Floating deck questions

[Anna]

I have all my ducks in a row for the front steps tiling project which I'm starting this weekend, so I'm planning the next project.

I have a small side yard where my shed/shop is located. My shed is only 10' by 12' and really pretty small, limiting the projects I can do. Right now, I can barely go in there without tripping on something.

I want to build a floating deck around the shed to allow me to move some of the tools outside and give me more room.

Since the yard slopes towards the street (we're on a corner lot), I'm thinking of dumping gravel on the yard to get a level base. The floating deck is just an unanchored deck with pressure treated wood for the base and probably cedar or redwood for the planks.

I have a pretty good idea on how to build the deck, but I'm not sure about the gravel part of it. Should I put sand on it, too? Is a floating deck even a good idea? My original plan was to use concrete anchors, but I'll still have to level out the ground. Then I thought I can put pavers on top of the gravel/sand instead, and finally settled with a floating deck because it's the easiest to do. I think. I've never done any of these before so I'm laboring under extreme ignorance.

It would be nice to have an even, semi-permanent/permanent surface to work on though. I would really appreciate any input/recommendations.

[LarryG]

By "floating," do you mean the bottoms of the joists will be in direct and continuous contact with the ground? If so, I'm not sure why you'd want to do it that way. You'll have to take great pains to get the subbase level, and even though you may use PT lumber it will still wick moisture from the ground. Over time, the edges of the joists will have a tendency to sink into the subbase, especially if they're resting on new fill instead of original, undisturbed earth. This can throw the deck out of level, as well as develop pockets between the joists that will inhibit drainage.

The more common method is to place concrete blocks at suitable intervals (a function of the joist size and span) and rest the framing on those. Strip the vegetation off the ground, make sure it slopes away from your shed to provide drainage, put down some landscaping fabric to control the weeds, cover it with a thin layer of gravel, set the block "piers" where they need to go, and build the deck platform.

[Anna]

Larry, wouldn't putting the gravel under the deck alleviate some of the drainage problem? I though that by using gravel and sitting the deck on it, I won't have to worry about ground contact with the treated wood.

[JR]

Larry, wouldn't putting the gravel under the deck alleviate some of the drainage problem? I though that by using gravel and sitting the deck on it, I won't have to worry about ground contact with the treated wood.

I'm not Larry, but I'll chime in with my much-less-professional opinion in support of his comments.

I think if you implemented your floating concept it would be a matter of time before you'd be unhappy. No matter the precautions you take, the thing would settle and decay as Larry described. Your suggested precautions might delay things a bit, but they'd eventually happen. You're talkng about operating tools on this deck. You don't want it to get out of whack by design!

Larry's suggestions are perfectly reasonable and easy to implement. I built a fairly complicated deck using the pre-formed concrete piers and it worked out great. Just sink the piers and take care to level things up when you install the joists.

JR

[pelligrini]

The gravel will displace. Blocks on firmly packed ground would be better.

I have a similar 'shop', a 10x12 shed. Just last summer I replaced the front deck and added a 5x12 wood storage enclosure to one side. The previous deck was a single 4x8 3/4" pressure treated plywood on a pressure treated 2x4 frame half on the ground and the other half on bricks. It had been there for at least 7 years, but I really should have replaced it the summer before. I bet it was much older than 7, I didn't know when the previous owner put it in. I also have a 2'-6"x10' concrete slab right in front of the 4' wood deck. I relocated that thing from the other side of the yard the year before.

My new deck was a similar construction, 4' deep but 10' wide. 2x4 pressure treated framing 24" O.C. sitting on bricks 12" O.C.. One long edge is screwed into the exterior rim joist of the wood shed. I packed and leveled the ground where the bricks were going to go with a big heavy 6' 4x8 post I had. The other long edge is parallel and flush with the concrete pad still.

I'd like to have a big, level, concrete pad, but for the price of some 3/4" ply and some 10' 2x4s it was hard to beat.

[Anna]

After thinking about it, I agree that you guys are right. I'll use the pre-cast concrete piers instead of a floating deck.

I found deckplans.com and used it to estimate how many blocks I'll need, etc. It's not so bad. I was hesitant about using concrete blocks because they're heavy (I want to do this on my own and not hire someone just to carry things for me). My husband then reminded me that I would have had to cart 17 tons of gravel anyway, and that would have taken quite a bit longer. With this, I'll just have the lumberyard deliver all of the concrete piers and 2-bys.

I will need a hand truck, though.

Couple more questions.

