modeling Roof / Rafter assemblies

[Anonymous]

AC15

Starting a new development and beginning to consider the level that our models will need to be taken to.

Roof / rafter tool.

I set my roof about the way i want. my questions are.

when i set the plate height, it seems that it does not take into consideration the birds mouth in the rafter. is there a setting to do so, or do i just lower the overall roof deck by that many inches? how do yall address this?

next, rafters. the design will have detailed rafter tails. is this practically modeled in AC? i noticed a rafter tool but not sure if this is best or the beam tool.

Thanks guys and gals!

[Anonymous]

You can set the plate height/reference line at the inside edge of the top plate.

[Anonymous]

So, for example, if my top story is a 9'-0" plate, and if i specify the roof to be at a 9' plate as well, ArchiCad will place the underside of the roof plate exactly on the outside of the wall at 9'0" which means there is no setting that takes into consideration a notched birds mouth?

i realize this is splitting hairs and i can always just drop the roof plate another few inches, but i wanted to make sure that i was not missing a setting someplace.

----how about the exposed rafter tails?

would these be modeled as separate elements?
-is it best to do this with the rafter tool, or as a beam?

thanks again everyone

[Anonymous]

knosaj wrote:
So, for example, if my top story is a 9'-0" plate, and if i specify the roof to be at a 9' plate as well, ArchiCad will place the underside of the roof plate exactly on the outside of the wall at 9'0" which means there is no setting that takes into consideration a notched birds mouth?

If you place the roof pivot line (setout) on the INSIDE face of the wall (as Matthew suggested) you have a birdsmouth the width of your wall. This is how I always set my roof out.

knosaj wrote:
----how about the exposed rafter tails?

would these be modeled as separate elements?
-is it best to do this with the rafter tool, or as a beam?

thanks again everyone

I have used several different methods for this depending on the flexibility you need for end cuts etc. If not the rafter object (easy to edit them all at once parametrically) I have used a small section of roof and the Multiply command to distribute around the building.

[Anonymous]

thanks! i didnt think of using a slice of roof.


is there a best method to detail the rafter tails?

[Steve Jepson]

You migh consider just modeling the rafters you need to show up in a section. Also, be careful not to exceed the limits for your birds mouth. 1/3 in most areas. Also, a birds mouth is not necessary when you use a Simpson H1. In order to get the depth you will need at that location for your insulation you may need a raised heel height rahter than a birds mouth anyway. You may want to put a rim joist on your ceiling joists and a plate on top of that for the rafters to set on. ??

[Karl Ottenstein]

knosaj wrote:
----how about the exposed rafter tails?

Complex profiles can make this very easy - see an illustrated example here:
http://www.archicadwiki.com/ComplexProfileTips

Alternatively, you can create a 'cutting' object with a profile and subtract it from existing rafter elements.

Cheers,
Karl