Brickman Consulting

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Board Cuts, Moisture Changes and Cupping

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Cross posted from Howard Brickman's article on Hardwood Floors Magazine: Inspector Blog.

This blog will explore simple moisture content changes of individual S4S RO boards and how that would be related to changes in shape and how that could be related to cupping. But first…

A quick review of the initial article: Cupping = boards that are concave on the face. I have initially proposed six experiments where variables are limited to see which actions cause which reactions. The list of experiments is summarized below, but you can see the more complete explanations in my Dec. 11 blog link.

Experiment 1: 10 S4S RO boards ¾” x 4” x 72” edge-to-edge into a panel ¾” x 40” x 72”. Place and tighten pipe clamps at 3” intervals across the 40” dimension. What happens?

Experiment 2: 10 pieces RO flooring ¾” x 4” x 72” edge-to-edge into a panel ¾” x 40” x 72”. Place and tighten pipe clamps at 3” intervals across the 40” dimension. What happens?
 
Experiment 3: 10 pieces RO flooring ¾” x 4” x 72”, MC 6%-8%, nailed to ¾” plywood with a MC of 6%-8%. Put a wet towel on the face of the boards with 6-mil ploy over towel. What happens?
 
Experiment 4: 10 pieces RO flooring ¾” x 4” x 72”, MC 6%-8%, nailed to ¾” plywood with a MC of 14%-16%. 6-mil poly on underside of plywood. What happens?

Experiment 5: 10 pieces RO flooring ¾” x 4” x 72”, MC 14%-16%, nailed to ¾” plywood with a MC of 6%-8%. 6-mil poly on underside of plywood. What happens?

Experiment 6: 10 pieces RO flooring ¾” x 4” x 72”, MC 14%-16%, nailed to ¾” plywood with a MC of 14%-16%. 6-mil poly on underside of plywood. What happens?

We are going to discuss the effect of a simple change in MC of individual RO boards. Since I did not include this in my original list of experiments, we will call this Experiment 1A. There is a cool graphic in the Wood Handbook that shows shape changes in boards with varying grain orientations:

Wood Handbook Figure 4-3.jpg

(Note that you can download the chapters of the Wood Handbook for free here; you can download Chapter 4: Moisture Relations and Physical Properties of Wood by clicking the illustration above.)

We are going to keep this simple and use a very slow and gradual change in MC with very small differences in MC within the board, which eliminates the effect of having large differences in MC on opposite sides of the board. Again, we are controlling conditions, so that we will only see what happens when a single factor causes the individual boards to change shape. These boards are unrestrained so that we don’t have any additional factors related to installation to worry about.

The intent of this experiment is to see what effect a simple gradual change in MC would have on the shape of individual boards without any other compounding factors such as:

  • configuration of the tongue and groove edges
  • mechanical fasteners along the edges or into the face
  • gluing of the boards to a substrate
  • configuration of the relief cuts on the bottom surface

We can see that changes in shape after individual solid boards are manufactured are to be expected and would vary depending on the amount of MC change and in conjunction with differences in growth ring orientation between the opposite faces of the boards. Quartersawn (radial) boards shrink and swell less than plainsawn (tangential) boards, so if opposite faces have different shrink/swell factors, voila. If just the occasional board is cupping, then it might be caused by a grain-orientation-related effect. If every board is cupping, it is extremely improbable that it is a grain-orientation issue.

Bonus information: Now remember that we are talking about boards that are completely unrestrained (that means not installed). So if you were to allow wide-plank flooring to “acclimate” under high RH conditions, the individual boards would definitely change size (swelling), and there could also be significant changes in shapes. Would the boards be cupped? Yes and no, because flooring is fed into the molder/matcher with the best-looking face as the exposed face, the orientation of grain would be random. Some boards would be cupped (concave) and some would be convex. Unless there was a really big change in MC, these shape changes would probably not be that noticeable other than some complaints from the installers about varying width and difficulty banging the tongue and groove together.

