Pre-construction planning

March 23, 2006

Hello, new to the GH forum of GW. My wife wants me to build her a GH. We're under the impression we can obtain fresh vegetables year round if we incorporate a GH into our current gardening scheme. Does anyone know for a fact that I can have fresh squash and romaine for my dining table in the middle of January by utilizing a GH?

What sorts of preliminary planning should go into this GH? How big should it be to provide two people with fresh salad and greens every week? I'll need to run utilities, is there anything else I should consider? Something that 6 months after it's built I might say "I should have done ____." Things you wish you had done during construction.

It's only purpose will be garden vegetables and a couple of houseplants. I'm thinking an octagon shape would be attractive as opposed to the usual rectangle or square. Kind of like building a gazebo with clear walls and ceiling. Would that be a practicle shape for a GH? Is their a reason most of them are rectangular that I'm not aware of?

Comments (21)

  • nathanhurst

    How much are you willing to spend? Bigger is better for greenhouses (easy to maintain temps for example) and the cheapest per sqft is about $1 for steel tube and film construction. But that looks ugly.

    I don't know what the yield might be, that will be a very local question - ask a local permaculture person or similar.

    Most are rectangular because you want to put benches in there, and rectangular benches are easier to make/get than trapezoid ones. Rectangles are easier to design and build, and don't waste as much cutting out the triangles.

  • agardenstateof_mind

    Greenjeans, I'm fairly new to greenhouse growing, having just set mine up in November, but I'll put in my bit.

    Though you're two zones colder, I believe you can count on some fresh veggies throughout the winter, though I can't say what kind of yield to expect. I have two 24" window boxes planted with lettuce and if I had not been distracted by some other issues and kept succession plantings going in other boxes, we'd have a nice harvest even for our family of six. The cherry tomato plant produced all winter but without supplemental lighting the yield was small - it's really picking up now. Several pea vines were started in late February, and are now flowering.

    Squash might take up a lot of room for a greenhouse. Do you have a rough idea what size greenhouse you are going for?

    There have been some discussions on good vegetable varieties for greenhouses, but I'm not sure where ... maybe the forums entitled "Growing from Seed", "Vegetables" and/or "Square Foot Gardening"? The GardenWeb search function might turn up some results for you. There's a book titled "The Greenhouse Gardener's Companion" which is an excellent resource; you might find a copy in your local library. I believe the author lists some varieties particularly good for greenhouse growing and you'll find lots of other good information as well. Some seed catalogs will note which varieties are good in the greenhouse environment.

    Don't forget to pot up a few herbs to grow in there; it was wonderful to harvest fresh herbs for cooking all through the winter. Also, I've taken cuttings of the tender ones and will set those out in the garden once the weather is mild enough.

    Small as my structure is (6'x8'), I made sure to leave room for a chair ... it's just a leftover white resin patio chair, but is sufficient. I'm not the only one in the family who enjoys escaping to the greenhouse for a little R&R now and then ... sometimes with a warm beverage and good book.

    Another reason for the rectangular shape is that it is easier to add on sections if you want to expand the greenhouse. I've seen some octagonal ones, and they do look nice, but there are some lovely rectangular ones and once in place, framed and grounded with some low-growing plants, they just fit right in.

    It sounds like you're getting a good start with your research. (I just jumped headlong into this, and so glad I did!) It's really difficult, I think, to avoid any and all "I wish I had ...", because I believe it's very difficult to imagine beforehand just how enjoyable greenhouse growing and the environment is until you experience it. Throughout the threads in this forum, many people have posted ideas, problems and solutions, ranging from heating and insulation to dealing with ants and mice. I hope you'll take some time to browse through them, as I think you'll learn a lot and get lots of ideas yourself.

    Good luck with the greenhouse and the winter gardening. Please keep us posted!


  • nathanhurst

    I believe it's very difficult to imagine beforehand just how enjoyable greenhouse growing and the environment is until you experience it.

