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Two 6x8 HFGH and central shed idea -- Additional suggestions?

Posted by Annalog none (My Page) on
Wed, Feb 19, 14 at 11:10

Six or seven years ago I bought a 6'x8' Harbor Freight greenhouse kit but did not assemble it. While researching online, a year passed and I bought a second kit so that I could have two together. At that time I planned to have two 3'x16' raised beds along the south and north sides of the combined greenhouses. We picked the location and found that the ground was about a foot higher on the east than the west. That would be fine as we planned to build a base using 8"x8"x16" cement blocks and also use those for the adjoining raised beds. I planned to put half inch hardware cloth under the greenhouse to keep out gophers. We put a boundary of 12" square pavers to mark the space and I started digging. I was still thinking about how to deal with the doors since they are about the same height as my husband and we did not want him hitting his head. The exterior door would be on the west with the largest step up. Also, here in southeastern Arizona, wind can be a problem.

Meanwhile, my husband finally agreed to us keeping chickens. :-) All efforts switched to moving an 8'x12' shed about 50 feet and converting it to a coop. Then the chickens, and other life events, kept the greenhouse project on hold. The oldest hens will be four years old in May. Both HFGH kits are still in the never assembled state.

Then, last week my husband bought a greenhouse and garden projects book. One of the photos caused us to rethink connecting the greenhouse kits. What if we had a shed between the two greenhouses with both greenhouse doors opening into the shed with the only door to the outside from the shed? That would solve the problem with the greenhouse doors in relation to the wind. It would also help if I wanted two different greenhouse environments. This led to a few days of brainstorming. Current plan:

12'x30' area to be leveled from at least 8" below lowest point on west end. (Some of the previous excavation will need to be filled in. Fortunately this is south of the raised beds.) In the 12'x30' area, the bases of the following would be outlined with 8"x1"x16" capstones for the two greenhouses, a central 12'x8' shed, and 3' raised beds surrounding the exterior sides and ends of the greenhouses. This area would then covered with 1/2 inch hardware cloth (4' wide sections joined to prevent gopher access). A layer of 8"x8"x16" cement blocks would go over the capstones to secure the hardware cloth. This will put the hardware cloth at least 8" below floor level. (This has been tested on bases for our chicken pens and on garden raised beds.)

Additional rows of cement blocks would be added, running bond, to bring each section to the desired height. The base, or knee wall, for the greenhouses would be 24" or 32" above floor level. The outside raised beds would be one course of blocks lower. The blocks at the sides of the central shed will be the height of the greenhouse knee walls while the blocks at the shed ends will be just above ground level. The blocks in the knee walls and shed foundation will be filled with concrete but the raised beds won't. (The first has been tested on a wall added under our manufactured house and the second in our garden.) One row of the knee walls will be bond beam blocks with bond wire added. There will also be anchors added at appropriate locations. We are thinking about how to add vent openings in the top row of knee wall blocks.

We are planning on using plastic composite decking material, such as Trex, laid on top of the knee wall for the base of the greenhouses instead of wood. (Desert termites are a problem here. We have six Trex 4"x4"x8' pieces that we have used over the years and they are holding up very well. Four are currently marking the new location of the greenhouse and planters on the west. :-) )

The central shed will be a modified pole structure with the vertical supports anchored to the foundation blocks. The roof line will be above the greenhouse roof lines. The door will be on the south end. The roof will have a turbine fan. There will probably be an exhaust fan in the north wall. There will be side walls wherever there is no greenhouse wall. The floor will probably be concrete pavers. Electricity and water will be available. The roof will be three tab asphalt shingles to match our house roof that will be replaced in the next couple months. We will put up the solar electric kit we bought a couple years ago on the south facing roof.

The greenhouse on the east will have the door on the west and the greenhouse on the west will have the door on the east, both opening into the shed. The two greenhouses will be assembled with many of the modifications mentioned in this forum including painting the polycarbonate panels with Top Secret UV coating, extra clips and at least one screw in each panel, an internal frame combining plant shelves and extra support, and the swinging door conversion.

The outside raised bed planters will have added frames made from metal electrical conduit and supported at each corner and the centers of the raised beds. These frames will be available to support netting trellis and other plant supports. These will be taller than the greenhouse by at least six inches. There will be a roof frame, also made from electrical conduit, over each greenhouse and attached to the inner top rail of the plant support frames. Wire rabbit fencing will be attached over this. (This is how we roofed our chicken pens to keep out predators and also to support tarps for shade and frost protection for the chickens.) This external structure can support shade materials in the summer and plastic in the winter. In this part of Arizona we have highs above 110F in the summer and lows below 10F in the winter. Our elevation is just under 3700 feet. The external structure will be far enough away to allow removing some of the polycarbonate panels and replacing them with screening in the summer. The external structure will also be easy to disassemble and reassemble if needed. Unused panels and covers will be stored in the central shed.

