20 X 40 2 Story in SW Colorado

[shmily524]

Hi all, this thread is an extension of a previous one I started in the General Forum here: http://countryplans.com/smf/index.php?topic=6682.0

The earlier question of how to extend the footprint has been decided. I am going to extend the existing 20x20 block foundation instead of trying to get an Engineer's stamp on Post and Pier attaching to the current block. Now I just have to decide exactly how far to extend... 10,12,16,20...

New question though, my inspector tells me that I cannot use a ridge board (vs ridge beam supported down to the foundation) with 4' knee walls unless I put rafter ties in the lower 3rd of the rafters. Is he interpreting the code wrong? How are all the 1.5 stories building with a ridge board (not beam) and no low collar ties? Or would I just be better off using the beam?

John, is this level of detail included in your plans? Perhaps I need to just buy them and stop trying to use my hand-drawn plans...

[glenn kangiser]

I would suggest you get the plans, but most use semi-balloon framing to eliminate the kneewalls.  You might ask your inspector if he will go for that.  Full length top to bottom studs with a let in ribbon to support the second floor eliminates the hinging.

[Source_to_Sea]

That be by far the easiest way to deal with this, assuming he'll go for it. Houses have used that system for only what, 300 years or so?

[glenn kangiser]

At least.  Less expansion - contraction than platform framing - no knees - lots of advantages.

Don't forget it will require fire blocking to stop the chimney effect per code.

[Don_P]

Even balloon framed there's a little more going on than initially meets the eye. A typical column is loaded axially, along its axis or lengthwise. Most vertical members are simple columns. But, this one is a bit different it is taking an axial and a bending load. The floor connection "ties" it and then the rafters above bend the column as well as delivering a vertical load.

Here's one analogy,
Take a thin stick and put it between thumb and forefinger. Push your fingers toward each other and you are axially loading the column. Now with the forefinger of your other hand push in on the side of the column, this is the bending load. The engineering is an interrelationship formula. Basically the more axial load the column has the less bending load it can handle, or the more bending load the less axial load. 

For a short "kneewall" it's probably not a big deal, as the wall gets taller and the roof more heavily loaded it can get into trouble.  The building code does not adress this situation prescriptively at any wall height so it falls into an engineered solution if the inspector calls for it, it's not an improper call. The code defers to the NDS for design. If a ridge beam is possible that is one solution, check the point loads it will deliver down from its ends and any interior supports. If you want to go with the high posted design this should be a piece of cake for an engineer, guessing a coupla hundred.

If you want some background these calcs are set up for heavy timber design values but the math is the same.
This one walks through a simple axially loaded column;
http://www.windyhilllogworks.com/Calcs/Simple_column.htm
This one goes through a column with bending and axial loading;
http://windyhilllogworks.com/Calcs/44axbend.htm

Balloon framing ~150 years, the calcs above were set up for timber framing, think lowered tie in a barn or medieval aisled hall ca. 1500. The loads get concentrated to fewer larger columns. The framers of old learned conservative design when they had to go get a new batch of serfs.

[John Raabe]

In the 20' wide 1-1/2 story plans the wall studs are continuous to the plates at the top of the loft knee wall. The loft floor connects to this via a let-in ledger. Thus the floor will act as a compression/tension member and locks the tall walls in place. In addition, the rafters are configured into a site built truss to further lock this into a rigid frame and offset the outward thrust of the rafters. In a code area you may not be able to use this site-built truss without a local engineer's stamp and recalcs for the local loads.


see more of this house here: http://www.countryplans.com/mcelroy.html

However, you can likely get a custom engineered truss from a local truss supplier to match the plan configuration. They do all the engineering for the inspector. Sometimes these are actually cheaper than building the site-built truss yourself. That truss is pretty heavy-duty, especially compared to most stamped out trusses.

The other way to go is with the collar ties in the bottom third of the rafters. I have that detail in the plans as well and it is used for cathedral ceiling areas such as over the great room.