    Well said Diane!

  • ohiojay

    Just my two cents. I too am in zone 5 and even though a lot of veggies are "cool" weather crops...lettuce, root crops, and such...most are not. Tomatoes will go dormant under 50 degrees. Peppers are definitely warmer weather crops as are cucs and squash.

    Is it possible to attach the structure to a wall of your home? This not only saves cost of the structure but you benefit some from residual heat from the home. I believe you will have to heat this structure if you want to maintain some of the above mentioned well as supplemental lighting. So the heating issue complicates matters. If you're going to heat, then you need to seriously consider a better insulated structure. It will be expensive to heat in our zones no matter what you do and what you build. Keeping nighttime temps down will help but you can't let them get down too far either.

    Nathan hit the nail on the head. Bigger is better and a better structure is better. Another thing to consider is that once you see you can grow veggies throughout the this going to satisfy your newfound vocation? Are you going to want to start growing something more than veggies and a couple of houseplants? If there is any doubt at bigger and build better. Not knocking all the HFGH folks out there but I don't believe a structure like that is going to cut it for where you are and what you want to do and may do in the future.

    Going to these lengths require a and time. Diane mentioned all the varied posts on this forum. Do a search on some key words and there is plenty of info on the web. Take your time and good luck. J

  • greenjeans_il

    Thanks for the replies!!

    I've got limited space to dedicate to this project. I've just built a stone paver patio with a lot of curves and rounded edges and was thinking I would like to keep the same rounded edges throughout the rest of my scape. I think I've got around 3000sq.ft. in my backyard, but it's pie shaped as my lot is on the inside of a curve in the street. I've also planted shade trees in two areas of my yard that will influence the location of the gh as well as the two story home itself. Figuring out microclimates is a new one to me as it wasn't until last Fall that I'd heard of such a thing. The last time I had a garden was on a 20 acre ranch in OK as a kid and since then it's been apartment and condo living : (. It'll be nice to get back into gardening. The rest of the scape in my backyard will be flowers and shrubs so the greenhouse will be 100% vegetable gardening. I'm thinking I'll go with about an 8' radius with a paver floor and waist high walls. The rest of the structure will be of white cedar framing (to match the fence) and whatever material I can find that's best suited for durability and insulation for the walls and ceiling. I'm not overly concerned about the expense as it will be a permanent structure that will add value to the home which has been the focus of all my landscape plans. I'd also like to make it as automated as possible as far as climate and humidity control. Going so far as having window vents open and close automatically with changes in temperature and misting systems for changes in humidity.

    That's all I've considered so far. Thanks for the book tip grdnsto'mnd. If anyone has any other valuable research tools (books, websites, etc...) other than what's posted in the FAQ's I greatly appreciate it.

    On another note: has anyone ever considered or heard of using radiant heating (similar to the electric icemelt systems for driveways) under the soil beds in the gh? I was thinking that may be an excellent source of heat to help maintain growing temps within the soil. I may still need an additional source of heat for the air when it gets really cold, but the radiant heat systems they have are extremely efficient to run. If I used a concrete base under my planting beds I could incorporate it into my original plans. Good idea???

  • nathanhurst

    It's not radiant if it's underground :)

    People often run warm water through the garden beds to keep the soil warm in winter. Some plants can deal with very low temperatures on the leaves as long as the soil is warm.

    If I wanted to grow veggies in a greenhouse I would leave the ground bare, get a large twinpolyfilm greenhouse with an insulated north wall and east and west lower sides and surround the soil around the base of the greenhouse with strawbales over winter to a length of say 2m. You can grow stuff in the rotted down straw in summer before putting new bales around in autumn.

    I would put a good sized store of water in the middle as a combined bench and thermal mass. I wouldn't use concrete as it is expensive, changes the soil and is hard to change.

