Pages Navigation Menu

Wood Seal FAQs

Product Series
Wood Seal
Wood Seal A
Wood Seal FAQs

What is Wood Seal™ Fire Retardant?

Wood Seal-A Fire Retardant (Class A)  and Wood Seal Fire Retardant (Class B) are penetrants designed for use on unpainted / unsealed wood and other cellulose type materials.  Wood Seal Class A is basically a more robust version of Wood Seal.

Testing / Flame Spread Ratings

Both Wood Seal Class A and Wood Seal were tested on Douglas Fir in the ASTM E-84-05 (Steiner Tunnel) flame spread test.  Wood Seal achieved a Class B fire rating;  Wood Seal Class A achieved a Class A fire rating.

What is the difference between the two?

Wood Seal is a water-based fire retardant, containing no other solvents.  Wood Seal-A  is also a water-based product with performance additives and alcohol based penetrant additives.  As such, Wood Seal-A should be stirred prior to use as some settling of the additives may occur.  Both Wood Seal-A and Wood Seal are low odor, non-toxic, non-hazardous and contain no halogens.  Wood Seal contains very low VOCs while Wood Seal-A  contains slightly more in the form of alcohol based penetrant aids.

How are the fire retardant products applied?

Wood Seal-A and Wood Seal are water thin fire retardant liquids and may be applied by brush, roller, spray and submersion methods to unpainted / untreated wood, paper, or other cellulose products.  The substrate must be able to absorb the water based chemical to provide fire protection.  A simple guideline test is to place a few drops of water on the material.  If the water is readily absorbed, it is probably treatable.  Recommended coverage rates range from 150-350 square feet per gallon, depending upon the results desired.

Do the retardants protect the substrate from fire damage?

Wood Seal Fire Retardant is a mild intumescent but will not prevent fire damage to the substrate.  It will slow the flame spread and prevent fire from propagating along the treated surface, which also reduces smoke production.  Wood Seal-A  Fire Retardant is a somewhat more robust intumescent and will protect the substrate somewhat better, but it will still not prevent wood damage from the flame.

Can / Should these fire retardants be top coated?

Both dry clear and odorless.  Wood Seal-A  may leave some residue on the surface, especially if heavily applied.  Remove with slightly dampened cloth before completely dry or fine sanding, if necessary for staining or fine finishing.  Both may be over-coated with paint or stain once completely dried.  A water resistant coating is recommended for exterior or high humidity interior use.  Be sure and test a small treated area or sample, for compatibility before going full scale.


Once treated the material should not need to be treated with the fire retardant again, unless it is not sealed and is exposed to surface moisture or high humidity for an extended period.

Will these products achieve the listed ratings on all woods?

No.  Many factors contribute to the flammability and treatability of different wood varieties such as oil and resin content, moisture content, the ability to absorb these water based retardants, etc.  As such, some woods are much harder to treat than others.  The official ratings given for these products were from testing on Douglas Fir, which is considered the standard for testing.  It absorbs liquid fairly well and has an untreated Flame Spread of 90 to 105.  Comparison charts of flame spread rating for most wood types are available on the internet.  Any flame spread ratings to be met or claimed must be determined by the customer.

Non-Code Adequate treatment

To test for general adequate fire retardant treatment apply a flame or torch to a sample of treated material.  If the flame does not spread rapidly away from the heat source and goes out soon after the heat source is removed, then your material is probably sufficiently treated.  If you are trying to meet code, check with your local fire marshal as to what is acceptable.  You may have to pass third party testing.