Observing Deck Plans
Started by
eric_zeiner
, Jul 22 2010 10:29 AM
21 replies to this topic
#1
eric_zeiner
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Posted 22 July 2010 - 10:29 AM
I am considering the construction of an observing deck in my back yard to start sometime in September or October. The attached photos show a hollowed out bowl into the side of a small hill in my back yard where an above ground pool once stood. My plan is to build the deck flush to the high side (where the bare patches are) and extend it towards the viewer by 16'. The high side of the hill is about 3' above grade and the whole deck will be 16'x16'. My plan is to use 2x8x10 double ribbon joists anchored into the hill with 6x6's buried 6' into the ground with no concrete and the subsequent joists will be also 2x8x16's placed 12" OC for rigidity. The out board end of the deck will also be anchored to the ground with 6x6's buried 6' into the ground with no concrete. The reason I am opting for no concrete is that if I were to use concrete, I would then need a permit from the county. My ultimate long term goal is to install some sort of prefab observatory on this deck. Of course there will be railings all the way around this deck except for the high side which I will leave open to the grade. The deck will only be about a 30' walk from the back of my house so hauling my gear out will not be too big a deal. There will be no need for a pier either as I am purely a visual observer and ultimately this deck will give me a much greater view of the sky overall. Here is a shot looking to the NNW.
#2
eric_zeiner
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Posted 22 July 2010 - 10:32 AM
And another looking NNE.
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#3
Bowmoreman
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Clear enough skies
Posted 22 July 2010 - 11:34 AM
Eric,
I think if you bury 6x6's into the ground as your foundation (of any depth) and they are going to ROT...
I understand your need to NOT get a permit though (I had same issue!)...
I would recommend you go with floating concrete "footers" (pre-cast concrete) instead... that way there is concrete between the ground and the wood supports for the decking.
Also, if you do get any setting and/or frost-heaves; you can always easily re-jack/re-level things... I know this because I've had to do it a couple of times...
If you are concerned about anchoring the deck to the ground (even though at 16'x16' its gonna be heavy!), you can accomplish this in a couple of ways
You can have non-load bearing wooden posts buried
You could have large metal "earth screws" with cable to bolts
Or the like...
Even PT-posts will rot if buried into the ground...
HTH
clear enough skies
I think if you bury 6x6's into the ground as your foundation (of any depth) and they are going to ROT...
I understand your need to NOT get a permit though (I had same issue!)...
I would recommend you go with floating concrete "footers" (pre-cast concrete) instead... that way there is concrete between the ground and the wood supports for the decking.
Also, if you do get any setting and/or frost-heaves; you can always easily re-jack/re-level things... I know this because I've had to do it a couple of times...
If you are concerned about anchoring the deck to the ground (even though at 16'x16' its gonna be heavy!), you can accomplish this in a couple of ways
You can have non-load bearing wooden posts buried
You could have large metal "earth screws" with cable to bolts
Or the like...
Even PT-posts will rot if buried into the ground...
HTH
clear enough skies
#4
droid
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rocketman
Posted 22 July 2010 - 12:56 PM
Eric; I simply sat my deck on patio blocks. I'm also purely observational. Haven't had an issue yet after two years going on three, other than bees, spiders, and an occasional visit from creatures that scare the bejesus out of you,lol.
#5
Mary B
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Posted 22 July 2010 - 01:07 PM
Pressure treated posts rated .4 or better retention are made for direct ground contact and can be buried. My mailbox has been there for 15 years on a treated 4x4 post and shows no signs of rot. It takes a LOT of abuse in the winter from snow plow drifts too.
#6
Bob Griffiths
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Posted 22 July 2010 - 02:25 PM
Eric:
I just checked and the frost line in Atlanta is all of SIX inches DEEP... but if I read your post correctly you were going to bury 6x6 posts SIX FEET.... which I assume is a mistype on your part...