[Don_P]

http://www.countryplans.com/images/mcelroy-3.jpg
John,
It is not my intent to be belligerant or offensive in any way.
There appears to be a small 2x4 or 2x6 truss that sits atop 2x12 angled columns. If that is the case then there is no thrust restraint of the roof load. 100% of the horizontal component of the roof load is absorbed by the kneewalls and then the floor. The floor is the only thrust restraining tie. Your truss hat is stable but is simply delivering load to an unrestrained set of angled columns. This may or may not be adequate but it is not rigid nor does it meet the definition of a truss.

Lets do an experiment. You say it's rigidly locked. Build the "A" structure only, without floor or kneewalls, set it on a slick slab and load it, I can do that to any true truss and it will be stable, it won't change shape. The lower 2x12 legs of the A on this will rotate outward pivoting at the plywood joint to the upper section, the only restraint being the nails in the plywood gusset. Technically a truss model should work with one frictionless pin at each joint, the joint is free to rotate, the configuration of the members prevents movement not the gussets.

This is what's called an attic truss. It is shipped without the peak installed because of road restrictions but is stable in this configuration. Think about my test on this, push, pull, load it, it stays the same shape, there is no thrust, nothing wants to slide out when I load it. This was an inspected home. The walls were built and the trusses sat on top, forming the floor, kneewalls and roof framing.


The more correct way to build this in a non enforced area is as a raised tie rafter set. The 2x12 rafters rise as one piece from top plate to ridge and a raised tie is then very well connected across the pair, you would then have some thrust restraint.

[bobtheengineer]

Check out a little close picture in the link listed.  It appears that a 2x6 is running continuous from top plate to peak.  The additional thickness comes from another 2x6 scabbed in place, I'm assuming to increase the depth for insulation.  The wall does see some side thrust load from the roof.  I'd be careful using a knee wall, of any great height.  Balloon framing sounds like the way to go with me. 

[Don_P]

I'm feeling much better about it now! 

[PEG688]

You may want to check this thread out , lots of interesting info on the let in ledger set-up,

  http://countryplans.com/smf/index.php?topic=1418.0


  DonP I'll raise you a attic truss and a bigger boom truck ,

 

 

[Don_P]

That is a big one. How about a high posted cape and another boom truck  

This was another engineered solution to the kneewalls. Medieval balloon frame  . The 2 bay garage in the background has 9' studs below, attic trusses and an apartment upstairs. There is another shed dormer on the backside containing a bath. It had all I needed, shop below and living above, 2nd floor deck off the back gable.

Off topic but thinking about big cranes, we were working outside of Madison in July '99, I had set the telehandler with a work basket down in gusting wind and called it a day. We were cleaning up when we heard on the radio that the crane "Big Blue" working on the stadium in Milwaukee had collapsed into another crane, killing 3 guys in a work basket, while Blue attempted to lift a 400 ton roof panel in the wind. The engineers said it was safe to lift, we heard 40 guys walked off before the lift.

Anyway,
One way to look at this kneewall wise trying to stay prescriptive.
If the ties were raised to no more than 1/3 height, ties attached to rafters that are prescriptively sized and the balloon framed wall was whatever it took to give an 8' room height, it would be prescriptive and accomplishing what I think is the desired goal?

Looking it up in table R802.5.1(5), I'm looking at the 30lb snow load table, a #2 SPF 2x8 can span 15'1" if tied at the plate. If I raise it 1/3 of the way up the note at the bottom of the table says I multiply the span by .67 to get the correct allowable rafter span. 181"x.67=121.27"... 10' 1-1/4". So it works prescriptively at that size rafter in a 30 lb snow load region.

the ceiling joist table looks like an SPF 2x6 works and the nail table at the end of the rafter span tables looks like 5- 16 penny commons in the raised tie would work. Thats going to be at least 7 gun nails

Sketching it up I'm coming up with about a 4' 6" kneewall, balloon framed or platform framed and it would pass fine. In a higher snow area it would take a 2x10 or 12, or higher grade or stronger species for the rafters. But that basic idea it seems like should get it through with a ridge board, without engineering, just following the prescriptions in the book.

[shmily524]

So the building inspector decided to finally inform me of an additional fee that I will be "required" to pay before issuance of a building permit...

It is called the "impact fee".  The citizens denied the governments suggested 3 mill increase to taxes two years ago, so the county went around them and implemented a new "fee" which will be collected at time of building permit issuance to offset maintenance and construction of roads and bridges.

