Replies

1. 
   DanH | Jul 12, 2014 06:16pm | #1

   There are two problems:

   1. The deck must be sufficiently close to the building that one can comfortably step from house to deck and back, and close enough that no one (including an infant) can fall between the deck and the house.

   2. Attaching the deck to the house provides one degree of ridigity that otherwise must be provided by the deck structure itself.  This can, eg, eliiminate the need for knee bracing.  (Of course, for a low deck this may not be a significant issue.)

2. 
   oldhand | Jul 12, 2014 08:08pm | #2

   I think....

   I'm a big fan of not attaching the deck to the house.

1. 
   MarkH | Jul 12, 2014 09:05pm | #3

   I'll take it further, why do people think attaching a deck to a house is a good idea?

3. 
   DanH | Jul 12, 2014 09:07pm | #4

   It should be noted that "attaching a deck to a house" does not necessarily involve installing a ledger.  You only need the ledger if the house will carry some of the deck load.  You can still have the deck in contact with the house and perhaps anchored to the house framing for lateral stability without using a ledger and hanging deck joists on it.

4. 
   MYBuilder | Jul 12, 2014 11:12pm | #5

   In two of the five jurisdictions we build in, two of them require decks to be attached to the house. Our last deck was in back of a slab on grade. I didn't imagine needing to attach to the block foundation, but I was tagged. They felt the deck would fall away from the house. All the way down six inches.

1. 
   DanH | Jul 12, 2014 11:38pm | #6

   But oddly, having the deck attached to the house is probably a bigger hazard than having it free-standing.  Virtually all deck collapses I've heard of (it seems like there are several up in the Twin Cities every year) are due to the ledger detaching from the house.

5. 
   deadnuts | Jul 13, 2014 06:21pm | #7

   Generally speaking, no.

   But leaving a 6" space between a deck and a house is asking for trouble. It's excessive. Besides, if you are required to meet code for your deck guard rail system, the maxium opening must be less than a 4" sphere.

   If you  want to design your deck to be independently structured from the house*, then IMO you shouldn't leave more than about 1" gap between the home and deck. I think that introducing more than this presents the user with a certain amount of unneccassary trepidation while crossing to and fro. I would argue that it almost creates a "cattle guard" effect.

   *you could argue the reasons for and against doing this until the cows come home. In my opinion, it's a fruitless excercise ---unless there are objective reasons for other. The only one can think of is that your HOA or local juristiction requires one or the other. And, FWIW, I don't believe the IRC weighs in on making either choice.

6. 
   renosteinke | Jul 15, 2014 12:53pm | #8

   Exceptional Replies!

   And I thank you all.

   So, if I understand the replies correctly, there is no requirement that a deck be attached - but there are specific requirements to meet IF the deck is attached.

   I can see where, especially for a larger, higher deck, where using the house for support can be useful. 

   Since my OP, I've looked at a number of decks and stair arrangements, and I've been surprised at what I've seen. Nearly every example I've looked at has had the supports at / on the extreme perimeter of the platform. This is not at all what I imagined - instead, I imagine the posts supporting widely spaced beams, with joists and decking above. Small wonder so many have problems with the "plastic" decking when they replace the old wood! 

   My imagined method - posts, beams, and joists under the decking - has the effect of creating minor (12-24") cantilevering at the perimeter. (After all, you don't want to disturb the footings the house sits on!)

   Creating an even, small gap between the house and the deck can be as simple as running your decking up to the siding, then using the siding as a guide for your saw. Presto! You now have a perfect 1" gap.

   Yes, footings and base preparation are critical. One effect a ledger has it that it makes sure the deck and the house move together. Naturally, this means that all manner of forces (expansion, vibration, torque) have to be absorbed at the ledger.  If the house is not connected to the deck, the two are free to move independently. The taller the deck, the greater this movement will be - and you don't want the deck rubbing against or slamming into the house every time the wind blows.

   There is also the matter of the ground settling, and the deck drifting off in another direction. Who wantts a deck that's pitched a bit to the left? For this problem, I don't think a ledger is really a solution .... I think a ledger would only help conceal the poor footing problem, until it gets so bad things are near collapse.

   Just a general reflection here:

   When I first started thinking about building this deck, I imagined using tools like a circular saw and a nail gun. The more I think this through, though, it appears that my most important tools will be my shovel and tamper!