View Full Version : HyJOIST rafters connection
19th Dec 2011, 11:15 PM
Anyone have any ideas of how I would connect HyJOIST rafters to the top plates of the building see brlow image
20th Dec 2011, 12:24 AM
The normal proceedure ( well the one that I was taught) is to have a beam the same depth as the joist running around the perimeter of the structure ( ring beam) and the hy joists are then attached using the special hanger brackets. They definitely need restraining at the ends. Why hy joists and not lvl's ? Hy joists are normally used as floor joists, I have never seen them used as rafters before ( not to say its never been done though)
20th Dec 2011, 06:49 AM
You can use hyjoist on relatively flat roofs, this image is straight from CarterHoltHarvey. Fixing and tie down should have be specified on drawings, as anything not the "norm" will raise interest at inspection time.
Is there any over hang?
20th Dec 2011, 09:07 AM
They are a bit of a issue up here with the BSA and timber QLD as trades that shall remain nameless like to butcher the web to run services, rendering them useless.
20th Dec 2011, 10:37 AM
They are cheaper (half the price), lighter, easier, quicker to install than LVL's.
However we did have a bit of trouble using them as rafters on a 10 degree roof, mainly as they are a bit fiddly to make them work with metal fascia (with the eave sloping the same as the roof), obviously had to cut out bottom flange & some of the web, still structurallyy sound (for an overhang), just time consuming for that part.
we nailed down through the flange into the top plate, & held it down with a cyclone tie (going down exterior of frame).
The supplier, or manufacturer should be able to give you an installation guide. Pretty sure you can 'birdsmouth' the bottom flange, you would have to check tho', we didnt birdsmouth.
20th Dec 2011, 10:44 AM
Because I cut out the bottom flange (to get the required thickness of eave), I think I stiffened the web that remained with a batten, nail laminated,
20th Dec 2011, 11:20 AM
Not enough meat on the bottom flange to birdsmouth I would think. The way I see it, just because they are half the price, lighter and easier to install doesnt make them a better choice for this application. Just my 2 c.
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