Wood framed greenhouse

Hey everyone!

I’m looking for ideas and inspiration to build a wood framed greenhouse. I’ve been planning to build a metal framed one, but recently came into just about as many free 2x8s as I want, many of them 8 feet long. I know 2x8s are a bit over kill but since they are free, I might as well use them. Plus there can be quite a bit of snow out here so maybe the extra strength will be a good thing. I already have a pile of at least 40 boards and today going to go load up the trailer again. Hoping this will save me money overall, I’ll still have to buy treated lumber for foundation but shouldn’t need much other material for the frame.
Any idea how long this might last? The lumber will be covered by the plastic, could I expect at least 5 years?

I would think that as long as you have it adequately covered, you'll get more than 5 years out of untreated lumber in this situation, but maybe it depends on your particular climate.

You could look into other methods to treat the wood - such as burning/charring.

I built a 12' long x 10' wide gambrel roof greenhouse last year using 2x4's, covered with home construction 6 mil vapor barrier. There are better materials I am sure, however it's what I had on hand.

You could rip the 2x8's down the centre to double your lumber...

search "gambrel greenhouse" and you'll find a popular common design that I mostly used.

So far the plastic is holding up to our heavy snow loads (I go and  knock it off when I can).

Greenhouses usually get a decent amount of humidity in them, I would be concerned with the lumber rotting. Where the plastic lays on the lumber might hold moisture also.

You could treat the lumber with a protective finish, that might help the life span. Personally I would use the 2x8s to build other stuff.

Thanks all for the replies...

I might add that the greenhouse I’m trying to build, is fairly large. I’m aiming for at least 15x25, we will see how big I end up settling on.
Ripping the 2x8s wouldn’t be a bad idea, as long as I could borrow the neighbors shop as I don’t have a table saw unfortunately. I’ve also thought about offering them up for trade, see if anyone in the community has some more favorable building materials.

I initially planned on using these for different projects, but I really don’t have many projects. I’m going to build a cold storage but have plenty for that. Only thing I really need built is a garden shed but I feel like the 2x8s would take up a lot more of the floor space than I’d like as the garden shed doesn’t need to be very big. Regardless, I could probably have enough for all the projects. I have a pretty much unlimited supply of this lumber. It’s lightly used I just have to tap some nails out. It’s used once as part of a brace to ship things from California to WA. Brace is taken apart once it gets here and the lumber is free for the taking. I won’t divulge any further info as I’d hate to lose my gold mine 😹

Also, I’m in a very dry area. We average I think 18” of rain each year, all of it being in the fall/winter. So hopefully I could make it last.

I once ran into a gentleman who was saving bubble wrap. His goal as to build an insulated high tunnel.  I have no idea if ever was successful.

A 2x8 will cast a not insignificant amount of shadow.
That would be my hesitation to building a  greenhouse with it.
With an unlimited supply, trading or selling would be a great way to go.
I'm a pretty aggressive lumber scavenger, but I would still pay out of pocket for long peices of 2x8.

If you are handy, selling completed items or site built structures could get you even more.
Price your materials as if they were new, and your labor as you're fit, and you will come out well ahead.

In particular you could offer to build and fill raised beds.
Painting the insides of the beds with a masonry waterproof sealer has been reported to have great results.
All of this could pay for whatever kind of greenhouse materials you want,but it presumes you have time and willingness to spare.

What would you like to build with?

William Bronson wrote:A 2x8 will cast a not insignificant amount of shadow.
That would be my hesitation to building a  greenhouse with it.
With an unlimited supply, trading or selling would be a great way to go.
I'm a pretty aggressive lumber scavenger, but I would still pay out of pocket for long peices of 2x8.

If you are handy, selling completed items or site built structures could get you even more.
Price your materials as if they were new, and your labor as you're fit, and you will come out well ahead.

In particular you could offer to build and fill raised beds.
Painting the insides of the beds with a masonry waterproof sealer has been reported to have great results.
All of this could pay for whatever kind of greenhouse materials you want,but it presumes you have time and willingness to spare.

What would you like to build with?

I didn’t even think about that. The shadows would be huge, I think I’ll ditch the greenhouse idea. I could probably use some of it for framing the lower section but I’ll stick with pipe for the top.
However, you did give me a great idea. I was planning on building myself a few planters, but perhaps I could sell some as well. Not to mention the trade value these have, maybe I could trade for some greenhouse supplies or at least sell my way to having enough. I counted up my boards today and have over 100. Some 5’, most 8’, and some 14’. I figure I have around $1000 in lumber, and I told the guy I’ll come back with an empty trailer to fill up. The last few loads I only take about 30-40 boards because I also get a straw bale that takes up most of space. I haven’t taken many but there are a lot of 4’ boards that would make great 4x4 beds.

just a couple thoughts. maybe brushing on some spar varnish would help preserve the 2x8's in moist environment and most likely in the long hot summer it will get real hot and dry in there and dry out any moisture that soaked into the wood during moist season.

I say go for it build greenhouse with supplies you have. bedding plants and flowers in the spring could be great source of extra income, might be possible to make enough to get more permanent type greenhouse building supplies.
if nothing else you can extend your growing season and have a whole new adventure in gardening just for your pleasure, enjoyment and enrichment.

i bought a hoop bender and i still plant to make a pit greenhouse with double layer hoops (two hoops one a foot away from the other)

for my 4 season greenhouse i plan on going with wood since it transmits less cold

i see a tiny greenhouse on my drive up north which has wood gothic arches
they seem to be 3 layers of board cut and attached together to make the arch shape
(at least thats what i figure as i drive by at 50 km/hr)

About the humidity in the greenhouse, it doesn't really come from the outside climate, it comes from condensation inside the greenhouse. The larger the difference beteen your indoor temperatures and outdoor, the more condensation you'll get. On a morning after a very cold night outside, my greenhouse will have a thick layer of frost inside the glazing, and as the sun comes out it trickles down and/or drips off as indoor rain. The frame likely gets wet every night to morning with condensation.

Ashton Soete wrote:

William Bronson wrote:A 2x8 will cast a not insignificant amount of shadow.
That would be my hesitation to building a  greenhouse with it.

I didn’t even think about that. The shadows would be huge, I think I’ll ditch the greenhouse idea.  

I sure would love to find a trove of such lumber...! It seems you're coming up with a good plan that involves finding another material for the bulk of the greenhouse.

However, I wonder what painting all of the inside lumber with a reflective white paint would do for the light situation? I suspect having thinner framing (i.e. pipe) would be the best for passing light through to the plants/heat store, but what would increasing the albedo of the framing do? Anyone have insight here?

Making gothic arch ribs could stretch the amount of lumber you have, but that would require quite some time at a table saw.