G’Day and welcome back to Buildsum and this is going to be the fourth video in my estimating
series and in the first three we looked at some different scenarios with ridges, in this
one we are going to start looking at the hip of a Hip and Valley or Broken Hip and Valley
Roof.
If we have a look on the plan our Hip always bisects the external corner and is generally
45 degrees and that is what we are going to assume in this case and this will also apply
to valleys as well.
So in this case the building is 7.572m long, we’ve got a 600mm eave overhang all the
way round and we’ve got a span of our building,
I’ll just put the walls in so you can see that, so the outside of the timber frame regardless
of whether there is a brick veneer or not the outside of our timber frame is 5m that
will just make my calculations easier later on and as i said 600mm overhang all around.
So we are trying to work out the rough length, for estimating purposes, of the HIp, that's
that member there and of course there are four of them on this roof.
So the first thing we need to know is we need to know how far the roof rises, so i'm going
to work this on a metre basis, so we are going to work out the rise of the roof per metre,
and all we need to do for that is Tan the roof pitch so in this case Tan 30, the roof
pitch for this roof is 30 degrees, so Tan 30 will you a rise per metre of 0.577m, around
half a metre or 577mm.
Thats the rise so every metre that the roof runs it rises 577mm.
So that is the first thing we need to know, then we need to know how far the Hip actually
runs per metre.
So, i’ll put that calculation up, so if you so a metre squared, do pythagoras, one
metre squared plus a metre squared you will get obviously two metres and if you square
root two metres you will get an answer of 1.414m.
This is a common measurement in roofing calculations, so basically what that means is for every
metre this way that, on plan, runs 1.414m.
So now we know that our hip for every metre this way, or that's sort of going along the
half span, but for every metre this way it rises 577m and it runs 1,414m, so now we can
so pythagoras again with those two dimensions,
so the true length of the hip per metre is 1.414m squared plus 0.577 squared and find
the answer square root of that and get a length of 1.527m.
So for every metre the building goes this way or every metre along the half span the
hip rises, travels, rises 1.527m.
So now we know that, that's constant for every roof that’s a 30 degree pitch that is a
constant measurement that will always apply, the only thing that is going to change is
the half span of the roof so now what we do is grab the half span and we times it by the
true length of the hip,
now just to make the calculation easier we can also add our eave width in here because
we are looking for the overall length of the hip right out to this corner.
So, half span plus our eave width times by our true length of the hip per metre will
give us our answer so 2.5 is our half span half of 5 plus 600 which is our eave overhang
times by 1.527 give us a distance of 4.734m.
So rounding up to timber orders we would order a 4.8.
Now just something to be really aware of there is not much of a round up there, we are talking
about rounding that up 66mm it's not a real big round up,
so because we know we are going to cut an angle on our hip, here is our plumb cut up
here the interesting thing that happens
down this end is we end up not having enough material.
So depending on what you are going to do with the end of the Hips, some people cut the overhang
of the Hip off a little bit, they reduce the width because they want it to match the rafter
size but other people don’t
so it depends on what your preference are, what the people doing the work preference
are, whether you stick with the 4.8 of round up to the next size, the next size will be
5.1.
So just something to be aware of if your
round up is not very much then maybe you want to round up to the next size alright to stop
that little phenomenon happening.
So what i have also done if your interested, I put a link in the comments, I’ve done
a quick little spreadsheet, so this spreadsheet and all my spreadsheets you just fill in the
yellow parts and the green parts will give you your answers.
So this is the same calculation that we have just looked at, 30 degree pitch, m half span,
600mm overhang, so it gives us our rise per metre of roof, our length of hip per metre,
overall length of the hip which is going to be the total length of the hip and gives us
our orderable length and how many we need to order.
So 1 / 4.8 but obviously you know you need to go around and count the number of hips
that you have got on your roof.
So there you go, that is a quick way on how to estimate the length for a Hip.
If you want to work out the exact cutting length I will include some lengths to some
other videos that i have done on actually working out the exact cutting length of the
hip using various different methods.
G’Day again, I’m back, just to let you know, if you like this video you can subscribe
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