GH Floor

hudson___wy(3)December 27, 2013

During the coming winter months I would like to finally prepare for a floor in our GH. Concrete seems to be our best option - but I would like your opinion for the best material to use for the GH Floor?

I was thinking of digging out the soil 6"s deep - screwing 2x4 redwood to the walk side of the 4x4 posts parallel to the raised bed on each side - installing perpendicular 2x4 redwood spacers at each 4x4 - then spreading gravel for a 3 1/2" thick concrete walk. There would be 3 1/2" of soil remaining between the concrete walk and the raised bed on each side of the walk. I would leave the 2x4 redwood forms in the concrete for appearance.

Does anyone see potential problems or concerns with installation of such a concrete walk in our GH from your experience with GH floors?

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Your present floor looks fine to me. I would much prefer gravel to concrete for ease of operation, drainage and a less hazadarous walking experience.

    Bookmark   December 28, 2013 at 10:30AM
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I agree with bmoser. I'd like to see mine get built this year. We have salvaged a lot of red chimney brick. Thinking that might work for me for my GH floor. I'm always one to try and save a buck or two.

    Bookmark   December 29, 2013 at 3:37PM
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Is there a thermal mass benefit from using concrete on the floor? Presently - the dirt floor gets muddy when I over spray and it is hard to clean. We have considered gravel but gravel is not as comfortable when standing for several hours, pea gravel sticks in your shoes, 3/4 +- gravel is not comfortable kneeling, gravel is hard to wash and lacks some of the thermal mass benefit?

We have budgeted for concrete so the cost is not the concern - it is all about function. I don't want to pour concrete and then find out I wish I had used other materials that may have better functionality? we will place 3 1/2"s of gravel between the concrete walk and the raised beds on both sides for drainage. With concrete I can open both GH doors and hose it clean. I will have a flat surface for ladders and kneeling pads, wheel barrows - etc. It will provide a pad for the GH furnace, keep weeds/grass from growing on the floor and add to our thermal mass.

Am I missing something that I will regret for pouring concrete? Those of you that have concrete floors are there any reasons why you wished you hadn't or things I should consider before pouring?

    Bookmark   December 30, 2013 at 9:57AM
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sand_mueller(z 7a, oklahoma)

Retired after 40 years professional horticulture. would never put in a concrete or gravel floor. GH floors should be mulched with organic material...sawdust, woodchips, etc. Gravel ruins drainage, concrete is cold, slippery, horrible. the whole greenhouse needs to be living and biologically active. Can say much more about this, but not now.

    Bookmark   December 30, 2013 at 12:30PM
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San_Mueller, I thought I read somewhere not to use anything for flooring if it is going to rot for it is a place for insects to hid and molds to grow. Myself I think it would be okay and would be the easiest flooring to install.

    Bookmark   December 30, 2013 at 3:23PM
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Indeed. Mulch is going to retain moisture and encourage rot in the wood. Even redwood rots....

You want drainage AND thermal mass. So use gravel as a base and concrete paving stones to get the best of both. In my greenhouse, I used about 10 tons of crusher run gravel; laid down landscape fabric to keep 1" of sand from disappearing into the gravel. More sand was swept into the joints between the stones.


    Bookmark   December 31, 2013 at 12:51PM
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sand_mueller(z 7a, oklahoma)

It is a common misperception that gravel improves drainage. the opposite is true. Gravel is packed down into your soil compacting your substrate. Since you are not growing in this floor the increasing water table underneath causes anaerobic conditions favoring eel worms and disease. Weeds that do grow are impossible to remove by hand. An organic floor loosens the soil beneath, encourages earthworms which make deep channels underneath your structure improving drainage. An organic floor captures leachate from your plants and eventually turns into a very useful soil itself. A dark organic floor is an excellent capturer of heat in winter and will cool and humidify in summer. Enough mulch on the floor provides a superior insulating floor particularly important in a cold climate where the ground freezes...don't let me start on the atrocity of a concrete floor in Wyoming. If you want to spend money and get fancy you can bury pipe beneath your floor and blow heat through that but 6 " of sawdust fantastic and by the way any weeds pull up with ease and a gentle raking lives a great appearance.

