Holes in ceilings - chimney, vent, light etc.

I have read old thread on having a hole drilled for a chimney etc, but wanted more information.

• How much has this costed people more recently?
  
• Do you need a permit for this kind of work?
  
• What is the maximum diameter hole people have had drilled?
  
• Do people use these holes for skylights/suntubes/suntunnels? and if so, how successful have these been to get and fit, and in lighting your cave?
  
• How much sound resonated in and out of your cave via ventilation like this? We have huskies and they make "wooing" noises quite often while talking to us and eachother. this could sound quite spooky to passers by hahahaha.
  

You have hit on one there!

When I was renovating my last cave in 2009/2010 I wanted a wood burner in the Sitting Room, at the back of the cave.

The Town Hall in Galera refused me permission.

It turns out that a grandfather and his son had been doing very similar in a cave in Freila and it collapsed and killed them both.  At that time all drilling down, or digging up out of caves was stopped.  I don't know if it still applies today, or if it was just then.

Roofs of caves are obviously very important.  If you did get permission, because your roof was shallow enough for you to drill down, or dig up, then you are still at risk of cracking the layer of rock proctecting water ingress into the cave.

Caves are not generally one lump of solid rock, but made up of hard and softer layers, with layers of rock in between.

It is a very tricky one.

Some caves already had chimneys dug out from below or places that were naturally thin and light tubes/vents were installed into.

I don't know of anyone that has had a light tube or chimney drilled into an existing cave, but maybe someone will come along with their experience.

Cheers Mariposa. Would be great if its possible, but not at the expense of safety or the integrity of the cave.