    I would grow squashes and tomatoes on the insulated north wall, beets and beans in the middle and lettuces and herbs on the south side so that the leaf profile forms an angle of around 60 degrees to maximise the sun absorbtion.

    I would get a ventless propane heater to run in the worst weather and to top up the CO2 levels. A large horizontal fan would create an air flow around the greenhouse. The greenhouse would be built on the south side of my house, and on sunny days I would open a window into the greenhouse to heat my house. There would be a resin garden chair near the door and a bench on the west or east wall for potting stuff.

    I'm sure that there are books around that tell you how to build what you want. A bit of research now is worth a lot of money later.

  • clavero

    Believe me I know the excitment of planning and building a gh...just finished a small one myself but....(I dont' want to rain on your parade)..

    Even in the planning stages, I never intended our gh to be for veggie production....only orchids and flower and veggie starts. Now, living in CA, that is a bit of a no-brainer as produce here is possible outside in winter and otherwise avilable at a price. When I was building and equiping the gh with heaters and fans etc I was aware of the money I was spending but , since I did not expect to get it back dollar for dollar, it made little difference. For us the payoff of the gh is the mind ease and play value, my wife was once a psychotherapist NOW a gardener!

    We once raised chickens for meat and eggs...loved it. Always had more than enough of both (and mighty tasty too) but after a few years, and adding up feed bills, electric to hen hosue for winter egg production, etc we could have paid $10.00/lb in 1985 dollars for chicken and come out ahead.

    If growing your own veggies, perhaps with construction amortization and energy costs of (maybe, who knows) $10 a lb for beans in December is OK....then OK. But you might want to think about how ELSE you could use the gh after the honeymoon of New Year's dinner homegrown greenbeans is over.

    Sorry, seemed somebody had to say it.


  • gw:otomato-o

    Money pit, plain and simple. Built a fab greenhouse last summer and love it, but somedays i think it is like burning dollar do you justisfy 50 dollars worth of kerosene to keep 10 pots of romaine and 50 pepperplants warm?

    BUT! It is my hobby and furthermore my passion and i am commited. It is a wonder that i sleep a wink at all tonight as i just moved all 30 flats and 100 small pots out of the kitchen and into the GH FOR GOOD. Heats on. They say the temps are going up for sure. Heard every weather report that i could get my hands on. Figured it was my best chance. Either is gets spindly and ugly or it learns to survive. I don't know how many heirloom tomato plants are out there-afraid to count..

    If it were up to me, i would live in the greenhouse, problem is, there isn't hardly a lick of room out there. and this is what you want? Make sure you build it REALLY BIG-I already need an addition to my 14X10X12..think i might hang baskets of herbs from the peak..

    ruth..good luck-it is totally worth it whatever you build!

  • chris_in_iowa

    Plan for a multi-use structure.

    To be honest, in zone 5 you are going to be spending a lot of money for heating from Nov to mid March to grow fresh vegetables. The stuff you will be growing will not be any more nutritional than the "fresh" stuff you buy at the store in winter.

    In zone 5 use a greenhouse for starting seeds, in say mid March. 8 weeks later in mid May you get them in the ground. June-October the greenhouse is used for some tomatoes and peppers in tubs.

    From Nov to early March your greenhouse is a really nice place to sit in and have lunch on a sunny day. (or rebuild your tiller engine or make glass beads or....)

    Money pit is a good description of a greenhouse in zone 5. A 24x14 could cost you $1200 a year in heating if you kept it at a minimum of 60F

  • greenjeans_il

    It gets worse: I have no room on the South side of my yard for a gh. On the North my neighbors house will protect it from wind, etc...and it would receive mid to late morning and late afternoon sun in that location. Say 3-4 hours sun in the morning, 2-3 hours no sun, then 4-5 hours sun in the afternoon. That's only going to last as long as the maple tree I just planted stays short. When it matures it'll block probably an hour or two from that afternoon sun. I don't think a gh is practical for my location. The only way I could build a gh with Southern exposure would be to put it in my front yard.
    This is very dissapointing. I was so looking forward to Winter gardening to ease the cabin fever. I love working with plants and it felt as though I'd be building my own green playhouse for the cold months.

