Can I Lower My Greenhouse Base for More Headroom?

I recently did something similar because of our sloped garden. It’s a bit of work, but it’s worth it! It ends up being a lot like a walipini greenhouse once you get everything set up. Just plan ahead for the labor involved!

You can definitely sink it! Just remember to place something at the door's sill to remind yourself of the drop—I've tripped out of my stepdad's greenhouse so many times because the floor is lower than the door. It can be a surprise!

Definitely consider the effort involved in digging out the soil. I preferred going for foundations using hardcore in shallow trenches and stacking oak sleepers for a rustic look and extra headroom. They look nice as they weather, and you can easily move them around if you ever change your mind. Breezeblocks are cheaper, but sleepers give you a great aesthetic and versatility.

I’m in the same boat with a polycrub! My main concern is drainage, especially if you’re close to the water table. Luckily for me, I’m on an alluvial plain, so it drains pretty well even at depth. It’s cool to learn that the Victorians did this too—check out sunken greenhouses in stately homes, they're pretty amazing. You might want to look into 'walipini' greenhouses—those seem like an interesting option!

I built a sunken brick wall for my greenhouse and it’s been great for head height! I used slabs on the floor but left drains on either side of the path for water runoff. You could also install a drainage channel to manage excess water if needed!