Fire  Retardant  Coatings       An  evaluation  of  fire  retardant  coatings  as  a  means  of  protecting  wood   panels           Fraser  Perry  Goldsmith                   April  17,  2011     WOOD  493                         i   Executive  Summary   The  protection  of  residential  buildings  from  the  effects  of  fire  is  becoming  increasingly  important.  For   example,  Alberta  has  altered  its  fire  codes  to  make  fire  protection  of  wood  sheathing,  including  plywood   and  OSB,  compulsory  in  the  design  of  residential  buildings  in  close  proximity  to  each  other.  Two  of  the   approved  methods  of  protection  are  through  the  use  of  fire  retardant  coatings  or  sheathing  the  OSB  or   plywood  with  exterior  gypsum  panels.  There  are  divided  opinions  on  which  method  of  fire  protection  is   superior  in  terms  of  performance,  convenience,  and  cost  effectiveness.  In  this  essay  I  conclude  that  fire   retardant  coatings,  when  properly  applied,  perform  well  and  are  a  convenient  method  for  protecting   wood  sheathing  from  fire.  However,  their  poor  resistance  to  weathering  and  increased  cost  make  them   a  less  cost  effective  solution  than  durable  gypsum  sheathing  systems.  Coating  systems  may  be  effective   when  used  to  compliment  a  gypsum  sheathing  system  to  protect  areas  of  buildings  that  are  difficult  to   sheath.                   List  of  Key  words:  Intumescent,  oriented  strand  board,  Alberta  Fire  code,  gypsum  sheathing,  pressure   treatment,  flame  spread  rating,  smoke  developed  index,  flame  retardant,  exposure,  leaching,  weather   resistance,  wear  resistance.             ii   Table  of  Contents   List  of  Tables  and  Figures................................................................................................................. iii   1.0  Introduction.....................................................................................................................................1   1.1  Fire  in  Buildings .........................................................................................................................1   1.2  Flame  Spread  Rating .................................................................................................................2   2.0  Advantages  of  Fire  Retardant  Coatings ..................................................................................3   2.1  Performance  Characteristics..................................................................................................3   2.2  Convenience  of  Coatings ..........................................................................................................5   3.0  Disadvantages  of  Fire  Retardant  Coatings ............................................................................5   3.1  Exposure  Problems ...................................................................................................................5   3.2  Application  Issues......................................................................................................................6   3.2  Cost  of  Coating  Systems............................................................................................................7   4.0  Comparison  of  Coatings  to  Other  Systems.............................................................................9   4.1  Coating  Versus  Treatment ......................................................................................................9   4.2  Coatings  Versus  Gypsum  Sheathing.....................................................................................9   5.0  Conclusion  and  Recommendations.......................................................................................12   6.0  References .....................................................................................................................................14                     iii   List  of  Tables  and  Figures   Figures   Figure  1  -­‐  Estimated  Costs  of  Coating  a  4’  x  8’  OSB  Panel……………………………………………………………8   (Ceasefire  Technologies,  2011)   Tables   Table  1  -­‐  Flame  Spread  Ratings  of  Building  Materials…………………………………………………………………2   (Williamson,  2002)   Table  2  -­‐  FSR  and  FDI  for  Coated  Wood  Building  Materials.……………………………………………………….4   (Quantum  Chemical,  2011)   Table  3  -­‐  Cost  of  Coating  System  Compared  to  a  Gypsum  System……………………………………………11   (Ceasefire  Technologies,  2011,  ToolBase,  2003)   Table  4  -­‐  Costs  of  Using  Fire  Retardant  Systems  to  Protect  a  House…………………………………………11   (Building  a  Home  Info,  2010)                       1   1.0  Introduction   1.1  Fire  in  Buildings   Residential  fires  have  always  been  a  cause  for  concern  for  designers,  specifiers  and  the  general   public.  