An impact analysis for the National Guide for Wildland-Urban Interface Fires

CC2 exterior wall cladding must be ignition-resistant. This means, approximately, that it can be of any material with a flame-spread rating of 25 or less under CAN/ULC-S102. An equivalent set of acceptance criteria under ASTM E2768 also applies. It is common, but not universal, for vinyl siding to satisfy this provision. Table 17 lists five leading manufacturers and two arbitrarily selected vinyl siding products from each manufacturer. Eight of the ten products satisfy the provision, and two do not. CC3 exterior walls may be limited ignition-resistant, which eliminates the restriction on fire spread rating for vinyl siding and allows for wood cladding and log wall construction.

Table 17. Vinyl cladding fire spread ratings for some leading manufacturers and common products Manufacturer

Product

Flame spread rating

Reference

CertainTeed

CedarBoards Insulated Siding

< 25

CertainTeed (2021a, p. 2)

CertainTeed

MainStreet

< 25

CertainTeed (2021b, p. 2)

CraneBoard Exterior Portfolio

< 25

Arcat (2016, p. 3)

Elm Grove

< 25

Royal Building Products (2021, p. 2)

Charter Oak

< 20

Alside Inc. (ND, p. 2)

Ascend

< 25

Alside, Inc. (2020, p. 4)

Nottingham

20

Variform, Inc. (2011, p. 5)

Timber Oak Ascent

20

Variform, Inc. (2011, p. 2)

Haven® Insulated Siding

40

National Research Council of Canada (2017, p. 4)

Select

85

National Research Council of Canada (2018, p. 6)

Crane Alside Variform Royal

Cost for new construction with fibre cement rather than vinyl: The cost issue for the sample buildings is essentially to replace vinyl cladding with stucco, the most common of the noncombustible cladding materials in either the full existing building database or the post-2000 subset.

Alternatively, the material most closely resembling vinyl siding is fibre cement board. A quick survey of vinyl siding retail costs at a big-box construction supply store (Home Depot) in Thunder Bay, Ontario, shows that vinyl siding products can cost $1.50 to $2.50 per square foot material cost, depending on the product line. HardiePlank cement board currently costs approximately $1.90 per square foot material cost at Home Depot. RSMeans (2019d) suggests a material cost of $1.40 per square foot for fibre cement siding – essentially the same as the Thunder Bay Home Depot retail cost after multiplying by the 1.11 location factor and bracketed by the material cost of vinyl siding, which suggests that RSMeans (2019d) is dependable, at least on material cost.

RSMeans (2019d, p. 135) estimates that installing 4-foot x 8-foot fibre cement board cladding on a new house costs between $3.10 per square foot (pre-tinted) and $5.20 per square foot (painted), with an average of $4.15 per square foot, including the first coat of paint or pre-tint. The same source suggests $6.30 per square foot for fibre cement board with lap siding, including paint.

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