Installing pergola under "valuable" tree

[MR GUS]

An Area I dug out some invasive plants in a sheltered aspect of the front "garden" ...I left to get back to a good state a few years ago as it was badly planted by the previous owner.
Questions are.

 The Coniferous type tree we have has since flourished, it's a haven for birds 9robins, blackbirds tits, wrens etc as it's dense foliage running along the frontage, a good height to avoid most predators whilst feeding.
Whilst i'm not cutting anything back I've swept the pine cone & needle debris away wishing to place some shallow pads for a pergola (aluminium & wood), how do I minimise damage potential for pads which do need to be spot on?
my thought is to use some spare bricks from chopping out the fireplace to minimise cementpouring but have them bound to what little I'd need to make a good pad & then drill whacking great retaining bolts into...

Possible or a straight out fail.
roots of the much loved tree are a concern as one foot may sit very tight to the trunk, therefore close proximity to the main tap.

I anticipate it'll be 9ft high the metal uprights are smooth & therefore minimise any chance of cat predation, however to reduce chances of cats jumping from the low fencing i'm thinking some form of trellis with cat spikes to deter them.

Anyone got experience of cat spikes & their effectiveness?
Any suggestions for pads that may need to be set shallow?

[acresswell]

At a previous house, we used spikes on the horizontals of a pergola to deter the neighbours' cat.  They worked very well, but we did have to cover almost all of the pergola with them (which worked out expensive) otherwise she was quite adept at avoiding the spiky bits!  We'd previously tried an ultrasonic cat repeller (useless) and a super-soaker water pistol from the bedroom window (very effective, until she learnt that she was safe if the bedroom window was closed). I reckon there might be a market for a combination of the two - a detector that activates a sprinkler for a few seconds... I'm confident that it'd deter the cat, but you might get a bit wet yourself when you wanted to sit under the pergola and forgot to deactivate the detector!

If you're going for thin pads then I'd recommend casting your bolts into them, since trying to drill into a thin pad at a later date may crack it.

Good luck,

Adrian

[solar_cambridge]

I reckon there might be a market for a combination of the two - a detector that activates a sprinkler for a few seconds... I'm confident that it'd deter the cat, but you might get a bit wet yourself when you wanted to sit under the pergola and forgot to deactivate the detector!

B&Q sell one for about £25.  Look on youtube for 'scarecrow sprinkler' for lots of fun examples.

[dhaslam]

Tree roots should be OK if you just make individual holes. The way the  local authorities kill valuable trees is by digging  a trench allong one side of a row of trees  cutting off all the roots on one side.   

Our local council took down a wall a couple of years ago and built this low wall with a railing.   Now all the trees in the background here  have to be taken down.   They could easily have bridged the tree roots  but they  cut away the main  roots with a mechanical digger.