Feb 22, 2015

Building Concepts Course CMCC Week 18 - Timber Frame Rafters

Our timber frame project has an end in sight! This week we focused on rafters. The pictures above and the picture to the left illustrate the method of joinery that we exercised to bring our rafters together at the ridge. Tongue and Fork is the term for it. 
Tongue and Fork

You can see we dry fit them on the ground before erecting them on our building. Also for our birds mouth cut since their is not going to be any overhang assemblies we are going with a plane-old birds mouth cut only the plumb cut is on the opposite end-edge of the timber. This is because when it is in place, the rafter ca not slide off the plates or top girder. See the photos below to better understand what I am trying to explain.

Feb 14, 2015

Building Concepts Course CMCC Week 17- Timber Frame Knee Braces

This week was devoted much of our time toward creating knee braces for the long walls of our timber frame. The purpose of these knee braces is to keep the long walls of the structure held square and also to offer support. Unlike the other knee braces we joined these 4 knee braces from the outside in instead of the true mortise (hole) and tenon (tongue) style joinery. Before any assembly happened their was a lot of planing and joining of the timbers to get them square and straight. 

Feb 7, 2015

Building Concepts III Course CMCC Week 16 - Hip Mock Up Completion

This week our focus we set on completing the Hip/Valley Roof System mock up. Our tasks were to calculate the five different hip/valley member ahead of time with given building dimensions. Based on what we have been taught about determining opposite interior and exterior angles inside of a rectangles. 


Hip- Valley Cripple Jack Rafter 

With regards to this image you can see a cheek cut, which is the line going at a 45 degree angle across the middle top of the member. The lines it crosses through are important as they are reduction lines for the hip rafter. Whenever a line length is determined you must take into account that members thickness so that the other member meet and connect perfectly. So to calculate angled reductions we determined that 1 1/16th" of an inch is the amount necessary to put you inline with the member on a 45 degree angle. Next you need to bring that back half the member thickness, in this case it was 3/4" and that butts you up right along the hip perfectly. 

 Valley Rafter Seat Cut

Valley Layout Rule: Always add 3/4" (half the thickness of the member) to the plumb seat cut line. This accounts for where the member is going to sit tight to the inside corner of the building provided they are cut on 45 degree angles pointing toward the building. 


Valley Rafter Tail Cut

Here is a series of layout and cut images of a valley rafter tail cut. Valley rafters are calculated using the same unit run as a hip, 16.97". With the given information that the roof system was a 5/12 slope, 5" rise for every 12" of run. Determining the valley line length requires you to replace the 12" run with 16.97". Now its a 5/16.97 slope. Using Pythagorean theorem we are able to calculate the line length and overhang to know what rough length member we will need to cut our valley or hip from. 


Feb 1, 2015

Building Concepts III Course First and Second Week CMCC- Hips Roof Assemblies Weeks 14 and 15

 Picking Up on the Timber Frame: Week 14

Week 14 was all of one full day of shop work and that shop day was spent working on pluming up and squeezing together the joints of our timbers on our timber frame shed. Once they were viced and clamped, we applied gusset plates to each side of every corner to hold them in place.  


Trick of the Trade for  Week 14: Loose Rafter Racking System

This system works well because occasionally you find yourself on the job site without an extra pair of hands and if you have every racked roof rafters it can be scary and difficult even with two people. The beauty of this method of racking is that it works better with a larger or longer roof. The two photos above and below are of that system used to "rack" a loosely secured roof system into a plum position. First join the two 2" member pieces with one nail which will act as the pivot point. Then have the lower 2 x 4 nailed at both end points, fasten a nail to the roof rafter closest to the pivot point next to the lower 2 x 4. Finally, your able to pivot two pieces and because of where they are fastened they will either pull the roof to the right or left depending on which direction you pull and push that pivot point. 


Hip Roof Rafters: Week 15

This photo below illustrates the complexity of a Hip style roof. Among the many different types of members involved comes the math with calculating each of them. Not a hard determination to make when the math is exercised enough and also applied. Its all geometry. What we are being exposed to in class are all the different methods to calculating lines lengths of a hips, valleys and jack rafters.  Using math to determine line lengths we can determine the length of every single member in this roof needed for an estimate lets say. If conceptually that's difficult simply look at this roof system in terms of an organized grouping of triangles and squares which will then make it make a lot more sense because that is all it is.   

Compound Miter Cut or the Double Cheek Cut

Here you can see our double cheek cut joining at the ridge rafter next to a common rafter.