I am still thinking about the floors of the greenhouses. I want to try composting as a heat source and raising worms in at least one greenhouse. We have enough wood chips for a temporary floor in each greenhouse. I will probably add a row of cement blocks on each side of the center aisle of each greenhouse to identify floor level, to provide support for the shelf supports, and to allow separate flooring for aisle and growing areas.

I haven't decided where best to put a sink and a drain leading to a dry well or to above ground drainage.

I suspect that it will be fall before we are ready to assemble the greenhouses (after re-roofing the house, raising more chicks, summer heat and rains, getting building permit, etc.).

Any comments, suggestions, or potential problems? What did I forget? Thanks in advance.

This post was edited by Annalog on Wed, Feb 19, 14 at 11:13


Follow-Up Postings:

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RE: Two 6x8 HFGH and central shed idea -- Additional suggestions?

Honestly, with that much good detailed planning, I am hard pressed to think of anything that you folks haven't already considered.

Your climate is even more challenging than ours here in southern NM. Sounds like you already know that cooling will be a challenge, (much harder for us to cool in summer than heat in winter.) The greenhouse on the west end could be a real hot box in the summer, depending on the location of trees or other buildings to block some of the afternoon sun, but you're already planning for ventilation with the roof turbine on the central shed roof, and an exhaust fan on the north wall.

As you go, you'll no doubt learn what the structures require in the way of shadecloth during the summer. I'm guessing shadecloth on the west wall in addition to the roof. So much of this (on our little greenhouse) just had to be learned by trial and error. With this level of planning, I have no doubt you'll be able to make judgements and adjustments along the way!

I do love the removable screens we made for our greenhouse. If I didn't have those, I don't think even my tough cacti could survive our summertime days with highs around 104. Fortunately we don't get many of those here (I know you do!)

If the cooling is just too tough, you could always consider adding some kind of evaporative cooler, down the road. I know that would help our little 10x12 HFGH, but I've wanted to avoid that complexity, so I just try to scrape by during the worst of our summer heat (screens in, west doors open to the breeze, east wall exhaust fan on high, plus two more fans to keep air circulating, and periodically hosing down the paver/gravel floor during the very worst hot afternoons.)

I've always thought it would be nice to have two different heating zones for the winter. Some of my plants don't want to go below 45F, but some cacti would bloom better with more cold. So I have to let the wimpy plants set the minimum allowed temperature, but you could possibly have two separate areas with some temperature variation.

I hope you will post back with your progress (would love to see some pictures!) when you get started.


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RE: Two 6x8 HFGH and central shed idea -- Additional suggestions?

You will need to caulk the panels inside and outside with silicone and extra clips are needed too. I didn't do this and my greenhouse is partially paneled now, I just ordered more clips and 2 new panels. More clips 1-800-444-3353 72 clips are approx. $10.00 plus $7.00 ish shipping. SKU# 27339. If you already plan on silicone reinforcing etc. Sorry, but you will surely need to do that and adding MANY more clips, my area gets some winds now and then but if you have wind on a reg basis, save some time and order the clips before you take on assembly, so you have them.


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RE: Two 6x8 HFGH and central shed idea -- Additional suggestions?

Thank you for the input, Mudhouse and Poaky1.

A six year delay in assembly does leave a lot of time for planning. :-) I wonder if I have set a procrastination record for greenhouse assembly? ;-)

Also fighting gophers and mice in the garden and elsewhere have forced us to develop skills using concrete blocks and hardware cloth. Finding full grown tomato plants with tomatoes almost ready to harvest separated from their roots by 3 inches of air overnight started my battle with gophers. Now all non-native plants, including my two apple trees, are planted in raised or sunken beds barricaded by hardware cloth and concrete blocks. Replacing the plumbing under the house after it had been nibbled by mice caused us to do without hot water for what felt like months. Replacing the siding under the house with a block wall to prevent mice from returning makes the knee wall for the greenhouses seem easy.

I will phone 1-800-444-3353 and order the bag of 130 clips, Part number 53 panel clip, and give them the SKU number 29457. I am sure that Harbor Freight will have plenty of time to deliver the clips before we start assembly as we need to put a new roof on our house first. :-) I'm planning on reinforcing with at least one screw through each panel into an aluminum support instead of caulking with silicone as I want to be able to remove some polycarbonate panels and replace them with screen in the summer. Mudhouse, I just read a thread where you described your removable screen panels; great instructions and a beautiful result. Although after reading that thread, maybe I need to order two of the large bags of clips.

