Rafters and Ridge Board

Having never done this before it was a case of phoning a builder friend to ask a few questions.

For terminology, have a look at:

http://collections.infocollections.org/ukedu/uk/d/Jgtz006e/14.3.html

 The advice went as follows.

1. In order to work out the location (& depth) of your birds mouth cut, cut over length rafters at the desired roof pitch. In my case the pitch is 45° to maximise head space in the loft.

2. Cut a short length of the ridge board and stand it on its end (see left of the orange nail gun).

3. Place the length rafters horizontally on the bottom plate to replicate how they would look when placed on the roof ie along the centre line of the two long walls.

4. Mark the desired overhang of the rafter.

5. Mark the position where the rafters contact the edge of the wall. This is where a "birds mouth" cut will be made. Make the depth of birds mouth cut with consideration to maintaining the structural integrity of the rafter.

6. Cut the birds mouth and reposition back on the ground as per step 3.

7. Measure the distance from the bottom plate to the bottom of the ridge board and write it down.

Before cutting more rafters, the ridge board should be installed to check that the two rafters fit.

To position the ridge board, nail a long length of timber to one side of the centerline of the frame. This structure will be removed later however it needs to be firmly secured.

Position a block of wood at the height of the ridge board as noted in Step 7 above.

The ridge board will rest on this block. Repeat this for the other end of the tiny house.

Position the ridge board on the blocks and clamp. Loose fit the two rafters that were previously cut and make any necessary adjustments in the position of the birds mouth, the angle that the rafter meets the ridge board or the height of the ridge board.

Note that I wanted an eve at both ends of the tiny house so the ridge board is over length.

Cut additional rafters as required. When cutting and fitting rafters, the assumption is that the walls are straight, level, plumb. Note that the rafters will want to spread or push the two long walls apart.

In order to minimize the potential of spreading, the loft bearers were fitted prior to the installation of the rafters.

The long length of timber that can be seen in the photo below is a plant that was worked off when fitting the rafters. Much easier than working off the top of a ladder. 

Construction was during an Australian winter and due to shorter daylight hours the majority of work was undertaken on the weekends. Black builders plastic was placed over the whole structure to stop the chip board floor from getting unnecessarily wet.

Internal view of the rafters. This was the first time that the internal space of the tiny house could be "felt". Note the working plank.