Anyway I'd use the concrete "floating footers " blocks as Dave mentioned above as you are not in the Frozen North by any means...
You mentioned that you would have "no real pier"
If so the first thing I would do would be to sink 3 individual 4-6 inch diameter 1/4 inch thick PVC pipes into the ground a couple of feet and have them extent a few inches above your decks intended floor height. (cut them off flush when you finish the decking material) and fill them with dirt or concrete ... These will be where you place your tripod legs .. on solid ground and isolated from the deck itself.. That way you can do jumping jacks on the deck and not effect the scope at all...
Bob G.
I just checked and the frost line in Atlanta is all of SIX inches DEEP... but if I read your post correctly you were going to bury 6x6 posts SIX FEET.... which I assume is a mistype on your part...
Anyway I'd use the concrete "floating footers " blocks as Dave mentioned above as you are not in the Frozen North by any means...
You mentioned that you would have "no real pier"
If so the first thing I would do would be to sink 3 individual 4-6 inch diameter 1/4 inch thick PVC pipes into the ground a couple of feet and have them extent a few inches above your decks intended floor height. (cut them off flush when you finish the decking material) and fill them with dirt or concrete ... These will be where you place your tripod legs .. on solid ground and isolated from the deck itself.. That way you can do jumping jacks on the deck and not effect the scope at all...
Bob G.
#7
eric_zeiner
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Posted 22 July 2010 - 04:06 PM
I was going with six feet because there will not be any concrete, and the deck will only be supported at least at this point by the four corners. The up slope side of the deck, North in this case will be flush with the ground but given the fact that the bank has been partially excavated away, I felt that six feet from grade level will still give me enough purchase. As for the south end of the deck which will be three to four feet above grade, again because there will not be any concrete, I felt that this would give me the rigidity that I am looking for.
As for the 6x6's being in direct ground contact, I was going for a 20 or 30 year rated treatment. If I out live that then we'll see about something more permanent
I am posting a view facing East to give you an idea what the slope looks like and again, the deck will be at ground level to the North (left in the picture) and about three to four feet above grade to the South or right in the picture.
As for the 6x6's being in direct ground contact, I was going for a 20 or 30 year rated treatment. If I out live that then we'll see about something more permanent
I am posting a view facing East to give you an idea what the slope looks like and again, the deck will be at ground level to the North (left in the picture) and about three to four feet above grade to the South or right in the picture.
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#8
RoundStars
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Posted 22 July 2010 - 10:20 PM
Even though you're a visual observer, and even though you're planning a massive deck foundation, I would still recommend a pier or tripod footing isolated from the deck. Regardless of how rigidly you build everything, walking across the deck or even changing your position in a viewing chair will certainly cause an unhappy movement of your scope while viewing. If you have a group of guests over for a night of astronomy, the person at the eyepiece will find it hopeless to try to view anything because of the others' movements. In the future you may want to try astrophotography, at which time an isolated pier will be an absolute necessity.
You should also consider building your deck on skids resting on a 4" pad of compacted gravel -- no footings required, and an age-old proven construction technique for even large sheds or decks.
Frost heave is a non-issue at your location, and 6-foot-deep footings are overkill.
You should also consider building your deck on skids resting on a 4" pad of compacted gravel -- no footings required, and an age-old proven construction technique for even large sheds or decks.
Frost heave is a non-issue at your location, and 6-foot-deep footings are overkill.
#9
Stewww
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#10
csa/montana
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Posted 23 July 2010 - 02:07 PM
Welcome to Cloudy Nights, and many thanks for the link! This will be most helpful to those building a deck for observing; or the floor for an observatory!
#11
eric_zeiner
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Posted 23 July 2010 - 05:44 PM
www.deckplans.com
Free deck plans.
