what to use for the floor of your greenhouse???

i'm wondering what is the best thing to use for the floor of your greenhouse? can i use mulch? and will it retain heat during the cold winter months?or should i use pea gravel to help with the heat retention? i'm so confused?? i want to use something that will help to hold some extra heat in? please help...
thanks,
cristina

I take it you have a permanent greenhouse? If so, I'm sure there are folks who will give you the pros and cons on pea gravel.

Mine (a PVC structure) was on a concrete pad (part of our driveway) for two (maybe three?) years. I moved it off the concrete onto a grassy area this fall. We put down weedblock as the flooring for this year, anchored with metal "pins" spaced pretty close together (I really don't want to deal with weeds growing in the GH!)

I'm hoping that I can get a "real" greenhouse next year (got my eyes and heart set on one, in fact.) If/when that happens I'm thinking we'll put down two layers of the REALLY heavy duty landscape fabric, and then a floor of pea gravel. Alternatively, I might do brick pavers. Just depends on what I can talk DH and my teenage sons into helping me do.

we used pea gravel. i am very pleased with it. i have no weeds. sometimes i do have unknown plants take root but that is because i am sometimes messy with my seed lol.

with the gravel it is good for moisture much needed in winter and i think it does help to keep it warm too. i think this is my gh's 3rd yr.

I think, - [as long as you don't want to plant anything in the ground],gravel will store and retain more heat and give it back at night, -mulch or compost will insulate and keep heat in the ground from warming the house at night.- and will store very little.

I used solid slab but sometime wish I had used pea gravel. Didn't because it is impossible to use dolly for big planters. Does slab hold and release heat the way gravel does?

i use upside down carpet! sweeps up nice and can be replaced easily-people are always tossing out old carpets! :)

My gh is 9 years old and was built as part of the garage so has a solid cement floor. If I had it to do over I would use heavy duty landscape fabric with pea gravel. I t is easy to clean the cement floor and maybe i would be more satisfied if drainage holes had been made when being built. That is the main problem with solid floor. When i leave my mist system on very long then there is standing water on the floor. Donna

Larrycook, yes concreet does store and release heat well, probly better than gravel, if you want more heat, paint the concreet black where the sun shines on it in the day.

A note to anyone thinking about using concreet for a greenhouse floor, make sure that there is enough fall [slope] to drain the water to the place you want it to go [usualy a floor drain]- having standing water on the floor is not good for several reasons,[disease and your safety are 2]wet concreet can be slippery.

I used a thick layer of mulch. I was thinking about drainage. I started to use pea gravel, but I didn't want to chance it sticking to my shoes and then into my grass.

Right now there is a huge amount of hardwood mulch available around here. Is there any reason not to use it for the greenhouse floor?

I've heard/read that hardwood mulch shouldn't be used because it can introduce mold spores and insects into your GH. That's not personal experience talking, though....

We use sand -
Pretty good stuff except tracking it all over the place.We have a 1-1 and a half ft. deep and about 2' ft.wide water trough that goes around the side and back It's made from plywood and 2x4's and lined in 6 ml. black plastic.Have been in use for two yrs.would not suggest the black plastic unless very careful .Go with rolled roofing next time.But could not afford at this time got a hole in it and had to replace quickly.Keep fish and plants in it have a pump to keep it circulating.
This yr.storring plants in mulch inside of it.Some down the center for extra heat where sun can heat the black mulch.

im telling you the upside down carpet is the best!!! Im so glad we went that way!
I have 6inches or more of packed sand underneath the carpet. I just sweep up all the dirt and leaves and its nice and neat again!

The up side of using any kind of plant based mulch is -- that should you decide to plant in the ground the mulch can be raked back and the decomposing mulch helps build the soil, also it is environmentally friendly and in your case cheep, - I think Ruth Stout would approve of that option also--and so would the Earth Worms --and me too, -- Michael

I use small pea gravel (about 5" deep) -- excellent drainage, but doesn't hold as much heat as solid concrete.

I've used upside-down carpeting inbetween planting rows outside, and it's great stuff. It stops weeds cold, but allows water to pass thru -- and it lasts a LONG time.

- Kathleen (Zone 6, NW Rhode Island)

I used the next size up from pea gravel. It was easily cleaned with a hose, acted as a heat sink and cooling with a hose worked too. In fact I had only two problems. The first was a minor collapse of a corner of the floor when a groundhog dug its tunnel under it. I had to put down more stone. The second problem was that tables and shelving would work their way down into it after a couple of years unless there were pavingstones under the legs. I put down a path of plastic 1x2 foot pavers for a walkway. Jessamine

Terry I've see 2 occassions where hardwood mulch grew mushrooms and other things. Both times mulch was 4-5" thick and had excessive moisture. One also had shade. Other than this, native hw mulch is very good , particulary in outside application.