Mudhouse, thanks for reminding me to recheck the location of trees and buildings in regards to shade. While I am sure that I checked this six years ago, I needed to recheck after the new plan changed the planned locations of the greenhouses, one greenhouse location has moved west by 8 feet and north by more than 4 feet. Our house is set with the long axis and roof ridge line pointing east/west with the front door facing south. All the other structures on our acre are either parallel or perpendicular with the house. The west end of the west greenhouse is about 40 feet east of the house and the roof ridge line of the greenhouse is about 8 feet south of the house roof ridge line. Today, shortly before sunset, the shadow of the awning on the south side of house shaded the north third of the planned location of the west greenhouse. In the winter there should be less shade from the house and in summer the west greenhouse will benefit from shade from the house in the late afternoon. There is a fairly large mesquite tree between the house and the west greenhouse. The trunk is about 10 feet west and 2 feet south of the southwest corner of the planting bed. The lower branches on the east side of the tree will need to be trimmed a little to allow easy access to the west raised bed. While there may be a little shade in the winter from the tree branches, the summer shade should fall on the south raised bed in the afternoon. I don't think it will shade the greenhouse significantly. There are two small mesquite trees (bushes) south/east of the east greenhouse. If these provide too much morning shade, it would be OK to cut these down. There is a soaptree yucca to the north and another to the south of the central shed. That should be OK for the greenhouses and I hope the shed does not shade the northern yucca too much. Both of these yuccas died back to ground level a couple years ago and then resprouted. There is a small yucca growing inside the excavation area that I am going to try to transplant. So far I have only dug around it and have not yet disturbed its root system.

Cooling is definitely a concern. Most of my plans for the greenhouse are influenced from trying to keep the chickens cool enough in the summer. Chickens can be stressed when the temperature gets much over 90 F. Three quarters of the western wall of the chicken coop is shaded by a large shed 3 feet to the west of the greenhouse. In addition, the chicken coop has a turbine fan, a small air conditioner, an interior box fan that runs nearly all day and night in the coop, a mist system that sprays the roof during the daytime, and a raised bed to the east with pole beans and luffas growing in the summer on a net trellis to shade the east wall, all in addition to insulated walls and roof on the coop itself. The outside pens have mist systems and shade cloth or tarps. The exterior raised beds to the east, south, and west of the greenhouses could be used to grow tall crops to partly shade the greenhouses, if necessary, as well as to support shade cloth. The planned exhaust fan on the north wall of the shed could be combined with wet walls in place of a panel or two in the east and west greenhouses if evaporative cooling becomes necessary. The raised beds should also provide some insulation to the knee wall for both summer and winter.

I am hoping that I can have a couple small citrus trees in pots in one of the greenhouses as the winters are much too cold for citrus here. I also want to grow vegetables and greens for us and the chickens through the winter. Finally, I have an Owl Eye Pincushion (mammillaria parkinsonii) that I bring into the house for the winter and keep on the front porch in the summer. While it has grown from a single owl eye pair to four pairs of owl eyes and has bloomed, it has never fruited. I am sure it would be happier not getting covered with cat hair in the house each winter. ;-)

I will post with photos and progress as it occurs. Right now there is just a hole in the ground partly in the wrong place and the chicken pens and garden beds that were the inspiration to some of the planning details.

This post was edited by Annalog on Fri, Feb 21, 14 at 1:18


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RE: Two 6x8 HFGH and central shed idea -- Additional suggestions?

Well, if it is a procrastination record, that's OK, because you seem very skilled at turning the procrastination period into a fruitful time for careful planning. (Around my house, procrastination usually results in no progress of any kind.)

You've probably already found it, but here's a link to the part of my blog where I listed more info about making the screens for the south side. Since they have almost no wind resistance, I usually only secure them with a couple of clips on each side, when in use.
Greenhouse Enhancements, Part Seven

I've transplanted soaptree yuccas a few times (Yucca elata I think) and I have mixed results. Those guys send down big straight tap roots even at a young age, and the odds of the transplant working seems to have a lot to do with getting all the root, if possible. I tried to save three medium soaptree yuccas when a friend was relandscaping, and only one made it. Smaller ones seem to be less fussy. Good luck with yours, it's always worth a try!

From your description I think I might want to move in with your chickens, next summer. I think they may have better cooling than we do.

