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stick-framed deck for a TF

Started by bigmish, May 29, 2006, 07:37:32 PM

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bigmish

I am currently planning the deck for my 24x36 1 ½ story timber frame home. I am planning on using a stick-framed deck built of pressure treated 2x10s.

My first question is: do the dimensions in the following image make sense (note that the different greens are only used to distinguish one board form another)?



My second question pertains to the hardware used for the deck and the image below:
1. I've diagramed where I envision nails being used: do these look right, would I need additional? What kind of nails should I use here?
2. I'm planning on using brackets to attach the floor joists to the sills: does this make sense? Any specific type I should be sure to use here?
3. Would there be any fastener required to attach the decking to the foundation or would the gravity from the posts be sufficient to keep it in place (note that I will be attaching the posts to the foundation with cast-in tie-downs); should tie downs be used to attach the deck to the foundation (if so, how far should they be spaced from on another)?


Thanks, Mischa

Raphael

  The Gif looks like a workable scenario but I think I'd decrease the tennon to 3.5 x 3.5 and let the shoulder of the post bear on more blocking.  My TF to stick connection in the middle bent of my office is done this way and it probably one of the simplest with an all stick deck structure.
  In the rest of my TF to stick connections the post bottoms bear directly on the sill and have a 1.5" deep 7.5+" tall rabbet to accept the rim joist .  They are tied to the rim joists and adjacent floor joists with a single lag bolt in each face.  I cut each post bottom to compensate for irregularities in the level of the concrete and sill and blocked the joist structure up to level before tying it to the TF.

  The sills are usually anchored with "J" bolts set in the concrete and around here rim joists are simply toe nailed to the sill.  In huricane country clips and ties are required, you'll need to find out your local building requirements.

  A portion of my frame is timber sills and the posts in the original design are held by only stub tennons.  My building inspector wanted straps added to tie the posts down on the timber sill.  You may be required to use similiar straps to hold your posts down to your deck.
... he was middle aged,
and the truth hit him like a man with no parachute.
--Godley & Creme

Stihl 066, MS 362 C-M & 24+ feet of Logosol M7 mill

Jim_Rogers

Using a standard stick build deck is ok if the posts are blocked up underneath enough to support the frame from the post to the foundation.
Here is a common way to do it:



In this case the tenon is around 4" long or more (down into the deck) and the thickness is only 1 1/2" same thickness as a regular piece of stick lumber, as the post is made of oak.

My adviser has just changed his method of nailing. He now uses two layers of pressure treated mud sill stock using the new nails for this type of wood. Then a standard piece of 2by stock making it the third layer of sill. This layer has to use the new nails to attach it to the lower pressure treated sills.
Then when toe nailing the standard lumber joists to the third sill you can use regular nails, which costs less then the special nails for pressure treated.

Here is a cross section drawing:



Just some things to think about....

Jim Rogers
Whatever you do, have fun doing it!
Woodmizer 1994 LT30HDG24 with 6' Bed Extension

Don P

Jim,
Looking at the photograph above. Why is the column notched at all? As I follow the load into the blocks it loads against side grain of wide blocking, side grain crushing would need to be looked at and then as that wide block shrinks in width the frame settles. If the tennon is long enough to bottom out then it is too small to bear on the sill.

Wouldn't the ideal be to have a large footprint of column base directly on the thin sill? If a single band needs to inset into the column, I can see doing that,allowing for the smaller footprint,  but I don't understand the reason for putting the load up on soft blocks  ???

Raphael

  I think tradition has a little something to do with it as the 2x material is mimicking a full timber sill.  If someone else is setting up the deck and you are bringing in a frame I think it's easier to get it done correctly Jim's way.
  When faced with concrete that isn't level my way requires either each post bottom be cut a different distance below a top of joist reference line or land solidly on flat level blocking that also levels the 2x deck, which pretty much rules out the usual tapered shims.

  My situation isn't typical as I was mating a stick decked addition to 8" deep fully dried timber sills so I blocked up 2x8s on 8" square pads of various thicknesses of plywood to get them level (+/-1/32") with my timbers.  The theory is that landing the post bottoms this way will keep the addition's frame properly aligned when all the wet 2x Doug Fir framing starts to shrink.
... he was middle aged,
and the truth hit him like a man with no parachute.
--Godley & Creme

Stihl 066, MS 362 C-M & 24+ feet of Logosol M7 mill

Jim_Rogers

Quote from: Don P on May 30, 2006, 10:19:09 PM
Why is the column notched at all?

Don:



For pegging to the rim joist......


And you said: "Wouldn't the ideal be to have a large footprint of column base directly on the thin sill?" Yes that is one way to do it.
There are many ways to do it, I'm just showing one way I've seen it done.....
I'm not saying this is the best, just one way it can be done using a stick built deck....

Here is what you describe:



I believe here the post sits on the mud sill.

Jim Rogers

PS. And I agree that the math has to be done to insure you have enough square inches of post bottom to support the estimated load it will bear, taking into account that the side grain support will not be there once the blocks shrink.

