Hanging beam and ceiling joists

Hi, a question about my roof timbers please guys.

I have a circa 1970 fibro clad cottage in the southern suburbs of Sydney with hardwood timber framing, a conventional roof structure and concrete tiled roof. Above my kitchen (5400 x 2800mm) I have 100x38 hardwood ceiling joists @ 450mm centres spanning the 2800mm from external wall to internal load bearing wall. Mid-way along these joists there is a 190x38mm hardwood hanging beam spanning the 5400mm from external wall to internal load bearing wall.

Unfortunately, as the hanging beam runs right down the middle of the room, it seriously limits my options for placement of a skylight. Ideally, I would like to move the hanging beam by about 600mm so the joist spans would be 2000/800mm instead of the current 1400/1400.

So to the questions :confused: :

1. Does moving the hanging beam as per the above sound feasible / advisable?

2. I've found some span tables that indicate that maximum span for 100x38 F14 joists is 2400mm, but how do I know what grade timber my joists are?

3. I've got a fairly limited table for hanging beams that only goes up to 4200mm spans. I assume that a 190x38 beam is large enough for the 5400mm span with joists at 1400mm - can anyone advise?

Any advice would be welcome. Cheers. :)

Why not move the hanging beam and then install another one on the other side of your skylight and then you will know for sure you wont have any problems.

Thanks Bazza,

I did think of that but if possible I want to avoid the expense and inconvenience of installing a second beam (it won't be easy to get a 5.5 metre 200x38 beam into my roof space). Does anyone have tables that can give me a fairly precise answer?

Cashy

200x38 of any stress grade wont do it in todays books, take some tiles off and put in another beam as bazza said, use a 240x45 f17 for the larger span cieling joists. The stress grade of the timber in roof if hardwood was probably F8 when constructed but would be technically now F11 however F14 plus would be more realistic. It is amazing how far the used to span 200x38 hanging beams with little or no sag.

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Originally Posted by Cashy

Thanks Bazza,

I did think of that but if possible I want to avoid the expense and inconvenience of installing a second beam (it won't be easy to get a 5.5 metre 200x38 beam into my roof space). Does anyone have tables that can give me a fairly precise answer?

Cashy

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Have a look at the tables in this post I made last night in another thread. You may find what you want in there.

http://www.woodworkforums.ubeaut.com...64&postcount=5

These truly are very comprehensive span tables and worth bookmarking for future reference.

Thanks for the help guys. The tables that Bazza posted are the ones that I found on the net and referred to above - you'll notice that the hanging beam span only goes up to 4200 mm with joist span down to 2400mm, which requires a larger beam than I've got. With a beam span of 5400 and joist span of only 1400, perhaps the 200x38 is enough? Seems to have done the job pretty well for the last 35 years anyway.:)

I'll take your advice and put a second beam in, but it bugs me not knowing the exact answer.:confused:

Cashy

Not having access to span tables prior to the BCA it looks as if a hanging beam according to those tables shoudn't span any more than 4.200 and looking at how your ceiling was constructed I would say that when they built the house they ran the joists the wrong direction. I would say they should have run the joists the 5400 way and the hanging beam the 2800 way. To my way of thinking it would have been better for the plaster if it is fixed directly to the ceiling joists. If it has plaster battens then maybe not.

Looking at the span tables 2000 is not a great distance for the joists and you aren't really changing the load on the hanging beam and as you say it has been there for 35 years any way.

But putting the extra hanging beam in would certainly cover you.

Maybe if you sent a PM to Journeyman Mick he could give a more definative answer.

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Originally Posted by Barry_White

................Maybe if you sent a PM to Journeyman Mick he could give a more definative answer.

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Nope!;) The only definitive answers you will get in a situation like this come from a paid, insured engineer. Probably cheaper to just put the second beam in, I'd say.

Mick

Hi Cashy.

What I'd do is get two 140X45 F17 hangers at 3 metres across the 2.8m span. They'll be easier to get in the roof being shorter, and they'll also be cheaper than getting a 240X45 F17 at 6 metres since a 5.4 won't be long enough.
Prop the ceiling directly underneath the ceiling joist/hanger intersection on either side of the skylight opening (make sure you get the props directly under a ceiling joist). Then just cut out the hanger where the skylight goes, notching the bottom 40X45 to bear on the new hangar. Install one on each side of the skylight (slipping it under the old hangar), parallel with the ceiling joists and connect the old hangar to them with hoop iron or multigrips or just skew nail it down. If the roof angle interferes with the end of the hangar you can taper the top. Just trim between the new hangars with some more 140X45 to pick up any stray ceiling joists in the skylight area and you've got your ceiling opening all framed up. (You could use the piece of old hanger that you cut out to trim one side ;) )

Nice thought, thanks for that. You're right, it would certainly be easier to get the two 3 m beams into the roof space.

