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Gravel Pad for ROR observatory?

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#1 Simply Peter

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Posted 16 June 2022 - 10:59 AM

Rather than a concrete pad which requires a permit in my area I was considering installing a gravel pad.  My thoughts are that I would build the observatory on green treated 4x4 skids anchored to the using ground screw anchors. Do you have any experience using this type of arrangement or see some issues which I may have overlooked with this construction method? The pier would be concrete block type and no portion of the building would come in contact with it.



#2 SgrB2

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Posted 16 June 2022 - 11:21 AM

You might have water problems inside the

observatory with a big rain.  I'd go with the

concrete pad 6 inches thick reinforced with

rebar.  A permit can't be that expensive.



#3 aaube

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Posted 16 June 2022 - 11:54 AM

Rather than a concrete pad which requires a permit in my area I was considering installing a gravel pad.  My thoughts are that I would build the observatory on green treated 4x4 skids anchored to the using ground screw anchors. Do you have any experience using this type of arrangement or see some issues which I may have overlooked with this construction method? The pier would be concrete block type and no portion of the building would come in contact with it.

 

That's roughly how i built my observatory.  It sits on screw piles while the piers are on sonotubes.

So far so good.  Link in my signature.

I believe it should work even better in your situation given the ground not freezing in winter.

 

Alain



#4 Simply Peter

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Posted 16 June 2022 - 11:56 AM

Our HOA requires a special approval process for a shed located on a permanent concrete pad.  I don't think that I will have trouble with water do to  the way the pad is constructed.  I would construct a 4x4 perimeter on the existing ground and fill that with compacted gravel on top of that I would put the 4x4 skids.  In essence this places the shed 8" above surrounding soil. 



#5 vsteblina

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Posted 16 June 2022 - 02:04 PM

Rather than a concrete pad which requires a permit in my area I was considering installing a gravel pad.  My thoughts are that I would build the observatory on green treated 4x4 skids anchored to the using ground screw anchors. Do you have any experience using this type of arrangement or see some issues which I may have overlooked with this construction method? The pier would be concrete block type and no portion of the building would come in contact with it.

I have an observatory in eastern Washington with a similar climate to Santa Fe, except we get a bit more snow, and lots less rain.  I was somewhat concerned about frost heaving but that turned out to be a non-issue.

 

I used a "thumper" to compact the area.  It is basically sand and on a side hill.

 

Then laid gravel, and pressure treated 2X4 floor with the plastic film covering the bottom of the floor.  I did NOT use ground screw anchors.  The floor just lies on top of the gravel.  I did level it, but that was it.

 

It is a 10X10 bolt-together sliding roof observatory.  The bolt-together part was that I could move it if needed.

 

It is has been up for 23 years.  Still works.  I viewed it as a temporary structure, but at this point it just might outlive me!!!

 

That ground screw anchors sound like a good idea.  But mine works fine without it.

 

Oh, my pier is TWO 8 inch steel pipes with  flanges welded on the end.  One pipe goes in the ground with the flange just sticking out of the ground, the other pipe and flange bolt to the ground one. That way I can just unbolt the top pipe and flange and bury the other pipe with dirt, if I move.


Edited by vsteblina, 16 June 2022 - 02:10 PM.

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#6 vrotondi

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Posted 16 June 2022 - 02:05 PM

Your going to get vaporization through the gravel into your ror. You will see condensation on your equipment, unless you put down a vapor barrier on the ground.


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#7 vsteblina

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Posted 16 June 2022 - 02:21 PM

I did put a vapor barrier on mine.

 

In winter, we get lots cloudy weather with a lot of 90% relative humidity.  A desert with cloudy weather??  How did that happen??

 

I still get condensation, so use a cover and a lightbulb to keep down the condensation.

 

In summer, our relative humidity is around 10% so a non-issue. 

 

Santa Fe is more like Wenatchee, except they have clear skies in winter.  I doubt that condensation would be an issue.

 

I have never lived in humid climates as a adult.  Have no clue on how to deal with that.



#8 Simply Peter

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Posted 17 June 2022 - 07:41 AM

Thanks for the tip about a vapor barrier, I hadn't thought of that.



#9 kathyastro

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Posted 17 June 2022 - 11:12 AM

I did essentially the same thing.  At my original site, the foundation beams were anchored to the ground by 2-foot long spikes driven through the beams.  At my current site, since the tops of the beams are no longer accessible (someone built a building on top of them!), I couldn't drive the spikes, so it is unanchored.  I had no problems at either location.

 

Gravel will drain better than concrete, so no worries there.  Definitely lay down vapour barrier on the gravel before setting the beams in place and building on top.



#10 Stevegeo

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Posted 18 June 2022 - 05:25 AM

I have moved mine twice because of harvesting of hardwood trees , each time i did gravel with vapor barrier under ,10 mil plastic with spots to allow pooling of any water  aand a hole for drainage . 

The entire building sits on a frame of  2 by 8s , 2 ft on center , then that sits on concrete deck blocks that sit on 2ft square concrete patio block on the gravel. This raises the building 2 ft ,  never had issues with humidity inside 

Stevegeo



#11 astrohamp

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Posted 18 June 2022 - 09:30 AM

Consider a heavy duty vapor barrier on top of the floor frame before you put down the floor boards.

 

I have been eyeing these ground anchors for a project.



#12 speedster

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Posted 20 June 2022 - 10:40 PM

There are some options to gravel.  Chat is sized between sand and pea gravel.  Sometimes used for baseball infields.  Decomposed granite also makes a good pad.  Bin10 is a crushed limestone with enough fines to bind.  Similar to roadway base but Bin 10 is a little less restrictive spec.




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