I think your M. parkinsonii will love the bright diffused light of a greenhouse year round (all my cacti do). Since it does bloom for you, it might be a lack of pollination that is preventing the fruiting. Some Mammillarias are self-pollinating, and some aren't; I don't know about parkinsonii. Some need to be sitting beside the right neighbors, blooming at the same time, to get the flowers pollinated. Others fruit like mad by themselves. I don't have the right patient personality to grow cacti from seed, so I'm not very wise about birds and bees cactus stuff!

I think cat hair on a cactus just gives it a nice natural patina. ;-)

Well, now I wish fall would get here so you could show us some pictures. Don't forget a photo of the chickens too.


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RE: Two 6x8 HFGH and central shed idea -- Additional suggestions?

After reading the thread on Subterranean Heating/Cooling System and followed some of the links referenced there, I have decided to abandon the thought of composting for heat inside the greenhouse and go with a SHCS instead. It will only mean digging down a foot or two more which won't be a problem with our soil. I am planning on following a plan similar to How to Build a Solar Greenhouse which was for an 8'x12' greenhouse.

I will not be adding insulation so that it will work better for cooling.

I am wondering if the central shed will add too much shade so am thinking about having it not extend south past the greenhouses. It is good that I don't need to make that decision until after the excavation is complete. ;-)


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RE: Two 6x8 HFGH and central shed idea -- Additional suggestions?

Hi Annalog and mudhouse,

I got to this site because you, Annalolg, posted on the one I'm following on the SCHS. ( :

I was going to tell you about this FANTASTIC site I found on the HFGH, and mudhouse, it turns out that it is your site. THANKS for putting it up there to help us out! The only site I'd found before was a small one (and it was helpful re: info to prevent the premature deterioration of the polycarbonate clear plastic panels) and that site (http://www.instructables.com/id/Building-and-Improving-the-Harbor-Freight-6x8-Gree/) doesn't hold a candle to yours!!!

Blessings,
Carolyn


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RE: Two 6x8 HFGH and central shed idea -- Additional suggestions?

Hi Carolyn, glad the blog is helpful. Most of the ideas came from other Gardenweb forum members here (many of those no longer post here, but they laid the groundwork for the rest of us.)

I just tried to assemble them in one place, while we took photos building our HFGH. The great thing about the internet is everyone can add their own good ideas into the mix, and we can all help each other.


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RE: Two 6x8 HFGH and central shed idea -- Additional suggestions?

Hi All,
Mudhouse, I also appreciate you collecting many of the HFGH ideas in one place. Your blog and posts are very helpful.Thank you!

Carolyn (Waterstar), Your comments have been very helpful on the SHCS thread.

I have been working on plans. The image below represents a view from above. The window in the roof of the central shed is meant to represent a solar panel. I will post two more views in following posts
Anna


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RE: Two 6x8 HFGH and central shed idea -- Additional suggestions?

This view is looking from the south. Our house is further west than the tree shown. What looks like a single short row of blocks under the greenhouses and shed is actually the bottom row of an underground wall that goes 2.5 to 3 feet under ground level to surround the SHCS heat sink.


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RE: Two 6x8 HFGH and central shed idea -- Additional suggestions?

This is a view looking east through one of the greenhouses and shows the side of the central shed as well as showing the raised beds surrounding the outside of the knee wall of the greenhouse.

I have not yet modeled the growing beds inside the greenhouses, the internal structures to hold shelves and pots, or the external structures to support plants in the outside raised beds as well as shade cloth (summer) and plastic (winter).


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RE: Two 6x8 HFGH and central shed idea -- Additional suggestions?

Wow Annalog, what terrific visuals. We are currently struggling with a planned kitchen remodel, and I wish I had your skills to produce images.

I love raising the 6x8 greenhouses on the kneewalls. Increasing the height should help a bit with cooling, and will make those ends more pleasant to work in (in my opinion.)

Are you planning on automatic openers for the HFGH roof vents? Maybe Bayliss or Univent? I eventually abandoned/eliminated my roof vents but probably should have explored that option before doing so.

Visually this could be a very handsome structure. So looking forward to seeing your progress.


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RE: Two 6x8 HFGH and central shed idea -- Additional suggestions?

