Civil Engineering Reference
In-Depth Information
Making the first connection of the rafters to the ridge beam
You will now make the first connection of the rafters to the ridge beam. Lift the square
cut end of the ridge beam up to the underside of the two rafters at the junction of the
rafters while the other end of the ridge rests on the ceiling joists. When the ridge is held
just below the rafters, have your assistant lift and separate the two rafters to allow the
ridge to be inserted between the rafters. It is easiest if they reach under the ridge beam to
lift the rafters, as this eliminates the problem of having arms in the way of the ridge when
it is being inserted between the rafters. As the ridge is held in place, allow the plumb cuts
of the rafters to come to bear against the sides of the ridge. It is not essential that they be
positioned perfectly adjacent at the ridge end; at this point near enough is good enough.
Allow the tension between the rafters to wedge the ridge beam between them as you allow
the rafters to drop in position. If the timber is dry, the friction between the plumb cuts of
the rafters and the face of the ridge will be sufficient to hold the ridge in position. This,
however, should not be taken for granted. A temporary fixing of the rafters to the ridge is
required. The nails that were earlier hammed into the top of the rafters are now to be
hammered into the ridge beam, while leaving a sufficient amount of the nail exposed to
permit its later removal.
The carpenter who didn't tack the rafters to the ridge
This reminds me of a carpenter I once worked with who was a little lax when it came to
safety. A man that it seemed would rather have a fight than breakfast any day. He was
working on the frame of a house in the middle of winter. Not the choicest of jobs at that
time of year. The site was wet and working in the mud was a constant battle. Leather
boots were rejected in favour of rubber gumboots. The ceiling had been completed, the
rafters cut and it was time to fit the ridge beam. This was back in the 1970s when the
primary timber used in house frames was OBHW, which stands for ordinary building
hardwood. To remove the somewhat exotic name, gum tree so green that the sap was still
dripping out of it. The sap from this timber was so prevalent that our hands were
constantly stained black, somewhat embarrassing when you were out at a good restaurant
and put your hand out to receive change. Each night we would go home with our pants
wet where we had been resting the timber against our clothes. Needless to say, it was
extremely heavy.
The ridge beam was 200 × 38 mm and 6 metres long. The rafters were fixed at the
external walls and resting together. He lifted the ridge beam up between the two rafters
and allowed it to gain its bearing against the rafters. There was just one problem - there
were no nails waiting in the top of the rafters. Rather than to go to the trouble of fitting
the nails from scratch, he made the mistake of trusting that if it was sitting all right at the
moment it would be fine. With his feet seated lengthways on the top edge of the ceiling
joists, he lifted one foot to take a step back heading for the other end of the roof. Just at
that very time, while effectively standing on one foot, the rain-drenched and waterlogged
ridge slipped from between the rafters and came crashing down onto the ceiling joists
below. It fell so cleanly that it remained in its vertical state until after it hit the ceiling
joists, making a crushing blow to the rubber gumboot below it.
The colour of his face was indication enough that he was not enjoying the experience,
and no doubt had the fleeting thought 'if only, if only I had nailed those rafters'. On
