are you planning to fill the gaps and nail holes? or is this just a smear a color over to make it look neater?

AdvanTech isn't meant to be a replacement for an actual floor surface, unless you are going to fill, seal, prime and finish... It is water resistant, not waterproof... especially outdoors.

it will breakdown overtime when moisture gets into the material.

@Lyn Nielson my rudimentary understanding is they will be finishing it with a protective clear coat which should be enough, but I don’t know about gaps being filled. I know they had reasons for going this route structurally instead of pouring concrete, but it was explained to someone besides me. I was surprised because it seems like a subfloor to me too but apparently this is an Amish method. So yes just a way to make it look a little nicer

SW Polished Mahogany in an oil base would be my suggestion.

Yes, a quick fix to a problem. We've all done it.

" my rudimentary understanding is they will be finishing it with a protective clear coat which should be enough "

You are not protecting that enough to make it usable as a floor. it will always be subfloor meant to covered no matter what you put over it.

@millworkman what would you recommend to protect it? This is very stressful as we already spent a lot of money for this repair and this feels like a large miscommunication that snuck by us not realizing the finished floor they referenced is actually subfloor. Garage tiles on top? It seems like online research says no to epoxy over it, but I need to research more thoroughly that option. What solution would you do? I’m wondering about oil porch paint on advantech and then cover with garage mats where car would potentially go, or garage tiles across whole floor? They were going to use thompsons clear water sealer which online says needs to be frequently reapplied. very frustrating. how would you approach it?

@PPF. that is a very helpful and excellent idea that I did not think about. Thank you so much! I will call them right away in the morning to see what they suggest.

I would not be comfortable parking a car in there. The spacing between joists and subfloor thickness is critical, you don't want 1200lbs (small SUV) point load from a car tire landing between joists if it's only a 3/4" thick subfloor, that also might happen to have had water getting between joints or through at fasteners and compromising the wood strand blend. 1 1/8" Advantech carries a more robust 40psf, but joist spacing matters. And for a car stopping, turning wheels, 2 cars, equipment, dead load of another layer, etc on the joist spec.

Choosing Advantech is mainly to have: some water resistance (compared to standard OSB) when a house's roof is not complete yet and a build gets rained on; keep a better surface finish during construction when a subfloor gets battered, so when a build is ready for flooring, there is very little or no sanding that is required.

Garage tiles allow water to pass through.

I would assume that the floor is not sloped towards the door, which would mean any water will sit, so even if you have a waterproof membrane, is not a good scenario.

@3onthetree I appreciate your thoughts, thank you; the floor is structurally sound and is not just advantech. There are endless posts and beams supporting it along with concrete footings, steel reinforcements, and another layer of flooring under the advantech. Structure is thankfully the least of our concern... I think?! But I am concerned how to cover and protect the current floor - maybe some porch paint and hardy garage mats in the meantime until we figure out or can afford a more permanent solution? Sigh. To be determined. Calling huberwood tomorrow. Our car doesn’t fit anyways so it will function as a glorified shed for a while until we sell in the future and a new owner moves in, which I think will turn out to be helpful in giving us some time to decide what to do.

If this was a workshop for wood working, or any thing similar You may get away with sealing the cracks and nail holes, and put on a good floor porch paint, or some poly material.

The problem comes in when the car is brought into the garage. In the winter it will bring in snow and ice. In in other seasons water will be brought in every time it rains. It will be impossible to seal it completely. One little scratch will expose the raw material. From there water will slowly get in and destroy the floor. Even the best composite material will degrade if exposed to water long enough.

" what would you recommend to protect it? "

Anything you put over it in the way of a protectant will be temporary at best especially driving on it. Needs an actual floor installed over it. Look at garage floor tiles if need be but just know that that is not designed to be an extended use finished product.

The Installation Manual makes it clear that Advantech is not designed for permanent exposure to the elements as it would be in a garage:

"EXPOSURE

"AdvanTech panels should not be used in applications that will expose the panels to weather permanently. AdvanTech panels are not approved or certified for exterior exposure. Classified as Exposure 1 under PS-2, AdvanTech panels are intended to resist the effects of moisture due to construction delays or other conditions of similar severity but are not suitable for permanent exposure..."

The Installation Manual lists floor coverings that can be installed over AdvanTech. I would think you would want to install a garage flooring such as Husky Coin 10x1 ft. Grey Vinyl Garage Flooring Rolls or G-Floor Coin 10 ft. x 24 ft. Sandstone Commercial Grade Vinyl Garage Flooring Cover and Protector.

@wdccruise thank you so much for your suggestion. That is exactly the kind of product we are leaning towards to protect the floor until a more permanent floor is chosen and installed. I appreciate the direct links you included.

"...until a more permanent floor is chosen and installed."

The vinyl garage flooring wouldn't be permanent? What type of flooring (see page 20 of the installation manual) would be permanent?

@wdccruise I guess I meant if someone decides to epoxy it in the future, or turn it into a living space and put down hardwood/lvp etc. I am now reading and seeing those garage mats could be used as a more permanent solution, but we would probably lay down without adhesive to give a future owner more flexibility with their own choices down the road. Our car doesn’t fit anyways because it’s too tall, so we won’t be parking a vehicle in there while we live here.