A few points about Magboard (from Ben Polley, alternative builder)

Recently we republished a post from Peter Francis from MagO building products, a distributor of magnesium oxide board (an alternative to gypsum wall board). 

Here’s a great post about magboard from Ben Polley, Evolve Builders, Guelph, Ontario.

Ben, thanks for sharing this with the 16,000 contractors who receive this e-newsletter! Thanks for starting the discussion, Peter.

“As an “alternative builder” (strawbale, Passive House, adobe floor & the like) we frequently test new-to-the market or even pre-commercialized products.

We first experimented with magboard in 2008. My reply speaks to Magboard as a product category and may not specifically apply to the brand Peter carries. That said, I believe that most (all?) magboard comes from just a few factories in China so there is some chance that differently branded products are actually sourced from the same overseas facilities.

Given this provenance, we must trust (as our own team currently do) that the product is indeed non-offgassing and/or doesn’t include toxic elements such as the widely publicized gypsum drywall from China that made it to the US market a few years ago. But I would argue that there may inherently be some risk in this regard when buying a product from manufacturers not affiliated with bigger, known North American brands.

Then there is the carbon footprint of the heat energy and shipping used to make the product though I recognize this may not be of specific concern to all builders.

In our experience a few points counter to Peter’s comments that do relate to builders:

* MB joints that don’t end over a stud must be backed by another narrow strip of MB, glued and nailed/screwed to the main sheets. This is not less expensive/quicker than typical frame and board processes.

*Beware fire rating claims. (In Ontario at least) Unless the manufacturer has acquired a BMEC number (or possibly a ULC or CSA approval) for their product it falls outside Part 3 or 9 of the Code; thus an engineer must sign off if it is to be counted toward total fire separation calculations. One learns this just once before being more cautious the next time.

*Inclusive of shipping – which can be pricey and not always timely – we have found the material to be 2x to 4x that of GWB. There can also be more waste/offcuts as there are fewer stock dimensions available to suit natural wall lengths or heights, as we would ordinarily plan for with GWB.

* Carbide blades are indeed required and you will burn through them pretty quickly Score and snap we have found to be all but impossible or at least impractical – MB as promised is dense and hard. Mostly though the need to cut boards means that the rapid fire pace at which GWB boarding takes place is not likely with MB. Consider it more like installing panel board ie. a role for a carpenter (thus slower work and at potentially higher wages).

* Can’t imagine not taping joints, factory or otherwise. One brand suggests caulking then wiping the joints however we tried that too and it is all but impossible to get a flush finish. Some joints are harder to tape than GWB – the butt ends of MB need to be machined on site if you wish to chamfer them for taping…cannot simply run an exacto blade down the board as one might on GWB.

*Overall we find the material cost to be higher than GWB, installation to be higher and mudding/taping to be marginally the same.

One might think from the above that I am dissuading MB use. In fact we continue to use it (doing so presently on a project in Ancaster, ON) but generally for specialized applications, where the limitations described above are minimal or where the advantages (paperless, strength, recycled material content etc as Peter describes) outweigh the other factors. If material costs were to decline substantially while also meeting regulatory norms (fire rating predominantly) of the local jurisdiction and offering more dimensions, there is no reason why it couldn’t be more widely applied.”