Making a underground cellar - any advice?

Evening all,

Due to lack of space at my home (I live with my grandparents and parents) I currently have no space to store any surplus produce I grow (until I get my shed that is).

So I was thinking of making several underground cellars for extra produce (in addition to storing items which are not safe to be left in site/in the shed such as fuel for the camping cooker).

The locations would include underneath my future shed in addition to within the polytunnel (between the raised beds so that you walk over it - see picture).

The area is 50cm wide by around 4 metres long.

The additional soil would come in great use for filling the raised beds as well.

I was just wondering if anyone had any advice on this?

Many thanks,

Samuel

I just had a thought of having a pump to utilise any water that collects within this space?

Google "barrel root cellar" and you will find examples. Keeping it dry enough could be a problem. Keeping it from getting too warm in the polytunnel could be a problem, you may need to put some insulation on top.

I think the polytunnel is too hot and wet for food conservation. Any roots stored there would tend to sprout. Do you have basement? A room that gets no heating? A crawl space under the house? You should check those.

Cheers,
Lucía