The  destructive  force  of  fires  in  residential  buildings  results  in  serious  injuries,  death,   and  the  loss  of  millions  of  dollars  worth  of  property.  The  choice  of  materials  that  are  used  in   buildings  can  have  a  large  impact  on  their  susceptibility  to  fire  and  the  rate  at  which  the  fire  is   spreads  through  the  structure.  Wood  and  wood  composites  are  combustible  materials  and  will   naturally  support  a  flame.  Hence,  fire  is  able  to  spread  across  the  surface  of  wood  and  affect   areas  and  structures  beyond  the  origin  of  the  fire.  The  flame  spread  over  structural  wood   panels  such  as  plywood  and  oriented  strand  board  (OSB)  is  of  particular  concern  to  end-­‐users.     Many  different  systems  have  been  used  to  reduce  the  combustibility  of  wood.  For  example,  in   the  past,  lumber  and  plywood  boards  were  pressure  treated  with  fire-­‐retardant  chemicals  to   reduce  their  combustibility.  Fire-­‐retardant  treatments  are  applied  in  basically  the  same  way  as   preservative  treatments  (CWC,  2000).  More  recently,  intumescent1  fire-­‐retardant  coatings  have   been  developed  to  protect  wood  and  to  slow  the  spread  of  flames.     Specific  guidelines  for  the  use  of  fire  retardant  coatings  have  been  developed  to  minimize  the   impact  of  fires.  Alberta,  in  particular,  has  taken  steps  to  minimize  the  damage  and  area  affected   by  residential  fires  by  introducing  strict  rules  in  their  fire  and  building  codes.  The  need  for   increased  fire  protection  can  be  attributed  to  the  occurrence  of  6300  fires  each  year,  which  kill   around  35  people  and  cost  approximately  $190  million  in  property  losses  in  Alberta  (HIRF,   2008).  In  May  of  2009,  the  Alberta  Fire  Code  (AFC)  was  altered  with  the  intent  of  minimizing  the   impact  of  residential  fires  (Markusoff,  2009).  One  of  the  main  objectives  of  the  fire  codes  is  to   minimize  the  spread  of  fire  and  to  protect  adjacent  buildings  if  fire  does  occur.  If  buildings  are   within  certain  proximity  of  each  other  then  the  structural  wood  panels  must  be  protected  from   fire  by  an  approved  fire  retardant  system.                                                                                                                               1  A  substance  that  swells  with  exposure  to  heat  (Price,  2001).     2    The  Alberta  Fire  Code  states  that  the  allowable  methods  of  fire  protection  are  fire  retardant   coatings  and  fireproof  gypsum  sheathing.  These  methods  of  protection  must  be  applied  when   the  construction  of  the  building  exceeds  exterior  grade  level2  (FPB,  2010).  There  is  no   consensus  as  to  which  fire  retardant  system  is  the  most  suitable  for  use  in  Alberta  or  in  other   areas.  To  adhere  to  the  new  fire  codes  builders  in  Edmonton  are  choosing  to  use  fire  retardant   coatings  whereas  builders  in  Calgary  are  using  fireproof  gypsum  sheathing  (Gratton,  2010).  The   benefits  and  potential  drawbacks  of  using  fire  retardant  wood  coatings  will  be  discussed  in  this   essay  and  a  balanced  conclusion  will  be  reached  as  to  whether  fire  retardant  coatings  are  an   effective  system  for  protecting  residential  buildings  from  fire.     1.2  Flame  Spread  Rating   Coatings  used  to  protect  wood  panels  must  be  approved  by  the  Underwriter’s  Laboratories  of   Canada  (ULC)  with  a  class  “A”  flame  spread  rating  and  be  applied  by  a  certified  professional.   Flame  spread  rating  (FSR)  refers  to  the  rate  at  which  fire  is  able  to  travel  along  a  building   material’s  surface.    The  FSRs  of  a  few  building  materials  and  the  relationship  between  the  FSR   and  the  flame  spread  classification  of  materials  are  illustrated  in  Table  1.   Table  1:  Flame  Spread  Ratings  of  Building  Materials  (Williamson,  2002)   Material   Flame  Spread  Rating*   Gypsum  Sheathing   0   Red  Oak  Lumber   100   Douglas  fir   70-­‐100   Structural  Wood  panels   76-­‐200   *Class  A  =  0  –  25      Class  B  =  26  –  75      Class  C  =  76  –  200                                                                                                                               2  Any  construction  above  the  foundation  of  a  building  (Gratton,  2010).     