Author Topic: Modified 20 x 30 1 1/2 Story  (Read 14971 times)

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Offline DCobb

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Modified 20 x 30 1 1/2 Story
« on: December 09, 2010, 06:31:27 AM »
John and crew,

Bought the plans for the 20 x 30 1 1/2 story this morning.  I've been playing around on Visio and have come up with this version that I think will meet my needs for a weekend cabin very nicely.  I've added 2 feet to the length.  I plan 12 foot sidewalls and a full loft.  I'm using the u-shaped stairs and will probably add a shed roof dormer over the stairs for added headroom.  I've added two 2-foot bumps, one for the dining area and one for the bathroom.  The front porch will have a shed roof.  

I would appreciate any thoughts, suggestions, and concerns that anyone might have.

Looking forward to getting started!

Doug Cobb



« Last Edit: December 09, 2010, 02:53:22 PM by DCobb »

Offline MountainDon

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Re: Modified 20 x 30 1 1/2 Story
« Reply #1 on: December 09, 2010, 06:39:33 AM »
That image appears to be on a secure server (https) and as such will not be able to be seen by anyone here.   Someplace like photobucket.com would make it possible
Just because something has been done and has not failed, doesn’t mean it is good design.

Offline DCobb

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Re: Modified 20 x 30 1 1/2 Story
« Reply #2 on: December 09, 2010, 10:08:29 AM »
Sorry for the bad link.  Should be OK now.

Offline John Raabe

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Re: Modified 20 x 30 1 1/2 Story
« Reply #3 on: December 10, 2010, 07:16:57 AM »
I like that layout! I really have no suggestions for improvement.

All the spaces are in good proportion to each other and the circulation is efficient. Light and ventilation should be good.

You haven't got a laundry area, but not every house needs that. You could probably find room for a stacked washer/dryer under the stair if you went to a tankless water heater.

I would suggest a commercial truss package for the roof so there are no outward loads to be resisted by the balloon framed walls (which you are punching big holes in). Once you do that you can platform frame the main wall and loft floor and build the kneewall on top of that to any height desired.
None of us are as smart as all of us.

Offline DCobb

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Re: Modified 20 x 30 1 1/2 Story
« Reply #4 on: December 10, 2010, 07:39:00 AM »
John,

Thanks for the response.  Could you explain to me a little more about why using a commercial truss package will relieve the forces on the side walls?  (If its explained in the plans, just say so and I'll figure it out when they arrive.) 

Thanks,

Doug

Offline John Raabe

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Re: Modified 20 x 30 1 1/2 Story
« Reply #5 on: December 10, 2010, 07:56:13 AM »
They just do all the internal stress engineering and have special plates and connectors that are not available to site builders. The taller balloon framed walls provide a extra stiffening factor for the site built rafter trusses I show in the plans for owner-builders who can't get trusses. Your pop-outs take away the bracing from those wall sections.
« Last Edit: December 10, 2010, 01:18:15 PM by John Raabe »
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Offline MountainDon

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Re: Modified 20 x 30 1 1/2 Story
« Reply #6 on: December 10, 2010, 12:37:17 PM »
Or in other words each truss resolves the forces from the roof within the truss itself and all that is left is the downward force where the truss sits on the wall plate. All the weight goes straight down, half on each wall. The spreading outward force is restrained within the truss.
« Last Edit: December 10, 2010, 01:51:20 PM by MountainDon »
Just because something has been done and has not failed, doesn’t mean it is good design.

Offline John Raabe

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Re: Modified 20 x 30 1 1/2 Story
« Reply #7 on: December 10, 2010, 01:17:00 PM »
What he said!  :)
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Offline Don_P

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Re: Modified 20 x 30 1 1/2 Story
« Reply #8 on: December 10, 2010, 04:29:50 PM »
Just thoughts from first blush. If you use attic trusses, I'd think about a matching dormer opposite the stair dormer... that section would be stick framed anyway. Then line the storage room walls up with the bumpout @8'8" and have full headroom all the way to the outer wall. It's another easy room, bath, study, etc.  26' cantilevered trusses would give 3' overhangs on the main areas and 1' over the bumps.

Offline DCobb

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Re: Modified 20 x 30 1 1/2 Story
« Reply #9 on: December 19, 2010, 06:02:27 PM »
John,

Got the plans (which are very clear--thanks!) and have a couple of questions.

First, my plan involves a couple of 2-foot bumps.  How would you handle the floor joists for those?  Can I use 22 foot 2 x 12s (are those even available?) or is there some other way to do it?

Second, page 7 of the plans discusses the framing of the loft floor.  If says that "the ledger is notched into the continuous studs..."  Does that mean I have to cut a notch for a 2 x 4 ledger in each stud?  Or I am misunderstanding?  Also, if I platform frame the loft, then won't the loft joists just sit on top of the cap plate at the top of the studs?

Thanks.  I'm excited about getting started.

Offline John Raabe

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Re: Modified 20 x 30 1 1/2 Story
« Reply #10 on: December 19, 2010, 09:31:27 PM »
I'll start with the ledger. See the detail and notes on sheet 5. The tall 2x6 studs are ganged together and a notch for a 2x6 ledger is cut per the detail. This supports the 2x12 loft floor joists. It also provides a balloon framed wall that helps support the outward thrust of roof rafters. If you have engineered trusses built check with the truss company but you can probably just platform frame the loft floor, eliminate the notches and frame each wall separately.

For the main floor joists, especially if you will be doing a cantilevered bump-out, use one of the engineered alternative floor joists I call out on floor framing called out on the Crawlspace Foundation Plan (Sht 1-A).

