Designing a greenhouse 1

[CCox]

Has anyone designed a large greenhouse? I am looking at designing a 50'x96' one. I would like to get some feedback from someone that has designed one before.

Thanks,

CJC

 

[IFRs]

If you want a dome style, there are lots of DIY books out there, or you could contact Growing Spaces in Colorado...

 

[SteelPE]

Why wouldn't your client just buy a greenhouse kit from a Mfr? There are plenty of them out there..... and I'm not sure I would want to design these systems as they have light structural member running everywhere.

 

[CCox]

Client is required to purchase an engineered design per the local jurisdiction. According to client, the greenhouse kit company wants to charge $25k for the stamped set. I am going to look into other companies for the client, but I also wanted to know if anyone else has designed one of these. I figure it would have to be steel moment frames and glass/polycarbonate cladding sheets. The client wants a traditional greenhouse with side walls and pitched roof.

 

[IFRs]

Too bad - the domes are sweet to look at and very strong. Most of the chicken coop rectangular sloped roofed ones I have seen utilize specialized and custom extrusions or shapes to deal with the expansion / contraction and corrosive issues in combination with the sealing and ease of replacing glazing. I would not want to reinvent the wheel for $25k.

 

[TopKnot]

I live in big heavy snow country, and our greenhouse put a few pre-manufactured greehouses that look really really weak. But the heat keeps the snow sliding and he's never had an issue. I'd never stamp it. But it works just fine.

_________________________
TKE

 

[SteelPE]

Something is fishy.... 25k to stamp their drawings? They don't have anyone that can do it for them who works for them? These things must be engineered by someone. My parents have 3 hoop greenhouses.... The oldest being 30 years old. Never had a problem with snow as long as you take care of them.

 

[TopKnot]

More likely there is $25K to upgrade the structure so that an engineer can stamp it.

_________________________
TKE

 

[Archie264]

>>>These things must be engineered by someone.<<<

Not necessarily...

 

[CCox]

I thought the same thing. They are horribly underengineered. I did some sleuthing online. There are companies that specialize in greenhouse engineering. One is Rough Brothers. Their designs are much stouter than the light tin ones I have seen. They actually use steel trusses and purlins. I don't have a problem designing/stamping a set of drawings as long as I do the design.

 

[BS2]

I work as a structural consultant for a greenhouse company who produces code approved greenhouses. In fact, I finished a 50' wide system a few weeks ago. The framing system consists of steel trusses, purlins, and girts. I can tell you that the structure we design follows the code to the letter - no more, no less. I can also tell you that not every greenhouse produced follows the code because many of them are rural and do not have a building code adopted.

Greenhouse systems are highly specialized with a tight profit margin. Every member is optimized to be exactly the size that it needs to be. Because of this, I suspect that a custom greenhouse will be even more costly. Additionally, TopKnot is probably correct - the 25k is to upgrade components of the greenhouse to be code compliant.

 

[msquared48]

I have never designed a large greenhouse, and probably never will, but I painted my little Fred Meyer greenhouse red.

Mike McCann
MMC Engineering

 

[Archie264]

Schwandon,

Thanks for the info.

 

[CCox]

I figured out what the additional cost was: He wanted to take several separate greenhouses and combine them into one. This would obviously drive up the cost.

Schwandon,

Thanks for your help. What is the MWFRS in a greenhouse? I am guessing that cables or x-bracing is used for the lateral bracing. Could you elaborate?

Thanks,

Cody

 

[BS2]

In the transverse direction, the MWFRS consists of cantilevered columns and knee braces. In the longitudinal direction, the MWFRS consists of x-bracing (although the columns are cantilevered in that direction also).

 

[CCox]

Schwandon,

I found a structural design manual online for greenhouses. It is put out by NGMA. I am sure you have seen it. Pretty generic, but an attempt to codify these things.

Cody

 

[BS2]

Actually, I have not seen that design manual. We simply design them like we would design any other building. We run all of the loads, taking advantage of every code nuance, and then apply the loading to a RISA model. The structural analysis is really not complicated; the complication is putting together an efficient, economical solution. Much of the design boils down to using (or working around) greenhouse specific items (vents, gutters, purlins, etc) to perform structural purposes, thereby producing a comprehensive system.

I hope that helps.