The problem is this, my foundation and sewer we already in place at the time this new special fee was created. Shouldn't that grandfather in my project? Anybody have any advice on how to approach this one?

BTW, this fee plus the building permit now has me up to $3080 before I can even build!!! Fees ONLY!! In other words, I have to pay the county just shy the same amount my rough-in materials will cost!!!

[ScottA]

Wow that sucks. They snuck it in on you. What county are you building in? I used to do alot of work in Jefferson county and they where real PITA. Unless you've got a friend in the county government I'd say you are stuck paying it.

[shmily524]

It is Rio Grande county... long ways from the Metro area.

What exactly could a friend at the county do? Would threat of legal action be enough to make them grandfather it in? I know i am asking the wrong audience, but still...

[ScottA]

That would be about it. Go to bat for you over the grandfather issue. A lawyer is another option but that might cost more than the fee. You could just ask and see what happens.

[MountainDon]

I'm confused about you you got the foundation in before being issued the building permit? Here, at least all that is a part of the same package.


Usually there is a grandfathering clause, unless the original permit had a time limit and it ran out. Here, there's normally a one year limit to construction permits.

I have a friend whose permit ran out about three years ago and he's still building. I have no idea where that will go. He's never seen an inspector.

[rwanders]

The "impact fee" in Citrus County, Florida (and in most of the other counties in Florida) is over $10,000.00! 

In Nevada in 1990 you were required to pay about $300 per acre in "desert tortoise fees"---not to the government, but to a private environmentalist group as part of a lawsuit settlement! Probably still in effect there. They use the money to fund more lawsuits for more fees for more lawsuits.

There is no end to it---just new permutations

[shmily524]

The foundation was there when I bought the land a couple of years ago, along with the septic. There was a building permit issued at that time, but it has long since expired. In any case, I think the project should be grandfathered in, because the current building inspector approved the existing foundation back then, and recently reapproved it to build on...

ANyway, I have decided to go with Build Block ICFs for the foundation extension. Price was the same as buying plywood, etc for poured concrete forms. Now that has me thinking... Should I just go all the way up the walls with the ICF, instead of stick building?  Hm... Thoughts anyone?

[Don_P]

The attic truss in one of my posts above was going to sit atop a 2 story icf wall done by an owner builder. It worked well.

[shmily524]

Well, we got a LOT done this week.

Paid all the fees. Argh!

Footings dug and poured and ICF walls poured. This was my first experience with ICF, and I loved them. Will use them again if the opportunity arises. They cost about $150 more than wood forms, but you do not have to take the forms down, and they provide 5 inches of continuous insulation.

I am still considering using them for all my walls instead of stick building. It would $9000 to go up two stories. The cabin would be completely "tight" and insulated. However, I would have to use a pump truck... Thoughts anyone?

Total cost of ICF and bracing materials was $1200.
Concrete was $750
Excavation was $278

Here are some pics. Cell phone pics, sorry. There are some better ones on the regular camera, but it is at home...

Breaking ground


Digging out next to existing block


Footings are poured and first couple of rows of block laid. We used the wet-set method. Worked great


My buddies came and helped a lot as you can see


Ready to pour


And finished:

[ScottA]

Looking good! 

[Bishopknight]

Ya I like it!

Sorry to hear about all the fees. One of the good reasons to go into the boonies. No vultures!

[shmily524]

Whoo Hoo!!!!!! Inspector approved the use of ICF walls all the way up!!

Now I can build exactly what I want!!!   I can't tell you guys how exciting this is!

A lot of people have thought about building an ICF house themselves, but I haven't seen anyone here that actually did it. Hopefully this journey will be of use to others interested in building with ICFs.

I am estimating about $10,000 to build and pour the walls for both stories, but we will see. That is without taking out doors and windows.

Now I have to decide what to do with the roof. Ridge beam and SIPs or engineered truss and spray foam...

[John Raabe]

This will be interesting to follow up on... Some new materials for some of us.

PS - Bobtheengineer had the site built truss right. (Hard to understand if you don't have the plans). And, yes, there is a bit of outward thrust on the 2x6 continuous rafter to wall connection thus the balloon framed wall w/ the let-in ledger for the floor tie-in