Thanks, Mudhouse. I used an old version of Google SketchUp to build a 3D model and then did a screenshot of three different views. The version of the program I have already had models of cement blocks, doors, windows, trees, bushes, and yuccas that I could use, as well as allowing me to paint surfaces with wood, rippled glass, roofing shingles, sand, pavers, etc. So far, laying the cement blocks in the model has taken the most time but has also identified places where we might have problems. It does let me plan while it is much too windy to start digging. Too much soil would blow away. :-)

I definitely like the options the kneewalls give us, especially with the outside raised beds. I am currently planning on inside raised beds on the end and both sides in one greenhouse and a raised bed on the south side of the other greenhouse with citrus trees in pots along the north wall. I am not sure which greenhouse will be easier to keep warm in the winter, the east one or the west one. The east one will get plenty of morning sun in the winter while the west one might be shaded too much in the afternoons. Currently I am leaning toward the citrus in the east.

I have not yet decided how to handle the roof vents. I am not sure how they will work with the subterranean heating/cooling system.


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RE: Two 6x8 HFGH and central shed idea -- Additional suggestions?

I like your design. Are the floors of the greenhouses going to be at the same level as the floor in the shed? Are you making any modifications to the short doors on the greenhouses? I figure you must be keeping doors on them since you want to be able to keep them at different temperatures.


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RE: Two 6x8 HFGH and central shed idea -- Additional suggestions?

Thanks, dekeoboe. Yes, the floors in the greenhouses are going to be at the same level as the floor in the shed. I will be modifying the greenhouse doors following steps shown in Building and Improving the Harbor Freight 6x8 Greenhouse.

Another reason to keep doors on the greenhouses is to help maintain the temperature inside the greenhouses when the door to the shed is opened. Small greenhouses often have problems maintaining a consistent temperature. The central shed can also function as an airlock.

The images in the previous posts do not show either the internal structure changes or the external structure I will be adding to support plants in the outside raised beds and shade cloth or plastic as needed in summer and winter.

This post was edited by Annalog on Sat, Mar 15, 14 at 7:30


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RE: Two 6x8 HFGH and central shed idea -- Additional suggestions?

Other links I have found helpful:
Building our Harbor Freight 10' x 12' Greenhouse by Mudhouse

Harbor Freight (6x8) Assembly Instructions by Conifers


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RE: Two 6x8 HFGH and central shed idea -- Additional suggestions?

That's going to be a nice setup!

I doubled the size of my garden and put my 6x8 up yesterday. I thought the assembly was pretty easy though time consuming. As another poster suggested I used aluminum tape to seal the panel edges but that was the only real mod. The door slides well and stays in place well if the frame is squared up good. We are going to build a small pergola to drink wine under just outside and raised beds with all kinds of stuff.


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RE: Two 6x8 HFGH and central shed idea -- Additional suggestions?

Our local Walmart currently has a metal rectangular grill gazebo for sale that is about 5'x8'. We will be using this as the framework for the central shed. The 8' sides would face the greenhouses with siding closing the open areas, one 5' side would face north and be covered with siding, while the other 5' side would have the door with a narrow panel of siding or polycarbonate on each side of the door. The roof is metal with a ridge vent. We will center the structure with just over half a foot sticking out on the south and north sides of the greenhouses. I will have less storage space but I think it will be sufficient since we have another shed nearby. This kit will need some modifications but should be easier and less expensive than building from scratch. The link below shows a similar gazebo carried by Sam's Club. The gazebo we purchased has single posts in the corners and single side shelves. We will not use the side shelves and will add additional framing for an exterior door in place of one shelf and a wall in place of the other. The open sides will also get walls with center openings for the greenhouse doors. The top vents will be screened with a way to adjust the airflow added.

Here is a link that might be useful: Similar, but fancier, gazebo

This post was edited by Annalog on Mon, May 5, 14 at 17:52


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RE: Two 6x8 HFGH and central shed idea -- Additional suggestions?

Hi,
I'm planning a similar project this summer. I have a 24 by 12 hoop house that I plan to put a 12 by 12 shed at one end, and then another 24 by 12 hoophouse; sandwiching the shed in the middle as you are doing. My question is do both hoophouses have to have end walls where they meet the shed; or can I use the shed walls to attach the film?
Any thoughts or ideas would be greatly appreciated.

Thanks,

Mike


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RE: Two 6x8 HFGH and central shed idea -- Additional suggestions?

Hi Mike,
I haven't built a hoop house and do not know if others following this thread have either. It may be better if you start a new thread with a title like "Two hoop houses with central shed question".

I suspect that the answer will be that it would be easiest if the end hoops next to the shed are attached to the shed and then the film is attached to those hoops. Then, if there is vertical space left between the hoop house ends and the shed, say if the hoop houses are taller than the shed, then that would either be film or solid depending on what is needed.
Anna


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RE: Two 6x8 HFGH and central shed idea -- Additional suggestions?

Hi Anna,

Thanks for the info. I am thinking that you are right, on both counts.

Mike


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