I am planning to extent the workshop and have to use a flat roof that needs to span 3meters . I have found tables to calculate conventional timber size on the net but i would like to investigate the engineered 'I' beams that are frequently used in new build i understand they are very strong but i cannot find any info on size required ,installation instructions, cost comparison etc can any one help please.
Timber sizes for flat roof.
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I think you'll find that normal timber will work out cheaper and be easier to source. Or you could have a go at making your own i-joists, they look pretty simple to me! 11mm osb glued into a groove on a 4x2, if it's even as big as that, probably more like 3x2. Bracing and strutting is where the strength comes from though.
The technical details of timber or lattice I-beams are specific to the manufacturer, so there are no generic tables like for timber.
You need to refer to a supplier/manufacturer - but IIRC there is one UK based manufacturer which has a downloadable program for working the spans/sizes out - but I have forgot the name - I only deleted it a few months ago due to not using it often
Do a google thats how I found it
You need to refer to a supplier/manufacturer - but IIRC there is one UK based manufacturer which has a downloadable program for working the spans/sizes out - but I have forgot the name - I only deleted it a few months ago due to not using it often
Do a google thats how I found it
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I think the main producers are iLEVEL Trussed joists...google it
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The timber I beams you are considering are essentislly designed for light loads over large spans. Your span of 2.3m is not enough to even consider using them. Normal softwood properly sized and spaced will be fine. Get it tanalised.
Beeches.
Beeches.
My comment that timber I beams are for light loads ( I consider domestic floor loading a light load), over long spans is a general observation based on the problem that solid timber joists over long spans suffer from excessive deflection under their own weight. The same goes for steel beams, heavy squat steel beams are not effective over long spans due to their self weight, and fall foul of the deflection limit of 1/365 of the span.
Remember castellated steel bems, cut and welded to give a deeper beam with "holes" in the web. They are found in long spans supporting light loads.
Beeches.
Remember castellated steel bems, cut and welded to give a deeper beam with "holes" in the web. They are found in long spans supporting light loads.
Beeches.
Beeches, deflection is a function of the modulus and inertia of the section, not solely the self weight. UC sections are heavier by virtue of the increased flanges thickness, the purpose of which is to increase the inertia and hence reduce deflection when used as a beam. Greater inertia for a given load = less deflection.
A heavier weight UC section will be required in comparison to a UB section for a given load and span, but does not mean that it is incapable of satisfying deflection criteria (L/360 btw ) for a long span.
For the same reason, as the modulus of timber is a fraction of that of steel, a former of the same intertia as that of the latter will deflect a commensurately greater amount.
A heavier weight UC section will be required in comparison to a UB section for a given load and span, but does not mean that it is incapable of satisfying deflection criteria (L/360 btw
) for a long span.For the same reason, as the modulus of timber is a fraction of that of steel, a former of the same intertia as that of the latter will deflect a commensurately greater amount.
Wow, this is all getting a bit heavy, so I am baling out. One final comment, you described UC in a beam stuation. Doesn't UC stand for Universal Column, which obviously has to be very stiff.
Cheers, Beeches.
Cheers, Beeches.
I will reply with such speak as to be in keeping with the technical nature of replies given thus far.
Depends what it's holding up!
UBs and UCs are interchangeable in terms of acting as columns or beams. It just is a method of identifying the section type: UC is like an H in section; UB is like an I.
I ran this through google translate, and it came up with ... "timber bends more than steel"
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