The recycled carpet upside down is a great idea. Wish I had thought of it a few years ago. I used 12 x 12 cement pavers in the 'pathway' and layers of newspaper with gravel on top around the edges. I like the fact that if I want to raise the humidity, I just wet down the floor. Also, I don't sweep, I just hose down the pavers. Don't know where these mushrooms came from.

Notmartha, I have placed old carpet upsidedown on the gh floor, it is warmer out there all ready! Thanks for the tip I will experiment with it for the winter. Thanks Joelle

My gh floor is dirt. I planted many of my tropicals right in the ground. And for ground cover, I have blackie potato vine everywhere. No need for mulch as all the ground is covered. I have a creek-rock path thru the gh and all the rest of the ground is planted. My only mistake is it isn't big enough. I just finished it a month ago and already I'm planning an addition. LOL

NancyAnn

I have had two greenhouses, one professional one I miss more than I can say, then a huge, excellent makeshift hillbilly collection of left over job windows and such. Both have cement floors, but only in the center walkway. The ground sides were dirt and pea gravel. If I ever get around to replacing the current greenouse with a better one, I will put cement down in the center again, but in blocks so the water runs off it easily, and pea gravel, several inches deep, on the sides again. The best of both worlds.

tropicalnut............I use crushed stone in my greenhouse.........Not sure what you would call it in your part of the US, but DH said you may know it as Dolimite. If I drop anything on it, it just disappears, potting soil, seed, etc.....If it gets too warm in there I just hose it down. My greenhouse is 12 x 12 is of double Polycarbinate, and the outside is Redwood.

Deann

well THANK YOU ALL!!! great ideas, i went and decided with the pea gravel 6" thick for now(seeing as we will be getting our first frost tonite) i hope with the heaters and the rock and today's sun, it'll be okay...tomorrow though, i'm gonna use some 1 gallon milk jugs(20) and painted black,filled with water and left in the south part of my yard to absorb some heat.Only bad thing about that is the constant carrying in and out of the GH...Do you think 20 would be enough for my GH that's 20x15?, i'm thinking "no"...and does anyone know how much heat gets transferred doing this?
thanks to all of y'all's input!
cristina

Floors are a matter of choice I chose solid concrete and have never regreted it for one minute. It is so user friendly to wheel the large 25 gallon tubs around there and my wheeled plant shelving that hold 24 flats of four inch pots, The concrete makes it super easy to wheel the shelves out on nice days and to take them in and out when hardening them off in the early spring. And yes the floor is sloped four ways to a center collector so drainage is not a problem. The slab will hold the night time temp about 10 degrees above the outside temp unless it is very cold and the wind is blowing. To do over again I would probably put a heat source under the floor and heat it because the heat would be distributed evenly.

Now before any of you think this is the way for you to go my gh is 16 x 32 and is highly insalated by thermopane sliding doors , windows, twinwall polycarbonate, And 6 inches of rock wool in the non glass areas. The zone I am in is spared the real brutal cold some of you experience. But this works well for me. Ernie

This message was edited Nov 8, 2004 7:15 PM

I have a confession to make. I am absolutely FLOORED by the drastic measures I am reading from you zone 8 guys (and gals) when insulating your greenhouses.

I'm at least a full zone colder than you, I have a single-layer plastic (4mm or 6mm, whichever's heavier) covering. In three years, I've not caulked or insulated the small leaks around the corners (guess I should), and I use a 1500W electric space heater for all but the couple dozen cold nights (temps down in the 20s or teens.) Do y'all not have any heat source in your GH and you're relying on passive solar heat only? I just can't imagine that you get many nights with freezing temps, let alone 20s, teens or colder....what gives? (please do tell - this inquiring mind is really wondering!)

We used red cinders...but pea gravel would be the same...covered with weed mat. It does keep the moisture level high (which is good) and the weeds down! A cement slab would be easier to keep clean...but I rake the weed mat with a leaf rake and it works. I would think that mulch would be hard to keep weed free and that molds and fungus would be a problem.

