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  1. #1
    Join Date
    Feb 2014
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    20

    Question Unusual outdoor project - need advice

    I'll go ahead and ask two questions first then explain in detail what I am trying to accomplish.

    If I screwed together eight 10 foot sections of 1/2 " galvanized metal pipe to make an 80 foot length of pipe that would be fastened to the top of concreted 9 to 10 foot high 4x4 wood posts at either end of an 80 foot long area, would that work without sagging in the middle ?


    If I spliced together enough 12 foot long 2x8 boards to make an 80 foot long ridge board that would that hold up by itself between the 2 4x4 posts ?

    (I would also concrete four 4x4 posts (about 4 feet high) just outside the fence on both sides (12 feet apart) at :the midway point and have a rafter board going from the top of each post to the ridge board for added support in the middle of the 80 foot length.)


    Now let me explain what I am trying to accomplish as it is not your usual home / yard DIY project, then I'll ask my specific questions.

    I have an area of our yard fenced in with a 4 foot high wire fence attached to metal fence posts, it is 16 feet wide by 80 feet long, it has a gate to go in/out, and it is for our Border Collie mix dog to have plenty of room to run freely and get her exercise when I take her outside and throw Frisbees and balls.

    The general problem I am trying to solve is covering the entire 16x80 area with 2 large tarps to have a canopy that would cover from the top of one side of the 4 foot fence to the top of the other side, the entire 80 foot length.

    Why ? Because here in South Carolina we can go thru times where it can rain enough over a few day period to have several days in a row where our dog has no outdoor running time (and a dog can get very frustrated with pent up energy when they are used to being able to run) and having her fenced in area covered allows her to get exercise on rainy days as well as the added bonus of both my dog and I being shaded from the hot sun during the summer months.

    I had it covered very nicely using 3/4" PVC pipe and connectors for an arched frame to put the tarp over (sort of like how a PVC greenhouse is made, but the pipe went from the tops of the fence posts). Then less than 2 weeks later we had a (very rare for here) very heavy snow that collapsed it.

    So now I am trying to figure ways to have a sturdy frame under the PVC that would hold up under such rare weather.

    I had thought of screwing together 10 foot sections of 1/2 " galvanized metal pipe to run the 80 foot length, between concreted 9 to 10 foot high 4x4 wood posts at either end,

    but would that work without sagging in the middle ?

    Another idea is to splice together many 2x8 12 foot boards to make an 80 foot long ridge board that would give support underneath the PVC framing.


    Now I would prefer to not have any support posts inside the middle of the yard to be able to keep a completely open running area.

    I would also concrete four 4x4 posts (about 4 feet high) just outside the fence on both sides (12 feet apart) at :the midway point and have a rafter board going from the top of each post to the ridge board for added support in the middle of the 80 foot length.

    Would that be enough support for that long of a ridge board, or would I have to use one or two support posts in the middle of the yard (either one in the middle, or two spaced at 1/3 intervals) ?

    Also, any other possible solutions are welcomed.

    We are on a fairly tight budget and I am trying to mostly use treated lumber we have sitting around from a past project we opted not to do for now.

    I have six 12 foot 4x4 posts, sixteen 12 foot 2x8 boards, four 12 foot 2x10 boards and some assorted hardware.

    If I had to buy a few more items that would be ok, as long as it was very little added expense.

    Thanks in advance for any help or other possible solutions.

    As you can see, this is not your average DIY project

  2. #2
    Join Date
    Dec 2007
    Location
    Tennessee
    Posts
    1,685

    Default Re: Unusual outdoor project - need advice

    An 80 foot span that doesn't sag supported by 4x4 posts, pretty much impossible. It may be possible to get an 80 foot span with very little sag. 1/2" steel pipe will sag badly.

    I take it that you want to be able to move freely within the enclosure with the dog and not hit your head. You will have to make a decision as to whether you want to be able to move freely all the way to the side walls or if you will give up a few feet of freedom near the side walls.

    If you want full freedom, you have enough materials to make 4 trusses that will span the sides. You will need one at each end so that only leaves two for the rest. They will have to be spaced about 26 feet apart. Set 8 4x4 posts, one at each corner and the others spaced equally down the sides, two on each side. Cut to desired height.

    Now make the trusses. Use the 2x8's to make the trusses with the 2x10's as collar ties. The collar ties need to be down as far as possible. You will need to lay this out on the ground, but after cutting the angle for the ridge and leaving a little for overhang at the posts. Your truss will be about 7 to 7.5' tall at the center.

    You still face other problems. You will need a ridge beam and finding materials to span nearly 27' will not be easy. You could use the remaining 2x8's spliced together but I'm afraid that really won't be very strong.

    You have enough material to make 7 trusses, but you would need to buy more 4x4's or cut the existing 4x4's in half, but if you do the latter, you will loose headroom along the sides. Ouch if you are not careful. 7 trusses will give you about a 12' span, just right for the ridge beam.

    Even with a supported ridge beam and the trusses, you will still need additional support for the tarp. It will sag between the ridge and the sides. I would suggest that you could use some sort of inexpensive wire fencing from truss to truss that might keep the tarp from sagging.

    I think you might consider just covering a smaller area with the tarp so the dog can get some shade during the heat of the day and protection from rain, but not try to cover the whole thing. Make two trusses, mount them 12 feet apart. Use 2x8's as collar ties so that you can use a 2x10 as the ridge beam. Then space the more 2x10's or 2x8's between the trusses at even intervals to support the tarp. That will give you an 12x16 shaded area that can be near the center or at one end of the enclosure.
    Last edited by keith3267; 02-21-2014 at 01:52 PM.