On a separate note, on Saturday, January 21, I am putting on a one-day seminar on Dyeing Dark Floors at the Bona Regional Training Center in Bridgewater, Mass. Topics will include mixing and applying aniline dyes and which finishes can be applied over dye. E-mail me for information. I need to limit the class to 15. Lunch will be served.

Calculating Shrink/Swell and Why It Matters

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Cross posted from Howard Brickman's article on Hardwood Floors Magazine: Inspector Blog.

Wood shrinks and swells when it loses and gains moisture content (MC). For example, if a piece of 2¼" wide plainsawn red oak flooring were to decrease in MC from 8% to 5%, the net change in MC would be 3%. Using standard values from the Wood Handbook Table 4-3 Shrinkage Values of Domestic Woods, the net change in dimension would be .021" (2.25" x .086 x .03 / .28 = .021"). Expressed as a fraction, .021" would be between 1/64" (.015625") and 1/32" (.03125").

How is this information useful? Let’s take a real-world scenario and show how a quantitative understanding of dimensional change helps us perform an analysis.

SCENARIO:
We look at a wood floor that we installed last year where the customer has called to complain about gaps between boards. As part of our normal procedure, we look at the surface of the floor to see if individual boards are flat, cupped (concave), or crowned (convex). In this case, the boards are still very flat. Then we determine the size, frequency and distribution of the gaps. We note the minimum and maximum gaps, then we eliminate the smallest and largest gaps to describe the range, which characterizes the majority of the gaps (80-90%). In statistics this is referred as “eliminating the outliers." Now we choose several locations where the gapping is the most severe and begin a series of accurate board-width measurements, along with MC of the individual boards. Our results are:

MC of all of the boards is less than 6%. We estimate the MC at 5% based on interior RH for the last three weeks using Wood Handbook Table 4-2 Moisture Content of Wood in Equilibrium With Stated Temperature and Relative Humidity. The widths of individual boards range from 1/64" to 1/32" less than the manufactured width of 2¼". The gaps are located between every board and range in size from 1/64" to 1/32".

Danger! FORMULA ALERT: IF YOU BECOME SHORT OF BREATH, BREAK OUT IN A COLD SWEAT, AND HAVE DILATED PUPILS WHEN YOU READ FORMULAS, please skip this section of the blog. For you brave souls, let’s proceed.

FIRST FORMULA (Change in Dimension)
Δ D (change in dimension) = Manufactured Width x St (Shrinkage factor from Wood Handbook) x Δ MC / .28

SECOND FORMULA (Change in Moisture Content)
Δ MC = [Δ D x .28] / [ Width x St ]

With these two formulas we can:

1 – Predict the amount that a board will swell or shrink (Δ D) and
2 – Estimate the magnitude of change in MC (Δ MC) based on the current width of the board.

IT’S SAFE TO START READING AGAIN. Danger over.

Now it’s time for some SHRINKAGE RULES:

Rule Numero Uno: If a board is less than its manufactured width, it has lost MC since it was manufactured.

Rule Numero Dos: If a board is exactly its manufactured width, it is at the same MC as at the time of manufacture.

Rule Numero Tres: If a board is greater than its manufactured width, it has gained MC since it was manufactured.

Applying Rule Numero Uno, we know that our boards that are smaller than the manufactured width have lost MC. Using the SECOND FORMULA for Δ MC, we can pretty accurately quantify the change in MC.

