I think you're on the right track with rocks -- if you need to walk through here, maybe you can do a central flagstone path (I guess you lift the mower over the A/C unit?) with larger/loose rocks and/or plantings on either side. Will get rid of the mud without wrecking drainage, but hopefully keep the functions you want.

Thanks. Believe it or not, I have an electric mower that just does squeeze through that opening. Even though it's not extremely heavy, it's got some weight to it and would prefer to minimize how much carrying I do. So if I do flagstones with some pebbles between, you're thinking the drainage will be ok?

I assume your house is on the right. Right?

The most common form of zero lot line is where the edge of the house is on the lot line and your lot goes around the other 3 sides. Each home is set up this way. Looking at the area shown in your pic, it looks like the the home on the left is the one on the lot line (glass block window is a dead giveaway) and the space between the two homes belongs to the home on the right where the a/c compressor is hooked up:)

A better way to tell is to look at your survey that you received at closing when you purchased the home. The boundary lines will be clearly marked on the survey.

An adequate way to tell is to look at your county property appraisers website where the lot lines are sometimes shown on the aerials.

If you are the house on the left, then you probably can't do anything to that side yard since it's not your yard.

If you are the house on the right then consider the rocks but install a drain and large enough slabs for the walkway so you can retrieve your lawn mower without difficulty. You will need a professional landscape designer (not the guys that just do maintenance) to get the drainage right.

In this insp pic the landscape designer goes into a little detail about the drainage they used for this posted project - click through to see more details

Side Yard Drainage Project · More Info

Does the water pool in this area after a hard rain or does it just stay wet and muddy from lack of direct sun? If no pooling or puddling (and one would have hoped the builders did address that) then no drain is necessary, And just a good thick layer (3-4") of rocks or gravel will eliminate the wet muddiness.

Here, zero lot line homes are those that adjoin their neighbors so only the minimum setback separates them....rarely more than 10 feet but often less. Therefore, that side yard would be split between the two adjoining houses.

You are right gardengal48 - it depends where you are located. In our area, virtually none (can't think of one community this way) of our zero lot lines split the side yard. It looks like the side yard is visually split when you drive down the street, however, the boundary survey shows that the house sits on one side and the lot forms a U around the house. Its a very common form of zero lot line configuration here in S Fl where I'm located. I don't know where the OP is, that's why I suggested he look at his survey before doing anything.

I'm glad you don't have to go through with new drainage.

I think gardengal is probably right about the thick layer of rocks or gravel since you have working drainage already.