Great site and great resource but unfortunately I now have a better idea of what this will cost me and I was surprised. Using that planner and plans and materials list my proposed deck came in around $1200.00 and that is about double what I guessed shooting from the hip. Soooo it will have to wait as I am in the process of having the engine in my car replaced to the tune of about $3.5K Perhaps next Spring
#12
csa/montana
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Posted 23 July 2010 - 06:39 PM
Eric, don't give up yet! Lumber prices vary from place to place. Also you might be fortunate enough to find someone tearing down a structure, that you could pickup some lumber for free.
#13
eric_zeiner
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Posted 23 July 2010 - 07:14 PM
Instead of using the blocks that are spec'd in the link, would regular cinder blocks work? The reason I ask is that I have access to an unlimited supply of those for free (legally ) and if those would work that would shave off about $350.00 from the project.
) and if those would work that would shave off about $350.00 from the project.
#14
mikey cee
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Posted 23 July 2010 - 07:23 PM
Eric....I agree on floating concrete. If you insist on not using concrete the 6x6's are overkill as well as the 6' depth. The advantage of depth is to avoid the freeze and thaw of the ground causing instability. Posts of 4x4 dimensions are more than adequate at a depth of say 18" to 24". That deck isn't going anywhere and anchoring it is a waste of sweat and time. It will probably weigh a ton and a half with a very low profile. I like the idea of the three pvc tubes filled. ;)Mike
#15
Bob Griffiths
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Posted 24 July 2010 - 09:09 AM
I agree with Mickey.... with a 6 inch frost line you really do not need either..
I honestly have to ask you just how many DOZEN of the pre made concrete piers you intended to use...???? $350 will buy you a truck load of them I would think... They are NOT that expensive...
And lumber varies all over the place even locally so check out several lumber yards as well as the big box stores ...I overbuilt my 12x10 foot free standing deck on which my Observatory is sitting used 6x6's and 2x12's floor joists spaced 12 inches on center for only $800.00 and that included all the lumber to also build the base 10x10 building on top of the deck which supports the Dome itself...
Bob G.
I honestly have to ask you just how many DOZEN of the pre made concrete piers you intended to use...???? $350 will buy you a truck load of them I would think... They are NOT that expensive...
And lumber varies all over the place even locally so check out several lumber yards as well as the big box stores ...I overbuilt my 12x10 foot free standing deck on which my Observatory is sitting used 6x6's and 2x12's floor joists spaced 12 inches on center for only $800.00 and that included all the lumber to also build the base 10x10 building on top of the deck which supports the Dome itself...
Bob G.
#16
eric_zeiner
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Posted 24 July 2010 - 03:43 PM
I agree with Mickey.... with a 6 inch frost line you really do not need either..
I honestly have to ask you just how many DOZEN of the pre made concrete piers you intended to use...???? $350 will buy you a truck load of them I would think... They are NOT that expensive...
And lumber varies all over the place even locally so check out several lumber yards as well as the big box stores ...I overbuilt my 12x10 foot free standing deck on which my Observatory is sitting used 6x6's and 2x12's floor joists spaced 12 inches on center for only $800.00 and that included all the lumber to also build the base 10x10 building on top of the deck which supports the Dome itself...
Bob G.
Hi Bob,
According to the link in this thread, when I entered in all of my deck requirements, the blueprint showed a bunch of them and if I remember right they were placed 16" OC in both directions over the entire expanse of the support structure. I am in complete agreement with the floating idea and I think I came up with a better and less expensive solution. That is to anchor the uphill portion directly to the ground and then place headers every four feet running perpendicular to the joists which are supported by 4x4's on the concrete piers. The headers will be nothing more than two 2x6's sandwiched together. I did a giant elevated deck like this several years ago and it seemed to work well. This will cut down the number of concrete piers to 16, and I can get away with about 10 8' 4x4's. Also I had priced it with 5/4 decking which was hugely more expensive than regular 2x6's. The price quote was also done with screws and I will just use ring shank, cement coated decking nails. Again reducing the cost.
