A friend asked me to help her build a garage with a wood floor in central Maine. The garage will be 20' x 32' with a 4' frost wall, and a 14' wide garage door on the gable end. I'm struggling with how to design the wood floor and what materials to use for the floor framing.
Currently we are planning to run a beam down the center of the long dimension and use either 12' - 2x12 PTL, 12" o.c.. along each side of the beam, or 20' I-joists run the full width, again 12" o.c.. My first question is whether or not we need to use PTL? The building site is fairly well drained and we plan to install a perimiter drain to daylight along the foundation footing as well as a 6 mil vapor barrier on the bare ground beneath the deck. We plan to use full dimensional 2x6 hemlock for the decking. Currently we have no plans to allow for ventilation in the crawl space. Under these circumstances, do you think it's necessary to use PTL???
My other question is how to design the joists under the garage door opening. Currently my friend plans to store snowmobiles, a tractor, atv's and a trailer or two in the garage, but no doubt the day will come when she decides to put a car or truck in the garage. I can't help thinking that the joists below the garage door will need to be reinforced somehow in order to withstand the force exerted when a car or truck is driven into the garage.
We intend to build a ramp for entry through the 14' garage door. My concern is the rotational forces exerted on the first few joists when someone drives a vehicle into the garage. Would it be sufficient to build a beam of 3 or 4 2x12's for position directly below the garage door opening? Would that be sufficient to overcome any tendency for the first joist to want to topple inwards when a large vehicle is driven up the ramp??? Or is this not an issue at all???
Thank you in advance for any assistance!