Personally I wouldn’t use deck blocks. I built my deck about the same size and not attached to the house. I’m in Florida so no frost line but I still dug to 24” for footings. My only advice is rent an auger, I didn’t and regretted it. My back still hurts just thinking about it. 😀. Good luck

Oh, if I had to go the footing route. I would ABSOLUTELY rent an auger. I'm too old and whiney to deal with that kind of pain

Only use a deck block if you know 100% that the ground won't move. If frost is an issue at all, pour the footings.

Canada means frost heave will be an issue for sure

Thanks. This was the answer I needed, but didn't want to hear

I did my deck with blocks and I dug down a few feet and under each block and tamped limestone down to make a good base. It’s been 3 winters and she hasn’t budged…. I didn’t attach it to the house either. Southern Ontario as well

Really? Ah man, you're making this decision harder

I'm not going to say whether you should or shouldn't, but I will point out that model codes require something to prevent uplift due to wind, which deck blocks will not solve. Otherwise you've just built a giant heavy sail-projectile wrecking thing for the next tornado or wind shear. You may find that the work to sufficiently anchor it down to be close to the work required to put in some sort of actual foundation.

Quick thought. You're going to want to make sure the ground underneath the deck has a nice slope away from the house. Any dirt you pull for piles is dirt you can use for grading.

Normally, I would say go with a couple feet of gravel and deck blocks, but a 12' x 24' deck is a little large to lift and adjust he blocks after, if need be. If that happens, you'll be very unhappy with the time you "saved" during installation.

For a deck that size in south ontario I would put posts in 42"- 48" deep sonotube. Deckblocks can be okayish for tiny decks but you will have problems with a 12x24 on them.

False, there are soils that are none frost susceptible (NFS) like dry gravel that don't heave.

In some soils a footing to the frost line isnt sufficient to prevent frost jacking. Where the freezing soil heaving lifts the footer out of the ground with friction along the sides instead of from heaving underneath.

We have a similar setup to what you have, in Ontario. We are now looking to add a gazebo or screen room on top of that deck, and we cannot get a permit unless the posts go down to frost level. If that is even a remote possibility in the future, save yourself the trouble and do it properly now. We wish we'd known that 10 years ago.

Check your local building codes. Most municipalities are more than happy to chat

Thank you for this. We were toying with the idea, so no doubt we'll do something in the future

You would go down 4ft for a deck that is 18 inches off the ground?

Sorry to be the bearer of bad news but frost makes decks miserable if there's no footings

What kind of deck? Drip through decking or vinyl? If you go the deck block route I’d still dig down a few feet and compact gravel in the hole then put the block on that. I would also make it a free standing structure and not attach it to the house via a ledger. I would still advise the concrete route though.

Northern Minnesotan here. I’ve had good luck using deck blocks. Just dig a little hole/trench, fill with play sand, tamp down, and place deck blocks.

The shits going to move regardless. After the first few winters you’ll need to shim around a bit, but after that you should be fine.

You need to penetrate below the frost line regardless of how far off the ground the deck is.

I'm also in southern Ontario and planning a deck build. Was thinking blocks, but will probably do footings.

Instead of an auger, go to home depot and rent the little skid steer thing with an auger on it. They're fairly cheap and you get the pleasure of a machine doing all the hard work for you. Bonus points for it because they usually send it on a trailer with a little bucket too so you can easily deal with the dirt from the hole.

That's the frost line in southern Ontario. There's no sense pouring a footing unless you get below the frost.

Southeast Michigan here - slightly north of Windsor, Ontario. I have about 1000 SF of decking, portions built in 1984, 1994, 2005. Did them all with a rented post hole digger and a couple bags of Redi-mix each. The last section was done with sonotubes. All are still rock solid. It wasn’t that expensive - and probably just a day or two to auger the post holes, pour and set the posts.

The decking and railings cost way more than setting posts.

I've built 2 different decks on blocks at 2 different houses. No issues whatsoever.

I did a big long wrap around step on 2 sides, and trimmed the 3rd side out with boards. No lattice. No wind getting up underneath whatsoever.

If code allows it, I say go for it.

If it were me I’d just hire someone to pour a patio slab. Way lower maintenance than a wood deck and probably cheaper than a composite deck. Just my 2 cents. I hired my 2nd floor deck done so I can’t really comment on your specific question.

I rented an auger and it destroyed me and my friend's backs. Deadlifting a 75 pound machine with 150 pounds of soil clinging to it 4 feet straight up out of a hole is not easy. The auger is certainly faster. . . but it sure as hell isn't easy.

I would not do deck blocks…I would do a 24”x24x18” footing with a Simpson post base….and a couple of #4 bars horiz. And a bent one going from horiz to vert in center … I would also do a sono tube -8” above grade , burying posts is a bad idea even if ptdf…I build in Ca so frost not an issue, wood has no business sub grade, and deck blocks unless set in a footing are shit. I have built many decks this way, no issues.

Get a post hole digger and dig a few feet down. Put the post in and pour the cement in around it. This is the only way to do it without a sloped deck in a year. I did a deck on a house I flipped without using posts and it was terrible looking after the first year.

If you're attaching the deck to the house you 100% need to get down to below frost depth, otherwise the deck will pull away from the house.

Barrie contractor - yes pour columns down below your local frost line about 36 inches, install 6x6 saddles for the post and carry on from there. Frost heave will not be pretty on the new deck, if your not attaching to the house then it will otherwise be truest floating with no anchor points.