Polytunnel Specs?

Welcome to the vine.
Tricky that one, it depends on your location and position of the tunnel and all sorts of stuff like that .

Have a play with this if you haven't already. It's how I worked out what I wanted on mine.

https://www.firsttunnels.co.uk/domes...ide-polytunnel

As you go through and select what you want it builds the tunnel so you can see what it's going to look like.

Hope that helps

I'd be inclined to put off the extra expenditure items and just get the stuff you need to start with - you can always buy the rest later, as and when you need it.

One thing you probably have already considered, but didn't mention is water. For myself I prefer to go with a large container outside the tunnel and a small tank connected to it inside, for dip filling watering cans. Depending on what you plan to do, it can be an advantage to put some pipework in the ground before you erect the tunnel. Obviously plants need a lot of water in the summer, particularly if you are growing fruit and veg, so you need an adequate supply.

Some things to consider (just been through this process, so still fresh in my mind)

Doors - for width of tunnel, expect single sliding door would be best unless you need to get "pallet" into tunnel. I didn't like idea of fighting "swing door(s)" in the wind. For the length of tunnel, expect a back door is also a good idea but you could just put mesh in place to reduce cost. Mesh and poly cover is a good starting point for ventilation.

Crop bars are fixed to all the internal hoops and will add approximatly 20% extra strength to both snow and wind load. Also handy for hanging or to tie plants to.

Ridge bars... Good for tying crops onto, but add very little to strength. Run alternate "bars" along crop bars to reduce cost?

Base rail or trench. Base rail every time ... so you can tension cover. Also turf over remainder of plastic to prevent wind getting under and lifting polytunnel away.

Perhaps put in a couple of wooden battens along one wall to give option of additional ventilation at a later date. Sandwich netting and plastic to give a cover you can roll up to give ventilation. I think vent along sheltered side (sill to do this myself - I'm is high wind area so not so keen) so that high wind can not get into tunnel.

Alignment - some pages advise long side to prevailing wind. Think is comes down to you site and what you can do to prevent wind getting into structure in the event of a storm.

All best.