PPS. I'll check with my adviser and see if my drawing is wrong and that maybe my small spacer blocks should be turned on end between the floor joists to support the post. This would eliminate some of the shrinkage factor....
Whatever you do, have fun doing it!
Woodmizer 1994 LT30HDG24 with 6' Bed Extension

bigmish

Jim: you say "tenon is around 4" long or more (down into the deck)". This implies that the rim joists (I believe that is the right term: the sticks that are forming the perimeter of the deck that the floor joists attach to) need only be made of 2x4s. I've been thinking in terms of 2x10s but it would be cheaper and easer to use if there is no reason not to...

OK, I've decreased the tenon size (also realized I had a dimensional error in my first rendering) to increase the bearing surface and also made a few changes based on some additional thinking. Please let me know if this seems to make sense:
<img src="http://mischawilliams.com/sills_dimentions_2.gif" border="0"/>


Finally, I began to question the whole notion of using a stick-framed deck. It does seem easer and faster and to have no aesthetic problems however, I began to question it's structural integrity. Can a stick-framed deck really be expected to last as long as the rest of the structure, or would it be considered the weak link? I came up with a hybrid solution that seems to have all of the integrity of the timber framed deck with the ease of a stick framed: it's a hybrid that uses sill beams but the joists are sticks. It's the constant outward pressure from the structure pushing the nailed rim joists out that worries me and this seems to solve this, but without the time consuming process of cutting all the joinery for timber joists. What do you think of this idea?
<img src="http://mischawilliams.com/hybrid_sill.gif" border="0" />


Thanks again, Mischa

bigmish

Jim, how can I get the images to appear in the post rather than as a link?

wiam

 bigmish, you need to put your pics in the Foestry Forum gallery

Will

Jim_Rogers

Mischa:
As stated you have to upload your photos to a gallery, your gallery, and then post the link from the gallery location into the thread in order to get your pictures to show in the post.
There are threads with procedures of how to do this somewhere on the overall Forestry Forum. I don't know the exact location of these but they should be easy to find.
You have to reduce the photo to a pixel size and file size to comply with the program limits, in order to post them to your gallery before the program will allow you to upload them.

As you can see in my reply (the one above #5) the rim joist is a standard 2x10 (1 1/2" x 9 1/4") and that the tenon stick down into it about 4" to have enough relish for the peg. The bearing of the weight of the frame, on that job, was at the shoulders of the tenon to the blocking around the tenon.
The rim joist and and other joists were standard 2x10 stock and I'm sorry if you mis-understood me to think they were 2x4's.

There are many correct ways to do what you're trying to do. I'm just trying to show options that all will work.

How you have draw yours maybe ok. I haven't studied it closely to see if it's ok or wrong.

A combination of timber sill and stick joists can work.

There shouldn't be any outward pressure on the rim joist, whether it is a timber sill or a standard lumber rim joists. All loads would be vertical at the foundation post connection area, unless acted upon by an outside force such as wind or earthquake. And with proper fastening this should be easy to overcome.

When trying to decide what to use, I ask my customers, what do you want to see when you're down cellar and you look up? Do you want to see a timber floor system or doesn't it matter.
If it doesn't matter then I design a standard stick built floor system, as it is easier and cheaper in cost. If they want to see a timber floor system as it could be a finished off basement then I design a timber floor system and work through all the plumbing details to hide them as best we can.

Jim Rogers
Whatever you do, have fun doing it!
Woodmizer 1994 LT30HDG24 with 6' Bed Extension

GregS

This thread has answered many questions and concerns I have had regarding the hybrid I am planning for.  Thank you everyone for sharing!

Jim,  Can lag bolts be used instead of pegs when attaching to the rim joist?

Jim_Rogers

GregS, I would think that they would be alright as long as the proper pilot hole is drilled so that the tenon isn't split by the lag bolt being tightened. A split tenon will have less holding power.

Jim Rogers
Whatever you do, have fun doing it!
Woodmizer 1994 LT30HDG24 with 6' Bed Extension

Don P

If I recall correctly, the pilot drill for a lag should be 70-90% of root diameter (inside threads). The harder the wood the bigger the hole.

Another factoid that has nothing to do with this use, maximum withdrawal strength is at 12 lag diameters piloted and buried in the second piece and a shank sized prebore through the first piece.

GregS

Don, thanks for the drilling tips!

scsmith42

Don - good info re max strength.  If I'm reading your formula correctly, for a 1/2" lag bolt, max strength would be to embed it 6" in the second piece, and for 3/8" lag bolt to embed it 4.5" into the second piece, etc?

Thx.  Scott
Peterson 10" WPF with 65' of track
Smith - Gallagher dedicated slabber
Tom's 3638D Baker band mill
and a mix of log handling heavy equipment.

Don P

Whoops, I just took another hard left with a thread  :-[ :D.
The short answer is that for withdrawal, yup you understood persactly.  ;)

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