3   FSR  is  a  measure  of  the  area  that  a  flame  is  able  to  spread  over  during  a  defined  period  of  time.   The  FSR  of  building  materials  is  calculated  in  the  lab  by  exposing  a  test  piece  to  a  gas  flame  at   one  end  and  measuring  the  area  that  the  flame  spreads  over.  The  area  of  flame  spread  for  the   test  material  is  then  divided  by  the  area  of  a  standard  material  and  then  multiplied  by  100.  Red   oak  is,  in  most  cases,  the  standard  material  that  test  materials  are  compared  to.   2.0  Advantages  of  Fire  Retardant  Coatings   2.1  Performance  Characteristics   Fire  retardant  coatings  are  good  at  improving  the  performance  of  structural  wood  panels.  First   of  all,  they  slow  down  the  spread  of  fire.  When  intumescent  coatings  are  exposed  to  high   temperatures,  the  coating  expands  and  insulates  the  material  with  a  layer  of  char3.  In  this   process,  the  coating  can  expand  from  anywhere  from  50  to  200  times  its  original  thickness   (Pryzbylak  &  Kozlowski,  1999).  This  thick  char  layer  is  able  to  perfectly  insulate  the  substrate   below  and  greatly  decrease  the  rate  at  which  the  fire  spreads  across  the  surface.  Even  when   fire  temperatures  exceed  800⁰C  in  extremely  intense  fires,  the  insulating  layer  will  remain  for   about  an  hour  (Fire  Retardants  Inc,  2010).  Hence  the  structural  integrity  of  the  wood  is   maintained  allowing  people  more  time  to  evacuate  the  building  and  for  authorities  to  try  to   control  the  blaze.     Most  commercially  available  fire  retardant  coatings  are  able  to  achieve  a  flame  spread  index  of   less  than  25  or  an  “A”  classification  when  applied  to  plywood  and  OSB.  SafeCoat® ,  one  of  the   leaders  in  the  fire  retardant  coating  industry,  manufactures  a  latex  intumescent  coating  that  is   able  to  get  a  flame  spread  rating  of  10  when  applied  to  OSB  (Quantum  Chemical,  2011).  This  is   well  within  the  range  of  a  class  A  fire  retardant.  The  FSR  of  SafeCoat  latex  intumescent  coating   on  different  wood  substrates  is  shown  in  Table  2.                                                                                                                             3  The  solid  material  left  over  after  the  initial  stage  of  combustion  (Pryzbylak  &  Kozlowski,  1999).     4   Table  2:  FSR  and  FDI  for  Coated  Wood  Building  Materials  (Quantum  Chemical,  2011)   Material   Coating   FSR   SDI4   Douglas  fir   lumber   Single  coat   5   0   SPF  Plywood   Single  coat  and  top   coat   5   0   OSB  (11mm)   Single  coat   10   20     Many  fire  retardant  coatings  also  have  the  ability  to  suppress  the  production  of  gases  by  wood   when  it  combusts.  The  gases  that  are  produced  during  the  combustion  of  wood  and  especially   wood-­‐composites  can  be  extremely  dangerous.  Approximately  70%  of  deaths  in  residential  fires   are  attributed  to  gas  inhalation  (Markusoff,  2009).     Suppressing  gases  is  also  important  for  reducing  flash  over.  Toxic  gases  and  superheated  air  can   reach  a  critical  point  during  a  fire  causing  the  gas  mixture  ignite  resulting  in  an  explosion  called   flashover  (Garrison,  2002).  Flashover  is  a  dangerous  time  in  house  fires  and  it  is  also  a   mechanism  that  enables  the  fire  to  spread  at  an  increased  rate.  Fire  retardant  coatings  also   decrease  smoke  development  which  delays  the  build-­‐up  of  toxic  gases  and  thus  helps  reduce  or   at  least  delay  flashover.  Smoke  development  index  (SDI)  is  used  to  quantify  the  amount  of   gases  that  are  released  when  a  building  material  is  exposed  to  fire.  Wood  panels  have  an  SDI   anywhere  from  25-­‐270,  but  when  coated  with  an  intumescent  coating  the  SDI  can  be  reduced   to  20  (Quantum  Chemical,  2011).  The  SDI  scale  is  similar  to  that  of  FSR  with  solid  red  oak  having   a  value  of  100  (Williamson,  2002).                                                                                                                                     4  SDI  is  a  measure  of  the  concentration  of  smoke  a  material  emits  as  it  burns  (Williamson,  2002).       5   2.2  Convenience  of  Coatings   Fire  retardant  coatings  are  also  convenient  to  use.  Fire  retardant  coatings  can  be  applied  in  the   factory,  on  the  jobsite,  or  on  panels  that  are  already  in  use  unlike  fire  retardant  pressure   treatments.  