    Bookmark   December 31, 2013 at 2:09PM
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That's why I used landscape fabric above and below the layer of gravel: the gravel isn't going to migrate into the subsoil, while the sand won't fill the voids from above. In any solar structure, thermal mass is the key. Around here, sawdust is unheard of for 'flooring'. Too many wee beasties like to eat it.

    Bookmark   December 31, 2013 at 4:55PM
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It appears there are strong opinions! I appreciate your passion and knowledge/experience. You have definitely given me some things to consider in making a decision!
Thanks for your opinions!

    Bookmark   December 31, 2013 at 8:08PM
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sand_mueller(z 7a, oklahoma)

I have never found soil biota to be anything but natural and beneficial. A grower can always control insects but can never eliminate them. thermal mass is very good and I like it myself, but it will do almost nothing to heat the air in a gh and if the temp inside falls to 25 degrees, I am going to lose all my citrus no matter how warm the soil. How much heat will gravel have after a week of cloudy freezing weather? How much heat does gravel pick up even on a sunny winter day? I actually think that insulation dollar for dollar is a better investment than solar mass...would love to have a giant American flag to drape over my house ant night. 6 " of mulch is a better floor insulator than gravel could ever be.

    Bookmark   January 2, 2014 at 1:15PM
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Insulating greenhouse floors is actually counterproductive. See attached references.

Here is a link that might be useful: greenhouse floor insulation

    Bookmark   January 2, 2014 at 2:46PM
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karin_mt(4 MT)

Great discussion!

I'd weigh in against poured concrete because of the permanence of it. What if you want to add a heated conduit underneath or a new irrigation line? Or change the layout of your beds? It's a total one-way street. If you want a concrete floor, I'd do pavers. Have you seen the big square 2 by 2 pavers they make nowadays? They are quite handsome. The re-used brick sounds lovely, as does the fluffy mulch.

Did you make a final decision yet?

    Bookmark   January 7, 2014 at 12:04AM
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livelydirt(Zn 4, Lively, ON)

Hudson, I think I would go with some type of paver, your choice. Pavers, properly installed on compacted, smoothed, compacted, smooth... did I mention compacted? Crusher dust (installed on top of 5/8" crushed gravel (also compacted - you will need this for poured concrete as well - rent a small compacter)). will give you a great floor, will be as impermeable to water as poured concrete, have about the same thermal mass, but as Karin says, will give you flexibility. I should add this disclaimer - I have no experience with gh floors, but I have with laying pavers.

You can also install Permeable Pavers, but they require a different substrate that I will leave to you to search out from your local paver supplier.

    Bookmark   January 7, 2014 at 10:06AM
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No - I haven't decided yet - I got to honest with you though - Pavers seem to be the best option and what you and LivelyDirt suggest makes sense but pouring concrete would be a whole lot easier for me and less - expensive. Most of the reason I don't have a floor yet is because I haven't convinced myself of the best option for our GH. Thanks for the info - there is plenty to do without worrying about the floor this year but we are tired of tracking mud - Now would be a good time to get it prepared !

    Bookmark   January 8, 2014 at 9:45PM
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bencjedi(6 - Central Kentucky)

I went for something radical in my GH since I built mine on a raised platform deck. It's a design I've never heard of anyone doing. Basically a deck inside an outer shell of glass, so the two parts are independent. The deck was built in a standard way with spacing between planks to allow for expansion, but obviously all the open spaces can't be a good thing if you are trying to keep it warm in the winter, so the radical part involves using free carpet underlayment from some rooms in the house I replaced with laminate. I put the underlayment down and on that pinned down a waterproof canvas from a discarded screen house over it. I'm not done building the GH and have to install a rain gutter as currently rain water coming down at the end of the slanted roof drips right into the GH. Since the floor is now impervious to water it pools up on the slightly lower side of the deck (pitched to the same angle as the adjacent deck off the house). From there it very slowly evacuates the floor to the rear corner. In retrospect I should have designed the platform in a way where that side would have a gutter also so inside water had an easy way to drain. Maybe a cheap shop vac will be an interim solution. Anyhow thought I would share my experiment in flooring. As you can imagine it is bone dry beneath the GH on the ground.

