Menu path
Mod-Roof > Dormer
🧩 Overview
The Mod-Roof > Dormer command lets you draw a dormer in several styles:
Gable
Hip
Single Slope
Barrel
🧭 Create a dormer (basic workflow)
Click Dormer.
You are prompted to select an eave.
Selecting the eave also selects the roof plane the dormer will affect, and the orientation of the dormer.
The point at the end nearest where you selected the eave line begins to flash, giving you a point of reference for placement of the Dormer.
🏡 Gable & Hip Dormers
After selecting the eave, the Dormer defaults dialog displays so you can set dormer parameters.
🧰 Full vs Simple dialog display
The Dormer dialog (and many other larger/more complex dialogs) has two modes [More] and [Less] buttons to hide the less used functions of the software until you need them. :
Full display
Simple display
⚙️ Gable/Hip dormer fields (what each setting means)
Type of Dormer: One of Gable, Hip, Single Slope, or Barrel dormer.
Pitch: Pitch of the dormer planes.
Distance to Dormer Centre / Distance to Edge: Distance along the eave to the centre line/ridge of the dormer (measured from the flashing point).
Alternatively, this toggles to distance to the eave edge of the dormer, and the width measures from this edge.
This function is a toggle button.
Setback from Eave: Distance from the eave to the face of the dormer.
Dormer Width: Width of the opening in the roof for the dormer.
Side Length / Height Above Eave: Length of the straight projection of the dormer.
Toggles to Height of Dormer Gutter if you want to fix the dormer by relative height to the eave line it’s attached to.
Front Overhang: Overhang of the gable end.
Side Overhang: Eave overhang on the sides.
Gap Width: Width of the gap created from the face of the gable to the eave (more exactly: to a distance from the eave based on the next value).
Gap Offset to Eave Gap: Distance from the eave to the gap (as above).
Side Style: Style for the eaves of the gable dormer.
“Both horizontal” is default; options include “Project left”, “Project right”, or “Project both”.
Dormer Material: Material category for dormer planes (e.g. Metal, Tile, Shingle, Low Slope, etc.).
Eave Type: Eave type on the dormer: Fascia & Gutter, Gutter Only, Fascia Only, None.
Draw Side Walls?
Yes: front and sides of the dormer are drawn.
No: they are not drawn.
You may not want to draw the sides if the dormer projects past the eave line.
Insert at Apex: Insert at the apex of the hips, or at a position along a hip (see below).
Insert along Hip: Insert a dormer along a hip like a flying gable (see below).
Preview: Preview the insertion before committing to insert it.
Typical hip dormer
🏔️ Dormers at Hip Apexes (Insert at Apex)
To insert a dormer wedged at the top of a hip:
Select Insert at apex.
Snap to the point at the hip apex.
The dormer is then drawn in preview mode, ready for you to either accept or change parameters. The dialog box changes to display additional parameters:
Here you can change:
Offset from the eave to the face of the gable
Width
You will notice these two fields are now toggle buttons.
If you click them, the dialog changes to look like the following:
Now you can:
Set the offset to the gable with respect to the base of the higher hip
Force the dormer to adopt the width at the face of the dormer from hip to hip
In this way you can use this approach to create dutch gables.
In effect, using this approach, the ridge apex point is fixed in position.
📐 Insert Along Hip
When you click Insert along Hip, you are prompted to:
Locate a hip line
Enter some initial fixing values
You enter:
The distance from the eave to the face of the dormer gable
The distance from the top of the hip to the ridge intersection with the dormer
After you click [OK], the Dormer Defaults dialog is displayed. Changes you make now assume the ridge apex of the dormer remains in a fixed position.
You would use this approach to create gables on hips much like the Modify Roof > Flying-Gable command.
🗻Single Slope
For a Single Slope dormer, you get the following dialog:
Type of dormer: Gable, Hip, Single Slope or Barrel.
Typical single slope or ‘skillion’ dormer
Single Slope fields:
Pitch: Pitch of the dormer planes.
Distance to Dormer Centre / Distance to Edge: Distance along the eave to the centre line/ridge (or toggled to edge) as described above (toggle button).
Setback from eave: Distance from eave to the face of dormer.
Dormer Width: Width of the dormer.
Length: Length of the Single Slope dormer.
Side Overhang: Eave overhang on the sides.
Front Overhang: Overhang of the gable end.
Gap width: Width of the gap created from face of gable to eave (or based on the next value).
Gap Offset to Eave: Distance from the eave to the gap.
Dormer Material: Material category to apply (Metal, Tile, Shingle, Low Slope, etc).
Eave Type: Fascia & Gutter, Gutter Only, Fascia Only or None.
🛢️ Barrel dormer
For a barrel dormer, you get the following dialog:
Barrel fields:
Type of dormer: Gable, Hip, Single Slope or Barrel.
Distance to Dormer Centre / Distance to Edge: As described above (toggle button).
Setback from eave: Distance from the eave to the face of the dormer.
Dormer Width: Width of the dormer at the base.
Height (Bulge): Height of the barrel at the centre line.
Side Length: Length of the straight projection of the dormer.
Toggles to Height of Dormer Gutter if you want to fix the dormer by height.
Front Overhang: Overhang of the gable end.
Gap Offset to Eave: Distance from the eave to the gap.
Dormer Material: Material category (Metal, Tile, Shingle, Low Slope etc).
Gap width: Width of the gap created from face of gable to eave (or based on the next value).
Picture shows a good example of the Dormer Gap used to create “pigeon roosts”.
Offset from eave to gap: Distance from the eave to the gap (as above).
Eave Type: Fascia & Gutter, Gutter Only, Fascia Only or None.
When you click [OK], the dormer is inserted.
↩️ Undo + what happens to the roof plane
If you make a mistake and want to change the dormer, select Undo and start again.
When you draw a dormer, a hole is created in the affected plane.
The width and projection of the dormer define the size of the hole.
The amount of actual roof coverage is the hole + the amount of eave and gable overhang.
🎨 Be creative with dormers (Gap example)
You can be very creative with the Dormer settings—different settings can produce very different results.
Example roof (same apparent dimensions in plan):
Dormer with gable overhang and no ‘Gap’ and dormer with gable overhang and ‘Gap’ at eave.
Settings for dormer with no ‘Gap’ (left side dormer):
Settings for dormer with ‘Gap’ (right side dormer).
