Cedar verses Cypress Construction

I'm doing research for 24 x 48 greenhouse construction material. It is quite large so I have posts, beams and rafters that need to be rot resistant and strong. I've researched White Oak $$$ (local), Cypress $$ + shipping, and Cedar (local). The cost for Cypress with shipping is about equal to Cedar purchased locally. I've read that Cypress is stronger then Cedar so it seems like an obvious choice. Does anyone have any experience to add to this topic?

Thank you,
Jason

Cedar would be more environmentally friendly. There used to be great swathes of cypress forest across the south -- until they were cut down to make, as you say, great posts, beams, and rafters that are rot resistant and strong. Cypress is being planted to replace the old growth that was cut down, and there is some sustainable production, but on the whole it needs more protection and less marketing. You could do your part by buying local cedar. As far as rot resistance, cedar may have a little more than cypress.

I appreciate what you are saying John, but Cedar doesn't seem to have the same strength of Cypress. I'll try to use Cedar for my none supportive members and use Cypress sparingly. The whole concept of a greenhouse is to be environment friendly.

I used cedar for the studs and top and bottom plates in my greenhouse. The roof trusses are standard fir. Eight years on, the fir trusses are in good shape, they look like they will easily outlast the triple wall polycarbonate used to sheath the greenhouse.

Cedar isnt the strongest lumber, but a greenhouse doesnt have that significant of structural loading demands. Snow sheds pretty rapidly and never builds up. So cedar should have more than enough strength for the job.

I think it would be better to use building design rather than rare lumber to meet your building needs. Building with lots of small structural members is preferable because it gives you smaller spans for your sheathing material, which will greatly contribute to the durability of the greenhouse. More attachment points for your sheathing reduces wear and tear from wind and thermal expansion.

Thank you Adam. When you say you used standard Fir, is that the treated or untreated lumber at the home depot or does that have to be special ordered just like cedar and cypress? My greenhouse is a being built as a solar year around 1000 sq ft Aquaponics greenhouse. 24 x 48 with a standard roof on the north for insulation and partial shading in the summer for the fish. This roof is going to cost more then a house of similar size so I really want it to last 50 years.

standard fir like you get from the luberyard, untreated.

for cost considerations, I went with prefab roofing trusses. my greenhouse is 24x38, and the entire structure of the roof (not including the sheathing), was about $2k. my roof is a hipped gable. I dont know about the thermal value of insulating part of the roof? With the way heat rises, I think you would just lose your heat out of the poly section. Path of least resistance. I highly reccomend the triple wall polycarbonate. It is the most insulative transparent material you can use, and it is very easy to build with. I used 6x24 sheets, and then cut them to size to fit the roof trusses. The entire structure, from concrete footing to polycarb sheeting, came in under $15k. I did all the labor and that was 8 years ago, but gives you some idea.

hope that helps

Since you have stated that it will be used for aquaponics, I would say to stay away from either pine/fir.
The added humidity of an aquaponics set up makes me think that either cedar or cypress would be a better choice.

The original doors to St. Paul's Cathedral in Rome are made from cypress.
Cypress has also been found (intact) within Egyptian pyramids.
It should easily last a lifetime.

John - thank you for your thoughts on the matter. The humidity, water, year around use and longevity is all something to keep in mind. Plus it is more humid here in WV then in CO already.

Adam - Thank you for your ideas, I would love to see your greenhouse. Do you have pictures posted anywhere? You have a lot more experience then I do but here is my design considerations. A lot of solar greenhouses I've seen have an insulated north wall and/or roof with the south glazed. The less sq ft of glazing you have the less heat you will loose, heat won't transfer out of the south wall faster just because you have the north wall insulated. My north wall is solid concrete to 9', insulated and back-filled into a hillside while my south wall is only 4' tall. This makes my south roof with a 12/12 pitch 18.5' from ridge to gutter. From Nov through April, the sun will hit the south roof very close to a 70 - 90 deg angle with a glazing profile close to the width of my greenhouse, the north roof will never see the sun in the middle of winter which is why I'm insulating it. In the middle of summer when the sun here is almost straight overhead, the profile from a satellite view straight down will be 12 foot of glazing and 12 foot of shade, plus the sun would be shining down at a 30 to 50 deg angle. I plan to use Solexx as my glazing which defuses light so the greenhouse won't actually have shade, but at noon on a hot day, the solar profile will be the same as a completely glazed roof with 50% shade cloth. A lot of my design is theoretical at this point. I attached some pictures.

well thought out Jason. Looks like you have a good start with your concrete work too. I dont have any pics, typing words is about the limit of my tech savy at this point. I agree that with your increased humidity in WV, plus the aquaponics, rot resistance should be a key feature. I think your plans and theory are really solid, and I look forward to seeing the massive abundance you are able to create in this greenhouse. Good job!

Thank you Adam. Should I start a build thread?

Should I start a build thread?

I think that would be great.

Watching a hands on project is a great learning tool. I think many could benefit from it.

An update for anyone coming across this thread. I would not recommend Cypress. I'm not sure why, but it seems brittle to me. When you cut off a small piece it will dry out considerably and you can snap it into little pieces. I hope my beams and rafters don't have issues down the road. I think I might have gone with a pine structure and then painted the heck out of it. But atlas, we'll see.

Some of the best species of wood for greenhouses are hard to work with. Don't get down on the cypress because it's brittle, it's definitely the a great choice. I took a class from a guy that refurbishes old glass greenhouses, he RAVED about cypress. He said he has unearthed cypress from greenhouses over 100 years old and once he refinished it the piece was absolutely pristine. This was old growth cypress, but cypress is still a great specie to use for greenhouses when reasonably available.

Black Locust is similar in that it is super rot-resistant but also a real pain to work with. It's almost like cutting stone with wood tools.

Painted pine works but wouldn't last half as long as either a cypress or locust frame. To be honest I'm not even sure painting helps that much, in Austria this August I learned that paints for wood only add 3% to the life of the wood. Managing moisture for the frame is much more important than if it's painted or not.

Zach,

Thank you for a vote of confidence. This is the first time I've done any building project like this so I'm nervous. Seeing the brittleness I just get scared the whole thing is going to topple in a good storm.

I like your idea for leaving it unpainted. What do you think about some tung oil down the road?

I also have a few spots where the wood looks rotten or that it was rotten at one time or had bugs at one time. Soft spots with pits in it. We tried to weed it all out, but my helpers put up a 2x12 beam with a rough spot. How should I treat that?

Best Regards,
Jason

P.S. All wood was rough cut green when I got it. You can see a little dark patch in the 2x12 on the top picture. That area is soft. I could dig it out with a claw hammer if I so desired. Not sure what causes those.

Jason,

3 years later, I still find your pictures and posts informative, as I am now building my own from an existing block structure, but very similar to yours.  Do you have additional pictures and recommendations or items you wish you would've done?

My "north wall roof" actually faces a bit north-west.  Would you still consider insulating that roof, or do you think it would be a good idea for 16mm polycarbonate?

Thanks!!

Lucas