Residencial Garage Floor

[nixs]

I have a 3" concrete topping with WWF over 1 1/8" thick plywood over wood joists at 12" o.c. and I am unable to obtain a permit. The permitting authority does not accept APA report T2005L-43, stating it does not have enough factor of safety. Any thoughts? I am unable to prove the concrete spans without increasing the reinforcing and then shear fails too and then the plywood fails in shear also for a 3000# load.

 

[PEinc]

Did you use the thickness of the concrete topping to spread out the tire load to a larger area of plywood?

http://www.PeirceEngineering.com

 

[Ron]

If this is for a garage floor, why are you applying a point load of 3000 lb? Most vehicles will weigh between 2500 and 4000 lbs, applied at 4 tire locations, resulting in concentrated loads of 625 to 1000 lbs at each location.

My most significant concern would be the joist bearing and attachment. Do the joists run parallel to the direction of travel or perpendicular? If parallel, check by rolling load. If perp, don't worry about that.

Ron

 

[woodman88]

Here is a copy of the APA "Research Report 139 Plywood Floors for Residential Garages". See if you meets these requirements. If so, try using this report to get approval.

Garth Dreger PE
AZ Phoenix area

 

[msquared48]

My 8 passenger '93 Suburban weighs 6000 unloaded and can weigh 8000 loaded, so I would use no less than a 2000 pound point load.

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[msquared48]

The tire print of a vehicle that would give a 3000 pound load is in excess of 6" X 6". That is the tire print of my Suburban. Assuming a 50 psi unreinforced shear strength for the slab, the minimum punching shear would be over 3600 pounds.

Also, the 6X6 footprint at the top of the 3" slab would be 12" X 12" at the bottom, and 18" X 18" at the bottom of the plywood, bearing on at least one joist.

Structurally, I fail to see the problem here with any of this.



Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[vandede427]

chances are your '93 suburban won't fit in his garage anyway, 8)

 

[nixs]

By code (ASCE 7-05) I have to design for a 3000# point load over a 4.5" square (table 4-1, garages, keynote a). I do meet the requirements of APA report 139 but the building official rejected it. And punching shear is not a problem but one-way shear along the joist is for the concrete. I was under the impression these floor systems were common and acceptable but maybe not?

 

[dcarr82775]

I believe the value of the point load has to do with the load on a jack when changing a tire or working on the vehicle.

 

[woodman88]

Why is the Building Dept. going to ASCE 7-05 on a Residencial garage? The IRC (2003 and I have not heard of it changing in the 2006 or 2009) allows for a 2000# point load in the garage per Table R301.5.

Garth Dreger PE
AZ Phoenix area

 

[slomobile]

woodman

In some states, like California, the IRC was not adopted as a model code for the CBC. The CBC is based on the IBC only, so from a outhouse to a highrise it applies, no matter the occupancy. I can only assume this is the case with nixs' jurisdiction as well.

 

[woodman88]

slomobile,
The IBC already has the 3000# requirement in it. So there is no reason (if you are designing per the IBC or CBC) to send you to the ASCE 7-05 for it.

Garth Dreger PE
AZ Phoenix area