Sister 2×6 from floor joists to deck
semisavant
| Posted in Construction Techniques on
Happy Christmas! Too much sugar, crappy music driving you nuts, tired of the family and now you’ve escaped to the Breaktime Forum for respite? Well, I was hoping you would – I have a request: I would like to add a 10’ + deck off of the back of my cabin without using a ledger board. I believe the term is “sister?†What are advantages/disadvantages of sister vs. ledger? If I do sister – how far in should the 2×6†go for
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Your question is not crystal clear for me. Do you hope to cantilever these joists from the cabin? If so, 10' is a long way to go and 2x6's won't do it. If it won't be a cantilever, I don't see an advantage to attaching the deck joists directly to the cabin joists. It seems this connection would be difficult to waterproof. Unless the deck is freestanding, I usually prefer a ledger with spacers for air circulation and water drainage with good flashing and plenty of 1/2" galvanized lags or bolts.
Al Mollitor, Sharon MA
Thanks for your reply.
Not cantilevered, planning on continuing the post and pier lay out. 4x6 posts on concrete piers was the plan. I have seen this layout before but with a ledger.
Thanks for the weatherproofing consideration.
Happy Holidays.
Steve;-) s2
The ledger design was there for a reason. Having the framing penetrate the siding package is a certain way to introduce water to the inside of the house. It might be an acceptable design in the desert where there is less than ten iches a year of rainfall and a large roof overhang for the shade value to also keep water away, but in most climates, you would be asking for trouble.
.
Excellence is its own reward!
Steve, you said cabin. Are the floor joists exposed at this time? May we assume that you will be framing in the same direction as the joists are oriented under the building? No problem with sistering if you're ok with the existing o.c. spacing of existing joists. Bolt these!!! Two or three feet of overlap under the building should be adequate if you're supporting with posts and girt or whatever outboard. HOWEVER, the ledger enables you to drop the deck frame by a comfortable step. We like this in the snowy North, and it does usually make for easier flashing and waterproofing. You do not want deck gack (weather) entering that fine shack under any circumstances. Send us a key and a map and a date, and we'll critique your beer and your work from the safety of the ground below!! Jim
Jim, hope this jpeg is clear. I would continue with layout if I sister but it sounds as though a ledger is preferable. Can you clarify: "posts and girt or whatever outboard."
Also, any ideas of footing on a 30 degree slope? I have looked at the "bigfoot" system. Again, I want it to be sturdy and weather proof. It snows there on occasion and rains a bit more than in the valley down below.
I like the micro brew suds. And am considering brewing myself..... The Cabin has great water and I am building enough space to brew (unless my wife appropriates the area ;))!
Steve-
First of all does your wife know you took her torche light to the crawl space?
Man, you're already in trouble.
As for the footings, you will have to go down as deep as you can on a 30 degree slope. 4' with a 12" sono tube is marginal at best. What are the soil conditions?
You might want to go to your local building department and just inquire as to what they would recommend for deck footings in your area.
Can you give us a shot where you intend to attach your ledger?
This is going to cost you one of those home brews.........
"Rather be a hammer than a nail"
Bob
Boy oh Boy does your photo look all too familiar! I've seen about a gazillion like that. Makes me feel right at home, LOL....
If you want it to be weatherproof, you will have to seal and insulate the blocking between the sistered joists with expanded foam on the inside of the house. Also pay attention to flashing details on the outside. Best to have a nice large overhanging roof to keep off most direct water. You should figure on sistering both sides of the joists with minimum 3' sections of 2x6; use ½" through bolts with big flat washers on 12" centers, staggered high and low, and squirt some structural construction adhesive in there for good measure.
If you elect to support the deck joists on a ledger, you have to make sure the ledger itself is well supported. Lag bolts into the end-grain of the floor joists of the house will have a good shear resistance, but won't do the floor joists themselves any particular good. If they split, your ledger will sink. I would use a doubled 2x6 ledger supported by 4x4 posts set on solid footings, every 6 feet or 3 sets of joists. The footings can be 'Bigfoot' bases, but if you're in a freeze zone, you should set the bases on a compacted gravel pit deep enough to let any water drain out so you won't get any frost heaving to lift your deck. Otherwise, go traditional and dig sonotubes down below the frost line; then pour concrete pillars to come a few inches above grade so the 4x4's won't rot out.
Dinosaur
'Y-a-tu de la justice dans ce maudit monde?
Obviously, I can't tell much from one photo, but you might want to consider some diagonal bracing on those existing posts to prevent sideways movement.
Al Mollitor, Sharon MA
a third of the total distance approx
My life is my practice!
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My first choice is to not attach at all but support with new post and beam structure this way you don't have a problem with water penatration and a change to lower elevation is a good idea.
ANDYSZ2
I MAY DISAGREE WITH WHAT YOUR SAYING BUT I WILL DEFEND TO THE DEATH YOUR RIGHT TO SAY IT.
Thanks for all the good input! I have added a detail of joists for those still interested. I believe I will add a ledger and lower the deck off of it. Water damage is a real threat as this is an exposure. Again thanks for all the words.
I'll hoist one for all this summer as I stand on the deck one fine summer day...
Steve