Good luck,

Carol

We have 4inch brick pavers down the center and weedmat with rock gravel on sides.Dont use the cheap weedmat! We had to pull grass out of it during the summer,however we had no problem during the winter.GH is 14x36 homemade with double poly and a blower. As to your question Terry,I do not heat the GH at all unless we are to get down under 33. I will put the 2 milkhouse heaters on at night and shut them off at sunrise. Most of my plants are tropical and seem to do fine. I also grow tomatos and peppers all winter with no problem. I think we only ran the heaters mabe 8 times last winter. The blower really makes the difference.We live by the river and I cant really go by the metroplexs forcast as I had to call in cause there was ice with 3 inches of snow at my house and it was dry in Fort Worth.Its just amazing what 40 miles can do!

Just the thought of hauling in enough gallon jugs to keep a greenhouse above freezing every day blows my mind. I'm sorry but someone has been giving you garbled information. The idea is to allow the jugs of water to release heat by freezing. You will need a whole lot more than 20. Closer to 200, would be more like it. I double checked your zone, in Wisconsin it would be 2000. 55 gallon drums painted black, filled with salt water and partially sunk in the floor does a better job. Use the top of the drums to support the benches. Put in as many of them as possible. The greenhouse probably won't be warmer that just barely comfortable but the idea is to allow the plants root systems to develop at a slow consistant rate rather than lots of top growth and to keep the soil temp up is more important than keeping the air warm. The black paint allows the drums to absorb more heat when the sun is shining (White reflects) so it has more heat to release at night when the sun (or other heat source) is gone. Salt water freezes at a lower temp than plain water so it will release more calories, BTUs etc. whatever measure you want to use. Insulation quilts over the greenhouse at night keeps more heat from being lost. Build a frame against the back wall of the structure to stack those 55 gallon drums three high and keep the front row low so the most surface area is hit by the sun. Do a search on heat sinks and thermal mass to get a better idea of how it works. Sandy

My old solar greenhouse is double walled poly film with an airspace between the layers. It's one of the original Northern Lights greenhouses. For the floor I used weedblock fabric over which I gradually put large concret pavers...the stepping stone type since I couldn't manage to get the gravel to the greenhouse or begin to carry it. For heat I have very large plastic garbage cans with flat lids that are completely filled with water and are up against the back wall (north side) of the greenhouse supporting my homemade bench top. The north wall and roof are reflective rather than clear and I am able to grow citrus and other tropicals without supplemental heat...a good thing when the ice storms take our power away for a week! Using the large pavers means that I can shift them to create an opening where I stick a tall shepherd's hook into the soil beneath so it can hold some of my hanging baskets, and they can be easily replaced with gravel if I decide to change things around. They are expensive, but after a few months I was pretty well covered and they work well to help hold the heat of the day as well as keeping the humidity higher.

wal-mart has the milkhouse heater for around $20. 2 with a blower should work fine. we have a squirrel cage blower in ours.
--
nadi

I'm glad tropicalnut asked the question about the floors because I was wondering what everyone else was using. I hope to be getting a gh soon, so I like reading about everyone's experiences before I go and do something costly and/or silly. I like the idea of the upside down carpet, but here in Louisiana, it would only cause mold and mildew problems, which is a bummber, because it's already so humid here. Our winters are not too cold, some nights might get to freezing, and we have had a few times where it's gotten intot the teens, but only for a matter of hours or less, so I don't guess I would need a lot of heat in mine, once I do get one. I do collect tropicals, and there are some I don't have because it does get too cold here, but with a greenhouse, that problem would be solved...:~)
I have limited myself to hardy only tropicals, which I know sounds like an oxymorone, to our area, and once the gh is built, well....let's just say " the sky is the limit "

grayse2.......might I sugguest you invest in a good fan and an exhaust fan, as you need to keep air circulating in there. You can not imagine how hot it gets in the greenhouse when the sun is shinning.....Even here in Northern Michigan, often I go in my greenhouse in the middle of winter just so I can get some nice warmth and its usually in the 60's to 70's if the sun is shinning outside and its 20 degrees.

Deann

A commercial greenhouse I worked at used granite dust that was leveled and packed, then covered with landscape cloth. The sand was several inches deep and made a solid base, but drained quickly. When the ground cloth got funky, we replaced it. Some smaller greenhouses they had didn't use the ground cloth and we had to spray a lot of algicides to keep the green goo under control. All that said, I'd go with pea gravel for a small personal greenhouse.

warning on pea gravel if you wear tennis shoes it sticks in ridges and tracks in and will blow up vacuuming clear bag .i have been trying to get rid of mine for years theirs a bigger size and all so crushed rock which is white and holds heat . ?