Fire spread concerns when using plastic moisture barriers.

Plastic or other materials placed on crawl space floor and sometimes foundation walls can make a big difference in crawl space moisture levels. But do we need to consider fire safety?

Flame Spread & Fire Resistance of Plastic Moisture Barriers

Reader Question: Building code & standard requirements for flame spread properties of polyethylene vapor barriers

Recently our town building inspector required a flame spread rating of 75 or better and smoke of 200 or less for crawl space moisture barrier. Do you know if this is really in the IBC and do you know of 6 mil or heavier moisture barriers that meet the requirement? - K.W. 30 October 2015

Reply: ASTM & NFPA Standards pertinent to flame spread of polyethylene vapor barriers

The building inspector on site is the final legal authority in requiring specific building features for compliance with local building codes, though one might mount a challenge and though some building code officials will happily accept alternative designs if they are specified by and signed-off on by a design professional such as a licensed engineer or architect.

A review of some polyethylene products that offer flame-resistant ratings includes a flame-resistant polyetylene product that is essentially a three-layer laminate: two layers of a high-strength polyester film that is fire-retardant/resistant laminated with a layer of polyethylene (or in some product descriptions a "molten polyethylene".

There are pertinent standards and some building codes that discuss flame spread in thin polyethylene sheeting such as the 6-mil poly that may be used in a crawl space: ASTM and NFPA. I include descriptions of these blow.

ASTM-E84 "Standard Test Method for Surface Burning Characteristics of Building Materials",

Excerpting:

4.1 This test method is intended to provide only comparative measurements of surface flame spread and smoke density measurements with that of select grade red oak and fiber-cement board surfaces under the specific fire exposure conditions described herein.

4.2 This test method exposes a nominal 24-ft (7.32-m) long by 20-in. (508-mm) wide specimen to a controlled air flow and flaming fire exposure adjusted to spread the flame along the entire length of the select grade red oak specimen in 51/2 min.

4.3 This test method does not provide for the following:

4.3.1 Measurement of heat transmission through the tested surface.

4.3.2 The effect of aggravated flame spread behavior of an assembly resulting from the proximity of combustible walls and ceilings.

4.3.3 Classifying or defining a material as noncombustible, by means of a flame spread index by itself.

Source: - http://www.astm.org/Standards/E84.htm - excerpting from ASTM:

(Here is some additional information on applying this standard: http://www.trend-group.com/uploads/sfTinyMceAssets/file/surface-burning-characteristics.pdf )

NFPA 285: Standard Fire Test Method For Evaluation Of Fire Propagation Characteristics Of Exterior Non-load-bearing Wall Assemblies Containing Combustible Components

Excerpting:

This standard provides a standardized fire test procedure for evaluating the suitability of exterior, non-load bearing wall assemblies and panels used as components of curtain wall assemblies that are constructed using combustible materials or that incorporate combustible components for installation on buildings where the exterior walls are required to be non-combustible.

Fire propagation characteristics are determined for post-flashover fires of interior origin.

NFPA 285 requires both visual observations made by laboratory personnel conducting the test and temperature data recorded during the test. It is important to note that NFPA 285 is an assembly test.

Source: http://www.nfpa.org/codes-and-standards/document-information-pages?mode=code&code=285

NFPA 701: Standard Methods Of Fire Tests For Flame Propagation Of Textiles And Films

Excerpting:

This standard establishes test methods to assess the propagation of flame of various textiles and films under specified fire test conditions. Two distinct test methods differentiate fabrics of different densities.

The test methods apply to textile materials used in interior furnishing for public occupancy buildings including curtains, window shades, draperies, table linens, textile wall hangings, as well as to fabrics used in the assembly of awnings, tents, tarps and other similar architectural fabric structures and banners.