1. With the concrete piers, a 4by4 is recommended to level out the deck surface. Should I be sealing the ends of the 4by4 that is facing up or not to worry about that at all? I'm assuming the 4by4 will be pressure treated wood.

2. I'm reading about using treated wood for the surface boards. Is that at all recommended? I always assumed that I should be using cedar or redwood for decking.

Thanks, guys.

[JR]

1. With the concrete piers, a 4by4 is recommended to level out the deck surface. Should I be sealing the ends of the 4by4 that is facing up or not to worry about that at all? I'm assuming the 4by4 will be pressure treated wood.

I wouldn't worry too much about that. Of course, anything's possible, so if you want a belts and suspenders approach, you can buy a quart of green treatment stuff at HD. Easy to use and it helps.

2. I'm reading about using treated wood for the surface boards. Is that at all recommended? I always assumed that I should be using cedar or redwood for decking.

Have you looked at the composite decking that's available now? No cupping, no warping, no decay. I haven't used this stuff yet, but it looks very appealing to me.

JR

[pelligrini]

Have you looked at the composite decking that's available now? No cupping, no warping, no decay. I haven't used this stuff yet, but it looks very appealing to me.

JR

That's a good option too. A bit more expensive at first, but well worth it in the long run. We use Trex or similar on all the roof decks that we put ontop of the condos we design. My boss did a pressure treated deck on his roof. He really regrets not using Trex.

[Anna]

That's a good option too. A bit more expensive at first, but well worth it in the long run. We use Trex or similar on all the roof decks that we put ontop of the condos we design. My boss did a pressure treated deck on his roof. He really regrets not using Trex.

Last year when I first wanted to do this project, I did a bit of research into composite decking materials. I read that there's a problem with mold or some fungal growth with Trex, and that it's very slippery when wet. Is that true?

[LarryG]

The other guys have covered the settling problem with gravel. It's difficult or impossible to compact adequately by hand.

You can use treated lumber for the decking, but unless it is already very dry when it goes down, you can expect it to warp and twist severely as it air dries.

I can't speak to the Trex brand specifically, but I've been on some synthetic decking that was slicker than you-know-what when wet. One such installation was the boardwalk near Old Faithful at Yellowstone NP. The walkway stayed wet almost all the time, as you'd expect, and was darn near lethal.

[rjwaldren]

Anna,

If your in N CA, or along the coast I wouldn't recommend it. But here in the central valley the a floating deck should be fine using redwood. My father added a 30x12 foot deck 28 years ago using contruction 2x4's for the floor and redwood 2x4's for the base. Every year or so he throws a coat of Thompsons Waterseal on it. Aside from having replaced a few top boards were the sprinklers overspray it's still looks much more professionally done than it was. The redwood joists are laid directly on the ground with redbrick used here and there to level it out. It does have a tin roof over it, so only the outer edges see alot of weather.

It's hardly the "right way" to do it, but if made completely from redwood and sealed occasionally, it would work suprisingly well anywhere S of Modesto.

[pelligrini]

Last year when I first wanted to do this project, I did a bit of research into composite decking materials. I read that there's a problem with mold or some fungal growth with Trex, and that it's very slippery when wet. Is that true?

I don't know about any mold or fungal growth problems. It is a composite material though. I wonder if that article came from the American Wood Council

I had been up on the roof decks a few times at the last jobsite checking the roof drainage during the rain. I didn't notice the decking being unusually slippery.

My pressure treated plywood gets pretty slick when wet, as well as a 2nd floor wood deck off a garage apartment shop I had for a few years. I think that's more of a function of a semi smooth surface and water being a lubricant.

The no splinters in my bare feet thing would be a plus.

[Wood_workur]

rent a post hole digger, pour footings, and then put 4x4's onto those with galvanized brackets lag bolted into the cement. do it right the first time. and also, make sure you use rebar with the cement, so it doesn't crack.

[chopnhack]

As wood workur mentioned the post holes, another thought came to mind, I don't know that your deck would see that much load, but I have seen the bottoms of 4x4's cross drilled to allow #5 rebar to pass through before the post was sunk into concrete - helps with uplift too. Don't know that you would be placing that kind of load or not, but its a thought. Also, use the coated/plated connectors on your joists to rim connection, they help during the install and add strength. Don't forget some z-flashing on rim joist between shed - so water doesnt eat away at rim board. Have fun!

[jaybee]

I used this stuff with adjustable supports to make the front door decking and steps on the house. I had to adjust twice in the softest corner, now it no longer moves.

http://www.decorprecast.com/code/HowTo/HTDekBlock.html