permanent pier on pre-existing slab?

[Rob]

I've just moved into a house with a small garden shed. I'm daydreaming about converting it to an observatory with a permanent pier. I haven't decided how to do the roof yet, roll-off seems to be the most popular method.

My question is how do I set up a permanent pier? The usual method seems to be to set the concrete around the pier, so that it's embedded in the slab. However, this is an existing shed, so the concrete has already been laid. I suppose I could jackhammer a small section of the slab and pour new cement. Any better ideas?

Thanks for any suggestions,
Rob
:screwy:

[mill]

Hi Rob.
My suggestion is to drill holes and use treaded studs.
Put a flange on the bottom of the pier and bolt it onto the treads.

[snowyskiesau]

As mill said, drill holes and put in some threaded studs or dynabolts. This may not work if the slab is not thick enough though.
There could also be vibration through a slab that you wouldn't get if the pier base is isolated from the slab.

[Gas Giant]

Hi Rob.
The Wollongong Amateur Astronomy Club has at leat 3 members I can think of who have put in piers - and at leat two with garden shed observatories, namely the current and immediate past presidents. They are always at meetings so have a talk to them before going ahead.
Cheers
Andrew

[Roger Davis]

Ah, be aware of vibration. Piers are normally separated from the surrounding floor by a small gap so that vibration is not passed from the floor you are walking on to your telescope.

[Rob]

Thanks for all the advice.

Cheers,
Rob