For boards that are 1/64" narrower than 2¼", the Δ MC is 2.26%:

Δ MC= [Δ D x .28 ] / [ Width x St ] Δ MC= [ 1/64" x .28 ] / [ 2.25" x .086 ] Δ MC= [ .015625" x .28 ] / [ 2.25" x .086 ] Δ MC= [ .004375 ] / [ .1935 ] Δ MC= .0226 = 2.26%

For boards that are 1/32" narrower than 2¼", the MC is 4.52%:

Δ MC= [Δ D x .28 ] / [ Width x St ] Δ MC= [ 1/32" x .28 ] / [ 2.25" x .086 ] Δ MC= [ .03125" x .28 ] / [ 2.25" x .086 ] Δ MC= [ .00875 ] / [ .1935 ] Δ MC= .0452 = 4.52%

If we add the Δ MC to our current 5%, the boards that are 1/64" narrow were originally at 7.26% (5% + 2.26% = 7.26%). The boards that are 1/32" narrow were originally at 9.42% (5% + 4.52% = 9.53%). This allows us to estimate MC at time of manufacture between 7.26% and 9.52%.

I find these quantitative methods to be useful tools when working through the analysis of a wood floor that has evidence of a change (or changes) in MC. In new construction there are frequently several MC changes, starting with the adsorption of excessive moisture from the subfloor, then the eventual drying during the following winter heating season.

Let’s explore how doing all this rigmarole calculating helps with analysis. Let’s change our scenario by a single factor: instead of gaps that range from 1/64" to 1/32", how about gaps that range from 1/32" to 3/64" with individual board shrinkage that ranges from 1/64" to 1/32"? We have already done the calculations on the board shrinkage, but that doesn’t account for the additional size of the gaps. SO… something besides seasonal low interior RH would have to be the cause of the increased size of the gaps. Maybe the flooring was left on the job to “acclimate" and picked up some excessive moisture before it was it was installed? Or… (to be continued)
 

Do You Need An Alibi?

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Cross posted from Howard Brickman's column in Hardwood Floors Magazine: Inspector Blog.

Only a guilty man needs to have an alibi prepared. Well, you are all guilty of being wood floor guys, so let’s get those alibis ready for prime time. And maybe the process of getting those alibis prepped will also provide a framework for preventing the need for an alibi.

Tool/Equipment List:

  • smartphone with camera
  • pin-type moisture meter
  • black Sharpie Marker
  • hammer
  • 6d and 8d finish nails
  • thermohygrometer
  • flashlight
  • spiral notebook
  • pencils and pens
  • string (fluorescent red, blue, green, or yellow)

Stuff To Do (or Not Do):

BEFORE WOOD FLOORING DELIVERY:

  • Do not sign a confession, err, I mean contract provided by the general contractor without carefully reviewing the provisions regarding warranties and terms of payment.
  • Check moisture content (MC) of the subfloor and inspect the crawl space. Use the Sharpie to write the MC readings directly on the subfloor with the date and your initials. Check MC near windows, plumbing, and doors, and by obvious signs of water staining or moisture intrusions. More readings are better. Record the readings in your notebook.
  • Make a label that lists the date, job address, and your name in large block letters for identifying pictures.
  • Take pictures of the high-MC readings with your smartphone. It will automatically time, date, and location-stamp the individual photos.
  • Take pictures of other non-compliant issues (e.g., missing windows or doors, tile saws on subfloor, unvented torpedo gas/kerosene heaters, etc.)
  • Check MC of joists and subfloor in basement and crawl space. Look for water, mold, and mildew, and take pictures.
  • Politely request that the GC or building owner correct any problems noted in a brief and concise e-mail (or using another method that documents the content and delivery of the request).

AFTER WOOD FLOORING DELIVERY:

  • Check subfloor MC again and verify the any problems observed during previous visits were corrected. If not, document them again.
  • Check wood flooring MC on at least 40 boards. Use the Sharpie to write MC and date on the back of boards. Record the readings in your notebook. Reject the flooring if it is outside the range from 6% to 9% MC.

