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Howdy!This is a friend asking for help to build a deck with myself as the lead. I've built a dozen decks over the years. Would appreciate some feed back before I get into this deck project (before the snow flies). I'm north of the 49th parallel. Frost line 6 ft. I'm from an area where there is an abundance of bedrock. Deck I'm working on is a new home construction on bed rock and places where there is clay. Friend wants me to build a floating deck by putting down "A" gravel and tamping with soil tamper. Deck blocks to sit on precast concrete pad. Deck height ground level to 2ft.. He built an entrance deck last year and wants to work off this. I'll put a level on the existing deck and see if existing deck has remained level.

I've read some of the feedback on other deck projects and have been impressed by the professional and skilled suggestions. (I'm building a deck on a house of mine at a 12 ft height that I've gleaned some important feedback especially on fastening the ledger to brick veneer.)

The Ask: Does anyone out there in "deckland" have any suggestions as to building on grade on tampered gravel? Also, a discussion I've had amidst DIYer's on setting blocks on grade is if it is a house that has had 30 -40 years of undisturbed soil then why not build on grade?

Thanks! Look forward to the feedback. ~ Dave
 

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hurtlocker
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As a rule of thumb for myself I do not connect anything without footings to something with footings. Your undisturbed soil theory is not good. All the footing failures I see have one or both of the following.
Poor soil capacity and or water in the soil.
 

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The frost will heave the deck. That's the reason for deep footings. Fine homebulding mag had a good story on the why a couple of issues back
 

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GC/carpenter
GC/Carpenter
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dave battaino said:
Howdy!This is a friend asking for help to build a deck with myself as the lead. I've built a dozen decks over the years. Would appreciate some feed back before I get into this deck project (before the snow flies). I'm north of the 49th parallel. Frost line 6 ft. I'm from an area where there is an abundance of bedrock. Deck I'm working on is a new home construction on bed rock and places where there is clay. Friend wants me to build a floating deck by putting down "A" gravel and tamping with soil tamper. Deck blocks to sit on precast concrete pad. Deck height ground level to 2ft.. He built an entrance deck last year and wants to work off this. I'll put a level on the existing deck and see if existing deck has remained level. I've read some of the feedback on other deck projects and have been impressed by the professional and skilled suggestions. (I'm building a deck on a house of mine at a 12 ft height that I've gleaned some important feedback especially on fastening the ledger to brick veneer.) The Ask: Does anyone out there in "deckland" have any suggestions as to building on grade on tampered gravel? Also, a discussion I've had amidst DIYer's on setting blocks on grade is if it is a house that has had 30 -40 years of undisturbed soil then why not build on grade? Thanks! Look forward to the feedback. ~ Dave
build decks on grade all the time out here, but its Southern California. Not only will you have heave from frost, but you mentioned it is partial clay, which can heave also with a lot of rain. Clay is notorious for swelling when soaked.
 

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Hack
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I think he means a crush base, then a precast (maybe 2x2'?) concrete pad, and then a post block.

Well...with a 6'frost line, it'll definitely float.
 

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It will definitely float - up and down many times a year and occasionally will come back to where is was. In the mean time, it will tear itself up at every connection.

Just get an auger (or hire someone) to punch in holes for Sonotubes to a sound bottom. - You will use a known amount of concrete and fill tubes at your own pace. The real benefit is that the sides of the Sonotubes are smooth and the concrete will not be pulled up by the freezing soil around the tube. Soil freezes from the top down and the actual depth varies every year, but the concrete will stay in the same place.

Use whatever connections embedded in the concrete at or above grade you chose.
 
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Discussion Starter #10
Thanks guys for the replies. Bob I was meaning a 2x2 ft concrete pad on tampered gravel with a post block on top of pad. I acknowledge the auger suggestion Dick which probably is the prudent way to go if I am to do it correctly.
 
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