Dormer with open bottom

[MrWizard]

Using Home Designer Pro 2016 v. 17.3.2.2x64, Win7

 

I'm trying to build a daylight dormer on a second level gable roof which projects beyond the second floor exterior wall and penetrates a first floor shed roof to provide daylight, ventilation and expansive interior.  I have attached an image of the exterior view, which I built with second floor supporting the dormer walls. 

 

Also, a section view for reference:

 

Because the shed roof automatically raises the interior walls of the first floor, the second level has an exceptionally short floor/ceiling dimension. As such, it is desirable for the high end of the shed roof to attach to the inner wall at a point higher than the floor location of of the second level.  (or to edit the first floor ceiling height without altering the shed roof pitch). 

 

In physical construction I think the way this would be built is to create first floor exterior and interior bearing walls to the required heights, lay rafters to support the shed roof, leaving an opening framed by doubled rafters and header, on which the dormer walls would be supported.  

 

There are two elements to my design dilemma;

First is how to control the ceiling height for the first floor while providing a taller wall to support the upper end of the shed roofs, and

Second, how to go about constructing the dormer spanning 2 levels, supported on doubled rafters?

 

Perhaps the solution is to build the model completely with manual framing?  Is it possible to do so?

 

If someone has some pointers about general approach and order of building I would greatly appreciate comments.

 

Bob Begin

 

[DavidJPotter]

Wall heights are controlled by 1. the ceiling height you set per Room Dialog box - Structure Tab and 2. Between the set ceiling height and the ridge of the roof the software is programmed to auto-fill in with Attic Walls (Marked "No Locate, No Room Define and Attic Wall" found on their "General Tab". These walls will be visible on the "<A> or attic plan view level and in cross sections and isometric views).

Where you have a clerestory situation you normally should NOT draw those walls in on the second floor but rather let the software auto-fill those in as it is programmed to do. So if you insist on manually drawing such walls on the second floor be sure and mark them "No Room Define" or name the enclosed space on the second floor as "Open Below".

On the first floor of such clerestory rooms you would remove the ceiling by way of that room dialog box.

The dormer can by way of its dialog be set to form a room which once done can be programmed to "Open Below" which then should give you a skylight appearance to the room below.

 

DJP

[MrWizard]

Thank you so much for your quick and cogent reply, David. I will study the details of your suggestions.  It appears from your discussion  that the HDPro can easily accomplish this without manual drawing.  

[MrWizard]

Hello Eric:

 

Thank you for responses.  No, I haven't done any framing.  That's basically my juncture.  I'm not sure if I should be doing this design by building framing, or pursue the automatic generation.  A real 3D model showing how the dormer will look from the inside will be invaluable.  It's a very small house, so it's not a huge amount of work, should it require some extra attention.  I'm not experienced enough to know what is the best approach for this design.  

 

What do you think?

 

Thanks again for your responses.  

[DavidJPotter]

Make sure all of your Default Settings for "Floor, Roofing, wall framing and ceiling framing are correctly set and that your model is exactly as you want it before building framing. The software succeeds or fails on how well you set your defaults and then following proper procedure (see Users Guide).

 

DJP

[solver]

You will not break anything by building framing, and it's typical to use the auto tools to start, even if you plan on manual modifications.

 

As David said, set your defaults to start, but keep Auto Rebuild Framing checked so it's kept up to date as you make changes.