BEFORE INSTALLING THE FLOORING:

  • Verify that you document everything that could negatively impact the wood floor. Use the list from the NWFA Installation Guidelines (the PDF is available free online for all NWFA members).
  • Communicate one last time to the GC if there are any issues. This is the point at which you need to present your disclaimer or waiver document for the GC to sign or at least acknowledge. This can be a delicate time in the job. You may want to tread lightly, because there is a fine line between being a concerned wood floor professional and being a pain in the neck who aggravates everyone else on the job, especially the GC. You know the deal. There are 10 flooring guys waiting on the sidewalk to come in and do the work without even “noticing” the all of the potential problems.
  • If you are called to help out a GC at the “last minute,” take a deep breath and try to figure out why the other floor guy that has been doing his work for the past three years is not available. Is there a money issue? Or what?
  • If you are installing a nail-down solid floor, there are some critical steps that help to inoculate you from problems during an inspection: 1) fasteners every 6”; 2) #15 asphalt-saturated felt; 3) Expansion space around the perimeter of the floor.

The typical inspector will check MC, expansion space, nailing, and will want to see your documentation. If you have done due diligence with your prep work, the chances of a job going South are greatly reduced. If it goes South, you should be certain that a really qualified person performs the inspection. The same qualities that make you a competent craftsman apply to the inspection craft: experience in the wood floor craft, experience in performing inspections, referrals from really knowledgeable people in the industry, and the proper temperament to stand up to the pressure from all of the associated parties. In addition to doing everything right, you have to be able to prove that you did everything right. Here’s to hoping that you never need that alibi. Good fortune favors the well prepared.

The Peril of Using Averages

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Cross posted from Howard Brickman's article on Hardwood Floors Magazine: Inspector Blog.
 
I’m going to start by answering the question Wayne Lee asked in his latest blog post: Wayne, the short answer on this job is NO. The 18% moisture content of the subfloor is the deal breaker. This is a complicated scenario when you toss the crawl space into the mix. You mentioned that the average MC is 18%, and I would like to take this opportunity to share some thoughts about using averages with moisture content. Averaging is a statistical method for making erratic data more uniform in appearance. But averaging also takes accurate data with a great deal variation and mathematically makes it a single number. With variable accurate data this is often quite misleading in that it can hide some very important information. It is much more informative to use the following format to describe accurate data. The minimum is ___. Maximum is ____. The majority of the measurements are in the range from MIN to MAX (which are adjusted to remove the outliers-extremely low or high data).  Let’s look at an example from our friends on Wall Street.

The advertising literature from Amalgamated Super Rich Guy Growth, Income, and Value Fund trumpets an “average” annual rate return of 9% for the past four years 2007-10. But as usual the devil is in the details. In 2007, the ASRGGIV Fund lost 90% of it value, but had returns of 42% in 2008, 2009, and 2010. (-90% + 42% + 42% + 42% = +36% / 4 years = 9%/year). Let’s look at $1,000 invested in January 1, 2007.

$1000 + (-90%) or -$900) = $100 balance on Dec. 31, 2007
$100 + (42%) or $42 = $142 balance on Dec. 31, 2008
$142 + (42%) or $59.64 = $201.64 balance on Dec. 31, 2009
$201.64 + (42%) or $84.69 = $286.33 balance on Dec. 31, 2010

The normal assumption with a 9% average would be that at the end of the four-year term $1,000 would be worth at least $1,360. That “average” IS hiding some very important information. Our original $1,000 is now worth $286.33, for a net loss of $713.67. So you call the fund manager, Kineon Goodhue Beelzebub and demand an explanation to which he replies, “But dude, the average annual return is 9%”. NOTE: Please don’t post any comments that I didn’t compute the annual return in accordance with SEC regulations. Dude, this is wood floor blog, and I am trying to make a point about how averaging may not always be a useful data analysis tool.

Now back to Oak Street from Wall Street. Flooring contractor Harry Picoides takes 30 moisture content readings of the plywood subfloor at a 1,500-foot job. If Harry is using a meter that gives accurate readings, he should evaluate each individual MC reading. For instance, the reading by the slider in the family room is 19% and all of the other readings are between 11% and 12%. This tells Harry that there is a water intrusion by the slider but the remainder of the job is good to go. So he asks the GC to fix the leak and dry out the subfloor. If Harry had averaged the 29 readings of 11% to 12% with one reading of 19% there would be no alert about the high MC location and Harry would be back at the job within the first year doing an uncompensated major repair and refinish.