Here's a couple pics

    Bookmark   January 9, 2014 at 1:07PM
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sand_mueller(z 7a, oklahoma)

I can remember a similar thread on this forum nearly 20 years ago. I think I said pretty much the same things then.

    Bookmark   January 10, 2014 at 1:53PM
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It has been such sunny weather this week - nice day to work in the GH! Although there are a lot of good ideas for a GH floor - the best option for us IMO is a concrete floor. No better time than the present to get at it. The first tool to buy when you move to Wyoming (if you want to do any digging) is a Tamper Digger Bar - it is a must! I would have had a hard time digging out the soil today if I hadn't had it (had a hard time with it! - haha). The soil was really compacted after walking on it for 5 years. It almost looks like rocks - but no - that is dirt. I got a good start (one bucket at a time) - almost 1/4 (55 square ft) of what needs to be dug. It will take me a few days so I am glad I got started. I got the snow blower and blew out a trail to the garden so I had a place to dump the dirt. We don't have as much snow as usual for this time of year and it has been so cold - the snow is granular - like sugar.

    Bookmark   January 25, 2014 at 7:48PM
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We finally have the GH ready for a floor - hope to pour concrete this weekend. We decided to put in a drain for a sink - a modified French Drain (48"s deep) - the sink will drain into a 16" diameter storm drain outside the GH which will have a lid for a clean-out and to protect the drain.

Digging the dirt out was way more labor than I expected and then bringing the gravel back in wasn't fun either - all had to be done by hand with 5 gallon buckets. It would have been much easier if we had done it at the same time that we built the GH and the raised beds!

    Bookmark   July 18, 2014 at 12:48AM
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We have a floor!! My daughter says that we now have a 5 star GH - haha. We still have some cleaning up to do after the concrete pour but we are enjoying the concrete already! Hope the cement doesn't get too hot in the summer but the plants appear to shade the walk way.

    Bookmark   July 20, 2014 at 2:34AM
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karin_mt(4 MT)

Definitely agree about the 5-star greenhouse Hudson!

That looks just great - all smooth and clean and ahhhhhhh. :)

Nicely done!

    Bookmark   July 21, 2014 at 10:34AM
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Congrats to you, Hudson, for making a decision that went against the popular opinion but was what you felt was right for your particular situation. It looks great, and will be easy to maintain. I look forward to your feedback about how it performs in the coming seasons.
May I ask a question about something else you mentioned? The drain that flows out of the GH - how exactly does this work? I get the basics, but what about in freezing temps? I am planning a similar design into my GH (just waiting on the contractor now...) but the suggestion was made that the drain from my antique sink would flow into a barrel that would stay inside the GH to avoid the issue of freezing. Or do you stop using it after it freezes outside?
I love seeing your pictures, so thanks for sharing -

    Bookmark   July 21, 2014 at 7:48PM
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We live in an area that has freezing weather over six months of the year. What works for us is to have the portions of the drain that are exposed to cold weather slope continuously so that no water remains in them. The draining water is warm enough to prevent any freezing problems.

    Bookmark   July 21, 2014 at 11:50PM
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Littlepond - our GH is too far away from our septic system and we don't anticipate needing the sink much during the winter months because we shut the GH down from Dec - February. We do expect that washing our planting pots and trays will result in a lot of dirt going into the drain so we decided to have an open drain outside the GH that we can clean out as needed. Yes - it will freeze/thaw in the winter but I drain 3 of our rain-gutter downspouts around our home into similar drains filled with 2"+ rocks (because I don't have to clean the drains) and on sunny winter days - the water does absorb into the ground even when night time temps are subzero - but we have rocky subsoil that drains very well - we do not need a drain for our full basement for example. And - there will be about 3' of snow on top of the lid to the drain - which will insulate some from the cold temps.

Your idea to have a barrel inside the GH may work but night time winter temps in our GH drop to 0 degrees or lower when OS temps are -30 or -40 degrees. You are in zone 3 so I assume your GH winter night time temps may be similar. Plus - we really don't have the space for a barrel inside the GH? How will you empty the barrel (or would the barrel be buried in the ground so it can drain under your GH - that may work - if you have an access to clean out the barrel)?

Do you have an idea where to find an antique sink for our GH online? We have been trying to find the right sink but haven't seen it yet - I may start a thread for ideas.