The only thing I think I would need to do that you didn't mention is chock between the existing hanging beam and the ceiling joist where I install the props (there is a 25 mm gap between them) - this would prevent all weight being borne by the steel straps joining hanger to ceiling joists. Anything else I've missed?

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Originally Posted by Cashy

The only thing I think I would need to do that you didn't mention is chock between the existing hanging beam and the ceiling joist where I install the props (there is a 25 mm gap between them) - this would prevent all weight being borne by the steel straps joining hanger to ceiling joists. Anything else I've missed?

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Yes, definitelly do that if it's strapped down with some sort of sheet metal strapping and there's a gap there. Usually with old ceilings they have ceiling dogs installed which are a thick zed shaped nail, and they're pretty strong but I'd still put a wedge in that gap before you prop. You're thinking ahead there, good move.
You'll have to be careful setting out exactly where your new hangars will go so they're right on the edge of the ceiling opening. Mark it out from underneath first, then cut the ceiling out of the skylight opening. You can get the new hangars up through the hole then. Once you've put your two props, or timber toms in, just cut the hangar. The section between the props might sag a bit but it shouldn't go too far. Remove that section from the ceiling joists that it's still attached to and save it to trim one side of the opening. Then install the new hangars. Remove the two props/toms and reuse them to prop the ceiling joists in the skylight area before you cut them. Then just cut the ceiling joists (allowing for the thickness of the trimmer), and trim between the new hangars using the hangar offcut for one side, and a piece of 140X45 for the other side. Put a multigrip fastener on all of the butting connections between hanger/ceiling joist etc. but I usually don't put them on the inside of the skylight opening so they won't interfere with the gyprock.

Bob's your uncle.

Thanks pawnhead. Yep you're right, they did use the big @rse Z nails that you mentioned, but I didn't know what they were called or how to describe them.

Thanks for the tips ... now I just have to find the time !!

:D

hey guys,
i was woundering if any of you could help me out with what will seem to be a very elementry question, but if any one could, would you mind clarifying the difference between a hanging beam and a counter beam.

my understanding is that a hanging beam:
- runs perpendicular to the ceiling joists
- is at mid- span to the ceiling joists
- is chocked up off the top plate so that it sits at the height of the ceiling joists, and is then attatched to each joist with a metal stirip.
- is intended to reduce the span of the ceiling joist and prevent them from sagging

- the counter beam runs in the direction of the ceiling joists, and intersects with the hanging beam to prevent it from sagging, and give it extra support mid span.

one thing im not too sure on is when they join, which of the beams butts up to the other. i thought the hanging beam ran the entire span of the ceiling, and that the counter beams butted up against the hanging beam on each side, but im not too sure.

the reason i ask, is that i'm a uni student with an exam tomorrow, and am not entirely sure if what i've written down is correct, so any advice would be much appreciated.

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Originally Posted by S346

- is at mid- span to the ceiling joists

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Usually, but it's not necessarily in the middle. There may be a circumstance where it's offset if there's a dogleg in the room. So long as none of the members are over spanned, it doesn't have to go half way. There also may be a circumstance where you have a long rectangular room that requires two or more hanging beams at even intervals

Quote:

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Originally Posted by S346

- the counter beam runs in the direction of the ceiling joists, and intersects with the hanging beam to prevent it from sagging, and give it extra support mid span.

one thing im not too sure on is when they join, which of the beams butts up to the other. i thought the hanging beam ran the entire span of the ceiling, and that the counter beams butted up against the hanging beam on each side, but im not too sure.

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No.
The counter beam carries the weight of the hanging beam, so the counter beam is continuous. The hanger butts into it:

http://i7.photobucket.com/albums/y26...ured-01-13.jpg

The rake cut on the end of the counter beam is to clear the roof when it goes on.
There is a perspective problem with that drawing as you may notice (It's not my drawing). The hanging beam and counter beam cannot be flush with each other at the bottoms as shown. The hanging beams should be shown higher at the bottom by the depth of the ceiling joists. :wink:

Quote:

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Originally Posted by S346

the reason i ask, is that i'm a uni student with an exam tomorrow, and am not entirely sure if what i've written down is correct, so any advice would be much appreciated.

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You've probably hit the sack, but you may read this in the morning, so good luck. :2tsup:

I fixed it for them:

http://i7.photobucket.com/albums/y26...ured-01-14.jpg

In this case, the hanging beam is the same depth as the counter beam, so the hanging beam is notched over the top of the counter beam.

Footnote credit: I got the drawing from a specification on a product called: " 'e-beam', engineered LVL beams for stick roofs". The company is Wesbeam Pty Limited (no affiliation).
There are more drawings, specifications, and span tables in the download:
1.4 MB pdf