View Full Version : Small Greenhouse Questions

Rich Riddle
04-19-2014, 6:34 AM
Have any of you built or know of a small greenhouse? What does one use to make the floor? Should it be concrete, gravel, wood, etc? I am looking for ideas and experiences for a small one and have an open mind to features. It's for she who must be obeyed.

Mark Bolton
04-19-2014, 7:37 AM
Ex wife and I ran a small nursery business for a couple years. Bedding plants, herbs, vegetables, and so on.

Concrete would be nice for thermal mass and ease of cleaning as long as up you allow for drainage (a lot of watering of course). Landscape fabric and pea gravel is common but hard if your going to be rolling in carts or potting soil and so on.

Ryan Mooney
04-19-2014, 11:07 AM
3/4" minus crush (watered and hand rolled) over landscape fabric worked well for me. Almost anything works though as long as you have drainage and can keep it from getting muddy where you need to stand. I just put the crush down on the walkway and left the rest dirt (I'm cheap). Boards can also work but you'd want to elevate them some or they'll rot out pretty quick.

Not a huge fan of pea gravel myself (except where nothing will be on it it looks ok) it rolls off of walkways, etc.. if you even walk on it.

Chris Walls
04-19-2014, 6:07 PM
My wife and I have a small green house 8 x 12' , we put down pea gravel in it when we built it. It has been good.

Rich Riddle
04-19-2014, 7:58 PM
I have seen some small greenhouses that look like they have a 6x6 framing the gravel inside. Wouldn't the 6x6 frame rot even if it was pressure treated wood?

Brian Deakin
04-20-2014, 5:52 AM
Two points

(1) What is the greenhouse construction if glass ,may need to consider taking care to have a level base that is stable ,reason if not constructed on a stable base frame of greenhouse could twist causing panes of glass to crack

(2) I would also suggest puchasing a greenhouse with the maximium width This will give greater growing space as less space is lost for standing area

(3) The following link may be useful for information on preparing a base ( the site is a Uk site but the use of curb stones may be a solution)

(4) See http://www.youtube.com/watch?v=NpLaXgu49XM http://www.youtube.com/watch?v=ITKOiFOLnu0 http://www.youtube.com/watch?v=vkIzODpmjxk http://www.youtube.com/watch?v=JKPSQrohslY

a Uk product but you may be able to find a similar product in the US.

(5) The best greenhouses money can buy www.hartley-botanic.co.uk

Please note this is uk based advise but may be a starting point when considering options

regards Brian

Michael Mahan
04-20-2014, 11:29 AM
concrete ,
anything that touches the ground make sure it's concrete that touches 1st , even if you have to just set the structure on pavers , cement piers , cinder block .
even PT lumber will wick water up & soon rot , remember it's a greenhouse as there will always be water .
as for the floor crushed rock as in the underlayment used for roads (it's blend of all different sized rock that is angled with the fines even ) works best as it compacts great & lets water drain thru . It's cheap compared to pea cravel OR any other rock as it's only processed once (the crushing )
Don't use PT wood for the anywhere but the bottom frame area , the salts & chemicals from PT kills plants or at least retards growth . If your growing vegetables to be eaten then no PT at all as It travels into the plants even minute traces are not good for anyone .
It;s best to lay down the rock pad before you build size the pad to be 1 foot on all sides larger that the G/H footprint .
IF you want a hard floor look at placing down large pavers in the aisles

Dave Lehnert
04-21-2014, 11:49 PM
I ran a retail garden center for years. We used a commercial sized green house from this company. They are the greenhouses you see pop up in parking lots in the spring. I can't tell you how many times I have built them over the years.
Anyway, they make home owners models. Parts were always easy to get if needed.


Charles Wiggins
04-22-2014, 8:54 AM
We have friends who have a small farm and are starting to do flowers. They recently build a greenhouse that is probably about 12' x 16'. The floor is bare ground.

Stephen Musial
04-22-2014, 9:22 AM
Is it attached to the house or free standing? If attached to the house, you may want to consider concrete. That way if she ever decides she doesn't want/need the greenhouse anymore, you can easily turn it into a sunroom.

Rich Riddle
04-22-2014, 9:42 AM

Thank you for all the information you have shared. You provided much better insights than the book we ordered.


Thank you for the link to those videos. They are in the UK and prove difficult to find online, but I could easily make molds for the concrete piers on which the rest of the "deck" rests. The metal pieces look easily replicated if needed.


Those look like very nice structures. I will write off to get some literature on them. Any ideas on the costs for one?

Ryan Mooney
04-22-2014, 4:39 PM

Thank you for all the information you have shared. You provided much better insights than the book we ordered.


Thank you for the link to those videos. They are in the UK and prove difficult to find online, but I could easily make molds for the concrete piers on which the rest of the "deck" rests. The metal pieces look easily replicated if needed.

Are what I used when I put in the foundation for my last greenhouse (available from basically any hardware store around here - would be surprised if you can't find similar locally?).
There are a handful of different designs: http://www.strongtie.com/products/connectors/EPB.asp?source=capsbscat# and more http://www.strongtie.com/products/categories/caps-bases.html# under "cast in place post bases".

Since it was small (8x10) I cheated a bit on the layout and basically built a pressure treated 4x4 frame with half lap corners and pre-attached the post-bases to the frame (two per side just offset from the corner a smidge) using a bolt through each. I then dug 4 holes around where the post bases would sit and leveled the pre-built frame with the post-bases hanging into the holes. Poured the concrete (bag and a half of quikcrete each) into the holes and let it set around the bolts and the whole foundation is now leveled, in place and ready for the greenhouse to go on top. Obviously this wouldn't work as well for a larger setup :D I didn't bother making molds for the concrete since I wanted it set into the ground a bit (around 2') to avoid frost heaves (that was deep enough where I was) and to help resist the wind load (we had 70mph+ wind gusts somewhat frequently at that house) and just covered them over with gravel when I was done. Looked fine.

