Development and Updates for the Medeek Truss Plugin

[Medeek]

I have been giving some thought to dormers and how to specify them.  Below is a dormer design I framed in Solidworks a few years back for a garage design:








Of course the numerous ways in which one could frame a dormer is probably beyond the scope of this discussion but I would like to consider what geometry needs to be determined in order to orient and size the dormer.


After some thought I think the following points, planes and lengths would define the geometry of a typical dormer:


1.) Main Roof Plane
2.) Attic Floor Plane
3.) Offset from exterior wall below (how far the dormer is out of plane from the ext. wall below).
4.) Pitch of Dormer roof
5.) Dormer width
6.) Dormer height (distance from attic floor plane to top plate of dormer wall)
7.) Window width, height, and header depth
8.) Dormer wall thickness (2x4 or 2x6)
9.) Dormer rafter depth
10.) Position of Dormer along length of building


Items 2,3 and 10 can be combined into a single point selection.

[Medeek]

Pondering complex hip roofs this afternoon and considering the graphic below:



A few rules seem to emerge:

1.) An outside corner will always create a hip that is 45 deg. from each leg of the corner.
2.) An inside corner will likewise always create a valley 135 deg. from each leg of the corner.
3.) Where two hips or flying hips meet a ridge will extend 135 deg. from each hip.
4.) When two valleys meet at 90 deg. they will terminate and a ridge will extend at 45 deg. from each valley.
5.) With a building with walls only running north-south or east-west all ridge lines will always be north-south or east-west.
6.) Likewise all hips, valleys and flying hips will be oriented northwest, northeast, southwest, or southeast.
7.) When a valley meets a ridge, (they will always meet at 45 deg) a flying hip is generated that is 90 deg. from the valley and 135 deg from the ridge. 
8.) When two valleys meet at 180 deg. from each other, the result will be either to flying hips perp. to the valleys or the degenerate case of 4 valleys and 4 ridges.
9.) When a valley and a hip meet each other at 180 deg. then two ridges that are 45 deg from the valley will be the result (typical L shaped roof).
10.) When 4 hips meet the result is a pyramid.

There may be a few other degenerate cases I'm missing but I think that covers it.

[Medeek]

Our natural world can always be broken down into simple patterns (mathematical relationships). When you identify those patterns and then act on them to your benefit that is when it becomes engineering.

[Medeek]

Variation in plate heights, pitches, overhangs and even mixing hip and gable (half hip, dutch gable) further complicate the matter.  To begin with I need a algorithm to generate the roof planes, then the framing just falls out from there.  To create the roof planes I need a fairly robust straight skeleton implementation.

[Medeek]

Version 1.2.6 - 01.18.2016
- Sill plate option (advanced) enabled for top and bottom bearing floor trusses.




https://3dwarehouse.sketchup.com/model.html?id=u98d5f3e7-8cab-4acc-8160-7e20617e1814

Work on the manual is progressing however for those interested the red colored boards in the image are called  "ribbon boards".  This is fairly typical for floor trusses.  The notch purposely left in the truss to accommodate the ribbon board is called the ribbon cut or ribbon notch.  Continuous ribbons provide stability for installed trusses, and also provide a solid nailing surface for the edge nailing of floor sheathing. This eliminates the need for larger and more expensive “rimboard” solutions required by dimensional lumber and other engineered wood products.  2x4 lumber is common, but any dimension of 2x lumber can be used for the ribbon board.

Similar to the complex hip roofs I need to program the floor truss/TJI module so that it can automatically frame out any non-rectangular floor plan.

[Medeek]

Version 1.2.6 - 01.19.2016
- Added Solid Sawn Floor Joists (metric and imperial)
- Sill plate and Sheathing options (advanced) enabled for TJI and Solid Sawn floor joists.

[Medeek]

Version 1.2.7 - 01.26.2016
- Added advanced roof options for hip rafter roof (sheathing, fascia).



https://3dwarehouse.sketchup.com/model.html?id=u3b08ddf6-b8be-405c-9ae6-912866e7a252

[Medeek]

I've uploaded a test L-Shaped structure with a hip roof:

https://3dwarehouse.sketchup.com/model.html?id=u8d384878-941b-4df9-a8c9-8bba849765bb

I've created both hip roof primitives with the plugin, that was the easy part.

