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I have built 3 observatories now.
Wall height of 2.1 metres sounds fine. My latest is 2.3 and that works for it. My country one is 2.2 metres.
Wind protection is probably more important with a country area observatory and if you are using long focal length.
You won't be able to image at all if your gear is wind affected so you don't want the top of your OTA sticking into the windstream above the walls. You can get away with that with a refractor and a decent mount but not a mirrored compound long focal length scope.
My current observatory has 2 pads. One is a pier about 1 metre deep and 850mm square with a fair bit of steel reo in it.
It is isolated from the main floor (I used pavers on top of road base and base sand, easy to lay, no transmission of vibrations.
I have a 2nd slab for a pier mounted setup.
The first pier has a Sirius Optics pier which is really solid and really well built. It is about 1.2 metres high and 6mm wall steel with reinforcing and a mounting plate on top with stainless steel rod and nuts to adjust and level the top plate. It was drilled for a Paramount ME.
I drilled anchor bolts into the pier and fixed it with about 6 or 8 large anchor bolts. No flex and solid for a Planewave CDK17 which weighs about 60kg with camera etc.
I suggest also using Aircell Insulbreak insulation which is put on under the roof and the walls. Even during recent 40 degree C days inside the observatory was never super hot and certainly no hotter than outside. It seemed a tad cooler.
I haven't taped the insulation sheet together which would make it even more effective although it is overlapped quite heavily. This will protect your gear from the extremes of heat in summer and also reduce heat plumes coming off the slab at night. Perhaps pavers cool off faster in that regard as they have smaller mass.
I also made a little side room with a bench for the computers etc. I have a heater and a fan for my comfort and it probably does not affect the scope.
Most imaging is the east to the west through the zenith and some to the south. Very little is in the north (Pleiades, Dumbbell and thats about it). The rest are too low to image properly. So consider your line of sight to these areas.
My pier ended up being a tad higher than I expected with the Paramount and the Planewave CDK17. In hindsight I would have made it a tad lower.
My country dark site observatory often gets strong winds so not sure what your site is like but country areas seem to get more winds than city areas so keep that well in mind when designing it. Don't make the walls too low.
Drainage. Make sure the resulting slab/floor is about 75mm or more higher than the outside ground. My country one isn't particularly and the edges get wet when it rains heavily. Dig a trench around the outside of the observatory and fill it with crushed rock for drainage. Make sure the
floor is considerably higher.
Insect control. I would recommend vermin guard to the floor of the slab and silicone the ends of the cladding sheets to it to discourage insects making nests. My country property observatory is a haven for spiders. Last year it was heaps of redbacks. This year it was heaps of mouse spiders. Big fat ones. If you live there I suppose you can spray regularly.
A roll off roof implies an air gap at the top so there is some access for insects to get in but a lot like to go on ground.
Greg.
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