Replies

1. 
   IdahoDon | Nov 15, 2006 04:11am | #1

   At least ARXX ICFs are easily cut for a gable roof.  However because of the extra work it is the last resort, used mostly for 100% stucco or vaulted ceiling applications.

   It's much faster and less expensive to use a gable end truss or even stick build the gable end.

   ICFs compress about 1/16" per course so the wood bracing required on a gable end complicates estimating the amount of compression since the wood often holds things together better in some parts than others.  The results are an inexact science at best so it usually requires some shimming to correct.

    

   Beer was created so carpenters wouldn't rule the world.

1. 
   MBaybut | Nov 15, 2006 04:27am | #2

   Thanks,
   Any loss of R factor doing it that way? Can a SIP gable be used?
   Mike

1. 
   IdahoDon | Nov 15, 2006 05:13am | #4

   Do you have a cathedral ceiling?  If not there isn't any loss of r-value since the gable end doesn't contribute a whole lot to upper insulation r-value.

   If you have a cathedral ceiling i'd probably recommend using the ICFs so the interior and exterior surfaces plane out well.

   The largest danger is that the pump truck isn't handling drier mixes well and you have to thin the concrete to the point where it takes a long time for each lift to set up.  It could take hours to do a single end.  Just yesterday we had a similar problem on a stepped window well and it turned a 30 minute job into 3 hours.

   A safer alternative is stick building the gable end and having it insulated with sprayed in polyurethane.  At over r-6 per inch it's easy to build a super-insulated wall.

   Locally polyurethane is about $1.25/square foot for the first 1" depth and $.75 for each additional inch. 

   Beer was created so carpenters wouldn't rule the world.

2. 
   ronbudgell | Nov 15, 2006 04:48am | #3

   As IdahoDon says, it can be done and it isn't even very hard, but there are reasons why it is seldom done.

   One is that it would usually demand a separate pour from the walls below because of limitations on the height you can safely pour in ICF forms. That means cost - pump charges, adapting a set-up for the bracing, and time spent doing a relatively small ICF pour when you could be framing the roof.

   On the other hand, if your gables enclose heated space then it makes just as much sense to ICF them as it does to do any other part of the house.

   When you pour into a sloped form, you slightly overfill the form and wait a bit until the concrete begins to set up before striking it off. You do not need to close the top of the forms for any slope up to 12/12.  Vibration is tricky, though. You want to get good consolidation through the centre but once you start getting up the slope, you have to let the mud go where it will.

   I have only done this once, but I poured 11/12 with no trouble. I have to admit to being pretty nervous about it beforehand, though.

   Ron