Renais has probly the best option if I understand correctly - basically a septic systems that drains the water below freezing - we just didn't feel we could justify the cost for draining a GH sink. We have to drain 6' below ground level to avoid freezing - on a cold winter year - many septic systems in our community freeze up - we put ours plenty deep to avoid that!

Thanks for the compliments Karin & Littlepond!! We have already found that if we are working in the GH during the hot day and water down the concrete - it cools the GH down - or at least - it feels that way.

    Bookmark   July 22, 2014 at 2:42AM
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One thing we have noticed and enjoyed is the fact that now we can spray the floor with a hose end sprayer after working in the GH and it cleans everything up nice! It also cools down the GH nice on a hot summer afternoon if we spray down the concrete - we have not noticed any negative problems with the concrete floor - yet.

    Bookmark   August 3, 2014 at 12:09PM
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karin_mt(4 MT)

It even looks cool with that calming, wet, smooth floor. I have noticed the same thing in ours and in fact that's what prompted me to build a misting system. I'm so glad it's working out for you!

Any luck on finding a cool sink? Have you been checking craigslist? That's where I look for stuff like that. Or maybe a Restore if you have one around.

    Bookmark   August 3, 2014 at 3:52PM
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Hi Karin - tell me more about your misting system - I must have missed that? I see you have a misting timer thread - in 2009 - can you post some photos of how you set it up and how it looks when running? Apparently you have it on timers? Do you use it to bring the GH temps lower on hot afternoon days - how about misting seedlings - I would like a mister for our Geranium propagation? Also - how are your plants doing this year - we would love to see some pics of your GH and plants!

That is a good suggestion to check Craigslist for a sink - we check there for other items - not sure why I didn't think to check for a sink. We have found a couple of options but they have been to shallow (we need it deep enough to soak trays etc - or too large to fit in our space (it has to be 22"x30" max). To be honest - we haven't looked very hard lately - we got side tracked on ordering Tulips, Iris and Peonies for fall planting and other waiting projects - I think we would like something galvanized - copper - chrome and probably a combination of the three.

    Bookmark   August 4, 2014 at 4:10AM
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livelydirt(Zn 4, Lively, ON)

Hi Hudson... my brother recently purchased a large "antique" ceramic kitchen sink from Ikea. Weighs 125 pounds - ugh! But it looks very nice and "antique-y". Not sure exactly what you're looking for. This one does not have a built in drain board. I once built a custom cabinet for a lady who had one such beast.

    Bookmark   August 4, 2014 at 6:53AM
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karin_mt(4 MT)

Hi Hudson,

Hm, maybe I never did post about the misting system. But it's awesome, I don't know what I'd do without it. The timer broke after 2 years and was a big PITA in general so now I just turn it on when it's too hot and turn it off in the evening. That seems to work great - there is very little water put out so I don't get puddles or overwatered plants.

I'll see if I can get some pics and pull together a post about it. It'd be a good PSA for folks looking for ideas about keeping things cool.

And our plants are doing great this year, thank goodness! Tomato plants are all up against the ceiling and I think I had ripe tomatoes in all 3 meals today. Life is good!

    Bookmark   August 6, 2014 at 1:12AM
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Hi Karin - we had a conversation about Raspberries a couple of years ago - I couldn't find the thread - but you may remember. I thought you may be interested in an update. It may just be that this year was a good Raspberry year (how was your Raspberry crop this year?) and had nothing to do with covering the Raspberry rows in our Wyoming spring to protect the blossoms - but that is what we did this year and - help or not - we had a huge Raspberry crop! I know it makes a big difference when we cover our Strawberries so we decided to try covering the Raspberries. The frost blankets were anchored to the supports and remained over the plants for about 2 1/2 weeks during a June - off and on - frost.

Many of our neighbors that can grow Raspberries had a good year too - so maybe it had nothing to do with it - but many had just a so so year as well. The berries were huge and plentiful. We have picked eight containers so far on our two 40' rows with more pickings yet to come. It will take a few more years of covering the plants to see if it makes a difference - we did have a bitter cold and windy winter and the primocane's tops were froze back 6-12"s - as usual - but the floricanes still produced - maybe just a perfect set of circumstances year?

    Bookmark   August 20, 2014 at 5:16AM
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