  • agardenstateof_mind

    It sounds like you're giving up on the idea?

    What is creating that shade you referred to - buildings? evergreen trees? deciduous trees? If deciduous trees, you might not have a problem since they only cast shade summer and autumn, at which time you might need some of that shade to keep the house from getting too hot. (Maples do usually cast a deep shade, though. My GH is under a very tall, highly branched oak that provides dappled shade from about 1:00pm on, summer-fall only.)

    If this is something you really wanted to try, and I think you said above money is not an object, why not try it out with one of the little HFGH models? I know, they're not pretty ... but it really looks better than I expected. My whole set up ran about $800 - most of that for the "accessories" like foundation, gravel, fan, benches, insulation, heater, thermometer, etc. The little HFGH greenhouse sells for $329, sometimes on sale for $299, and then there's that 20% off coupon. Treated 2x10 lumber for the foundation was just under $100. We built it all in one day, I've been enjoying it ever since, and the entire family (not even gardeners) have come to enjoy just being there.

    Anyway, for a pretty modest sum, you could get an idea how you take to greenhouse gardening and how useful it might be to you. Being in zone 5, for a permanent structure you might want something better insulated than the HFGH, but it is a start. (But wait ... MilwaukeeDave has a HFGH, he's in zone 5 ... probably almost 4!) Someday I'd still like to have a larger, higher quality GH, but I've already learned a lot through having this one. Big item: I'd always thought I would want an attached GH, even though it would mean putting it on the front of the house and trying to gussy it up with foundation plantings, etc. The convenient access and heating benefits for both greenhouse and home cannot be denied. However, I found the freestanding GH in the back yard to be a wonderfully peaceful retreat - something an attached greenhouse could not offer. Even with the solar pool cover on, the hazy colors of leaves and flowers are visible from our kitchen window ... a beautiful sight on a dreary winter day that pulls me out, regardless of weather, for a little R&R.

    I often admired greenhouses, always figured it wasn't "doable" for us for one reason or another ... well, we did it, I'm sorry we waited so long, and if I can help it we'll never be without one again.

    Just my two cents.


  • clavero

    Yow...don't give up on the idea. I was just throwing in a sober moment. My gh is in a compromised position...not as much sun as it "should" get and no where near as big as we could easily fill. We just worked with what we had and, while the venture is still in the early stages, the smiles on my wife's face are worth A LOT.

    I'm not a HFGH fan but hey, try one of those little puppies.

    Fresh veggies are not the only use for might find that the attempt leads you to a hitherto unknown passion for some plant varieties that work in your "compromised situation"


  • greenjeans_il

    I keep going over it in my head, there's really only one place to put it. The only other alternative (opposite corner from where I'm originally planning) is on a utility easement. I can't build permanent structures there.

    I need more yard or a shorter house. My house is the obstacle of the only feasible location. Other than that it's the Maple that I planted last Fall. I'm really not looking forward to digging that up plus it's the only tree I have that offers the back of the house any shade during the heat of summer afternoons.

    The back of my home faces west with windows all the way across and a patio in front of most of it. The side of my home with southern exposure is only about 6' from my neighbors property at one point (pie shaped yard) and at its widest has electric and gas meters not to mention basement window wells with emergency exit (has to remain clear of obstacles). The other side of my home has nothing but a gently slope to my neighbors yard, but alas, it's on the north.

    So, I'm left with the North-West corner, more West than North, that will leave me with the sun exposure mentioned above.

    I would build a semi-permanent structure, but the rest of my plans call for so much manicurism I'm afraid it will taint the overall beauty of the landscape especially for such a small area.

    What do you guys think, go for it? I have a digital camera but don't know how to post pics. Any suggestions?