Source: http://www.nfpa.org/codes-and-standards/document-information-pages?mode=code&code=701

Building Codes & Other Standards for Flame Spread & Combustible Materials Involving Vapor Barriers, Retarders, Water Barriers

• Fairfax County VA Building Department, "Insulated crawl spaces are permitted only when they are unvented and there is a suitable vapor barrier over exposed earth." in "Problem Codes, Report No. BPR018, 2015, retrieved 2 Nov 2015, original source: http://www.fairfaxcounty.gov/dpwes/construction/rej_residential.pdf
• Lakevill MN Building Department, "Fiberglass insulation left exposed in exterior walls must be covered on the interior by not less than a 4-mill thick flame retardant vapor barrier. " in "Basement Finish Permit and Building Code Requirements, rev. 3/20/2009, Lakevill MN building department, retrieved 2 Nov 2015 original source: http://www.ci.lakeville.mn.us/departments/departmentspdf/Basement.pdf
• North Carolina Building Code, Section R409: Closed Crawl Spaces [describes vapor retarders but does not cite flamer spread retardance - Ed], (2012) Excerpting:
  
  • R 409 - Closed Crawl Spaces
  • R409.1 Air sealed walls. Closed crawl spaces shall be built to minimize the entry of outdoor air into the crawl space. Specifically prohibited are foundation wall vents and wall openings to ventilated porch foundations.
    
    When outdoor packaged heating and cooling equipment is used, solid blocking and sealants shall be used to seal gaps between the exterior wall opening and the smaller supply and return ducts that pass through the opening.
  • R409.1.1 Caulking and sealants. Air sealing caulk, gaskets or sealants shall be applied to the foundation wall and floor assemblies that separate the crawl space from outside and other ventilated areas such as joints around access door and frame, between foundation and sill plate, at penetrations for plumbing, mechanical, electrical and gas lines and at duct penetrations.
  • R409.1.2 Access panel/door. A minimum access opening measuring 18 inches by 24 inches (457 mm by 610 mm) shall be provided to the crawl space. See the North Carolina Mechanical Code for access requirements where mechanical equipment is located under floors.
    
    To minimize air entry, provide a tight fitting access panel/door with a latch mechanism. Access panels or doors shall be insulated to a minimum of R-2.
  • R409.2 Groundwater vapor retarder. Closed crawl spaces shall be protected from water entry by the evaporation of water from the ground surface.
  • R409.2.1 Ground vapor retarder. A minimum 6-mil (0.15 mm) polyethylene vapor retarder or equivalent shall be installed to nominally cover all exposed earth in the crawl space, with joints lapped not less than 12 inches.
    
    Minor pockets or wrinkles that prevent total drainage across the surface of the vapor retarder are allowed. The floor of the crawl space shall be graded so that it drains to one or more low spots. Install a drain to daylight or sump pump at each low spot. Crawl space drains shall be kept separate from roof gutter drain systems and foundation perimeter drains.
  • R409.2.2 Liner. The ground vapor retarder may be installed as a full interior liner by sealing the edges to the walls and beam columns and sealing the seams. Single piece liner systems are approved.
    
    The top edge of the wall liner shall terminate 3 inches below the top edge of the masonry foundation wall. The top edge of the liner shall be brought up the interior columns a minimum of 4 inches above the crawl space floor.
    
    The floor of the crawl space shall be graded so that it drains to one or more low spots. Install a drain to daylight or sump pump at each low spot. Crawl space drains shall be separate from roof gutter drain systems and foundation perimeter drains.
  • R409.2.1.1 Wall liner termite inspection gap. Provide a clear and unobstructed 3” minimum inspection gap between the top of the wall liner and the bottom of the wood sill. This inspection gap may be ignored with regards to energy performance and is not intended to create an energy penalty.
    
