Let’s talk about low-density board.

Recently, there have been quite a few inquiries about low-density boards, so I’ve decided to write an article to explain everything clearly.

First, let’s clarify: the low-density boards we’re referring to here are fiber-reinforced cement products, including fiber-cement boards and calcium silicate boards.

 

 

So, what exactly is low-density board? Here, we’re primarily discussing asbestos-free boards; chrysotile asbestos-based boards are not within the scope of this discussion.

 

 

In fact, the current industry standards for fiber-cement boards and calcium silicate boards—namely, “JC/T412.1 Fiber-Cement Flat Boards, Part 1: Asbestos-Free Fiber-Cement Flat Boards” and “JC/T564.1 Fiber-Reinforced Calcium Silicate Boards, Part 1: Asbestos-Free Calcium Silicate Boards”—do not contain any provisions specifically addressing low-density boards. With regard to “density,” there is only a brief statement: the apparent density shall not be less than the specified value indicated in the manufacturer’s documentation.

 

 

This is awkward—when it comes to the low-density boards and high-density boards that everyone often talks about, the standards actually fail to provide a clear definition. The phrase about “density” in the standard above, translated into plain language, boils down to this: The name doesn’t matter; I’ll decide the density myself. It truly confirms that old saying: If you’re not embarrassed, it’s others who are.

 

 

As we all know, the current industry standards for fiber-cement boards and calcium silicate boards were issued in 2018 and came into effect on September 1, 2018. But did the earlier standards contain more detailed specifications regarding “density”? Surprisingly, they did. Not only do the standards JC/T412.1-2006, "Asbestos-Free Fiber-Cement Flat Boards," and JC/T564.1-2008, "Asbestos-Free Calcium Silicate Boards," include statements related to "density," but we also found relevant clauses in the standard JC/T566-2022, "Perforated Fiber-Cement Boards for Sound Absorption." However, taken together, these provisions—scattered across various now-abolished and current standards—are not consistently worded. The following table provides a detailed breakdown:

 

Standard Name	Relevant provisions	Excerpt from the terms and conditions
JC/T412.1-2006 Asbestos-Free Fiber Cement Flat Sheets	6.3 Physical Properties	Low density: 0.8 ≤ D ≤ 1.1 g/cm³; Medium density: 1.1 ≤ D ≤ 1.4 g/cm³; High density: 1.4 ≤ D ≤ 1.7 g/cm³
JC/T564.1-2008 Asbestos-Free Calcium Silicate Board	6.3 Physical Properties	D0.8:D ≤ 0.95 g/cm³; D1.1: 0.95 < D ≤ 1.20 g/cm³; D1.3:1.20 < D ≤ 1.40 g/cm³; D1.5:D > 1.40 g/cm³
JC/T566-2022 Perforated Fiber Cement Board for Sound Absorption	6.4.1 Physical Properties	Low density ≤ 1.0 g/cm³; Medium density > 1.0–1.3 g/cm³; High density > 1.3 g/cm³

 

It should be noted that although the standard “JC/T566-2022 Perforated Fiber Cement Board for Sound Absorption” does not explicitly mention calcium silicate boards in its title, Clause 3—Terms and Definitions, Item 3.1—Perforated Fiber Cement Board for Sound Absorption—defines such boards as those made from asbestos-free fiber cement slabs or asbestos-free calcium silicate boards, which have been perforated to produce panels with identically shaped holes arranged symmetrically (or asymmetrically). Note: These boards are commonly referred to as perforated boards. It is thus clearly stated that this standard applies to calcium silicate boards as well.

 

 

Now, here’s the issue: Although both “JC/T412.1-2006 Asbestos-Free Fiber Cement Flat Boards” and “JC/T564.1-2008 Asbestos-Free Calcium Silicate Boards” contain provisions regarding density, these two standards have already been superseded by newer ones. Yet, the new standards fail to carry over the original standards’ specific density classifications. In other words, many manufacturers today are simply making unsubstantiated claims about “low-density boards”—they’re just playing with words and engaging in semantic games.

Why do you say that?

Because as long as you’re willing, even if you’re talking nonsense all the time, no one can fault you for it.

 

 

Doesn’t that sound kind of magical? Reality is always more fascinating than any story. Let me give you an example: Suppose you’ve developed a board with a density of 1.25 g/cm³—whether you call it fiber-cement board or calcium silicate board. Now, you decide to give it a brand-new name: “low-density **board”—and then publicly claim its density is actually 1.0 g/cm³. What’s going to happen? Absolutely nothing. As long as this board isn’t used for perforated panels, no one will dare accuse you of outright lying. Even if a testing agency conducts a spot check on your board at the site, they’ll still stamp the report with a “pass” label. Haha—that’s pretty funny, isn’t it? And yet, it’s dead serious.

Of course, extreme situations may arise, but they won't last long—eventually, the market will give those who merely talk about innovation a satisfying answer.

 

 

Regarding inquiries about low-density boards, to sum it up in one sentence: Since the new standards categorize boards into three classes—A, B, and C—each corresponding to different application scenarios ranging from outdoor to indoor use, boards must possess varying physical properties to meet these diverse requirements. As long as they satisfy the performance criteria for each of these A, B, and C categories, there’s no need to obsess over density. Wouldn’t it be even better if they could achieve both light weight and high strength? Conversely, even if your board has an extremely low density, but its physical performance is utterly poor—rendering it as brittle as crumbled cookies—what’s the point of pursuing low density for its own sake?

For users, simply clarify what you need and choose accordingly—after all, the three categories of fiber-cement products already cover most of our application scenarios. If you’re dealing with special applications where density is particularly important and you’re looking for lower-density inorganic boards, there’s no need to stick exclusively to fiber-cement products. Instead, consider alternatives such as magnesium oxide boards or gypsum boards. On thicker boards within the so-called low-density range, you might find even greater cost-effectiveness.

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