Coatings  can  be  applied  using  the  same  methods  as  most  paints;  using  a  sprayer,   roller  or  brush  (CWC,  2000).     Fire  retardant  coatings  can  be  added  to  existing  buildings  to  upgrade  the  fire  retardant   properties  of  panels  to  comply  with  modern  codes  and  regulations.  Having  the  ability  to  apply   the  fire  retardant  coatings  in  the  field  allows  end  users  to  coat  highly  customized  projects.   Hence,  fire  retardant  coatings  can  be  applied  to  key  areas  of  importance  instead  of  being   applied  to  full  sheets  of  fire  sheathing.  The  AFC  does  not  state  that  all  of  the  structural  wood   panels  have  to  be  fully  coated.  Instead  only  the  inside  face  of  the  wood  panels  and  the  outer   rim  of  the  wood-­‐flooring  panels  must  be  coated.  So,  by  applying  the  coatings  in  the  field,  the   fire  retardant  is  only  applied  to  those  areas  which  need  it  most  and  thus  minimizing  the  amount   of  fire  retardant  materials  that  are  required.     3.0  Disadvantages  of  Fire  Retardant  Coatings   3.1  Exposure  Problems   There  are  some  issues  which  make  fire  retardant  coatings  them  less  suitable  for  their  purpose.   First  of  all,  not  all  fire  retardant  coatings  can  be  used  outdoors  without  losing  their  fire   retarding  capabilities.  Fire  retardant  chemicals  can  leach  from  the  underlying  wood  substrate   when  exposed  to  high  humidity  or  rain,  rendering  the  materials  unprotected  from  fire  (CWC,   2000).  Some  coatings  are  “exterior  rated”  and  can  stand  up  to  the  elements,  however,  these   are  typically  more  expensive.  Other  coatings,  such  as  SafeCoat  latex  intumescent  coating,  can   have  a  water  resistant  coating  applied  on  top  of  them  to  make  them  suitable  for  use  outdoors   (Quantum  Chemical,  2011).   In  most  cases  the  wood  sheathing  will  not  be  exposed  to  the  elements  in  its  final  application.   Siding  material  made  from  wood,  composite,  or  plastic  will  most  likely  be  on  the  outer  face.   However,  in  the  construction  phase  of  the  building,  the  wood  sheathing  material  will  be     6   exposed  to  moisture.  The  duration  of  exposure  to  moisture  is  difficult  to  predict.  It  can  take   days,  weeks,  or  even  months  for  the  building  envelope  to  be  closed.  Before  such  closure  the   sheathing  can  be  exposed  to  sun,  wind,  rain,  and  snow  without  any  protection.  Hence,  if   interior  rated  fire  retardant  coatings  are  used,  the  fire  retardant  may  be  leached,  reducing  the   performance  of  the  coating.     To  be  classified  as  an  exterior  rated  fire  retardant  coating  by  the  National  Fire  Protection   Agency  (NFPA),  the  coating  has  to  be  subjected  to  a  laboratory  test.  Coatings  that  will  be   exposed  to  the  weather  or  conditions  of  80%  humidity  or  higher  must  pass  the  “Standard  Rain   Test“  (NFPA,  2009).  The  test  involves  exposing  samples  to  12  one-­‐week  conditioning  cycles  with   extreme  water  exposure  and  drying  cycles.  The  amount  of  water  exposure  is  the  equivalent  of   over  2000cm  of  rain  over  the  12  week  period  (WWPI,  2005).  This  test  ensures  that  the  FSR  of   the  coated  material  does  not  change  when  it  has  been  exposed  to  extreme  conditions.     The  Alberta  Fire  Code  does  not  specify  whether  exterior  or  interior  coatings  must  be  used.  It   only  states  that  the  fire  retardant  coating  must  have  a  class  “A”  FSR  (Markusoff,  2009).  The  fire   code  assumes  that  the  wood  sheathing  will  be  used  in  an  interior  application,  but  it  does  not   take  into  account  that  the  sheathing  may  be  exposed  to  the  elements  in  the  construction  stage.   If  an  interior  fire  retardant  coating  is  used,  much  of  its  ability  to  retard  fire  could  be  lost,  as   mentioned  above  (CWC,  2000).   Fire  retardant  coatings  may  also  be  subject  to  mechanical  wear  and  damage  when  they  are   used  to  coat  panels.  Building  materials  are  not  usually  treated  with  the  utmost  care  and  can  be   damaged  by  accident  or  carelessness.  Fire  retardant  coatings  are  not  capable  of  withstanding   much  wear  and  damage  which  can  greatly  diminish  their  effectiveness  (Price,  2001).     3.2  Application  Issues   To  comply  with  the  Alberta  Fire  Code,  a  fire  retardant  coating  with  a  class  “A”  FSR  approved  by   the  Underwriter’s  Laboratories  of  Canada  must  be  applied  to  panels.  