24x40 1.5 Story Construction

[mgramann]

I'm planning a cabin for our property in the Michigan U.P. after being inspired by this site.  I started with the intention of building a 20x40 and purchased a set of plans, which were the inspiration and foundation of our final plans.  The extra width did require a few changes, so I wanted to talk it through with some of the experts here who's opinion I have come to respect.

Let me start with some photos from my planning software:

Above is the front.  As you can see, it will have a porch on 2 sides, and 2 6ft gable dormers.  The porch will be approximately 5 feet off of the ground.  The foundation will be a full basement, with only half of it below grade.  Below grade will be concrete, above grade conventional 2x6 framing.  This will cut down on concrete cost, and allow for the easy installation of egress windows.

Here is a picture of the opposite corner.  Please disregard that the basement appears to be all concrete.  On thing to notice on this side of the house is that instead of gable dormers, larger shed dormers are used instead.  This adds a significant amount of space to the rooms.

Upstairs layout.

Main Floor Layout.

Here are my thoughts regarding construction:
The extra width requires the use of a central joist support if I want to use conventional lumber.  My dormer choices also require the use of a ridge beam.  The layout allows for 2 column supports running from the basement through the interior walls of the house, in addition to columns in on the ends in the exterior walls.  Looking at the main level, one column would be in the wall to the left of the stairs, and the other would be in the wall next to the refrigerator.  These columns would support 3ply 11 7/8" x40'lvls on for the 1st and second floor which the floor joists would hang from, and the ridge beam which would be 3ply 14"x40'. 

The exterior walls would 2x6x12 framing with 2x4x8's sistered to them to support the 2nd floor joists, creating a knee wall upstairs.  2x12 rafters(16" OC) would be used from the top of this wall to the ridge beam.  2x8's would also rest on this wall as rafters for the 10' horizontal span porch.
Here is picture illustrating the above:


Keeping in mind the snow load for this region is 70 PSI, will this work?  I ask because the first supplier I have spoken to seems to have an obsession with selling engineered trusses, and is absolutely convinced this, what I would call conventional framing, will not.  His suggestion is that I switch to a 10/12 pitch, match the gable dormers on both sides, allowing the use of a more expensive parallel cord truss.  He is convinced this is the only logical thing to do.  Once thing to keep in mind is that when he was looking at his span booklet, instead of basing calculations off of the horizontal span(in my case 12ft) he was using board length (20ft) in his figures.  I had to point this error out to him on 2 different occasions. 

Am I wrong in thinking he is crazy?  Thanks for the help in advance!

[UK4X4]

Just a quick look

you have in 1 dwg the posts comming down centrally in the end walls....and in another you have both windows and doors in the center of those walls meaning some heafty headers and dual sets of posts.

I have 90# snow load to deal with and went your route first, but when you take those ridge beam loads concentrated down through two stories adding both floor loads too it starts to add up and the foundation would need designing to support it

Eventually I swallowed the cost on engineered trusses, as the load gets spread better along the whole structure.

Upstairs I have no roof supporting posts or walls  - but the ground and second floor do- both taken down to the foundation, basicly for the beam look- I'm running a glulam beneath 4x10 beans and 2" T&G flooring

If I had used large I-joists I could have done both floors free span too, but again i was looking at spreading loads out

My trusses  are 10/12 on the outside and 8/12 on the inside with raised heels

So I still get the vaulted ceilings.

I have 4 identical 12ft wide gable dormers 2 on each side- really only to add a feature and windows as my side walls are only 6FT to keep things within the HOA rules

Some pics are on my build thread- Colorado 26x36

[mgramann]

I haven't had a chance to update the window/doors in the picture yet, as I wasn't sure if moving them was necessary.  My thought was some LVL headers would do the trick in both cases, but I was hoping this subject would come up.

I really would rather not change the pitch of the roof, as the fast slope allows for more usable space upstairs without big dormers.  The upstairs bathtub requires this to be useable.

I guess I'm still wondering if my framing method is acceptable, and if there are potential issues.  Now is the time to find them!

