G'day and welcome back to Buildsum and this is our eleventh
presentation in the series on the Timber Framing Code
AS 1684
And this one's on working out the size of our hanging beams for our for our roof
or ceiling frame
So if you're looking into the timber frame code you'll find that rule 7.2.5
refers to hanging beams
The rule 7.3.7 gives us some information on where we can find
The spans for hanging beams and it points us at Table 23
So rule 7.2.5.1
says that hanging beamsshall support ceiling joists and the attached ceiling materials only
Hanging beams are usually at right angles or may be placed
I'm sorry or may be angled or placed off-center to ceiling joists and located directly above them
requirements for ceiling
Sorry requirements for beams
supporting roof and ceiling loads are given in clauses
7.2.7 and 7.2.8
Okay, so to start that we'll start looking at strutting beams and counter beans etc
Rule 7.3.7
Says that the hanging beams shall be determined from Span Table 23 of the supplements and
that hanging Beams shall support ceiling loads only via ceiling joists
the top edge of the hanging beam with a depth to Beath
ratio exceeding seven shall be laterally restrained at their supports
So if the height of the beam is more than seven times
The thickness you have to restrain them so they don't want to fall over
so here's Table 23 and you can see
The information the table wants, it wants to know the ceiling load width
For the hanging beam and I wants to know the span of the hanging
So the span of the hanging beam, so let's have a look at our plan
so
let's have a look at bedroom 1, here the ceiling joists are running in this direction, so
That the hanger has to run at 90 degrees
to our ceiling joists, so
The span of this hanger will be 3.500m. Which is the internal
dimension of that room
the Roof Load width is
Generally half
the
Length or the Span of the ceiling joist so the ceiling joists are spending from here to here
half of 3.5 is
1750 So the Roof Load width for this hanging beam which runs up here is going to be 1750
So if you go back to a little table, I've made up the span of the hanger for Bedroom 1
It's 3.500
the ceiling load with the 1750 and if you need a reminder
I'll put a link to my ceiling load width video up in the top of the screen and
Now we can work out our beam so first thing
Soon my width we said 1750 the closest we've got to that. Which is above it is
1800 so we're going to use the 1800 Column and
The Span was 3.500m
So come down here until we find it's 3.400 that's close
But no good because it's under so you have to go to 3.600
So there's our span
So that means that we can use
170 x 35 for our hanging beam
So we can put that in our table that in our table
So now we just have to work at the way around the rest of the house and work out each individual beam as we go
so the next room is has a span of
3.5 and a ceiling my width of
1250
We still have to use the 1800 column because there's nothing less than that
So we're going to end up with the same beam size because the span is similar
Bedroom # we've only got a span this time of two point four
Ceiling Load width is not going to make any difference to us
So same Column however of course the hour
Span was only 2.4
We can pick this 2.6 and we can use 120 x 35
Go down to the next one
Very similar I know that we end up with 2.6 so we can use 120 x 35 again in that situation
the laundry
span of 2.5
again even though our ceiling load width is only 0.9
It's not going to change because we started to use the 1800 column
so 120 x 35 is the
Hanger for that room as well
kitchen, 3.540m is our span and
1.750 is our ceiling load width
so same column again
We can get away
Let me go back
yep, it's still under 3.600 so we can use 3.600 there and
170 x 35 for that hanging beam
now the dining room is just over 3.600, so we're gonna have to go up a size and
Same ceiling load width so in this case
We'll actually have to come can't use 3.6 because it's under have to go to 4.1
So we need to use 170 x 45
now
170 x 45 throws up an interesting little
Quandary because we want to be as efficient as possible, and this where what we call in sections come into it
they have a look at the end section of our piece of
170 x 45
You'll see that there's s7650 square millimeters of timber in it
However, if you look at a piece of 190 x 35, which is the next standard size up
It only has 6650 Square millimeters
so there's less timber in this beam than there is in this beam and
What are things being right the left timber then the less price
so to be more efficient
We should use the 190 x 35
one we are using less timber - it should be priced less, so I'm going to say we're going to use the 190 x 35
You'll have to check your local prices to see if that's the case in your area
But that's the way we're going to work this out
So I'm going to use 190 x 35 in that case and that just means I'm gonna get technically I could span further
But it's more efficient to use the 190 x 35
Keeping going down the next one the family room is 2.740
With a ceiling load width of 1750
We're gonna use have to use this time 140 x 35
and
Now we're starting to get some repetition going on for this style living room has the same span as a dining room
So we don't need to get back the table. We can just use the same as what we used before
190 x 35 and
Entry 2.400. We've got a 2.400 up there and a 1750
So we can use the 120 x 35 so now we have all the different sizes of timber that
we can we need to use for our
for our building or for our ceiling frame
You could you know if you really wanted to just buy one size as long as it was all
190 x 35 and use that for all of them, but as you can see it's a fair bit overkill
And we're trying to be as efficient as possible with our
Timber in these exercises
So there you go. I've worked out the timber required for our hanging beams in our frame