I then placed a valley rafter with its centerline (top) inline with both roof planes.  I think I've got it right.  What I am unsure of however, is the best way to terminate the framing at the intersection of the valley, lower ridge and flying hip.  Once I have a handle on how a carpenter would actually construct that junction I think I can proceed to start work on a secondary roof module for both hip and gable rafter roofs.

The secondary roof module will allow one to add secondary roof geometry to a main roof and have it automatically adjust the rafters accordingly.

[Medeek]

The intersection of the supporting valley rafter, valley rafter and lower ridge I had framed incorrectly.  The corrected method is shown below:



Also note that the segment of the supporting valley rafter between the upper ridge and lower ridge would need to be beveled or "backed" otherwise it clashes with the sheathing.  I noticed this when I originally added the supporting valley rafter but confirmed my suspicion when perusing DeWalt's carpentry and framing handbook this morning.  I probably should have pulled this book out before beginning this study but it only confirmed everything I had managed to discover myself once I started examining the model.

[Medeek]

This is my first crack at a dutch gable roof framed with rafters:





Without the sheathing:





Please examine the model here:


https://3dwarehouse.sketchup.com/model.html?id=u060d4827-fbb5-400e-8270-0b244d958750

[Medeek]

Dutch Gable Rev. 2:


https://3dwarehouse.sketchup.com/model.html?id=u32c4c79d-603a-4363-99db-df726b281151


Same as previous except for doubled up common rafters at dutch gable.

[Medeek]

Dutch Gable Rev. 3:

Doubled up gable common rafters with the dutch ridge/ledger is sandwiched between them. Found a paper by Larry Haun, Mar. 1995 "Framing a Dutch Roof" that was published in Fine Homebuilding magazine, that describes a very similar method of framing.



View model here:

https://3dwarehouse.sketchup.com/model.html?id=ude19cd3c-e059-42e0-8e7d-2b0b6b0852a8

Disregard the common rafter sizes they are undersized but look at the method of sandwiching the dutch ridge/ledger between the last common rafters. I would probably also install some blocking between the double gable common rafters. I'm also not showing all of the ceiling joists and bird blocking etc...

If the roof gets large enough then one could go to a double ply dutch ridge, or even a deeper LVL member, assuming there is no internal support available from internal walls.

[Medeek]

Version 1.2.8 - 02.02.2015
- Added Shed Rafter Roof with Ledger (all advanced options enabled).
- Added ceiling joist option for Shed Rafter Roofs.
- New submenu item and toolbar icon added for secondary (minor) roofs.



View model here:

https://3dwarehouse.sketchup.com/model.html?id=u972818f0-96f0-4f85-9781-087a2db95199

I used this option to create a monitor style roof line but it can also be used for porch roofs, carports etc...  I still need to add a standard shed roof with and upper and lower birdsmouth cut.

[Medeek]

More "Fun with Roofs".

This roof was generated by first creating a hip roof primitive then deleting all but 3 components which were then copied and rotated into place for the lower roof hip corner.  The shed roof /w ledger component was created with one primitive and then copied and rotated into place.  Overall a fairly painless process now that I am somewhat familiar with navigating my way around SketchUp.  The fascia required a couple of trims.

The pyramid at the top required no manual intervention. Approximately 10-15 minutes of work for a fairly substantial roof.



View model here:

https://3dwarehouse.sketchup.com/model.html?id=ue55bf7ab-c669-4cd7-8f05-305dee4e2519

[Medeek]

Testing the real world application of the Medeek Truss Plugin.  This model combines a double fink truss, raised heel fink truss, monopitch truss and shed roof with ledger.  While creating the shed roof special attention to the birdsmouth cut was required to ensure that the fascia height of the rafters and trusses lined up.  Also note the use of the raised heel type truss on the upper roof portion.  Structural outlookers were specified for all gable overhangs. 

5:12 pitch roofs with rafters and trusses 24" o/c.  I did not apply a level cut to the rafter overhangs but that would probably be a given.  Span of the double fink is 48 feet with 2x6 top and bottom chords.





View models here:

https://3dwarehouse.sketchup.com/model.html?id=u98040448-af54-4d79-af30-a3aefca9b941

https://3dwarehouse.sketchup.com/model.html?id=ud8f4c186-1836-4d16-928a-2ba8c10c99a9

If anyone has some real world applications using the plugin that they are willing to share I would be very interested to see how it is being used and it would also give me some direction for further development and improvements.