But we didn’t discuss the issue of the crawlspace and the temperature and RH readings… yet. Wayne, thanks for presenting this scenario which will keep me thinking and writing for the remainder of the summer. Some quick thoughts about temperature, relative humidity and crawlspaces: While we should know and understand how these things work, HVAC contractors and general contractors are responsible for this piece of the puzzle. That being said, we own that subfloor once we install a wood floor over it and ignore high subfloor MC at our own peril and bank account.

Are You Whimpering?

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Cross posted from Howard Brickman's article on Hardwood Floors Magazine: Inspector Blog.

“Sir, we clocked you installing a wood floor on a high moisture content subfloor. May I see your documentation on moisture content of the subfloor?”

You whimper, “But officer, it looked dry to me.”

This is the wood floor guy equivalent of getting bagged with the radar gun going 50 in the 30 mph speed zone. So, how do you protect yourself? Get a radar detector. It’s called a moisture meter. Here are the step by step instructions.

-Buy a proper moisture meter.
-Use the moisture meter.
-Learn how to take the right amount of moisture tests.
-Learn how to properly use your proper moisture meter.
-Take your proper moisture meter everywhere you go.

Now let’s break it down.

– Buy a proper moisture meter: I use the Delmhorst J-4 or BD-10 electrical resistance (pin type) meters and also keep a Moisture Content Standard (also sold by Delmhorst) to check the meter for accuracy every time I use it. I am not familiar with all of the other moisture meters currently available. And Mom used to say if you can’t say something nice, then don’t say anything.

– Use the moisture meter: Check every place where there could possibly be some excessive moisture, including near exterior doors and windows, plumbing, tile wet saw, masonry and plaster mixing locations. It is not the average of the MC readings that damages flooring, it is high MC locations. Your options are to dry or replace the wet subfloor.

– Learn how to take the right amount of moisture tests. You can probably stop when you get to 50 tests in 1500’. Even on small jobs you should take at least 15 readings. Another hint: Write the date, MC, and your initials on the subfloor with a black Sharpie. Test the flooring on the bottom face and also write the test results on the pieces of flooring. If the floor has to be replaced you will have the documentation there for the world to see. It is also a great idea to record these MC readings on the work order or flooring delivery ticket or other job related paperwork that can be tucked away in the job file.

– Learn how to properly use your proper moisture meter: What does the MC number mean? Learn what “normal” MC in subflooring and flooring is for your part of the world during different times of the year by testing existing houses. Get in the habit of constantly checking your own house. Push those pins to the full ¼”/ 5/16” depth and orient the pins with the longitudinal axis of the grain (with the grain). And what does variance of the number mean? If the MC varies by more than 1% there is something changing in the building. The greater the variance, the more substantial the changes that are in progress.

– Take your proper moisture meter everywhere you go. Please…. Pretty please with sugar on it…

The best source for information on moisture meters is our friends at the Forest Products Laboratory. One of my favorites is FPL-08 Electric Moisture Meters for Wood by William James. And you can download a copy from the FPL web site.

And remember the magic words: shrink and swell.

Try Ignorance

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Cross posted from Howard Brickman's article on Hardwood Floors Magazine: Inspector Blog.

If you think education is expensive, what do you figure the going rate for ignorance is? Or, do you think no one will notice when you are faking it? The “good” news is that most of your customers are very poorly informed and won’t know if your information is not correct. So if everyone uses the same incorrect information, who will notice? My intent in writing this blog is to challenge some of the mythology regarding wood flooring that has been incorporated into the collective consciousness of the wood flooring industry and to share some excellent sources of basic knowledge. But I will start with the warning that you should not believe anything unless you truly understand its basis in knowledge. With technical and scientific knowledge, this means that you need to understand the physical world described by physics, chemistry, biology, botany, and math.

