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How deep to dig for pier base!

Mukv

By Mukv
in DIY Observatories

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Mukv

Mukv

Posted
Posted

Greetings

Just started a new dig for a base for a photographic setup this is how deep I got today but not sure how much more to do...

post-28592-0-49258600-1393449228_thumb.j

I'll keep going tomorrow and at the end of the day work out how much concrete to order.!

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nmoushon

nmoushon

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Thats a GIANT pier base lol. Both in depth and size. Most people in the UK tend to dig only about 24" or so. Your goal is to get below your local frost line....I think you've accomplished that lol. For the footing size (might as well do a footing since you have the space) is double the diameter of your pier and centered on it. So a 12" diameter pier with have a 24" square footing. But you could prob get away with less since there really isnt that much force on the pier and the fact you dug it so deep.

What are you planning for your obsy floor and its size? One problem I see with you digging out so much is that you now have to fill it back in. This will lead to settling no matter how much you compact it. You can get around this depending on the size of the obsy.

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BenDavis

BenDavis

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Greetings

Just started a new dig for a base for a photographic setup this is how deep I got today but not sure how much more to do...

attachicon.gifnew dig.jpg

I'll keep going tomorrow and at the end of the day work out how much concrete to order.!

Blimey!

Well that's about an average house foundation level I guess!

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pete_l

pete_l

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Personally I've never considered the need to dig down very much at all. Most foundations are massive overkill. Even a house only needs 700mm deep foundations. For something as small as a telescope, I doubt that any depth more than 6 inches is necessary - if you're not walking around on the slab. Just make sure it's wide/long enough.

The usual argument for going deeper (and the reason for 700mm for houses) is to remove the possibility of movement due to frost heave. However unlike a house, this is very unlikely to cause any permanent problem for an observatory. The worst thing that would happen is that you'd have to re-work your polar alignment (which you will probably do at regular intervals anyway) if the ground moved slightly during a cold winter.

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ollypenrice

ollypenrice

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Very impressive but I'm sure you already have about ten times the volume you need! All our imaging rigs, including the 14 inch with 2.4 metres of FL, simply stand on flat concrete bases about 5 inches thick. This has always been fine. Digging deep won't do any harm but unless your ground has some specific issues I don't think it's necessary. I'd say it was time for a pint!

Olly

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yesyes

yesyes

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I get the feeling there's more to this than meets the eye. ;)

This is either going to be a massive pier, maybe going up to the 2nd floor, or it will be an obsy with basement, or this might not be a pier base hole at all (what's that trench leading into the hole for). Noone would dig such a big hole just for teh sake of it! (though it might be cheaper than going to the gym) ;)

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Ptarmigan

Ptarmigan

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 (what's that trench leading into the hole for). 

Ah that is obviously for the pipeline thro' which regular deliveries of coffee will be made by the domestic staff in't'big'house.

Mind you, if't'were for a sceptical tank it might be for somat else ;-)

Although,,, some might have you believe it is for the mains cable and intercom/usb, dont you believe it, chuckle , , ,

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michaelmorris

michaelmorris

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It looks too big to me. You want the pier foundation to inside the footings for observatory. This way the two are isolated from each other, reducing the amount of vibration transmitted through the ground from the observatory to the pier.

Sent from my Nexus 7 using Tapatalk

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Mukv

Mukv

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greetings

done a little more digging today just about finished it now got to square the corners and that's it

you can see the trench for the ducting that will carry the services.

post-28592-0-04075400-1393536815_thumb.j

and got the pier construction material also

post-28592-0-89686600-1393536817_thumb.j

this piece of timber is 70mm x 70mm and is 1.3m long!

just need the 50mm anchor screws and plastic rawl plugs and this baby aint going nowhere!

the finished pier hole is 2m x 2m x 2.1m deep.

Andy

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