So, we're Back out on the Site and what I want to do in this Video is show you how
We can set out a pattern Rafter for a hip roof
So last Video, we cut a Gable Roof for this building so this Time
We're going to change the design and put A hip roof on to this so a couple more members in a Hip roof
then there is in a Gable in the Gable Roof we only had
what we called our Common Rafters
And that was pretty much it now we've got. A Hip roof, I've actually got to have our hips which are these members here
we're going to have this rafter here Which Is pretty similar to a Common Rafter but it's actually called a
Crown end Rafter because obviously it's on the end of the roof and then we've got these shorter rafters
which are our what we call Creepers
They're on both sides of the hip on both sides of the roof so that's what, we're going to work out
so
when, we finished our Gable Pattern Rafter we had our Pattern Rafter set out and we had
The Centerline of our Roof Marked, we had a
reduction for where our hip
sorry, where our Ridge was and where our Rafter was going to butt Into the Ridge that was our
Ridge Reduction
We had our Plumb and Level Bevel mark for our Birdsmouth and
we had our overhang marked on our
Pattern Rafter so now what we need to work out Is
the length of our Crown End Rafter and the long point of our Creepers
So if you go and have a look at, the set out of our roof
with a hip roof what we need to work out is exactly where our
Common Rafters and our Crown End Rafters going to meet so way to do that is take our Half Span which Is
this distance here 1.810 in this Case
Measure it down the Roof
and that will give you the Centerline of our Centering Rafters so
that's those ones there so obviously on both ends of the roof
on both ends where there's a hip, we're going to have a Centering, Set of Centering Rafters and then
from the outside of the Centreing Rafter that's where our Crown end goes in
and if you have a look at that on plan
you can see that
our Common Rafter, was 10mm or half the thickness of the Ridge
shorter than at centerline
Now our Crown End Rafter Is
half the thickness of our Rafter
shorter than our Centerline so in this case
22.5mm
and they're both planned dimensions so if you get back to our
Pattern Rafter
from our centerline and we can measure back 22.5mm that will give us
the reduction for our Creeper, sorry a Crown End
so our first one is Ridge Reduction
second one is our reduction for a Crown End
Now the next thing, we need to do is look at our Creeper Reductions so
for our first one
we know that our Creeper or Rafter Spacing IS 450mm in this case
It could assume that
we just simply have to measure 450mm on Plan and that will give us
the
reduction for our Creeper but as you can see this little Illustration here
if we do that
our Creeper actually ends up in the wrong spot because one
it's obviously sitting halfway through our
hip
but it's, also it's not centered. This
dimension here should be from the center of the centring Rafter to the Center of
our
Creeper so what we need to do is we need to make some adjustments so
what we actually need to do is move this back
this distance here
which is half the mitre
thickness of our Ridge and
the way, we can work that out is you can either do Pythagoras
So half
the thickness of the Ridge which is 10 and
we then you'd have to use becourse it's a 45-degree Angle
10 Squared
Plus 10 Squared Would Give you 14.14 or you can, do
10 Divided By 45 COS
Equals
So it gives you the 14.14 so, we're Just using
half the thickness of the Ridge and looking at what the mitre distance of that Is
that's our 14.14
that brings the Rafter back to there and then needs to go
across
22.5mmto this point here and
obviously, we don't have a big gap so then, we need to move it back up the roof
22.5mm or half a Rafter thickness
so obviously this Is for 45mm rafter if you're using 35 you'd be looking at 17.5mm
so that would actually move that Creeper up Into position there which would be exactly where, we want it so
Once we do those Calculations We work out that our plan reduction is actually
42mm
plan measurement not
450
So when, we go over to a pattern rafter there's a couple of ways, we can do it
We can either use our
Steel Square
measure down our 450mm
then add on our
half hip of mitre Which Is 14.14 then take away our
Half our Rafter Thickness Which is 22.5
to give us our dimension or actually a long point of our Creeper
we could transfer straight off the Square our
442
which gives us the same mark
or the other option Is
to simply calculate what the True length of that would be so to do that
We Can Take our 442
divided by that by 30 COS
which Is our Roof Pitch and that gives us 510.3
but thats hardly worth worrying about so 510mm
down the roof as a true length for our reduction
so once we've looked at our first Rafter and made the adjustments, we can then go down and
add in our remaining
Creepers so, We can do that a couple of ways as well
here's our Steel Square
is our Plan length which now is just going to be the same as our spacing so 450 at a time
down the roof
until we get past or it's close to or, less than 450mm
to our Birdsmouth so you usually end up with one that's sitting pretty close to the birdsmouth but you need that one
because it's going to pick up your Fascia out at the eave line
The other option again if we calculate is we can take our
450mm
divide that by our Pitch
COS and equals like this Is 519.6
So we could actually measure
Our 519.6 down the roof and that too would give us the position of our Creeper Rafters.
Another method Is
if you are actually mark out
where your Creepers, were going to sit on your Plate you
can actually then directly measure the planned distance and the reason, we can do that Is
that we measure from
this point here
which already allows for half our miter thickness
So it gives us the Plan length a rafter
fairly directly
The problem with this Is that you know it's generally
2.5 to 3m up in the air so the other option is to
recreate that setout on the back of
your Pattern Rafter
So we've got our Centering Rafter 450 Centers
actually marked the position of our hip
put a Half Span distance there and
we can actually then measure from
this edge of the
hip
to the long point of our
Creeper and actually get the exact
plan distance
straight off that setout and
then you could use a Steel Square
or you can use
the COS method and
we can take those distances convert Into true lengths as I've done there and
then
mark those
directly
from the back of the Birdsmouth directly onto the Pattern Rafter
and once we've done that we've marked out our Pattern Rafter
So now the Information we've got on here is
still got our Centerline of our roof
our first mark Is
our Reduction
for our Ridge
the second marks the reduction for our Crown End Rafter
We've then got a number of reductions
through our Creepers depending on how many we need
Birdsmouth is still there and our overhang
So with that setup as our Pattern Rafter
We now have all the Information we need to go ahead and cut out
Common Rafters our Crown and Rafters all our Creepers for our hip roof