Is It Possible to Preservative and Fire Treat Wood?

[Mike Mike]

Hi all, is it possible to pressure treat and fire treat lumber in say an exposed above ground wood deck scenario?

Here's what I think I know so far:

My office has done hundreds of 5-story light frame buildings over the last decade and all my superiors say no, you can't pressure treat and fire treat.

Link SlideRuleEra says yes and cites Exterior Fire-X®, however Fire-X says it's a "leach resistant fire-retardant treatment and may be installed with direct exposure to precipitation; however, it cannot be substituted for preservative treated wood" Link He also cites AWPA UCFB use category. Does anyone have any additional info on how specifically manufacturers achieve UCFB? A quick google search came up fairly empty-handed.

Specification 060573 Fire Retardant Treated Wood For Exterior Applications exists, which would hint that it is possible, but just because the spec exists does not mean it's a good idea. And for some reason under 1.04 Performance Requirements, only fire resistance requirements are listed, not preservative requirements (ASTM E-84, standard test method for assessing the surface burning characteristics of building products to explore how the material might contribute to flame spread in the event of a fire, and ASTM D2898, Standard Practice for Accelerated Weathering of Fire-Retardant-Treated Wood for Fire Testing)

Chemonite (ammonical copper zinc arsenate) was tested on Douglas Fir lumber pressure treated with 1.86 pcf and was found to have a 24.8 flame spread rating, qualifying for a Class A rating under E-84. Chemonite's main purpose is wood preservation, not fire treatment, and I couldn't find any third-party testing reports on it. Link

Flameproof Companies’ "exterior fire retardant wood products have been submitted to both the ASTM E84 testing for surface burning characteristics and to ASTM D2898 for accelerated weathering (rain) tests. However, exterior fire retardant products are not rot resistant. Therefore, it is suggested that cedar fire retardant wood products be used for outdoor applications, as it is a species of lumber that is naturally rot resistant." Link

I'm seeing quite a few other products out there but nothing else seems to be of great promise so I won't mention them here. All products seem to bear a common theme: they are able to retain their fire protection through weathering, but they do not provide weather resistance. Sorry if that sounds silly, but that's what I'm seeing. My thought is why can't you just mix the fire chemicals with the preservative chemicals before pressure treating like in this FPL paper? Link We can land a man on the moon but we can't figure out how to double treat wood? What the

Mike

 

[SlideRuleEra]

1) SlideRuleEra says yes and cites Exterior Fire-X®, however Fire-X says it's a "leach resistant fire-retardant treatment and may be installed with direct exposure to precipitation; however, it cannot be substituted for preservative treated wood"...

2) ...is it possible to pressure treat and fire treat lumber in say an exposed above ground wood deck scenario?

1) You fail to point out that the post where I made that statement was 9 years ago (2014).
Things change...

2) Since 6 years ago the answer is a clear NO

Here is the Link to the complete Technical Note, published and posted by the manufacturer of Exterior-FireX.
Also, notice the date of the Technical Note (located at the bottom) - "12-2017".

I don't make this stuff up.

 

[Mike Mike]

thanks for the tech note slideruler, it's okay I left a spot open for you on our team, welcome aboard sport!
just kidding I don't have a team I'm not sold yet