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 More advice needed on pier foundations |
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Proto Star
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More advice needed on pier foundations -
17th January 2010, 02:29 PM
Hi All
Finally got round to digging out my footings, the orginal plan was to dig out a area of 2m by 1m by 1m deep for my pier's however once I got to a depth of 18" the hole stared to fill up with water. It looks at though this is the level of the water table.
Anyone have any suggestions? Is 18" deep enough for pier foundations?
Cheers Jon
C8-SCT, HEQ5 pro, WO72, WO90, QHY8, Atik 16hrc, DFK21, DSI pro II, Hyperstar V3, Microtouch focuser, SW190mm MakNewt, EQ6, PST, Cannon 400d and not enough cloud free nights.  A member of the AA
http://www.jons-astro-images.com/
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 Re: More advice needed on pier foundations |
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Sub Dwarf
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Re: More advice needed on pier foundations -
17th January 2010, 02:33 PM
The depth is probably ok, if in doubt make the hole wider to counteract any over turning moments....
Carl
Women are like a question all wrapped up inside a conundrum
Orchard View Observatory
Sky Watcher 8", Pier mounted EQ5 Synscan Goto
Nexstar 4 XLT
Nikon D80
Atik 1HSII
Westbury, UK
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 Re: More advice needed on pier foundations |
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Sub Dwarf
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Posts: 1,016
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Re: More advice needed on pier foundations -
17th January 2010, 03:00 PM
That would be your winter water table - in the summer, assuming it is dry, it will be quite a bit lower. By the way - if you are concreting - wait for the warmer weather. Concrete does not like temps below about 5 deg C when setting. Colder can wreck it especially if it freezes!!! Seriously bad news if you have to dig it all out because the ice has cracked it up.
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 Re: More advice needed on pier foundations |
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Brown Dwarf
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Re: More advice needed on pier foundations -
17th January 2010, 04:05 PM
What bizbuilder said 
My mount is set in a 2 foot by 3 foot cube but I'm lucky that my underlying foundation is boulder clay which Im told is pretty stable and doesn't move around much, for good measure I hammered in lots of steel bar at different angles before I poured the concrete.
Don't listen to the Americans and their multi tonnage cubes.....its just not needed
SW 250PX + ED80 Piggybacked
SW EQ6 + EQmod
Modified Canon 350 & 1000D
QHY5 Guider
All housed in a 8' x 7' Roll off modified shed
Stockport UK
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 Re: More advice needed on pier foundations |
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Sub Dwarf
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Re: More advice needed on pier foundations -
17th January 2010, 04:10 PM
Yep, my pier foundation is about the same as George's...
Carl
Women are like a question all wrapped up inside a conundrum
Orchard View Observatory
Sky Watcher 8", Pier mounted EQ5 Synscan Goto
Nexstar 4 XLT
Nikon D80
Atik 1HSII
Westbury, UK
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 Re: More advice needed on pier foundations |
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Super Giant
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Re: More advice needed on pier foundations -
17th January 2010, 04:14 PM
And mine... I used three 5 foot lengths of 2" x 1/4" thick angle driven into the ground at angles with the tops crossing in the concetre block...mainly because I was on "made up" ground about 10 feet above "natural"
Billy...
Scopes : CPC800XLT Pier & Wedge | WO Meg72 & FFIII : ETX 105 EC
Cameras : Canon 1000D (BCF mod) , 350D (Filter Removed) & 500D (Standard) | Nikon D200 & D50 | K-M 5D | DMK21AU04AS
Guiding : 500mm f8 & DSI IIc | TS OAG-9 EOS & DSI Ic | SkyWatcher SynGuider
Mounts : EQ3 Pro HEQ5 SynTrek/SynScan 2 x Eklipse Goto EQ Mounts & SkyWatcher SupaTrak Alt/Az
Snapping the night sky with DSLR's when the weather allows...
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 Re: More advice needed on pier foundations |
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Moderator
Proto Star
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Re: More advice needed on pier foundations -
17th January 2010, 04:22 PM
Thanks for the advice, im located in the fens, so water is not too far away what ever the time of year
cheers Jon
C8-SCT, HEQ5 pro, WO72, WO90, QHY8, Atik 16hrc, DFK21, DSI pro II, Hyperstar V3, Microtouch focuser, SW190mm MakNewt, EQ6, PST, Cannon 400d and not enough cloud free nights.  A member of the AA
http://www.jons-astro-images.com/
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 Re: More advice needed on pier foundations |
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Moderator
Hyper Giant
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Re: More advice needed on pier foundations -
17th January 2010, 04:39 PM
Jon.
My No 2 pier dig, struck Clay just under 2 feet down.
I bought one of those steel post holders, that taper down to nothing. They are about 3 foot long, and I smacked one of those down in the hole centre, leaving about a foot protruding above ground. I placed the pier over the stake, and filled the hole with crete, and the pier too. Prior to filling though, I put conduit up through the pier and also waste pipe. These led underground to where the puter sits in the warm room bit. A draw tape in each pipe for drawing cables through. Brace the pier in a vertical position, and wait a few days for the crete to set sufficiently.
Most of this is as you would do it anyway.
Don't forget the piccies mate. We like to see what progress
is made.  .
Ron.
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 Re: More advice needed on pier foundations |
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Brown Dwarf
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Posts: 2,690
Join Date: Apr 2008
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Re: More advice needed on pier foundations -
17th January 2010, 07:18 PM
Out of interest, this month's S@N has an article about setting up an external pier - could be helpful?