  • agardenstateof_mind

    Steve, I know I've said it before, on another thread: I never thought I'd go for a HFGH, for many reasons. Had bigger plans ... but then some health issues came up here and I realized it was going to be a HFGH or nothing at all. I am very glad I decided to go for the HF, because it has been a delight, I've learned a great deal that can be applied to selecting and using my next greenhouse ... and I've also experienced (again) that old adage: "Don't knock it 'til you've tried it." Honestly, this little inexpensive structure, that some assert is not a "real" greenhouse ... nothing more than "a glorified coldframe" ... has really surprised me. So did the ingenuity, resourcefulness and generosity of the other HFGH owners in this forum.

    Greenjeans, you and your wife have a dream? Don't be too easily dissuaded. Identify your goal. Is it just to put low cost fresh produce on your table in the winter? Or is it to enjoy the experience of gardening regardless of the season, enjoy the ambience of a greenhouse, and add a feature that reflects your interest in and dedication to gardening?


  • agardenstateof_mind

    Greenjeans, I was composing my last message when you posted your last one, so didn't see it 'til now.

    LOL - you finally got me to get out a pencil and paper and do my best to sketch out your situation! Just for the sake of comparison, my back yard is about 4,000 square feet and is due north of our home, our side yards, too, are unusable: 10 feet on one side (driveway) and 7 on the other. There are a LOT of trees here, on my neighbors' properties too. Very limiting. Along the west side, in the only really sunny spot, is a little vegetable garden - 8x16 feet - and I try to keep it as attractive as it is productive. Behind it, there's a 10x12 storage shed (whose days are numbered, as it's sitting on some valuable sunny land.) Over by the east property line is what I've been advised is an "advanced water garden" about 14'x16' (true koi ponds don't have shelves, plants, etc.), with a bog garden, waterfall, landscaping and sitting area; nearby is a gazebo. My greenhouse is tucked between the shed and the AWG. (At the right time in the late afternoon, reflected sunlight from the water dances on the greenhouse walls.) There are flower beds and borders all around. Briefly: I understand your constraints. Although our style is definitely not manicured ... just wouldn't fit in the woodsy atmosphere here.

    What about the southwest corner - no room there? This is just me, but I'd take out the maple. In my experience I've found them to be very shallow rooted and cast deep shade - both of which make it difficult to grow anything beneath them. Many varieties are also prone to root girdling. There are many types of trees that are hardy, deeper rooted, and will cast a more forgiving dappled shade.

    The sloped contour of the land to the north/northwest alone should not be a problem. I think it is MilwaukeeDave who built his greenhouse on a slope ... built up a foundation (knee wall if you will) to level the structure. This could easily be decorative or camouflaged. However ... the northwest exposure might be an issue and I don't have enough experience to address that one. Though I think the bottom line is how many hours of sunlight would it get during the season(s) you intend to use it heavily, and is there any protection from cold, heavy winds.

    Best of luck to you. The planning and deciding is the toughest part ... which is why I sometimes (just sometimes) just follow my heart, plunge ahead, and work it out as I go.


  • clavero

    Di- (at the risk of derailing this thread topic)...I can absolutely see how the HFGH is great for folks. Just meant its not my "cup of tea" that's all.


  • jimmydo2

    Greenjeans, your situation sounds a lot like mine, you might have seen some of my posts as I hummed and Hawed about what green house to get, where to put it, etc.

    Although, I dp not have a small lot, most of it is not suitable for a greenhouse.

    As I was trying to figure it out, a place sudenly presented itself.

    My greenhouse is going to be basicaly attached to one side of my patio, and will be a place where I can escape and relax. I do not expect the greenhouse to make cheaper produce, but I will know what pesticides have been used. (I am very alergic to pesticides, so I generaly avoid comercial produce.

