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Constructing Environments  

Week 8  Journal  –  In  Detail  (Part  one)   By  Wenjie  Cai  (634077)  

Case Study:  Extension  of  Queens  College   Interrogation  of  detailing  decisions   1. The  canopy    -­‐  The  canopy  outrigger  is  used  for  supporting  the  overhanging  roof.  PFC  is  used  to  support  the  outrigger.  Colorbond   flashing  that  connected  with  the  flat  sheet  is  used  to  prevent  water  seeping  into  the  house.  A  half  round  gutter  is  used  at  the  end  of  the   roof  for  better  drains  of  the  roof.  Flexible  sealants  are  used  at  the  bottom  of  the  roof  to  seal  the  gap  between  the  compressed  sheet  and   other  structural  members.  Bolts  are  used  as  the  joist  of  outrigger  and  the  flashing.  The  battens  are  used  to  locate  the  roof  covering  sheet.    

Figure 1:  The  canopy  

Figure  2:  The  glass  block  window                  


2. The window  -­‐  It  is  a  glass  block  window  between  two  precast  concrete  panels.  Two  steel  frames  are  used  between  the  concrete  panel   and  the  glass  block.    For  the  joist  of  the  glass  blocks,  mortar  joint  is  used.  The  steel  frame  above  the  window  is  connected  with  an   expansion  material  and  the  one  below  the  window  has  two  reinforcing  rods.  The  use  of  the  reinforcing  rods  is  to  strengthen  its  force  for   the  compression.  There  are  two  studs  at  the  top  and  bottom  of  the  window  beside  the  precast  concrete  panel.  The  plasterboard  that   covers  the  steel  stud  is  connected  with  the  stud  by  nails.  Timber  sill  is  located  on  the  bottom  one  and  connected  with  the  steel  frame.  The   gap  between  the  plaster  board  and  the  sill  is  painted  to  match  plasterboard    

Composition 1. For  the  overhanging  roof,  the  main  composition  includes  plywood  (plywood  under  flat  sheet  and  battens),  steel  such  as  flat  sheet,  half   round  gutter  and  PFC.     Plywood  


2. For  the  windows,  the  main  composition  includes  precast  concrete  panel,  steel  for  studs  and  frame  and  glass.      

Glass Block  

Precast concrete  panel  

Steel stud  

Building process   1. The  canopy  outrigger  is  the  first  step  of  the  construction.  It  is  connected  with  the  precast  concrete  panel  by  bolts.  Then  the  battens  will   be  built  on  both  the  top  and  the  bottom  side  of  the  outrigger  following  by  construction  of  the  plywood,  the  flashing  and  the  flat  sheet.  The   last  step  of  building  process  is  the  half  round  gutter  connected  with  the  PFC.       3  

2. The steel  glass  block  frame  is  built  right  after  the  construction  of  the  precast  concrete  panels  (the  expansion  material  is  constructed  at  he   same  time).  Then  the  glass  blocks  will  be  constructed  between  the  steel  frames  and  the  mortar  joint  connects  them.  The  plasterboards   and  the  timber  sill  are  then  built  and  connected  with  the  steel  frame.  After  that  is  the  construction  of  the  steel  stud  nailed  with  the   plasterboards.  

Pros and  Cons   1. In  this  detailing  design,  there  is  a  gap  between  the  flashing  and  the  flat  sheet.  Water  may  flows  into  the  canopy  by  this  gap  so  there   should  be  silicone  to  seal  this  gap  and  also  the  gap  between  the  plywood  and  flashing  so  that  the  construction  does  not  damaged  by   water.     2. Timber  sill  is  used  to  provide  protection  from  water.  However,  in  this  case,  there  is  no  slope  of  the  sill  which  means  it  does  not  drains   well.  This  may  cause  damage  to  both  the  windows  and  the  sill  in  long  term.  The  gap  between  the  plasterboard  and  the  sill  should  insert   an  silicone  so  that  the  stud  is  not  damaged  by  water.   However,  the  uses  of  the  sealants  provide  well  protection  to  the  canopy  and  the  half  round  gutter  provides  better  drains  when  the  water   flows  from  the  flashing.    

Sustainability and  Environmental  Analysis   1. The  use  of  colorbond  roofing  helps  with  reducing  cooling  and  heating  costs,  which  is  also  the  advantages  of  using  steel  roof.    The  material   using  for  the  canopy  is  steel  that  is  recyclable.  This  provides  conservation  of  the  natural  resources.    Plywood  using  in  this  construction   reduce  the  energy  cost  by  transportation  because  it  is  lighter  than  other  materials  such  as  concrete.  It  used  relatively  lower  energy  to   complete  its  construction.   2. Construction  glass  often  ends  up  with  landfill  which  is  not  very  sustainable.  However,  there  is  a  lot  of  recyclable  materials  used  in  this   construction  such  as  timber  and  steel.  


Economic Implications  of  Decisions   The  materials  that  used  in  these  constructions  are  mostly  precast  concrete  panel,  steel  and  glass.  For  the  canopy,  colorbond  is  used  for  the   flat  sheet,  flashing  and  the  gutter.  Colorbond  roofing  is  relatively  more  expensive  than  some  roofs  such  as  tile  roof.  This  causes  more  money   during  construction  but  it  makes  the  color  of  the  roof  last  longer  so  it  reduce  the  cost  of  maintaining.    Glass  block  is  also  an  expensive   material  compared  to  some  other  material.  However,  the  cost  of  the  precast  concrete  panels  and  timber  are  lower.    

Where and  why  things  goes  wrong  in  this  type  of  detail   Cracks  may  occur  on  the  plasterboard  after  years  because  of  the  ages  and  the  lack  of  supporting.  The  gap  between  the  flashing  and  the  flat   sheet  may  cause  leaks  that  damage  the  construction.  The  timber  sill  without  slope  may  also  cause  leaks  when  the  water  does  not  flow  away   and  stay  on  the  timber  for  long.    


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