To  maintain  this   designation,  the  fire  retardant  coating  must  be  applied  by  a  trained  professional  or  a   representative  from  the  company  that  manufactures  the  product  (Schwarz,  2003).  This  ensures     7   that  the  coating  is  applied  evenly,  and  at  the  specified  thickness.  The  lather  is  important  to  the   coating’s  ability  to  achieve  the  desired  fire  retardant  properties  (Fire  Retardants  Inc,  2010).  The   requirement  of  having  an  expert  apply  the  coating  increases  the  cost  and  the  time  involved  in   coating  panels.   There  are  also  many  issues  with  onsite  application.  The  surface  of  the  wood  sheathing  needs  to   be  dry,  clean,  and  relatively  smooth  (No-­‐Burn,  2008).  On  a  construction  site,  conditions  are  less   than  ideal.  Keeping  a  wood  panel  clean  and  dry  can  be  difficult.  Also,  the  low  temperatures  at   the  jobsites  can  increase  the  time  required  for  coatings  to  cure.  Some  latex  intumescent   coatings  have  a  curing  time  of  about  48  hours.  In  this  time  the  ambient  temperature  must   exceed  10⁰C  for  the  coating  to  cure  properly  (Quantum  Chemical,  2011).  During  the  winter,   such  temperatures  rarely  occur,  particularly  in  Alberta.   It  is  also  difficult  to  apply  coatings  to  OSB.  All  fire  retardant  coatings  require  that  the  surface  of   the  substrate  be  somewhat  smooth  and  free  of  surface  imperfections.  OSB  usually  has  a  rough   surface  (Evans  &  Cullis,  2008).  Furthermore,  the  surface  is  often  contaminated  by  resin,  wax,   and  various  chemicals  (Quantum  Chemical,  2008).  These  components  can  reduce  the  adhesion   of  a  coating  to  the  surface  of  the  OSB  and  thus  reduce  the  performance  of  the  coating.  Hence,   prior  to  application  of  fire  retardant  coatings,  oils,  waxes,  and  resins  must  be  removed  from  the   surface  of  OSB.  The  removal  of  the  substances  is  difficult.  Sanding  the  surface  of  OSB  can   remove  such  contaminants  but  sanding  of  OSB  reduces  its  resistance  to  fire  (Evans  &  Cullins,   2008).  To  deal  with  the  contamination  of  the  surface  of  OSB,  a  basecoat  of  primer  should  be   applied.  Fore  example,  a  basecoat  of  latex  primer  is  highly  recommended  when  a  SafeCoat   latex  intumescent  coating  is  applied  to  OSB  (Quantum  Chemical,  2011).  This  requirement  is   costly  and  time  consuming.     3.3  Cost  of  Coating  Systems   Fire  retardant  coatings  can  be  an  expensive  way  to  improve  the  fire  retardant  abilities  of  wood   products.  The  coatings  themselves  are  quite  expensive.  Product  prices  are  on  average  around   $90-­‐100  per  gallon.  Prices  of  coatings  vary  depending  on  their  quality,  performance   characteristics,  whether  they  are  exterior  rated,  and  whether  they  have  the  ability  to  inhibit  the     8   growth  of  fungi  or  mold.  CeasefireTM  latex  intumescent  coating,  another  “class  A”  fire  retardant   product,  retails  for  approximately  $100  per  gallon  (Ceasefire  Technologies,  2011).  Two  (low  and   high)  estimates  of  using  a  Ceasefire  coating  system  are  shown  in  Figure  1.       Figure  1:  Estimated  Costs  of  Coating  a  4’  x  8’  OSB  Panel  (Ceasefire  Technologies,  2011)   The  low  estimate  does  not  include  a  primer  basecoat  or  a  weather-­‐protecting  top  coat.  To   achieve  the  best  fire  retardant  results  on  OSB,  a  primer  basecoat  is  required.  Also,  if  the  panel  is   to  be  exposed  to  excessive  humidity  or  rain,  a  topcoat  of  weather  and  wear  resistant  finish  is   required  (Ceasefire  Technologies,  2011).  Both  the  basecoat  and  the  topcoat  will  greatly   increase  the  cost  of  the  fire  retardant  coating  system,  as  the  graph  above  shows.  Also,  the   graph  above  does  not  include  the  costs  of  applying  the  coating.  Since  the  individual  applying   the  coating  must  be  certified  by  the  Underwriter’s  Laboratories,  the  cost  of  using  the  coating   will  increase.  Labour  cost  will  be  almost  tripled  if  a  basecoat  or  topcoat  are  required.   Furthermore  it  is  time  consuming  to  apply  the  three  coatings  and  wait  for  them  to  fully  cure.   The  costs  associated  with  fire  retardant  coatings  decrease  their  appeal  as  fire  retardant   systems.       9   4.0  Comparison  of  Coatings  to  Other  Systems   4.1  Coating  Versus  Treatment   Fire  retardant  treatments  were  once  the  primary  way  of  making  wood  products  more  fire   resistant.  