    The main benifit of my greenhouse, is for relaxing, not for cheap food. I am seriously thinking about installing a waterfall and small pond. I could use a 55 gallon barrel as the resovoire, and the Lift for the waterfall. The drum would also act as a heat sink, and the waterfall would help keep the humidity up. Not to mention the peacefullness of having a waterfall.

  • greenjeans_il

    My main goal isn't neccessarily cheaper produce, but fresher and more convenient. I live 15 miles from the nearest grocer that carries decent produce, and none of that drive is expressway. When I go to the store I'll buy enough produce for a week, but by the end of the week a lot of it will go bad or generally soft and unappealing. There are produce stands that pop up here and there but only when I'm able to grow my own vegetables. I suppose if I build my gh big enough I could set up a winter produce stand in my town and make back a few of the proceeds. ; )

    I'm just going to build it where I originally intended. Probably not until Fall, though. I had wanted to make a Spring project of it, but I also need a fence and concrete on the driveway. I do all my own work so I think this year it's cut out for me. When I get the utilities laid, foot wall built and the frame up I'll look you guys up for ideas on best materials for the walls and ceiling.

    Then again, maybe I could wait until next Spring and use this year to research the amount of sunlight the intended construction zone receives. Does anyone know of a product or meter that can measure such a thing? Some kind of photo-sensor?

  • agardenstateof_mind

    It sounds like you do have your projects lined up. We do all our own work too, so know how that is.

    There are several light meters on the market; don't have one yet myself. I think you'll find them at just about any of the gardener's or greenhouse suppliers.

    The new SunCalc really interests me, but I can't vouch for it and welcome comments from anyone who has experience with it. I just saw it in the Gardener's Supply catalog for $29.95. You place this battery-operated unit in the ground, set it, and leave it in place ... twelve hours later, you have a reading on the amount of light the area receives. It gives readings as full sun, partial sun, partial shade, full shade. Seems like a great idea for situations that get mixed sun/shade conditions throughout the day.

    Not to rush you, but if you can manage to build it in the fall, you'll be able to use it next winter (don't really want to think about winter now, as we're finally just shedding it!). Don't forget to allow for seasonal differences in figuring the sunlight - the sun is lower in winter (buildings, fences and evergreens will cast a longer shadow), but the leaves of deciduous trees are gone.


  • puffysmom

    Just want to put my 2 cents in here. When it comes to health, taste and safety growing your own veggies is much better for u. Not any cheaper but when one sees how much pesticides is sprayed on veggies that comes from Florida it is hard to believe that we live to be as old as we do. I used to live down there and have seen what they do to get a good crop. One cannot grow good veggies in pure sand. I tried to grow a garden and it takes so much added fertilizers and such to get something out of it and then to fight the nematodes. I dont know bout California but I can say this much. At least California strawberries have a good taste to them unlike watered down ones like Florida has. I just want some decent veggies that dont taste like lightly flavored whatever it is suppose to be. I bet i have better luck with a greenhouse than i did with my florida garden. teehee

    I am willing to spend the extra money to have some decent safe veggies and possibly fruit. U can grow some fruit trees in a greenhouse if it is tall enough(greenhouse I mean). I live in Zone4 and know it will cost me quite a bit to heat next winter but am willing to do it. Will do whatever I have to to keep the heat bills to a minimum and just hope it all works out for me. :>)

  • jimmydo2

    Trees, specificaly Citrus trees are the primary reaso I purchased the HF 10x12, It is unusualy tall for a 10x12 greenhouse, with 7.5 foot sideways, and like a 10.5 peak. I ha ve been working on creating some Hardy Grapefruit trees, so during the winter, I will only have to keep the house above freezing. I am putting the grafts on super dwarfing rootstock, so even full grown, the trees will fit in the greenhouse.

    Greenjeans, even though you said you will be waiting till fall, it sounds like you are acrualy starting it now, paving, and routing utilities. That is more my pace, I do not like to rush things, so that I have plenty of time to find all the glitches before it gets cold

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