Back of the bench/bell. Material clearance

I have built a stone batch box heater in my kitchen, should I be putting anything between the bell/bench and the existing plasterboard wall, for example fire blanket or insulation. I certainly should have sorted this before building as it would've been much easier but such is life. Thanks for any help or suggestions
Martin

Hi Martin,  Welcome to Permies!
What is the distance between your bell/bench and the plasterboard wall? Depending on the gap and how much you burn your stove continuously will play a factor in whether you need to do anything further about it.
Often, a small air gap of 2" is enough but monitoring the wall temperature with a thermometer or even your hand will let you know for sure.
Would like to see pictures of your creation if you don't mind.

Hi Martin;
Well yes, it might have been easier before you built.
But it is so exciting to see your first RMH growing before your eyes that it is easy for details to slip past you.

How close to the wall is your bell?
Do you have a laser temperature gun?
Generally, bells are not screaming hot although above the riser they sure can get warm.
Can you put your hand on the wall (if you can reach in ) and see how hot it feels?
If it feels too warm then you have options.  The most popular is a piece of sheet metal with 1" spacers .
A ceramic blanket can be hung in the back.
A fire blanket is asbestos and not an insulator so it would not be a suitable choice.
Even fiberglass insulation might be enough.

Laser temp guns are fairly inexpensive, it might be a good investment for you to monitor things.

Thanks for your replies, I am a joiner and was over confident in my ability when I came to masonry I must say but it's getting there. Made some mistakes along the way but luckily everything is in a position that can be altered. I can remove the plasterboard. I need to do this anyway as I found a few smoke leaks at the back during a smoke test which I am hoping the lime plaster/cob will solve. Once I've removed the plasterboard and plastered I will attempted to stuff some insulation down the gap. It's around 2 inches. My thoughts were that radiators can get very hot and are very close to walls. My flue is going out the wall currently, no vertical section fitted yet and it is not drawing well. Getting intermittent smoke backs. Hoping the vertical flue will solve this issue. Scotland is windy! Thanks again

Hi Martin, that is an nice looking heater, the door size looks a bit unusual, did you build your batch box to Peters spec?
Where is the chimney?

The door and thus the burn chamber were due to compromise, it was the only door I could get hold of at the time, not an ideal situation but have allowed enough space to the lintel incase I need to change it. Burn chamber is turned on its side to facilitate the door shape. I am aware this might not work and may need changing sadly. Chimney is to the right of the bench. Twin wall flue runs out horizontally from the end of the bench then makes a 90 degree to vertical.

Have you had it running full bore, does it work OK?

Not yet just a few bits of kindling. The wind blowing across the horizontal opening was blowing air back down the bench intermittently. My 90 degree and vertical section of flue arriving this week. Hopefully running at full chap will help it draw also. Playing with cutting a small hole towards the end of the bench for pre warming the flue