How accurate to be with Dead Loads? 7

[crozroz0000]

Verbage in IBC code says we must consider everything when calculating dead loads. How accurate must we get? Is it ok to say:
Beams: 5psf
Purlins: 2psf
Deck: 1psf
Sprinkler: 5psf
Other collateral: 5psf
Total: 18psf
Is this too simplified?

 

[lkjh345]

No. That looks pretty close to the way I do it. If this is a roof, don't forget insulation and roofing (particularly if it is a ballasted roof). Otherwise, I probably would round up to 20 psf and be on my way.

 

[dik]

Beams and purlins about 3 each and deck 2 and sprinklers 3. Roofing as it shakes out and MECS (mechanical, electrical, ceiling and sprinklers(already included)) varies from 5 to 15

All adjusted as reqd... the beam and sprinkler load you use may be on the upper end.

Dik

 

[COEngineeer]

When I do house design I do 15 psf DL for all floor, deck and roof (just to safe me time). Then if we put gypcrete or veneer, I just add it to the DL. Or sometimes for the roof they want to use tile roof, then I just add the load on the top of 15psf I already have. So my minimum DL is 15.

 

[crozroz0000]

Thank you everyone...this helps much.

 

[csd72]

If you have wind uplift, then you should remove the sprinkler and collateral loads from the resisting dead loads.

Also I was taught that the sprinklers are fixed to every 2nd purlin therefore you would have twice the load on each purlin as a maximum downward load. This would obviously even out for the beams.

 

[dik]

csd72... unless you have a real massive sprinkler system, you'd be hard pressed to have a load of 3 psf...

Dik

 

[civilperson]

Do an accurate summing of a typical project or two. Then your estimated psf rules will have a basis in fact to compare to.

 

[whyun]

I carry the sig. figs to the tenths for each item. Then I add 5 to 10% of the total (minimum around 5 psf) as miscellaneous dead load to round it to some nice even number.

 

[crozroz0000]

Good advice y'all...from Georgia

 

[JLNJ]

Be careful with the dead loads in ASCE 7. I have found some of them (e.g. CMU walls) to NOT be conservative.

 

[TXStructural]

But don't overestimate DL when using uplift combinations, or you'll be unconservative. If you want to add for just-in-case, you can add LL to avoid this.

Be accurate and be realistic, since using loads significantly heavier than the customer needs will cost them money they didn't ask to spend.

 

[lsmfse]

I think it prudent to be accurate, especially for floor loads. In the past I used 12 psf for residential floors, however, in todays market for hydronic heating systems, you add +/-2" of concrete topping, likewise, marble/stone flooring over topping slab and cantilevered floor joists where another +/- 1" stucco to the underside of the joists can actually push the DL to 25-30 psf.