Have any of you used those concrete pyramids with the tops cut off (and the slots in the tops for joists) for decks? How do you do it? Do you have to have footings under those blocks, or just lay them in a bed of gravel, or what? I figured they’d move around too much if you just lay them on the ground and put your joists into the slots. Anyway, son-in-law was wondering if I should build their porch/deck using those instead of posts going down below frost line. I was thinking “no,” but thought I’d see if any of you had experience with these concrete pier thingys. He said a deck at his parents’ house was built on them, but didn’t know anything else about them.
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Replies
I am curious about these floating decks, myself.
Until someone with practical experience comes along, here is some info I dug up:
http://www.deckplans.com/
Edited 8/26/2007 11:37 pm by Heck
Thnaks for the link. Since this is a porch and small and steps are the main reason for it and eventually the lowest step has to rest on the ground, I think I'll just go with my original plan to frame it in three tiers, one on top of the other and supported by posts into the ground. Have to have a railing anyway, and eventually they are talking about a roof over it, which I think can just be tied into the posts too, so I guess posts is they way to go. Unless the ground has lots of rocks or clay or tree roots, then I'll have to consider the blocks.
I've used the Dek block brand and they are fine if you follow the directions. They have to sit on well-drained, compacted gravel, so you'll still have to dig a hole for each one. If the site has a grade you space the deck joists with 4x4s inserted into the blocks. Movement can be minimized by putting the blocks 3 inches below grade (in a bigger hole) and surrounding them with gravel. The taper will keep them in place if the surface soil heaves in the winter. Make sure the deck doesn't have running water under it or the blocks can be washed out.
Thanks for your reply. As I told Heck, I need to have at least part of the "deck" (porch actually) on grade, I was going to just go with posts, but your talking about digging under the deck piers to set them made me think that I could possibly imbed them almost their full dept in the ground and just put the joists on them and still build the rest in tiers. Hmm...gotta figure this out by Thursday!
Edit: Just thinking that imbedding the blocks may make them susceptable to frost heave unless I put gravel under them and then I may as well just put posts in.... Still thinking--look out world!
Edited 8/27/2007 7:43 am ET by Danno
Put gravel both under them and around them and there will be less frost heave, but obviously in any deep frost region they're gonna move. You don't want to use them for an attached deck in such conditions.There is the issue that these don't provide a good way to anchor the deck. A strong wind from the wrong direction could send the whole thing flying. Ideally a couple of mobile home anchors should be installed to keep the deck from going too far.
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
Thanks--good advice about tying the deck down--didn't even think of that when considering using those Dek-blocks. Since the reason I'm taking old porch out and putting in new one is that the old steps had tilted and were dangerous, I think I'll go with putting posts into post holes that go down at least 42" (Michigan).
My way -
http://forums.taunton.com/tp-breaktime/messages?msg=72036.1
Pic -
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Forrest
Good pic. Like I said, if dug into the soil, either has to be very well drained, or below frost, and in that case I guess they'd be as good as footings for the posts, but then I'd have to dig big holes and I'm lazy!
Why would you use these in place of pouring a concrete footer?
Jon Blakemore
RappahannockINC.com Fredericksburg, VA
Fast, cheap, and easy.
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
I often do both - place a concrete footer in an oversize hole; floated off level, then slide the pyramid block around to XY position it perfectly.
Forrest
What DanH said.
Project is done. Had to rent a "breaker" hammer--gas powered, what I call a jack-hammer. The three steps were poured along with the sides in a monolythic pour and tied to foundation with one re-bar at each joint (was one time I was glad I weigh over 200 lbs.--the more weight the merrier when leaning into a breaker (breaking?)hammer). (The top of the last "step" was about 1" below the sidewalk that goes up to the porch. Then the interior was filled with rocks and sand and bricks (some of the rocks were so heavy I couldn't pick them up--had to break out the sides and roll them out after prying them up with a big bar).)
Used two "Dek-blocks" under the second level near the ends of two beams that support the top deck. Whole thing is only 24" high, top is 8' x 4' and steps make the leg of an "L" about 64" wide and 32" deep (each step about 16"). Built the steps in two layers first and then the top, which cantilevers 32" beyond one side of the steps (16" beyond the "Dek-blocks").
Was glad to get it done in the allotted time!
I've built a few decks using pier and beam structural support. The piers I've used don't have joist "slots" - just a piece of 2x6 cast into the top. I usually puddle some concrete under each pier and use a piece of 4x4 between the pier and the deck joist. I also make sure that I have good drainage under the deck. We have lots of clay here and good drainage is essential to minimize the "swelling" of wet clay.
This works fine here in CA where we never get freezing weather, but I wouldn't do it if there's a chance of frost heaves.
We have done 2 of these decks. One was about 200 square feet, and a simple rectangle. The other was a 640 square foot deck on three levels. These decks have their place, but there are some restrictions. The deck plan site that someone else posted is very helpful, and they have a tech. line, as well.
First, you cannot use these blocks over a certain height - I think it's 5' high. Also, if the deck is over 30" tall, you have to tie the outer posts together.
Second, you CANNOT attach this deck to your house. It is designed to be a floating deck. If there's frost heaving, it will come back to it's original place when the heaving ends. The blocks sit on the topsoil, where they can move freely if there is heaving, and then move back when it stops.
The building process is fairly simple, and we like both of our decks very much. Use their website for more info....