Note that a bump-out detail is not part of my plans and you must be sure to check out the structural consequences of this. I would suggest that you use something like the optional TJI-360 floor joist I call out. They are pre-engineered for cantilevers.


This image shows the cantilever supporting 1/2 the roof load.

Click here for more information from TJI: http://www.ilevel.com/literature/TJ-4000.pdf

I would also suggest you NOT make this cantilever fully load bearing from the roof. Instead, put in a header over the openings thus carrying most of the loads down along the wall line. This makes framing simpler and reduces the load on the floor joists. You can probably have the truss supplier just attach a rafter extension to those trusses where they go over the bump-out. This leaves only about 1' of roof load going down to the floor joists.

Be sure you confirm your modifications with the truss supplier and also the engineered joist cantilever detail with the I-joist supplier.
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Offline DCobb

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Re: Modified 20 x 30 1 1/2 Story
« Reply #11 on: December 19, 2010, 11:28:54 PM »
John,

Thanks for the reply.  I hear you loud and clear about adding a header above the bumps.

The TJI brochure shows that their I-joists are only available up to 16 feet.  I need 20 (22 for the bumps).  Do I need to modify the foundation to add a center support?

Thanks.

Offline John Raabe

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Re: Modified 20 x 30 1 1/2 Story
« Reply #12 on: December 20, 2010, 07:25:35 AM »
Check with your local supplier. The long spans are the whole reason for using them. Several other homes on this site have used these for 20' spans - they might be special order items.
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Offline Don_P

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Re: Modified 20 x 30 1 1/2 Story
« Reply #13 on: December 20, 2010, 02:36:52 PM »
It must be a supplier issue, I've gotten them up to 35' long  ???

Offline DCobb

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Re: Modified 20 x 30 1 1/2 Story
« Reply #14 on: December 25, 2010, 06:08:35 PM »
OK, I've studying the plans and most everything seems to make sense.  The one thing I don't see is details about how to arrange the loft joists if I use the u stair.  Have a missed that in the plans or do I need something I don't have yet?

Thanks!

Offline John Raabe

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Re: Modified 20 x 30 1 1/2 Story
« Reply #15 on: December 26, 2010, 08:36:01 AM »
RE: the optional "U" stair shown on page 3 of the plans booklet. This opening is framed by doubling the joists on either side and then using a double header (hung from the double joists) to support the intermediate joists. This frames the opening into which you build the stairs.
None of us are as smart as all of us.

Offline cbc58

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Re: Modified 20 x 30 1 1/2 Story
« Reply #16 on: December 26, 2010, 10:43:22 AM »
like your plan.  had you thought about putting a full bath on the second floor where the storage area is... and a half on the first w/ laundry?

Offline DCobb

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Re: Modified 20 x 30 1 1/2 Story
« Reply #17 on: January 14, 2011, 11:25:29 AM »
CBC,

I thought about that but I'm leaning against it in an effort to keep cost down.  I don't think I'll need laundry since this is a purely weekend kind of place.

Doug

Offline DCobb

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Re: Modified 20 x 30 1 1/2 Story
« Reply #18 on: January 14, 2011, 11:32:20 AM »
New question.  Is there any reason that this approach to u-shaped stairs won't work?  The use of winders really saves space.  Thanks in advance for the opinions.



Offline MountainDon

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Re: Modified 20 x 30 1 1/2 Story
« Reply #19 on: January 14, 2011, 12:05:44 PM »
Check this document for minimum tread measurements, Drawing 10 in particular.


http://smai.roundtablelive.org/Resources/Documents/2006%20Stair%20IRC%20SCREEN%20web%20download.pdf


Then think about how easy it might be to take things up and down. Furniture for example.
Just because something has been done and has not failed, doesn’t mean it is good design.

Offline John Raabe

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Re: Modified 20 x 30 1 1/2 Story
« Reply #20 on: January 14, 2011, 12:22:53 PM »
That landing is similar to a spiral stairway where the right and left feet travel different distances as you go up or down. This takes more concentration and a spiral normally has a winding handrail to add stability. This is hard to do in a rectangular landing.

The most I like to do is put a single riser in the middle of the landing. It is better still to have a flat landing connecting two 1/2 flights of risers (as in the plan diagram).
None of us are as smart as all of us.

Offline DCobb

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Re: Modified 20 x 30 1 1/2 Story
« Reply #21 on: January 14, 2011, 06:19:40 PM »
Thanks, John!

Doug

Offline Don_P

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Re: Modified 20 x 30 1 1/2 Story
« Reply #22 on: January 18, 2011, 03:12:05 PM »
Notice in the visual stair guide that treads cannot go down to a point, this makes it pretty much impossible to swing tight around a U.

Offline DCobb

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Re: Modified 20 x 30 1 1/2 Story
« Reply #23 on: February 01, 2011, 04:51:01 PM »
What's the best location for utilities (pressure tank, uv/filter water purification, water heater, heat pump) in a 20 x 30 1.5 story?  I've been assuming they would go under the stairs (u-shaped) but can they go under the eaves outside the loft space?  Any other good ideas?

Offline MountainDon

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Re: Modified 20 x 30 1 1/2 Story
« Reply #24 on: February 01, 2011, 05:07:02 PM »
I'm not sure where the plans put them, but if possible, I'd suggest placing them in pans that have drains to the outside. That way when a leak develops the water won't run through the house. You don't want to deal with that if it's preventable. Trust me.  :o  It was not a big deal when the water heater was in the basement near the floor drain to the sewer, back home. Totally different thing with a tank on the main floor.
Just because something has been done and has not failed, doesn’t mean it is good design.

 

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