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Deck Slowly Moving Down the Hill

Post in 'DIY and General non-hearth advice' started by Mo Heat, Jun 4, 2007.

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  1. nshif

    nshif New Member

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    BG
    There is 2 types of PT lumber, one made to be in contact with the ground (retaining walls, fence posts etc. ) the other for use off of the ground ( sill plates, deck rails etc. ) Perhaps you had the 2nd type.
    The 1st type is brown and the 2nd is greenish.I used to know the technical names but dont remember right now. If need be I can find out.

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  2. begreen

    begreen Mooderator Staff Member

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    It was the brown type that failed. I think I have some of the sticks left. They were buried 30" into the ground. Most of what was in the soil just disintegrated. The round posts are greenish from the copper solution they treat it with.
  3. nshif

    nshif New Member

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  4. Mo Heat

    Mo Heat Mod Emeritus

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    nshif, nice photos. It looks like you used all cedar joists and posts, and used some sort of plywood for the actual floor of the deck instead of cedar 2x floor boards spaced for water to fall through. Is that right? No PT joists? No 2 x 6's floor boards? Is that cedar veneered plywood? (I've got some of that under my front porch overhang and like it.)

    Question on the lag bolts that attach the ledger to the house:

    How are those attached? Are they actually lag "screws"? Or did you have access to the back of the ledger connect area so you could thread on some nuts and maybe some lock washers? I have no access to the back of my ledger board, so could I use some sort of "lag screw" that just screws right in there with no nuts on the other side?

    Wow. With all this help, and elk emailing me, I'm starting to feel like I might actually be able to pull this thing off... one of these days...

    Goose, Good idea about partially burying the RR ties on the hill. That does make more since. In California, I saw them used a lot for trail maintenance where they were drilled, partially buried like you suggest, and then re-bar was driven down into the ground, through the drilled holes, as a bit of an anchor. I might try that if I can get a big enough drill bit.

    I read nshif's link re: PT lumber. Good lord! I can just see Billy Bob's Deck Building LLC employees shopping for one of the plethora of new PT rated lumber and PT safe fasteners at HD now... "Uh, hey Clem (Billy's brother), make sure you git dem G-185 electro galvanized fasteners so we don't have no copper galvanic electric chemical corrosion reactions to dem sub rated fasteners likes we use on our premium cedar decks. You knows I hates rebuilding decks in jus a few years."

    Now to be a carpenter, you've got to understand advanced chemistry!? This means trouble if you ask me.
  5. nshif

    nshif New Member

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    Mo
    I gotta run to diner at the neighbors, Ill get back to you in an hour or so.
  6. Gooserider

    Gooserider Mod Emeritus

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    Don't know about Nshif's specific job, but "lag bolts" are really lag screws, the giant wood screws on steroids type items, but by confusing custom they are called bolts rather than screws... :-S If you put those in properly, however, you will pretty much have to demolish the boards to get them apart. You should choose a length that is just shy of penetrating the full width of the boards you are lagging together, or a shank (unthreaded bit) about the same length as the peice you are going through. Put a clearance hole the diameter of the shank in the first peice, and a relief hole just under the minor thread diameter for the depth of the bolt in the peice you are screwing into, and use a flat washer under the bolt head. Crank them down tight and you will have an assembly that is arguably stronger than if it had been a solid wood beam.

    You can get through an RR tie with a 'spade bit' (i.e. Irwin "Speed bore") and it is also possible to buy extensions for spade bits, but it's a bit of a pain as after a couple inches, spade bits have trouble clearing the chips out of their hole and tend to overheat and / or bind up. A better job can be done if you get one of the extra long auger style bits - the long spiral does a better job of clearing the chips.

    Yep, it's getting more complicated all the time, although the industry claims to be getting better at finding a workable solution.

    Gooserider
  7. nshif

    nshif New Member

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    Or know how to use the internet!
  8. jjbaer

    jjbaer New Member

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    UR,

    In my engineering opinion, it's not wise to build a brick wall that high as a retaining wall.......something that high and wide on a hill needs to be built of poured concrete........THEN if you want to, use a decorative brick facade but under NO circumstances should you count on that brick having much structural integrity.......
  9. Gooserider

    Gooserider Mod Emeritus

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    Agreed, I'm not an engineer, but it is fairly well known that brick, concrete blocks, etc. has tremendous compressive strength, but virtually no shear or tension strength Poured masonry is better, but not by a huge amount - poured concrete structures get most of their shear and tension strength from the steel rebar that's embedded in it.

    Gooserider
  10. jjbaer

    jjbaer New Member

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    Yes Goose but with a one-piece poured-reinforced concrete wall, all parts tend to reinforce other weak parts that might want to (as I see in the photo) locally "bulge out"............there's NO WAY a stone wall that high, even if it's interlocked, can hold up against earth that wants to move......and that's what I see in the photo........the owner should really be going after the contractor who built the wall.........50 ft tall and made of pieces of stone.....YGTBSM.........think of a dam....it's arched backwards against the water so that the pressure from the water: 1) puts the concrete in compression (where it is strong) and 2) forces the dam against the side supports to prevent the entire structure from being dislodged .......
  11. jjbaer

    jjbaer New Member

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    Mo,

    do you have a "zoom out" photo showing where those slabs are located that you're measuring....?
  12. Mo Heat

    Mo Heat Mod Emeritus

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    Is this one good enough?

    The slab I'm measuring is the one closest to the camera and on the right side of the frame. The deck post that's in the same portion of the photo is about where the corner of the slab ends, although it is just out of the frame.

    Attached Files:

  13. Gooserider

    Gooserider Mod Emeritus

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    That movement would be considerable IF it was "REAL". However I see problems with the measurment - first the equipment is not that great! Nothing against Dino, but the specs on that ruler are probably not all that accurate to begin with. Next you don't seem to have a good way of ensuring that you are always measuring EXACTLY the same place, but your slabs aren't perfectly straight, so you might just be measuring "noise". Lastly, your slabs have rounded edges, so it is a bit of a judgement call as to just what the measurment points should be... Bottom line is I wouldn't trust your measurments to be more than accurate than about +/- a full centimeter, so I don't know if there really is a significant movement or not.

    I would suggest trying to permanently attach a sharp cornered peice of metal angle to each edge of the slabs and SCRIBING a measuring line across them so that you know exactly where to measure each time. Alternatively put a small disk of metal permanently on each slab, and inscribe a crosshair on each one to define your measuring points (Note that if done right you can also use these marks to check for N/S movement as well as E/W) By permanently attaching the markers to each slab, you will know you are measuring from the same point each time, and the sharply scribed lines will eliminate the doubt about where the points are. Lastly, give Dino back to the rugrat, and get a good steel engineers scale that will accurately measure down to as good as your eyesight...

    IOW, it's hard to do good science with junk data...

    Gooserider
  14. Mo Heat

    Mo Heat Mod Emeritus

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    Now you've gone and hurt my feelings... and Dino's, too. :p

    But I get your drift and agree, but I can also tell you this, when I moved in here, those slabs still had the one inch wood in the spaces between them, and there was zero gap between the wood and slabs. And all the spaces were exactly the same. That was about 7 years ago, so while anecdotal, I'm confident that all that movement occurred in the last 7 years, or so, since I moved in here.

    Still, I should probably get a gauge on how fast they are moving. I'll re-read your instructions and see what I can come up with. Thanks.
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