However,  fire  retardant  coatings  have  many  advantages  over  fire  retardant   treatments.  First  and  most  importantly,  fire  retardant  treatments  can  only  be  applied  to  solid   wood  and  plywood  and  not  to  OSB  or  most  other  engineered  wood  products  (Williamson,   2002).  This  is  a  problem  because  OSB  is  a  widely  used  for  sheathing  in  residential  construction.   The  second  drawback  of  fire  retardant  treatments  is  that  the  treatment  cannot  be  applied  to   the  building  material  in  the  field.  Pressure-­‐treatment  must  be  done  at  a  special  treatment   facility.  Hence,  the  fire  retardant  panels  cannot  be  customized  to  their  purpose.  Fire  retardant   treatments  require  large  loadings  of  chemicals  compared  to  coatings  with  retentions  of  10-­‐20%   by  weight  (Plotnikova,  Egorov,  &  Khaliullin,  2003).  Such  high  retentions  increase  the  total  cost   of  fire  retardant  chemicals.  Furthermore,  many  of  the  fire  retardant  treatments  can  have  the   adverse  effects  on  the  wood’s  strength,  hygroscopicity,  stability,  toxicity,  adhesion,  and   receptivity  to  paints  (Price,  2001).  The  drawbacks  of  fire  retardant  treatments  and  the  inability   to  apply  them  to  OSB  make  them  unsuitable  for  a  fire  protection  system  for  the  Alberta  Fire   Code.     4.2  Coatings  Versus  Gypsum  Sheathing   Exterior  gypsum  sheathing  can  be  used  instead  of  the  application  of  OSB  coated  with  fire   retardant  paint  to  comply  with  the  Alberta  Fire  Code  (FPB,  2010).  Gypsum  sheathing  is  a   cementitious  material  that  can  simply  be  nailed  or  screwed  to  the  exterior  face  of  OSB  panels  to   protect  them  from  fire.  The  main  advantage  that  fire  retardant  systems  have  over  gypsum   sheathing  is  the  ability  to  apply  the  coatings  to  irregular  or  custom  areas.  Coatings  can  be   applied  to  walls  without  having  to  measure  or  cut  any  pieces  to  specific  dimensions.     Gypsum  sheathing  has  many  advantages  which  make  it,  in  many  cases,  a  more  suitable  system   for  improving  the  fire  retardancy  of  OSB  or  plywood  sheathing.  Firstly,  gypsum  sheathing   performs  better  than  coated  panels  in  fire.  Gypsum  is  a  completely  incombustible  material  and     10   thus  its  fire  retardant  abilities  are  excellent.  Since  gypsum  is  incombustible,  the  FSR  and  SDI  of   gypsum  sheathing  are  both  zero  (Williamson,  2002).  Hence,  fire  will  not  spread  across  the   surface  of  gypsum  and  the  emission  of  toxic  gases  and  the  risk  of  flashover  are  eliminated.   Gypsum  sheathing  will  thus  be  a  better  system  for  reducing  intensity  and  the  spread  of   residential  fires  which  are  the  primary  goals  of  the  AFC.   Gypsum  sheathing  conforming  to  the  AFC  must  be  exterior  rated  and  able  to  stand  up  to   exposure  to  weather  and  mechanical  wear.  Exterior  gypsum,  unlike  many  fire  retardant   coatings,  does  not  lose  its  fire  retardant  abilities  when  it  has  been  exposed  to  the  elements   (ToolBase,  2003).  This  is  a  key  advantage  considering  that  panels  may  be  exposed  to  the   elements  and  mechanical  wear  during  building  construction  as  mentioned  above.  Hence,  fire   retardant  systems  using  gypsum  sheathing  will  retain  their  fire  retardant  ability  better  than   coatings  and  will  be  more  effective  in  buildings.     Unlike  fire  retardant  coating  systems,  the  installation  of  gypsum  sheathing  does  not  require  a   high  quality  surface.  Gypsum  sheathing  can  be  directly  installed  onto  the  wood  panel  without   having  to  worry  about  the  condition  of  the  surface.  This  is  particularly  advantageous  when  OSB   is  the  sheathing  material  that  requires  fire  protection.   Gypsum  sheathing  is  a  more  cost  effective  method  for  improving  the  fire  retardancy  of  panels   than  intumescent  coating  systems.  This  may  be  the  most  important  advantage  of  choosing   gypsum  sheathing  as  a  fire  retardant  system.  The  cost  of  a  gypsum  sheathing  system  includes   the  material  cost  of  the  gypsum  sheathing,  and  the  labour  cost  associated  with  installation.   Exterior  gypsum  sheathing  that  meets  the  Alberta  Fire  Code  can  be  bought  in  a  variety  of  sizes.   Sheets  8’  by  4’  and  a  thickness  of  0.5”  can  be  purchased  for  approximately  $16  compared  to   $21.50  or  $27.50  for  the  cost  of  coating  an  8’  by  4’  sheet  with  fire  retardant  finishes.  