#17
RoundStars
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Posted 24 July 2010 - 05:10 PM
Instead of using the blocks that are spec'd in the link, would regular cinder blocks work?
Yes. The benefit of the deck blocks is that it's easy to build on a sloping site by cutting 4X4s to the appropriate length, to fit the blocks' top socket. If you take time to level your site, you can set your deck foundation's sill plates on solid rectangular concrete blocks. It works best to set the blocks on a 4" pad of compacted gravel, which will also make it easier to level the foundation. For correcting small leveling issues, just shim between the blocks and the sill plates with pieces of asphalt shingle. Since you're building in a bowl, just excavate the hillside enough to make the entire site level, while bringing the bottom of the bowl up by stacking the appropriate number of blocks. No need to anchor the foundation into the hillside soil -- it's not going anywhere, unless you later build a shed or observatory atop the deck.
-Joe
#18
eric_zeiner
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Posted 24 July 2010 - 05:36 PM
Instead of using the blocks that are spec'd in the link, would regular cinder blocks work?
Yes. The benefit of the deck blocks is that it's easy to build on a sloping site by cutting 4X4s to the appropriate length, to fit the blocks' top socket. If you take time to level your site, you can set your deck foundation's sill plates on solid rectangular concrete blocks. It works best to set the blocks on a 4" pad of compacted gravel, which will also make it easier to level the foundation. For correcting small leveling issues, just shim between the blocks and the sill plates with pieces of asphalt shingle. Since you're building in a bowl, just excavate the hillside enough to make the entire site level, while bringing the bottom of the bowl up by stacking the appropriate number of blocks. No need to anchor the foundation into the hillside soil -- it's not going anywhere, unless you later build a shed or observatory atop the deck.
-Joe
Hey Joe,
I totally understand what you are saying but I think the point that I am going to make the North end of the deck level with the ground on the high side of the bowl was missed. I think the ground there is really well compacted as a 24' above ground pool once sat sat there. So I think I will start with the sill plates or ribbon joist or perimeter joists, pick your flavor:grin: get those assembled and squared up and anchored into the hill, and just loosely support the opposite end and then drop plumb lines to where the concrete footers will go. I can get the lengths of the 4x4's from there less the length of the joists, headers and blocks, and basically custom fit each support member to its location. Though this will be more labor intense, I will be able to set these without disturbing the ground. I can then place the assembled headers, 4x4's and footers and then I can lay in my joists. This gradual loading of the structure should not cause any major shifts in level and if it does I can then use your leveling method. As for anchoring it into the hill, I do plan in the future to put a pre fab observatory of some sort on top.
#19
eric_zeiner
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Posted 29 July 2010 - 12:59 PM
Here are a few more pictures with blocks placed to show the foot print and to give a better prospective of the elevation change. The outside corners of the blocks are at 16' OS roughly, but as I had said this will give a better view of what I am dealing with. This one is looking NE.
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#20
eric_zeiner
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Posted 29 July 2010 - 01:01 PM
This is looking due North.
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#21
eric_zeiner
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Posted 29 July 2010 - 01:02 PM
And this one is looking NW.
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#22
avarakin
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Posted 04 August 2010 - 08:48 PM
Eric,
Do you really need 16x16? Something like 10x10 should work just fine if it is observatory only and would reduce the cost more than twice.
I agree with other poster that you really want to have some sort of pier there. You never know when AP bug bites you...
I myself just started looking into building an astrodeck, in my case it is mostly to help with AP - I want to build walls around my deck so I can leave some of my gear outside. At the same time the wall will shield LP.
Alex
Do you really need 16x16? Something like 10x10 should work just fine if it is observatory only and would reduce the cost more than twice.
I agree with other poster that you really want to have some sort of pier there. You never know when AP bug bites you...
I myself just started looking into building an astrodeck, in my case it is mostly to help with AP - I want to build walls around my deck so I can leave some of my gear outside. At the same time the wall will shield LP.
Alex
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