Building an Attached Greenhouse: How to Connect Your Greenhouse to an Existing Structure

Building an Attached Greenhouse: How to Connect Your Greenhouse to an Existing Structure

When building a greenhouse or high tunnel, a common question is whether the greenhouse can be attached to an existing building, such as a house, shed, barn or storefront. There are a wide range of approaches that can be used for connecting a greenhouse to a building, but your success in doing so will depend upon a few key factors. If you are thinking about building an attached greenhouse, here are some key questions to consider.

Do either of the structures have the potential to move?

If your building and greenhouse are going to be tied together, they need to both be structurally sound. Our recommendation would be to first ensure both the greenhouse and the building are independently stable and structurally sound, and then flash them together to make the connected unit water- and air-tight. That way, neither building is dependent on the other for structural integrity.

Where are you going to make the connection?

In Rimol’s experience, we find it easier to connect the gable end of a greenhouse to a building, rather than trying to build half of a greenhouse onto to a building. 

In other words, more like this:

And less like this:

Another key factor to think about when designing the connection is snow drifting. Will the roof slope of the building dump snow onto the greenhouse? Most of the time, you will need to ensure the greenhouse is built to withstand the increased load of possible drifting or sliding snow. Strengthen the greenhouse in the area that connects the building, which can be done with an extra bow, narrower bow spacing or extra bracing.

What materials will you use to make the connection?

The right materials must be used to connect the greenhouse and the building securely, and to ensure the greenhouse remains water- and air-tight. For poly-covered structures, consider using a polycarbonate section next to the building so you have room to work when attaching the roof poly.

Then, flash the greenhouse to the building structure to create an airtight seal. This can be as simple as using metal flashing connected to both structures. You can also consider using expandable flashing to account for small movements in the structures.

Finally, if you have a humid greenhouse connected to a building that does not need humidity, such as a home or retail center, consider adding a vapor barrier at the connection. This will prevent the high humidity of the greenhouse from affecting the other building, which is especially important with wood structures.