If there are issues, I'm not completely opposed the the parallel chords with the 10/12 pitch, but I really, REALLY like my current setup.

I've been keeping an eye on your build-I really like it!

[John Raabe]

First the kudos. You have a well-thought out very workable layout. It will be a handsome house and your general structure is sturdy.

The one problem I see for the layout is the stair starting at the back of the LR. That room works much better without a traffic route through the middle. You might consider a "U" shaped stair that starts all the stairs from the center of the house. If you do a continuous shed dormer across the back (sprung from the ridge as shown in the section), then you will likely have the headroom and width to the get the adjusted bathrooms to work.

If you're supporting the roof rafters from a ridge beam, you can platform frame the second floor and upper walls. This is also true if you end up with trusses. You haven't shown a ceiling joist in the upper bedrooms. Are you wanting to go cathedral all the way to the beam?

I also like the 12:12 pitch and would not go with scissor trusses. The truss company may be able to do heel bearing parallel chord trusses that would have the same look as the 2x12s with a ceiling joist.

After you have your layout worked out completely I would review it all with a practical local engineer. The load trace will size all the beams, headers and foundation footings and he will spec out the appropriate connections.

[mgramann]

First the kudos. You have a well-thought out very workable layout. It will be a handsome house and your general structure is sturdy.

Thank you!

The one problem I see for the layout is the stair starting at the back of the LR. That room works much better without a traffic route through the middle. You might consider a "U" shaped stair that starts all the stairs from the center of the house. If you do a continuous shed dormer across the back (sprung from the ridge as shown in the section), then you will likely have the headroom and width to the get the adjusted bathrooms to work.

I'll have to think about the stairs.  It might open up the room a bit.  We had actually considered the continuous shed dormer, and will probably play around with it on the software.  We don't want a window in the bath, and aren't sure how we would like the appearance.  If we stick with the 12/12, there should be more than enough headroom to make the tub usable.  It would be additional storage though, which could be nice.

If you're supporting the roof rafters from a ridge beam, you can platform frame the second floor and upper walls. This is also true if you end up with trusses. You haven't shown a ceiling joist in the upper bedrooms. Are you wanting to go cathedral all the way to the beam?

We talked about this with my builder friend.  By using the balloon framing, we think this takes a potential "hinge" out of the equation.  It would definitely save on materials though.  He had some converns about some of the walls being "tall walls"-but we weren't sure if that would be an issue.  I go back and forth on the cathedral ceiling.  I think the biggest factor is going to be what we decide to do for insulation.  Spray foam would mean cathedral.  Fiberglass would mean ceiling joists.

I also like the 12:12 pitch and would not go with scissor trusses. The truss company may be able to do heel bearing parallel chord trusses that would have the same look as the 2x12s with a ceiling joist.

I believe he was talking about using trusses like you describe, but with a 10/12 pitch for transportation purposes.  If he used P/C trusses with a 12/12 pitch, they would require a "piggyback" (I think) and the cost goes up significantly.  I figure, if I can get the 12/12 using conventional lumber and a ridge beam, why not?

After you have your layout worked out completely I would review it all with a practical local engineer. The load trace will size all the beams, headers and foundation footings and he will spec out the appropriate connections.

Would the building inspector count?  That is who i planned to go to.


Thank you very much for the input.  The material guy has me paranoid that what I have laid out here won't be up to code, and that trusses are required.  I just needed to know that I wasn't missing anything major.  I would think that, if anything, I'm overbuilding.

[John Raabe]

You could certainly do the ridge beam and 2x12 rafters. Then see if you want ceiling joists in some areas later.

Your helpful inspector could probably keep you out of trouble, but a good engineer would consider the entire building and size things appropriately. It used to cost me about $300 for a project like this. You might find you sleep better too.

[mgramann]

I figured I would post an update to this.  After shopping around, and getting some better prices, I have opted to go with trusses, floor and roof.  More information to hopefully follow in a build thread.  I say hopefully because we are waiting on one more thumbs up regarding financing.  Wish us luck!

[John Raabe]

Best wishes on the financing. It is an inconvenient necessity. The trusses should help make things pretty straightforward.