Building on a Wooden Deck/Foundation-how to avoid making a home for rodents.

Putting small buildings on wooden deck or foundation makes a lot of sense economically.
Upcycling pallets makes it even cheaper and easier.
But it creates a pest sized void under your building.
Now, you could fill that void with gravel or cement , but that would cost about as much as a

Tamped earth might work but the point of a wood deck/foundation is to escape the moisture of the soil, and create a level surface to build on, without having to grade the site.
The soil at my site is extremely hard to move by hand, being full of rocks.

If the foundation is high enough off the ground, the space underneath will offer little or no refuge for small animals, but this could make accessing the building difficult.

If the floor and walls of the building are built tight enough, maybe it doesn't matter that rodents nest underneath?

I'm thinking I will need to either do the work or spend the money, probably both.
Some grading, followed by recycled plastic moisture barrier, wood forms/joists on top of concrete posts, filled with tamped earth.

Finding a cheap, easy,  water resistant, rodent repelling filling would be better.
Any ideas?

From memory, rodents appear when there is food for them. IE Chooks and horses are great sources of fallen food.
If you keep things tidy, surely the rodents will not appear?

Hello my friend,
My old place was infested with rats when I bought it. In the garage and the crawlspace and under my deck. They carry lots of diseases so they had to go. John makes a good point that they need to be close to a food source. The problem is rats eat damned near everything. And I learned immediately that they loved my veggie garden. It took me 3 years to finally get rid of them all. After lots of research the solution was.... don't give them any place to nest and they won't stick around. I found that to be true. Apparently they like to go back to their comfy beds every day. And the worse issue I found was that they multiply like crazy. And all the babies seem to have a really good memory of where they were born and keep trying to come back, relentlessly!  Stopping them from nesting in my crawlspace and garage was easy enough but the hardest part of all was getting them to stay out from under my deck which was built similar to the structure you are contemplating. Close to the ground.

I tried all the things that you have already mentioned to some degree with some but not complete success. Then I finally found a much easier solution. Long strips of hardware cloth. Dug down 14” right under the edge of the deck. Stapled the top of the 14” pieces of hardware cloth to the edge of the deck vertically so the bottom would be deep underground and then back filled it. Seems to work very well. They can't get under the deck anymore. I only occasionally have one come into the yard now even though plenty of my neighbors still have the problem.

.Just a few years ago my next door neighbor built a shed in his backyard right next to my fence, just a couple of inches off the ground and the rats immediately began nesting there and raiding my garden again. I insisted that he dig down and place the hardware cloth around it. He kept hemming and hawing and did nothing. So I complained to his wife! He placed the hardware cloth down the very next day and the problem was solved!

It's not totally perfect though. A couple of years ago a little rat ba!}#@! chewed a hole right through a 2x6 deck board! I think that's why god made snap traps!

And I did read what you said about your yard being full of rocks and very hard to dig in. Welcome to my world! Nothing but rocks and concrete! Which is why I usually use a mattock pic. Works great........... even for an old broad lie me!

Thems a great rock collection!

One of many! I've got wrinkles and blisters and callouses! And I feel pretty!

Oh my! Happy gardening everyone.

Debbie, this is a great solution!
It will take a fraction of  the earthmoving compared to what I was considering.
It also can be retrofitted,  a real plus.

Your soil looks like mine!
I usually only dig in it for to plant a tree or bush.
I've broken a fair number of tool handles there.
The worst are the large flat stones, they force me to dig a much bigger hole than I need.

Food does attract pests, but I'm trying to grow food!
I have a hard time getting any fruit from the trees over there as it is.
When I build the big shed, I don't want to create a home for them.