This   material  cost  can  also  be  converted  into  a  price  per  square  foot  and  compared  to  the  price  per   square  foot  of  a  fire  retardant  coating  (Table  3).     11   Table  3:  Cost  of  Coating  System  Compared  to  a  Gypsum  System  (Ceasefire  Technologies,  2011,   ToolBase,  2003)   Fire  Protection  System   Cost  ($/ft2)   Low  Estimate  for  Coating  System   0.67   High  Estimate  for  Coating  System   0.85   Exterior  Gypsum  Sheathing   0.50     The  price  per  square  foot  of  gypsum  sheathing  is  0.5  $/ft2  which  is  0.35  $/ft2  less  than  the  high   price  of  a  fire  retardant  coating  system,  and  0.17  $/ft2  less  than  the  low  price  for  the  coating   system.  The  former  saving  is  probably  more  accurate  since  gypsum  sheathing  should  be  able  to   match  the  performance  of  the  full  fire  retardant  coating  system.  Table  4  shows  the   approximate  costs  of  different  fire  retardant  systems  used  in  a  small  house.     Table  4:  Costs  of  Using  Fire  Retardant  Systems  to  Protect  a  House*  (Building  a  Home  Info,  2010)   Fire  Protection  System   Cost  ($)   Coating  System  (fire  retardant  coat  only)   1,951   Coating  System  (basecoat,  fire  retardant  coat,  topcoat)   2,475   Gypsum  Sheathing  System   1,456   *1500ft2  three  bedroom  house  with  attached  garage   The  cost  of  the  coating  systems  for  the  house  mentioned  above  are  significantly  more  than   using  a  gypsum  sheathing.  The  less  expensive  coating  system  is  about  34%  more  than  gypsum   sheathing  and  the  more  expensive  (exterior-­‐rated)  coating  system  is  about  70%  more  than  the   gypsum  system.  A  significant  amount  of  money  can  be  saved  using  a  gypsum  system  over  a   coating  system,  especially  in  larger  residential  buildings.       12   The  prices  and  costs  listed  in  Tables  3  and  4  only  show  the  cost  of  the  raw  materials.  The  use  of   gypsum  sheathing  also  has  the  advantage  of  lower  labour  costs.  Gypsum  sheathing  can  be   installed  by  the  construction  personnel  onsite,  unlike  fire  retardant  coatings,  as  mentioned   above.  This  means  that  the  installation  can  be  done  at  the  discretion  of  the  builders  and  there  is   no  need  to  hire  a  certified  individual,  which  lowers  the  cost  of  the  gypsum  sheathing  system   versus  fire  retardant  coatings.  The  lower  material  and  labour  costs  make  gypsum  sheathing  a   much  more  cost  effective  solution  than  the  use  of  fire  retardant  coatings.   5.0  Conclusion  and  Recommendations   The  use  of  fire  retardant  coatings  can  be  an  effective  way  of  protecting  structural  wood  panels   in  residential  buildings.  However,  they  have  some  limitations  that  affect  their  suitability  for   certain  applications.  The  lack  of  weather  and  wear  resistance  of  fire  retardant  coatings  limits   their  use  in  exterior  applications.  The  AFC  considers  fire  retardant  coatings  as  an  acceptable   means  of  protecting  wood  panels  for  new  construction  projects,  but  the  exposure  of  the   coatings  to  the  elements  is  not  considered.     If  fire  codes  are  to  accept  the  use  of  fire  retardant  coatings  then  they  should  specify  that  the   coatings  must  be  protected,  almost  immediately,  from  the  elements  and  potential  sources  of   damage  and  wear  during  construction.  The  AFC  should  also  specify  whether  exterior  rated  fire   retardant  coatings  are  required  in  cases  of  prolonged  exposure  to  the  elements  during   construction.  Also,  research  must  be  done  to  ensure  that  panels  coated  with  interior  rated   coatings  retain  their  fire  retardant  ability  when  construction  of  the  building  is  complete.   Another  issue  with  coating  OSB  that  will  continue  to  inhibit  the  role  of  fire  retardant  wood   coatings  is  the  need  to  carefully  prepare  the  surface  and  apply  a  basecoat  of  primer.  This   increases  the  costs  and  the  time  required  to  coat  panels.  Unless  coating  companies  are  able  to   develop  cheaper  products  that  work  better  with  OSB,  their  usefulness  will  be  limited.   The  lower  material  and  labour  costs  associated  with  installing  a  gypsum  sheathing  system   makes  it  a  much  more  cost  effective  solution.  Than  fire  retardant  coatings.  Gypsum  will   maintain  its  cost  advantage  unless  cheaper  coatings  become  available.  The  considerable     13   performance  and  cost  advantage  of  gypsum  sheathing  makes  it  more  economical  and  effective   than  fire  retardant  coatings  as  a  means  of  inhibiting  the  spread  and  impact  of  residential  fires   and  satisfying  the  Alberta  Fire  Code.   