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ktulu05 07-18-2008 10:14 AM

Ground-level deck
 
Hi,

I'm planning for our next project, which is a 14x16 deck. We want the deck to be low to the ground, because of the door that we'll be using to go out to the deck. The main problem I'm trying to work through is that the deck either needs to be bolted to the house foundation (hollow concrete block with brick covering) or concrete post footings next to the house.

From reading online, it looks like attaching ledgers to hollow block isn't a great idea, because they may not hold well. A few years ago we had to have the house waterproofed, which means that there's a 2' ring of river rock (smooth, not packable) around our house. I'm not sure that a concrete footer in the river rock would be so stable, since the river rock doesn't pack well. I'm not sure if the first concrete piers could be a few feet away from the house, where they would be buried in solid material.

Any thoughts/comments/pictures would be appreciated.

-Kevin

47_47 07-18-2008 11:01 AM

You are correct that you can't attach a ledger to brick and the river rock will not support the concrete piers. You will need to get the piers into undisturbed soil. How high is the door above the grade?

ktulu05 07-18-2008 11:14 AM

The door is about 16" above grade. Telephone wire is about 10' above grade. Powerlines are about 14' above grade. I did just read that deck cantilevers are allowed, usually 2-3' maximum. So it seems possible that I could get away with having the first footing 2-3' away from the house, but I'd have to run this by the inspector.

47_47 07-18-2008 11:53 AM

You don't have much height to work with for a wooden deck. If you used 2x8's for the beams and joists (2x7=14") and used 1" stock for the decking, you are at 16" with your beam sitting on grade. I do not know how much you can cantilever a 2x8 or if this will be (2x8 beams and joists)strong enough.
That river rock is drainage stone and it won't make a suitable underlying base for even a paver patio.
My only thought is if you could remove the brick and grout the block you could possibly mount a ledger to your house. Your inspector will tell you if it is ok.

ktulu05 07-18-2008 01:46 PM

A neighbor put up a deck that is probably 6-7" off the ground, not using drop beams. Just joists sitting on concrete columns. I realize that you would need substantially more concrete columns to properly support the weight if you didn't go with a drop-beam design. If I went with 2x10's or 2x12's, that might be enough for the cantilever.

Do you know if utilities will bury their wires on your property? I would do it myself, though I'm guessing they probably wouldn't like that. That would give a lot more clearance.

I'm also trying to keep it low to the ground, because I was hoping to also build a pergola structure overtop part of the deck. Attaching the pergola to the house is easy, but the gutter line is about 10' above grade (roof slope goes from there).

BuiltByMAC 07-19-2008 03:36 PM

Quote:

Originally Posted by ktulu05 (Post 140492)
Just joists sitting on concrete columns. I realize that you would need substantially more concrete columns to properly support the weight if you didn't go with a drop-beam design. If I went with 2x10's or 2x12's, that might be enough for the cantilever.

You wouldn't be able to cantilever joists if there isn't a beam under them to carry the load, unless you wanted to put a footing down for EACH joist.
Try this:
concrete footings dug at 2' from house (you'll need to hold the river rock back from falling in the hole)
Pour concrete footing 1" above grade, footings level w/ each other (1")
4x6 beams w/ footing support every 5' (5 1/2")
2x8 joists, 16" o.c., cantilevered over the house side beam 2' (7 1/2")
1 line of joist bay blocking staggered over house side beam and one at 10' out from house
Decking, start it 1/2" away from house (1 1/2")

Plan your pergola post locations before you build your deck so you can dig and pour all footings at once.
Check local codes for clearance issues w/ power line and pergola.
No, you can't bury lines yourself. Call the power co. - they might...for a fee.
Careful attaching the pergola to the house - rarely is the fascia board(what the gutter hangs off of) strong enough to carry that additional weight. It's not a structural member and the rafter tails aren't usually built to carry that load.

Mac


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