My wife wants me to build a deck off the back of our house and we are
on a slab. There currently is a 10 x 10 concrete patio that I would
build over top and the deck would be approximately 18 x 12. My
question has more to do with choosing joists for the deck. I currently
have approx 5 1/2" from the concrete patio to the bottom of the patio
door. This raises a couple of red flags in my mind and am trying to
figure out my options.
My initial idea would be to use 2x4s for joists and have lots of
supports (block supports on top of the patio and concrete anchored
posts in the area around the patio.
My other question is I would rather not have critters living under the
deck. Could I fill in between the joist with drainage gravel before I
lay the deck boards?
Thanks for the help
Try to convince your wife that this is a bad idea. Having a deck is
like adopting another child, one thing after the other. If she likes
the idea of a wooden fence around her outdoor area, just build one on
or next to the concrete. Remind her that there will be fewer rats,
vermin, spiders, ants and all the other things that ruin outdoor
frolics. Convince her that painting the concrete to look like redwood
boards will save enough money to buy granite topped table and patio
chairs. You might even mention that tipping over a charcoal grill will
set fire to the deck, but concrete is forever.
On the other hand, if you need an aggravating new hobby to fill your
time, then go for it. But your lawn will suffer. Cheers
Joe, as a SWMBO, that aint gonna work ;-) However, now adays they have some
very *nice* looking exterior carpets which should be investigated in a case
like this. Yes, they can get rained on and all that and weather well. They
take to either a vacumn cleaner or a broom just fine. They can go directly
on that cement patio and spiff it up alot. They are generally 3$ a yard or
less but the really nifty ones can run up to 6$ a square yard. They come in
solid pieces so wont 'peel up' in squares.
I have one now, 12x13 solid piece in a sunroom built on a slab. I could
have gone with interior carpet but hedged my bets 'just in case' and am
quite happy with it. My porch, which is screened and roofed but otherwise
open to the elements, has another. It's 36x12 and one big piece.
Here's another advantage to outdoor carpet. The legs of you chairs wont get
stuck between boards. Costs a heck of a lot less than a wood deck and there
will be money left over for spiffy lawn furniture. You can even select a
spot for an outdoor caldera, cut a square of carpet out then raise a section
with paving stones right on the slab, and have a picture perfect outdoor
spot useful in chilly times.
Sounds like SWMBO wants a wood surface to walk on?
Best to step down slightly from door to deck surface? Especially if
snow build up in that area.**
Maybe you could strap thin slats of wood to the concrete using drilled
in plug-bolts or fired down fasteners (Hilti-gun etc.).
At suitable 12 or 16 centres etc,Those slats could be pressure treated
to minimize rot against the damp concrete.
Then fasten decking to the slats.
Suggest that ventilation between slats below decking will reduce
moisture build up and minimize mould and rot. Blocking it off may not
be good idea, despite 'critters'. Our wooden deck is no more than 15
inches max. above ground and leaves etc. do blow in there. But we keep
it ventilated to avoid mould and dampness under. We occasionally get a
visting cat under there stalking birds but banging or jumping on deck
scares them away.
Hopefully the OP's concrete pad is level or slightly sloping away from
house and is in good shape to accept other material fastened to it?
Our decvk is built strong enough to take snow drifts and snow off the
roof, most winters, the size of a couple of Volkswagens, without
The real solution is to not build a deck. Concrete or other masonry patios
require just about no maintenance at all for years and years. Adding wood
atop it is only going to make breeding places for bugs, rodents, mold,
fungi, worms, odors, and collect trash, crumbs for the rodents to feed on,
Decks that are well above the ground are fine, but on ground level or a few
inches above is just going to make a lot of work. If you want to change the
appearance, look at adding a veneer of flagstone or brick. Extend the
existing patio and save many hours of labor caring for a deck.
As others pointed out, I would look at my options b/4 going through with
Here's something I did years ago for someone, which wanted a "budget" deck.
(Sorry the pictures are so small, I scanned them years ago, and had cropped
them too much)
I edged the concrete with 2"x6" treated, using PL400 and lags with anchors.
The look was an inset of the concrete with wood. The rail posts were 4x4,
cut to height, notched to fit over the 2x rim. The rest speaks for its
self. The important part is making sure like any deck railing, of tying it
all together so your corners are strong.
If you stain the concrete, or cover it with outdoor carpeting as one poster
suggested, you can totally change the look of "concrete".
If you want bigger than your 10x10, pour another concrete slab besides the
existing, it probably would be more cost efficient.
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