High end cedar porch construction: the rafters

In the last two blogs, the ledger and the main beam (top plate) were discussed.   After having put these two structural members in place it was now time to make and place the rafters.  There were a couple of challenges that I had to  overcome with the making and placing of the rafters.  One of the challenges would be I had to make my first birdsmouth ever on a large beam without any second chances and the other was I had to place these awkward rafters up higher than I could reach.

The porch required 10 4" x 10" rafters.  8 of them were exactly the same.  Each of them had to be cut at an angle at one end so that they would be flush to the house and account for the roof pitch of 12/2.5.  In addition I had to run a router bit down the two edges to make the rafters more appealing to the eye.

Each rafter also had to be drilled at an angle at each end for two countersunk 14" 1/2" lag bolts which secured the rafters to the ledger and main beam.  The lags provide 1000 lbs withdrawal strength and have the nice feature that they are hidden from view.

In addition each end of the rafter needed a birds mouth which allows the rafter to sit nicely on flat surface on the ledger and main beam.   The positioning of the birdsmouth is important.  If you don't get it right then there will be an unsightly gap or it will cause the wall it sits on to become out of plumb..  Also the angles of the heel and seat must be perfect to make it look professional.

To help me with these challenges I made a guide out of 2"x8" lumbers.  I already knew how to position the birdsmouth against the wall of the house.  So I made a birdsmouth in the end of the guide.  But for the other birdsmouth that rests on the main beam I did not know the position.  In fact the position is slightly different depending on what part of the main beam the rafter sits on.  So I left that birdsmouth off the guide.

Once the guide was made I attempted to put it on the ledger and main beam by using brute strength and a ladder.  It didn't take much to cause it to fall to the ground and leave a mark on the ledger.  Time for plan B!

To assist with the placement of  the guide, I built a crane using the cheap harbor freight winch and dock lumber which is shown below. 

This helped stop the guide from falling to the ground and allowed me to mark where the birdsmouth should go at my leisure.  Only there was one problem, if the rafter were to be installed with the crane I had built it would be difficult to get the crane removed from the rafter.  Woops!

The next step was to cut the birdsmouth.  I followed the procedure used in this video for the seat cut in the birds mouth.  I actually had to come at the birdsmouth from both sides of the beam because it was too thick and my circular saw was too shallow.  To make sure the angle was correct I marked it on the rafter and followed the mark with my saw.

For the heel cut I had to tilt the saw to 21.8 degrees and make the saw the appropriate depth.  Since there were a number of birdsmouths to make I took a spare block of cedar and cut it when the saw was adjusted.  The block served as a means to quickly setup the saw when going back and forth between saw adjustments.  I would just put the saw in the block and make the saw match it.  Once adjusted I made the heel cut with one pass.

Since the saw blade is circular the wood was not completely freed from the rafter, I had to use a chisel to knock out the wood from the birdsmouth where it was left attached.  It was easily done but left an undesirable uneven surface so I used my Makita 1/2 sheet sander and smoothed it off.  The end result is shown below.

 

Next I drilled the countersink hole and the shaft hole for lag bolt holes, sanded the rafter and applied Olympic elite woodland oil to finish it off.

After the beam was ready I redesigned the crane and installed the beam shown below.

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As was said before 8 of the rafters were the same but there were two rafters that were not.  These beams rested on the ledger but not the main beam.  The reason that these different rafters came about was because the way the house sits on the property.  The porch I wanted ends up crossing the set back line.  This required that one corner of the porch to be cut off at an angle in the design.  Well if one corner gets cut off then so does the other to make it nice looking.  Even though the set back line is a pain in the ass, the end result was much more architecturally pleasing cedar porch.  So I'm kind of glad I had the problem to deal with.

Because the 2 different rafters did not sit on the main beam they had to sit on posts.  This called for a more complicated joint.  It required a two oak peg mortise and tenon joint and an embedded lag to secure the rafter to the post.  In addition a birdsmouth is involved.  The mortise was difficult for me to make due to its angle in the wood but I'm happy with the end result.

At this point the cranes broad base made it impractical to use at the end of the porch without wasting a bunch of time to try make it work.   So I placed a call into the cavalry and asked my friend Glen to help me put in the last two rafters.  Nice to have backup when you need it!   The end result is shown below.

  

Now that the rafters were all installed, it was time for the cedar planking.  The planking job came out perfect and after having done it I can see how it is easy to totally screw it up making the job look unprofessional.  In the next blog we will discuss what techniques I used to make the planking come out as good if not better than a professional would have done even though it was my first time.

Happy Building!

The Dr.