Side note on the wind load: make sure you lay out the greenhouse with the vents on the normal downwind or sheltered side otherwise they can be ripped loose and sent flying over the barn.. Sometimes the obvious things are only obvious to me later :o

Mark Bolton
04-22-2014, 5:44 PM
I think some things you can consider to narrow or focus your plan is first what are the winds like in your area and second are you looking for somewhat of a permanent "pretty" greenhouse or are you looking for more of a high tunnel that will function well but in a few years if it fizzles out its no big deal.

Beyond that the decision becomes how long do you want to extend your growing season?

The first two considerations somewhat dictate whether or not you can even have a high tunnel style (greenhouse film over bows for instance) due to wind or if you and your wife would even be happy looking at a house like that.

The growing season issue pertains directly to insulating value and a heat source.

A simple high tunnel covered with greenhouse film will only extend your season slightly with some minimal internal heat source (perhaps a month or so). The next step up is the same style high tunnel/hoop house but with a double layer of film and an inflator which fills the space between the two layers of film with air acting as a large insulating blanket. The third (pretty option) is poly carbonate panels which are insulating but expensive however they look nice.

The thing to consider with extending the season is a single layer greenhouse will loose its internal heat within minutes. So even if its beautiful in the day, within 30 minutes the house is cold inside and if it frosts/freezes your tender plants inside wont make it through a single night. Hence the need for heat and hence the need for better insulation the longer you want to extend your season. If your climate gets very cold in the winter, and you want to walk out in the dead of winter into a beautiful oasis of plants, youd better get a head source, the best insulating shell you can, and cash.

We had a single layer house that was small by greenhouse comparison. About 24x30. Heated with wood. There was nothing better than going down there in February with snow on the ground and walking in to a bunch of plants popping out of the flats. That said it was a major job to heat and Im glad I didnt have to pay a fuel bill with cash. We would turn about 1200 flats a season. The woodstove was (still in there) 36" diameter and 5' tall. You could load 14" diameter chunks into it.

Im guessing your looking at a small house for your wife to enjoy but that said, its best to quantify the growing season to get started in my opinion. You could put up a small hoop house for a couple hundred bucks and try it for a year or two and if she loves it then build a serious house. Youd be able to carry many of the components over (vents, actuators, fans, tables, and the like). We always shopped around for the best price on 4 year film with a dew control and it was always inexpensive.

It was a ton of fun but I dont know that I would even bother trying it without some form of a heat source. Attached to a south facing side of the house would be really nice and you'd be close to power, water, and even perhaps heat from the home and back into the home in winter. I cant say how cool it is to sit and have coffee in there in the winter. I really enjoyed it but I dont miss the work.


Rich Riddle
04-22-2014, 6:47 PM
It will situate in an area with high winds and be a free-standing unit quite a distance from the house. Right now the winds are blowing about 25 mph. It needs to look "pretty" and quaint for the owner to be happy. Three seasons is all that's expected from the greenhouse. It will have one electrical line and water that can be turned off in the winter. The electrical can offer the heat source or a little stove would work. There's almost and endless supply of wood if it was a wood stove. The north side will have a little deck for a couple of chairs. It's more-or-less going to serve as a woman cave even though I cannot imagine why she would want to get away from me.

Michael Mahan
04-22-2014, 7:07 PM
I used double wall polycarbonate for the roof when I built mine with a upside down Tee shape concrete type house foundation , it's built off the south wall of the house 32' x 22' 2 x 10 redwood rafters with 2 x 6 fir stud walls , recycled safety glass patio door dbl panes for the walls ( I stripped out the frames ) , you can get the 'Old' doors free if you ask at the glass companies as they trash them , the doors I made with skinnier used dbl panes . One set of framed dbl doors I got at the Borg

Dave Lehnert
04-22-2014, 8:39 PM
If you click on the individual links you will see a tab for pricing. For example. http://www.poly-tex.com/snap_grow6series.html#.U1cLo6LSCF8


Thank you for all the information you have shared. You provided much better insights than the book we ordered.


Thank you for the link to those videos. They are in the UK and prove difficult to find online, but I could easily make molds for the concrete piers on which the rest of the "deck" rests. The metal pieces look easily replicated if needed.


Those look like very nice structures. I will write off to get some literature on them. Any ideas on the costs for one?

Brian Deakin
04-23-2014, 4:42 PM
Dear Rich ,
Please see links below ( you may need to copy and paste the web sites )

www.hartley (http://www.<strong>hartley</strong>)-botanic.co.uk/‎

best greenhouses money can buy

www.altongreenhouses (http://www.<strong>altongreenhouses</strong>).co.uk/

‎ best ceder greenhouses money can buy


useful for ideas eg design of raized beds


best mini lean to greenhouses and cold frames

http://www.vegetable-gardening-with-lorraine.com/homemade-compost-bin.html the best home made compost bin I have seen (a US site)




The best home made cloche I have seen using water pipe (please note I cut pieces of rectangular wood the same diameter as the water pipe and chamfer the edges I then insert these pieces of wood into the ends of the water pipe and the ground
I did not use the cross members but simply placed 4 pieces of water pipe one yard apart and covered with netting to keep birds off the same principle could used with polythene

Please note the products listed above may not be avaiable in the US but the design and construction principles remain the same Further information could be used as a starting point for designing and building your own structure

regards Brian