  3. #3
    Join Date
    Feb 2014
    Posts
    20

    Default Re: Unusual outdoor project - need advice

    Quote Originally Posted by keith3267 View Post
    An 80 foot span that doesn't sag supported by 4x4 posts, pretty much impossible. It may be possible to get an 80 foot span with very little sag. 1/2" steel pipe will sag badly.

    I take it that you want to be able to move freely within the enclosure with the dog and not hit your head. You will have to make a decision as to whether you want to be able to move freely all the way to the side walls or if you will give up a few feet of freedom near the side walls.

    If you want full freedom, you have enough materials to make 4 trusses that will span the sides. You will need one at each end so that only leaves two for the rest. They will have to be spaced about 26 feet apart. Set 8 4x4 posts, one at each corner and the others spaced equally down the sides, two on each side. Cut to desired height.

    Now make the trusses. Use the 2x8's to make the trusses with the 2x10's as collar ties. The collar ties need to be down as far as possible. You will need to lay this out on the ground, but after cutting the angle for the ridge and leaving a little for overhang at the posts. Your truss will be about 7 to 7.5' tall at the center.

    You still face other problems. You will need a ridge beam and finding materials to span nearly 27' will not be easy. You could use the remaining 2x8's spliced together but I'm afraid that really won't be very strong.

    You have enough material to make 7 trusses, but you would need to buy more 4x4's or cut the existing 4x4's in half, but if you do the latter, you will loose headroom along the sides. Ouch if you are not careful. 7 trusses will give you about a 12' span, just right for the ridge beam.

    Even with a supported ridge beam and the trusses, you will still need additional support for the tarp. It will sag between the ridge and the sides. I would suggest that you could use some sort of inexpensive wire fencing from truss to truss that might keep the tarp from sagging.

    I think you might consider just covering a smaller area with the tarp so the dog can get some shade during the heat of the day and protection from rain, but not try to cover the whole thing. Make two trusses, mount them 12 feet apart. Use 2x8's as collar ties so that you can use a 2x10 as the ridge beam. Then space the more 2x10's or 2x8's between the trusses at even intervals to support the tarp. That will give you an 12x16 shaded area that can be near the center or at one end of the enclosure.
    Thanks for the reply and ideas Keith, I will keep various possibilities in mind before deciding for sure how to proceed.

    As far as using 1/2" galvanized pipe, would it be enough extra support if at the midway point I used 2 "T" connectors pointing downward at an angle to run a pipe to the top of 4 foot high posts on either side of the 16 foot width ?

    Also, if I did opt to make an 80 foot ridge board, would it be enough extra support if I did use two 4x4 support posts spaced at 1/3 intervals ?

    From what I read elsewhere about splicing ridge boards, it seems to be a common practice, and I read that properly done using a pencil point cut and plywood gussets that it can be very sturdy.

    (I've done a lot of various DIY projects over the years, but this is the first time I think I tried making a partial roof type frame)

  4. #4
    Join Date
    Jul 2010
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    SoCal
    Posts
    6,305

    Default Re: Unusual outdoor project - need advice

    I think that Keith is generously optimistic here. Not only you would need more supporters, you would need them closer.

    I use to use 1/2" and 3/4" galvanized pipes for slope irrigation, and some 20-25 years later they sag...and they are on the ground, not suspended in the air.

    So it's back to drawing board for you, to come up with a flawless support system.

    My advice is redesigned and improved support.

    Send pics if you can.

  5. #5
    Join Date
    Jun 2009
    Posts
    303

    Default Re: Unusual outdoor project - need advice

    Can you switch it to a cable system ?
    Two large ground anchors at each end at an angle to the post and use rollers on top of post attach cable to a turnbuckle at each anchor tighen to max tension for dia. of cable used ?

  6. #6
    Join Date
    Feb 2014
    Posts
    20

    Default Re: Unusual outdoor project - need advice

    Quote Originally Posted by dj1 View Post
    I think that Keith is generously optimistic here. Not only you would need more supporters, you would need them closer.

    I use to use 1/2" and 3/4" galvanized pipes for slope irrigation, and some 20-25 years later they sag...and they are on the ground, not suspended in the air.

    So it's back to drawing board for you, to come up with a flawless support system.

    My advice is redesigned and improved support.

    Send pics if you can.
    The original 3/4 " PVC frame actually worked great until that rare snow, I had the tarps stretched tight over it and it looked good. The extra support I now want to have under the PVC is just to guard against a future rare snow, otherwise I'd have to take the tarp down at the first alert of a possible snow.

    It is pretty much just the 16x80 fenced in area now, I haven't put anything else up yet since about 2/3 of the PVC collapsed so there is no new construction to take pictures of yet, but I could see about uploading a picture of how it looked before the PVC collapsed.

    Quote Originally Posted by Clarence View Post
    Can you switch it to a cable system ?
    Two large ground anchors at each end at an angle to the post and use rollers on top of post attach cable to a turnbuckle at each anchor tighen to max tension for dia. of cable used ?
    That had crossed my mind before, but I wasn't sure how well it would hold up if a lot of extra weight got put on it. (has anyone here used a cable to support something that got covered with snow ?)

    I'd have to figure how thick of a cable it would need to be for an 80 foot span that could possibly at rare times be subject to a heavy snow load. (when I had to pull the collapsed tarps out from under the snow it was amazing how heavy even a few inches of snow can be !)

    If I did do it with a cable I guess I also could drill a hole near the top of the two 9 or 10 foot 4x4 posts to run it thru and use a turnbuckle to keep it tight as you mentioned. (I imagine there would be some stretching over time)

    Thanks to DJ and Clarence for your ideas !

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