The simplest option is a gravel floor. It won't improve drainage in the soil below, but at least you won't be walking in mud.

I bought these for mine. I recommend putting them next to each other and not leaving a gap. I left a gap and it is hard to clean out. I am going to change that this summer.

https://www.lowes.com/pd/Square-Red-Concrete-Patio-Stone-Common-12-in-x-12-in-Actual-11-7-in-x-11-7-in/3018985

What do you mean by flooding? If you just got a bit and some mud, you might be able to do gravel with pavers on top. If you get into inches, you might want to consider something more like a raised deck inside the greenhouse.

Flooding is a improper yard grading issue, and improper siting issue, not a flooring issue. Fix the root of the issue, not the symptom.

Hello all,

I have built a small barrier around the structure and it has helped some. The entire yard is mostly flat with a slight grade. The greenhouse is next to the patio so water runs down the patio and seeps in. There isn’t really much in the way of standing water and never more than a quarter of an inch in small puddles that dries away by the next day. It just gets extremely muddy. That being said, I can build up and dig out around the structure more the make the problem of ground water better

I was thinking of building the ground up around the structure and then getting gravel and pavers for the inside. I really like the look of what tigereye has shown. I do have wire shelves of plants against the walls that need to drip to the group. Should I leave that space as just gravel or should I put pavers below the shelves too?

I put the pavers everywhere, so I could move things around, but it will work fine either way.

Hello Tigereye,

Did you put the pavers on top of gravel or directly on the ground? Also, if I am supposed to use gravel, what size rocks should they be? Smooth or jagged?

Concrete. You only need a little more than a cubic yard at a 4" thickness. I have about 2,000 square feet of greenhouse and find it works well where you are not planting in the ground in the greenhouse.

I would consider interlocking rubber matting, perhaps over a course sand bedding. We got some heavy duty anti-skid restaurant style matting relatively inexpensively at a big box store for use in a semi outdoor setting, and it held up well.

I have heavy clay soil. Zone 7b North Alabama. I put the paver sand down and compacted, then put the pavers on top of that. I think I could of just skipped the sand.

https://www.lowes.com/pd/American-Countryside-0-5-cu-ft-Tan-Paver-Base-Sand/50408222

They also make a rock base.

https://www.lowes.com/pd/American-Countryside-0-5-cu-ft-Paver-Base/50408224

If you scroll down a little, you can see a picture of how to lay out a paver patio. I did not need anything that solid. I just wanted an easy to walk on floor and no mud.

https://www.lowes.com/c/Pavers-retaining-walls-Outdoors

If you want rock for drainage, I would think almost anything you could use in a driveway would be fine.

They have the same stuff at Home Depot also, You might want to try a few down the middle without anything and see how they do when it rains. Like I said, I wasn't building a patio, so I did cut out quite a few steps that would be needed for one. They have stayed in place for 10 years now. The only thing I wish I had done different is to not have the gap between the paver. It is sized, nominal 12" x 12", is really 11.75" x 11.75", so you can put the small pebbles, groundcover, or polymetric sand for a patio.

We put landscape fabric, then sand, then gravel. We then used some Home Depot concrete blocks for a path.

@kudzu9 What a nice greenhouse!

I have always used ground cover in my personal greenhouses without any issue. Here is a blog post I wrote discussing different options. Hope it helps. Tammy https://www.blog.advancegreenhouses.com/greenhouse-flooring-options/