to avoiding failures like this one in my humble non PhD or PE opinion based on 30 years in hardwood.
Now we're comparing apples to bananas. But they are both consumer products, so lets do it. Some talking points:
1) Most reputable nurseries offer a one-year, no questions asked, warranty on plants.
2) Whose fault is it if you had hired a landscaper to plant your plants, and they planted them in full sun rather than the required shade?
3) Would a landscaper even plant a Zone 1 plant in your Zone 7 yard? "Sure, I'll plant this palm tree in your Michigan yard, but it won't grow there, and I won't be liable." or "Sorry, I won't plant one there. Lets pick something else."
4) How many homeowners even know the RH in their house? How many know how low it gets in the winter?
5) How many new homes have hardwood floors but no RH control? Is that the homeowner's fault?
6) ASHRAE has no lower limits for indoor RH. Is that because they know adding humidity could cause damage?
7) Building codes don't require RH control or even air conditioning.
8) Humidity control is not cheap. It requires significant maintenance, and can cause very bad things if something goes wrong.
9) What guarantee does the homeowner have that adding humidity control will actually prevent a problem? Or are we just pushing liability to the HVAC contractor?
9) Wood floors have been around for hundreds of years without humidity control.
and lastly
9) What incentive does a wood floor installer/retailer/distributor/manufacturer have to inform a buyer that RH control is needed for that product? If you told me that I needed to add humidity control so this flooring product would work correctly, I'd likely pick some other product, possibly even sheet vinyl or carpeting. Hows that work for the wood floor industry?