green house

[Phil Ruger]

I'm going to build a 14 ft by 18 ft green house on an old cement slab. It has some cracks but is quite stable.  I was thinking of putting 3 inches or so of small river rock in to absorb heat and spills.  Is this a good idea?

[Rob Nash]

I wouldn't.. the river rock will feel like walking on the beach.. it never packs down.
just go with the cement.. add 60 % shade in the hot months.

[Alex Veidel]

Grow power in Wisconsin uses wood mulch. Good for walking and the slow decomposition of the wood helps heat the greenhouse.

[Jim Enterline]

My floor is concrete and after finding out that it absorbs heat well would not put anything over it. As for spills, they dry up quickly anyway from the heat. It is also easier to keep things better stabilized and level.

[Phil Kabza]

Wood mulch would be a great place for all kinds of bugs to breed inside your greenhouse. I'd stay with the bare concrete slab. Perhaps seal the cracks with an epoxy concrete crack repair sealant. Consider an epoxy coating if maintaining a clean slab is important. Light colors will enhance light diffusion, if much of the floor would remain uncovered.

[Jeremiah Robinson]

Hi Phil,

Greetings from Wisconsin!

My take is that as long as nothing structural is sitting on the river rock you'd be fine to use that.  Might help keep the floor from getting slippery.  But you'd also be fine without.