I am framing a greenhouse for an elder in my community and need some advice on effectively installing plate glass windows?

The size of the roof rafters is a direct function of the size of the structure and especially the expanse it needs to cover. In all cases I have never heard of 2x4s ever being used for rafters. Walls, yes; weight bearing elements (such as rafters), no.

The fact that glass is very heavy is a MAJOR issue to consider when choosing the size of rafters. Considering the devastating effect of a piece of glass from the ceiling falling on someone's head, you want to err on the side of caution, not saving money. At the very least I would suggest 2x10s or larger.

You are on the right track of using strips of wood on both sides of the glass to hold them in place. For the roof glass you will want to space rafters 16" on center and lay the glass across several of these to bear the weight. I strongly suggest you go down to the building department with some sketches of what you are doing and have a conversation with an inspector.

They are very knowledgeable. If you want the conversation to remain anonymous even though you are there in person, just tell him you're thinking about building a greenhouse structure in your back yard with materials someone gave you and what does he think? Also, the public library will be full of how-to books you can borrow for free.

Glass is wonderful, but it can be lethal. Do some good research. Build a safe structure.

Below are a couple of websites with information too. One last comment - check if the reclaimed glass is "tempered. " Don't think that just because it's "plate-glass" that it is tempered.

You have to find the tempered seal on the glass to know for sure. If it is not, do not use it...it's just not worth the risk.

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