Fire  retardant  coatings  may  have  a  role  when  used  in  combination  with  gypsum  sheathing.   Gypsum  could  be  used  to  protect  as  much  of  the  paneling  as  possible  but  certain  areas  of  the   building  that  are  difficult  to  sheath  with  gypsum,  could  be  coated  with  a  fire  retardant  spray.   This  would  ensure  that  the  building  is  protected  better  than  by  an  entirely  gypsum  system  and   it  would  be  a  much  more  cost  effective  solution  than  applying  a  fire  retardant  coating  to  the   entire  building.                                                             14   6.0  References     Building  a  Home  Info,  2010.  Building  Materials  list  for  a  Three  Bedroom  Bungalow.   http://www.building-­‐a-­‐home-­‐info.com/building-­‐materials.html.  Accessed  March  30,  2011.   Canadian  Wood  Council  2000.  Fire  Retardant  Treated  Wood.   http://www.cwc.ca/NR/rdonlyres/77351FA7-­‐CC2B-­‐480B-­‐8EF4-­‐ 0DCC5379D17A/0/FireRetardantTreatedWood.pdf.  Accessed  February  11,  2011.     Ceasefire  Technologies  2011.  Order  Ceasefire.   https://www.ceasefiretechnology.com/index.php?option=com_virtuemart&page=shop.browse &category_id=1&Itemid=3  Accessed  March  15,  2011.     Evans,  P.D.  &  Cullis,  I.  2008.  Effect  of  sanding  and  coating  with  UV-­‐cured  finishes  on  the  surface   roughness,  dimensional  stability  and  fire  resistance  of  OSB.  Holz  als  Roh  und  Werkstoff  66(3):   191-­‐199     Fire  Prevention  Bureau  2010.  Alberta  Fire  Code  2006.  AFC  5.6.1.2  –  Protection    of  Adjacent   Building.  http://www.calgary.ca/docgallery/bu/fire/alberta_fire_code_5_6_1_2.pdf  Accessed   February  11,  2011.     Fire  Retardants  Inc.  2010.  Fire  Retardants  101.   http://www.fireretardantsinc.com/fire_retardants101.html  Accessed  February  11,  2011.     Garrison,  E.  2002.  Intumescent  Paints.  Architectural  Finishes.  Wiley  &  Sons,  New  Jersey.    pp.   249-­‐253     Gratton,  R.  2010.  Code  Changes  Related  to  Fire  in  Alberta.  Canadian  Home  Builders  Association.   http://www.chba.ca/TRC/October%202010/Alberta%20Report%20-­‐%20October%202010.pdf   Accessed  February  11,  2011.     HIRF  2008.  Sparking  Fire  Safety.  Learnings  report.   http://aema.alberta.ca/documents/ema/HIRF_Learnings_Summary_F2.pdf  Accessed  February   23,  2011.     Markusoff,  J.  2009,  March  13.  Home  builders  feel  burned  by  new  Alberta  safety  rules.  Calgary   Herald.   http://www.udialberta.com/2009.%20%20March%2013.%20%20Calgary%20Herald.%20%20Ho me%20builders%20feel%20burned%20by%20new%20Alberta%20fire%20safety%20rules.pdf   Accessed  February  23,  2011.     National  Fire  Protection  Association  2009.  Standard  for  Fire  Retardant  treated  Wood  and  Fire   Retardant  Coatings  for  Building  Materials.  NFPA,  Massachusetts.         15   No-­‐Burn  2008.  No-­‐Burn’s  Specialty  Intumescent  Coating  Continues  to  Amaze.     http://noburn.com/all-­‐news-­‐articles/158-­‐from-­‐good-­‐to-­‐great-­‐no-­‐burn-­‐specialty-­‐intumescent-­‐ coating-­‐continues-­‐to-­‐amaze  Accessed  February  28,  2011.     P1M  2008.  Paint  Coverage  Chart.  http://www.p1m.com/pcc.htm  Accessed  March  15,  2011.     Plotnikova,  G.  V.,  Egorov,  A.  N.,  &  Khaliullin,  A.  K.  2003.  Fire  Retardants  for  Wood.  Russian   Journal  of  Applied  Chemistry,  76  (2):  310-­‐313.     Price,  D.  2001.  Chemistry  of  Fire  Retardancy.  Fire  Retardant  Materials,  9.2,  pp.  297-­‐306.       Przybylak,  M.  W.  &  Kozlowski,  R.  1999.  The  Thermal  Characteristics  of  Different  Intumescent   Coatings.  Fire  And  Materials,  23  (1):  33-­‐43.     Quantum  Chemical  2011.  SafeCoat  Latex  Intumescent  Coating.  MSDS  and  information  sheet.   http://www.quantumchemical.com/images/stories/PDFs/SC%20Latex%20March%202011.pdf   Accessed  February  28,  2011.     Schwarz  2003.  Coatings  that  can  save  lives.  Coatings  World.   http://findarticles.com/p/articles/mi_hb053/is_11_8/ai_n29044423/  Accessed  February  11,   2011.     ToolBase  2003.  Alternatives  to  Structural  Plywood  and  OSB.     http://www.toolbase.org/Design-­‐Construction-­‐Guides/Interior-­‐Partitions-­‐Ceilings/plywood-­‐ alternatives.  Accessed  February  28,  2011.     Western  Wood  Preservers  Institute  2005.  Fire  Tests  for  Pressure  Fire  Retardant  Treated  Wood.   Treated  Wood  News.   http://www.wwpinstitute.org/mainpages/documents/Dec05_FireTests_WWPI.pdf  Accessed   March  21,  2011.   Williamson,  T.  G.  2002.  Basics  of  Fire  Protection.  APA  Engineered  Wood  Handbook.  10.1.1