An important part of understanding the knowledge is the words that comprise the vocabulary of every profession, skill, or specialty. Where it is feasible, it is best to avoid reinventing the wheel with regard to terminology. It is especially useful to bring terms from the basic fields of science into our specialty to build a bridge into the basic knowledge and establish a direct link with our specialty and what we can prove. Does this mean that everyone needs to become a physicist? No, but we should respect the terminology that describes the physical world and not invent our own mock science to describe what goes on around us.

So, here we go. Wood “shrinks” and “swells” when it loses and gains moisture content… like that fancy wool sweater that you should not have put in the dryer at the high heat setting. The words “expand” and “contract” generally refer to dimensional changes that occur due to changes in temperature. Although very similar in meaning to swell and shrink, it is not technically correct. The Wood Handbook is the one of the best sources for information about wood that is technically accurate. It is published by the Forest Products Laboratory in Madison, Wis. Better yet, it’s free if you have a computer with Internet access. It is a technical book that requires some understanding of basic science and math. It also contains almost all of the fundamental knowledge about wood and lumber that professionals would need for their entire career. If you are only going to have one book in your professional library, make it The Wood Handbook.

The wood floor bidness has developed some less-than-accurate habits over the years with the words we use to describe wood and how it works. We are not disciplined about using technical words. And using the correct words is a great habit to develop, because it greatly limits misunderstanding. Misunderstanding can easily transition into differences of opinion, which can easily transition into disagreements, which can easily transition into disputes and problems. Disputes and problems are bad for business, which wastes a great deal of our mental energy and material resources. Distractions that you enjoy are called hobbies, while distractions that are not enjoyable are called problems. It makes no sense to cultivate any hobbies that are not enjoyable . So when you refer to dimensional changes related to changes in moisture content, please use the magical words “shrink” and “swell”.

The Concrete Jungle

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astmlogobWeek before last, I attended the Resilient Flooring Committee (called F-06) meeting at ASTM* Headquarters in Philadelphia. This committee is on the cutting edge when it comes to outlining methods and standards for testing moisture in concrete. I must say, it is impossible to not be impressed by such a smart group of hard working professionals striving to create good documents based on the best available science. The F-06 committee is the driving force behind developing the internal Relative Humidity testing of moisture in concrete (ASTM F-2170).  

Having studied the science behind drying and curing, I am always surprised by the amount of controversy surrounding the moisture testing of concrete. There are many millions of dollars in failures of coatings and floor coverings due to excessive moisture in concrete subfloors. Large commercial job failures are financially devastating for flooring contractors. How does the song go?  “Send lawyers, guns, and money.” It seems to me that it is easier to test the concrete for moisture than to figure out how to weasel out on a failed floor.

The fascinating part of this meeting was the discussion and balloting concerning a proposed new guideline for using electronic concrete moisture meters. Anyone knowledgeable about these meters realizes that while they are useful for finding building leaks (high readings for wet areas versus lower readings for dry areas), they do not actually measure the quantity of moisture in the concrete. In fact, the proposed guideline stated:

This meter is not intended to provide quantitative results as a basis for acceptance of a floor for installation of moisture sensitive floor finishes.

It was a spirited discussion and while the vote was close, the document was sent back for further revisions.  In case you were curious, I voted for further revision.  It seems that there is no pressing need for a prestigious organization like ASTM to produce a document which might be misinterpreted, or worse yet, mis-used by unscrupulous individuals.

All in all, it was two days well spent furthering my understanding of the concrete industry, and highly recommend becoming involved with ASTM to anyone interested in doing the same.

*ASTM = The American Society of Testing and Materials is an organization that helps groups of interested volunteers work to create documents that standardize test methods and procedures for concrete.  It is a transparent and open process for anyone who wants to participate.