Help with Ceiling joists layout

mightymouse2045June 13, 2013

Hi there,

I am designing my own home and need some help with a large open area, on how to best lay out the ceiling joists.

I've attached a basic plan of the walls, with the layout of the joists so far. All measurements are in meters.

The dark orange walls are all load bearing walls, and the 3 lighter orange walls on the right side are load bearing but only waist height (930mm).

I want to embed all the joists in the tops of the external walls with the base of them supported on the tops of the internal walls on the left side of the house (any issues with doing this?).

The joists you see sticking out of the walls are also acting as rafter ties, for the 8/12 pitch roof. The joists will also be supporting a bamboo floor and attic space\rooms upstairs, with minimal furniture etc.

The left side of the house is relatively easy to work out due to the load bearing walls providing additional support for the joists, the middle and right side of the house is somewhat more difficult.

Firstly the right wing span is 7meters, and I don't want support beams in the area I have already marked with joists. I'm having difficulty sourcing or finding beams that will support a 7m (23ft) span, that will provide support for the loads required. If anyone could suggest anything for these would be great.

Also the open area that doesn't have any joists I could really use some assistance with as to the best layout for the joists. It would be preferable for me if I didn't have to use any support posts in this area also, but I just can't see how that will be possible. I've marked two black squares roughly where I am thinking of putting support posts, but if I can do without them, I'd really love to.

If anyone needs any more information I have the revit files, and a load more details if required.

Thanks in advance for any assistance with this :)


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The joists appear to be attic floor joists that carry a ceiling below. The live load would be 30 psf and the dead load would be 10 psf so just design the joists for the longest span. Since that span is not included in a building code table the design would have to be done by an engineer.

    Bookmark   June 14, 2013 at 5:51AM
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Type of rafters planned?

The ceiling support and rafters are normally designed together (for a framed roof or a truss roof).

    Bookmark   June 14, 2013 at 11:39AM
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Well I'm thinking of using light steel rafters, to reduce the weight.

I was thinking light steel beams for the rafters, joists, purlins and collar ties.

But quite frankly I'm not sure what's best. We live in typhoon country, so I'm not sure if light weight is the way to go?

I will be getting these to an engineer to go over and approve, but I want to get the layout done so I can finish laying out the rest of the ceiling and roof space, windows, stair locations etc.

So as far as a concept design is concerned what would be the best way to lay the beams out for that open space is what I'm after.

Also I guess any suggestions, advice, or OMG don't do that help as well :)

    Bookmark   June 14, 2013 at 2:31PM
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You should not attempt to separate the design tasks of layout and member sizing; one directly influences the other.

    Bookmark   June 16, 2013 at 7:55AM
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