    - Retrieved: 11/2/2015, See http://www.ncdoi.com/OSFM/Engineering_and_Codes/Documents/2009_NCBuildingCode_amendments/approved/2009NCResidential.pdf
  
  
• NAIMA, "Use only flame-resistant facings for exposed applications" and "If no stud wall is available, the insulation can be applied in blanket form with a perforated flame-resistant facing." [in discussing vapor retarder installation on or in building wall structures] in "Use of Vapor Retarders, Insulation Fact Sheets #71", NAIMA, North American Insulation Manufacturer's Association, retrieved 2 Nov 2015 original source: http://www.certainteed.com/resources/Use%20of%20Vapor%20Retarders.pdf
• Carmody, John, Mosiman, Garrett, Harneen, Daniel, Huelman, Patrick, Jeffrey Christian, "3.1 Recommended Design and Construction Details, Vented versus Unvented Crawlspaces", Excerpt:
  
  
  Interior crawl space wall insulation (Figure 3-6b) is more common than exterior, primarily because it is less expensive since no protective covering is required, and can present a reduced hazard of termite infestation.
  
  On the other hand, interior wall insulation may be considered less desirable than exterior insulation because it
  
  (1) increases the exposure of the wall to thermal stress and freezing,
  
  (2) may increase the likelihood of condensation on sill plates, band joists, and joist ends,
  
  (3) often results in some thermal bridges through framing members, and
  
  (4) usually requires installation of a flame resistant cover. Interior insulation is not recommended on non-core filled masonry block walls, due to an increased risk of moisture accumulation within the assembly.
  
  In addition, interior insulation should not be used if a positive capillary break is not present between the top of the foundation wall and wood framing system due to the potential for moisture accumulation in wood framing materials. ",
  
  Oak Ridge National Laboratory, Oak RIdge TN, USA, - retrieved 2 Nov 2015 original source: http://web.ornl.gov/sci/buildingsfoundations/handbook/section3-1.shtml also cited as "DOE Building Foundations Credits" U.S. Department of Energy.
• IBC 2009, Chapter 14: Exterior Wall Coverings, Vapor Retarders and Water Resistive Barriers. This section in turn cites (for Type I and II construction):
  • ASTM D 226 (15 pound roofing felt)
  • AC-38 Building Warp or Self-Adhering Sheets
  • AC-212 Fluid-Applied Membranes
• IBC 2009 Chapter26: Platic Foam Insulation, cites in turn
  • ASTM # 84, Smoke and flame spread properties

Some flame-spread resistant 6-mil plastic poly vapor barrier products including sold at Home Depot - listed later, below.

Product Sources: flame-retardant poly coverings:

HUSKY 20 ft. x 100 ft. 6 mil Flame Retardant Plastic Sheeting

and here is an MSDS for a flame-retardant sheeting

http://inlineco.com/msds/Poly_America/Flame_Retardant_Test_Results.pdf from Poly-America.

Global Plastics also lists a range of such products. http://www.globalplasticsheeting.com/nfpa-701-15

Thank you for asking - I'd welcome any further comment, questions, photos etc.

...

Continue reading at FIRE STOPPING in BUILDINGS or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see these

Recommended Articles

• CRAWL SPACE MOISTURE BARRIERS
• CRAWL SPACE GROUND COVERS
• FIRE DAMAGED BUILDINGS, ASSESSMENT, REPAIR

Suggested citation for this web page

PLASTIC MOISTURE BARRIER FLAME SPREAD at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

Or see this

INDEX to RELATED ARTICLES: ARTICLE INDEX to CRAWL SPACES

Or use the SEARCH BOX found below to Ask a Question or Search InspectApedia

Ask a Question or Search InspectApedia

Try the search box just below, or if you prefer, post a question or comment in the Comments box below and we will respond promptly.

Note: appearance of your Comment below may be delayed: if your comment contains an image, photograph, web link, or text that looks to the software as if it might be a web link, your posting will appear after it has been approved by a moderator. Apologies for the delay.

Only one image can be added per comment but you can post as many comments, and therefore images, as you like.
You will not receive a notification when a response to your question has been posted.
Please bookmark this page to make it easy for you to check back for our response.
Our Comment Box is provided by Countable Web Productions countable.ca

Citations & References

In addition to any citations in the article above, a full list is available on request.

---

ADVERTISEMENT

---