The project-gable command lets you realign a gable end to match a specific alignment (eg a property boundary) or to project the gable into an existing roof plane to form a raised or lowered entry way arrangement (as shown in the examples below).
You would typically use this command to help join two roofs of different eave heights into one roof.
Assuming you have already drawn a gable roof and wish to realign the end to be other than square and you already have drawn a line defining the new alignment of the gable end.
After selecting the command, you then locate the ridge connected to the gable end. Then you select a menu item from the text menu. This is one of
2-Points In this case you want the alignment of the gable end to follow the two points you are about to digitise
Line In this case you want the alignment of the gable end to follow the line you are about to select.
Plane In this case you want the gable end to project into the plane (roof plane) you are about to select.
When you select the 2-Points or Line command option, you then select the 2-points or line respectively and the gable end is realigned to match.
If you select the Plane command option, then the gable end is projected along the ridge alignment to hit the target plane. Now, one of 5 things can occur in regards to automatically editing the target plane:
If the new roof is totally within the target plane, then a hole is punched to suit.
If the eave heights of the gable and the target plane are the same, then the eave of the target plane is cut back to suit and the new roof is accommodated.
If the gable eave is lower than the eave of the target plane, then you are prompted to enter a tuck under distance. This is the amount the eave of the gable roof is projected under the target plane. Normally you would enter a value equal to the eave offset so the eave runs into the wall. In this case, a lowered entry way is formed.
If the ridge of the gable roof is higher than the ridge of the target plane, then no automatic editing takes place.
If the ridge of the gable roof is lower than the eave of the target plane, then no automatic editing takes place.
This first example, shows you how a gable (or even a hip end) can be realigned. After selecting the ridge, then the 2-Points command option, you then digitise 2 points (d2 and d3). You can see how the end is affected.
In this example, you first select the ridge, then the Line command option. Then you select the line. You can see how the hip end is now realigned to the alignment of the line.
The following diagrams show what happens when you select the Plane command option
In this example, the gable to project fits within the roof plane. In this case a hole is automatically cut out in the target roof plane. You will also notice that the hatching for the roof planes has been turned off.
To select the roof plane, you then select the “tick mark”.
In isometric, you can see the hole in the target roof plane.
This example shows what happens when the eave height for both roofs is the same.
In isometric view, you can clearly see that the two eave heights intersect.
When the eave height for the gable roof is lower than the target roof, you are prompted for a “tuck under” distance.
You can clearly see in this diagram, the tuck under, which in most circumstances projects to a wall.