As to the water table, it's going to be much higher than usual at the mo - all that metling snow and most of it melted by heavy rain is just making it higher and higher. Pity all those people without tanking in their cellars!
The Thing
Soligor reflector, 152mm (6"), 750mm, f/5;
SW reflector, 200mm (8"), 1000mm, f/5;
Orion StarShoot Solar System Camera II
'The surest sign that intelligent life exists elsewhere in the universe is that it has never tried to contact us.' - Bill Waterson (Calvin & Hobbes).
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 Re: More advice needed on pier foundations |
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Sub Dwarf
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Re: More advice needed on pier foundations -
19th January 2010, 06:10 PM
Remember that concrete will set underwater. It will be weakened, but I doubt that would be an issue for pier foundations.
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 Re: More advice needed on pier foundations |
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Super Giant
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Posts: 13,590
Join Date: Aug 2008
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Re: More advice needed on pier foundations -
19th January 2010, 06:20 PM
Scopes : CPC800XLT Pier & Wedge | WO Meg72 & FFIII : ETX 105 EC
Cameras : Canon 1000D (BCF mod) , 350D (Filter Removed) & 500D (Standard) | Nikon D200 & D50 | K-M 5D | DMK21AU04AS
Guiding : 500mm f8 & DSI IIc | TS OAG-9 EOS & DSI Ic | SkyWatcher SynGuider
Mounts : EQ3 Pro HEQ5 SynTrek/SynScan 2 x Eklipse Goto EQ Mounts & SkyWatcher SupaTrak Alt/Az
Snapping the night sky with DSLR's when the weather allows...
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 Re: More advice needed on pier foundations |
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Sub Dwarf
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Posts: 1,259
Join Date: Feb 2008
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Re: More advice needed on pier foundations -
19th January 2010, 06:21 PM
I was wondering if half the Concrete in water really mattered..whats the possibility of water seeping back up through when the concrete has set during pier use?
I know the Romans could set concrete in the sea...aahh um anyway look forward to seeing your pics.
Neil C
EQ6 syntrek, LXD 75, Artemis 285, DSI, Nikon D50
80ED, ST80, SPX 200mm Newt,
Shed (not leaking), Pier (awaiting EQ6 connection)
ACP, EQMOD(via FTDI cable), MAXIM DL.
Last edited by ncjunk; 19th January 2010 at 06:22 PM.
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 Re: More advice needed on pier foundations |
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Super Giant
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Posts: 13,590
Join Date: Aug 2008
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Re: More advice needed on pier foundations -
19th January 2010, 06:51 PM
I suppose you could pour into a Heavy duty plastic bag to minimise the risk of washout...
Billy..
Scopes : CPC800XLT Pier & Wedge | WO Meg72 & FFIII : ETX 105 EC
Cameras : Canon 1000D (BCF mod) , 350D (Filter Removed) & 500D (Standard) | Nikon D200 & D50 | K-M 5D | DMK21AU04AS
Guiding : 500mm f8 & DSI IIc | TS OAG-9 EOS & DSI Ic | SkyWatcher SynGuider
Mounts : EQ3 Pro HEQ5 SynTrek/SynScan 2 x Eklipse Goto EQ Mounts & SkyWatcher SupaTrak Alt/Az
Snapping the night sky with DSLR's when the weather allows...
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 Re: More advice needed on pier foundations |
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Sub Dwarf
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Posts: 1,978
Join Date: Dec 2008
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Re: More advice needed on pier foundations -
19th January 2010, 11:42 PM
I thought concrete got stronger if in contact with water as the curing process is slowed down. Concrete continues to gain strength over a prolonged period of time after the initial setting period of 28 days. Bail out as much water as possible then just empty a good few bags of dry post-crete in the hole, position the pier and your away. Don't worry too much about the water, you'll have a concrete pad as hard as steel
Carl
Women are like a question all wrapped up inside a conundrum
Orchard View Observatory
Sky Watcher 8", Pier mounted EQ5 Synscan Goto
Nexstar 4 XLT
Nikon D80
Atik 1HSII
Westbury, UK
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 Re: More advice needed on pier foundations |
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Super Giant
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Posts: 13,590
Join Date: Aug 2008
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Re: More advice needed on pier foundations -
20th January 2010, 06:53 AM
As long as you stop washout yes...
Scopes : CPC800XLT Pier & Wedge | WO Meg72 & FFIII : ETX 105 EC
Cameras : Canon 1000D (BCF mod) , 350D (Filter Removed) & 500D (Standard) | Nikon D200 & D50 | K-M 5D | DMK21AU04AS
Guiding : 500mm f8 & DSI IIc | TS OAG-9 EOS & DSI Ic | SkyWatcher SynGuider
Mounts : EQ3 Pro HEQ5 SynTrek/SynScan 2 x Eklipse Goto EQ Mounts & SkyWatcher SupaTrak Alt/Az
Snapping the night sky with DSLR's when the weather allows...
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 Re: More advice needed on pier foundations |
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Moderator
Proto Star
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Posts: 828
Join Date: Jan 2008
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Re: More advice needed on pier foundations -
20th January 2010, 07:16 AM
May thanks everyone, your advice is much appreciated as always.
cheers Jon
C8-SCT, HEQ5 pro, WO72, WO90, QHY8, Atik 16hrc, DFK21, DSI pro II, Hyperstar V3, Microtouch focuser, SW190mm MakNewt, EQ6, PST, Cannon 400d and not enough cloud free nights.  A member of the AA
http://www.jons-astro-images.com/
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