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Pier help????

Started by bobblack, 10/03/2007 05:28PM
Posted 10/03/2007 05:28PM | Edited 10/03/2007 05:31PM Opening Post
I have just built a dome style observatory. Because of the trees, houses and other blockage I decided to build it up through my barn roof.
It is a great looking observatory but it needs a pier.
Hence the problem:- to get down to the concrete floor below, the pier will have to be 22 feet long. My question is has anyone ever done a pier this long and if so how did it work?
I was thinking of a 6" water well pipe but I think with the length it will vibrate.
I was also thinking of a 4' pier sitting on the floor but won't that vibrate just as bad from walking around?
Me thinks I should have gave this a little more thought before starting. Duh!!
If anyone has any thoughts on my problem I would sure like to hear them.
Sincerely, bob black
Posted 10/04/2007 07:10AM #1
A concrete pier poured in two pours. first a large footing in the ground with plenty of rebar and then a concrete form tube (Sonotube)poured up to just below floor level of the observatory with bolts on top. then a short pipe pier in the dome from the floor up.
Posted 10/04/2007 09:47AM #2
I would consider a cinderblock pier several feet on each side, if you do this and insulate it depending on your climate you could also have a unique wine cellar on the interior of the pier. With out knowing where in your barn your observatory is going it is hard to truely estimate the pier.

Doug Grebe
Posted 10/04/2007 10:53AM #3
Hi Bob,

You might want to consider concrete block to get you most of the way up - filled with concrete if you don't mind the thermal mass, but even hollow, they're pretty sturdy (and relatively cheap).

If you'd like, I can send some pictures off-line of my pier construction.

I have a 3-story 20-foot observatory, with a pier constructed as follows: Went down to bedrock (6 feet below grade). Installed large concrete footing (6' per side), anchored to the bedrock. On that, installed 7 courses of 10" cement block (18 blocks per course) - this part of the pier (below grade) was 48" per side. Backfilled and filled with rebar and cement. On that, first 8' level (above grade) consisted of 12 8" blocks per course (12 courses). Second 8' level consisted of 8 8" blocks (12 courses). Third level tapered even more - from 4 blocks per course to 3 blocks per course. So the final pier was 16" x 24". Only some of the above-grade block was filled with rebar and cement (to reduce thermal mass somewhat). But since the pier is inside the observatory (not exposed to the sun like a brick building is), I don't find any thermal problems.

Finally, it was mentioned to consider what your purpose is. Very true, but also consider how close you are to the street and heavy traffic. At the University of Kansas, a sensitive transit instrument was located on the third floor of the science building. That was normally fine, but when a heavy truck went past (the street was at least 100' away), the building (and transit) noticeably tilted! And vibrated.
Anyway, good luck!

James