[mbmsv]

In particular, can I build a platform on the top of a deck as shown?

The main deck is about 22-1/4" above the grade and the additional platform framing is made of 2x8, i.e. it adds one step with 7-1/4" rise.

The beams are 2-2x8, joists are 2x8. Posts are 4x4 and I am planning to install them into TuffBlocks because standard deck blocks are too high.

Will there be any problems with lateral stability?

Thanks!

 

[chandler48]

How are your beams connected to your posts? 6x6 would fare better, since you can embed the 2-2x8's and bolt them to the post. You can't just bolt the beams to the post's side. You can always (if you can find them) use post caps that fit the posts and conversely fit the doubled 2x8's, and sit them on top of the posts.

IF your raised portion brings the total height above 36", you will need to guard rail that portion, whereas the remainder won't be required.

 

[joed]

You will most likely need a railing. I believe anything over 24" needs a railing.

 

[lenaitch]

I think you are asking two questions. Whether it will be stable is valid question for the folks here (not me). Otherwise, here's the Ontario Building Code, happy reading. Layered onto to that is you municipality, who are the code enforcers. Each has their own particularly requirements, often based on local factors such as soil conditions. Many would not require a permit for a deck of that height; some go by construction type (floating vs. fixed), others by area.


http://www.buildingcode.online/

 

[mbmsv]

How are your beams connected to your posts?

Post caps

6x6 would fare better

Possibly but I couldn't find deck blocks that would take 6x6 except for Titan Deck Foot Anchors, which are great but quite expensive.

IF your raised portion brings the total height above 36", you will need to guard rail that portion, whereas the remainder won't be required.

I hid the railing for clarity. The top portion of the deck sits at about 30". I would make the whole deck of that height but there is a local zoning restriction forbidding a deck taller than 24" to project from the house for more than 2 meters.

 

[mbmsv]

Many would not require a permit for a deck of that height; some go by construction type (floating vs. fixed), others by area.

In my area a permit is required for any deck if it is bigger than 108 sq.feet.

 

[House Designer]

Lateral stability for a deck refers to it's ability to stay fixed in its position over time, and not rock or rack sideways or away from the house. You also don't want the deck to "walk" away from the house after successive frost heave cycles, and you don't want it to fall off of its deck blocks.

Deck blocks do not contribute any lateral stability whatsoever. My deck that rested on grade beams got its lateral stability from four gazebo posts that passed through the deck and became captive "slides."

You can't anchor a free-standing deck to the house, since the house doesn't heave with frost and the deck will heave with frost.

One thing you can do is install a vertical 4x4 post in the ground, just inside the two outside framing corners of the deck. Embed the posts 36" - 48" into the ground. Then captivate the deck to the posts by boxing around the posts with wood blocking to create a "sleeve." The posts need not protrude through the decking. Then, the deck can slide along the posts up and down as the frost heaves. This provides lateral stability to your deck.

 

[mbmsv]

Lateral stability for a deck refers to it's ability to stay fixed in its position over time, and not rock or rack sideways or away from the house.

I was mostly asking about rocking and swaying. I saw in some "municipal code" that diagonal bracing between posts is required if the deck is 30" above the ground or more. My main deck is below that number but the platform is approaching 30", however the posts are so short that there is simply no room for any bracing.

 

[SPS-1]

I assume that is a step-down from your patio doors. The height seems to be code acceptable. I have a step down from patio doors on my deck, and it passed inspection. Mine is only about 3 feet long, but I can't see how it would make a difference to code if its 10 feet long. But I think there is possible that the inspector can say its too deep (i.e. the run) to be a proper step. But mine is about 14" deep and it passed.

Edit : 7.25" plus .75" is your actual step height. I think Ontario code is worded that a step is 200mm max, which is a hair higher. Not sure how fussy they are about that. You can't be the first to have done that.


.

 

[Nealtw]

Use 6x6 posts and notch and bolt them with 2 bolts, that should lock them up stiff.

 

[carpdad]

4x4 doesn't last as long as 6x6. If only choice is 4x4, do your best to keep water off it. Where beam meets the posts, you can cover the end grain with weather tape, example. Make the tape bigger and overhanging so water sheds off it. Normally I'd say skip such weather barriers but in this case 4x4 is kind of weak. Also use washers or such to leave a air gap between the block and the post end grain.



If planning rails, raised platform must have 36" high. Even if it's a low deck, railing itself must be the rule's height. That would make other sides high, if you keep the height uniform. if different heights, you may need extra post. Take the benches, example. I would want 36 high rails around the bench so any kid fooling on the bench would have properly high rails.



I never read such a platform before. What's it for?

 

[Nealtw]

Cut a notch in a 6x6 to fit it in the 4" saddle.

 

[carpdad]

If 6x6 is cut down to 4x4, isn't that cutting away that much more chemicals and meat?



OP: I think 4x4 is fine for that height. I just meant that 6x6 has more meat, so it makes sense that 6x6 will last longer. Same chemicals so after the chemicals are leached out, bugs/bacteria/fungus will do their jobs at same pace. Keeping the endgrains dry helps.

 

[Nealtw]

If 6x6 is cut down to 4x4, isn't that cutting away that much more chemicals and meat?



OP: I think 4x4 is fine for that height. I just meant that 6x6 has more meat, so it makes sense that 6x6 will last longer. Same chemicals so after the chemicals are leached out, bugs/bacteria/fungus will do their jobs at same pace. Keeping the endgrains dry helps.

We see them cut all the time to fit misaligned saddles, but you are right about the bottom being exposed to water. Our decks are usually solid surface so dry below.

Then I would use a blank pyramid and drill it for the 6" saddle.

I like the 6" so it can be stepped and and bolted to the beam, adding stiffness.

I guess he could use 4x6s :wink2: