16' vs 20' ft house width

[ken henry]

I noticed there doesn't seem to be very many plans based on a 16ft width.  Is it any cheaper building that width?  it just seems like a nice width given the availability of 16ft lumber and 8ft plywood.  Also, for a 2 story house it seems easier to span a 16ft  width for the 2nd floor or even the first floor if there is a basement.   Just looking to reduce costs and speed up build time.

here's a photo of a house that has my interest:



I like the design with the 2nd floor porch, on the east coast there are quite a few lakes with full and part time living around them, so If no one is living in it, it can be rented out.  The 2nd floor porch gives a nice view for sunset - sunrise and gives it some curb appeal.  the plan shows just 16 ft deep, but it could easily be increased.  Also, the 2nd floor porch give the option to make the internal staircase very small.  furniture, mattress could be brought in from the outside.

[ken henry]

here's a link with more info about the house in the picture:

https://sites.google.com/site/excellentfloorplans/house-plans/16x16h1

when I look at the floor space for a 16 ft house, it does seem rather large, but once bathroom, wash-dryer, kitchen are subtracted, maybe its not so big after all.

[flyingvan]

...And staircases.  Staircases eat up a large section of floor space, both levels

[ken henry]

Like i said, it would be possible to have a really narrow set of steps going upstairs, furniture and mattress could be brought up from outside.  Maybe its possible to use some attic stairs to get up to the second floor.  Instead of having full bath upstairs, just have a shower and wash-dryer.  Then clothes could be kept upstairs so no need to carry them on the stairs.

[flyingvan]

Here's a pretty good article on stair requirements http://greeleygov.com/docs/default-source/community-development/building-inspection/building-guides/sma-handout.pdf?sfvrsn=4  There ARE some clever non-code compliant options (Jefferson stairs, attic ladders like you showed, winders...) Some cabins in our area designed the shower/tub under the stairs which is a pretty good use of space.   I've been in enough structure fires though to really appreciate a good, solid, wide staircase.  Imagine trying to escape a fire down an attic ladder in heavy smoke; now imagine you're carrying someone else out, too

Jefferson Stairs--

[MountainDon]

There are good reasons why stairways are made wider. That becomes evident and very important when you have to move furniture and appliances up and down. Even more so if the stairs have a winder or landing half ways. Give that some serious thought.  If this is to be built anyplace where building codes are going to be observed or enforced nothing less than a full size staircase would pass. If stairs are awkward to use I believe the risk of accident increases.

[ken henry]

I did a search on Jefferson Stairs, and google recommended loft stairs. 

https://www.google.com/search?q=loft+stairs&biw=897&bih=920&tbm=isch&tbo=u&source=univ&sa=X&sqi=2&ved=0CEMQsARqFQoTCPLHiYDo5cgCFQVUPgodvqEONg

Some of them seem pretty minimal, does a different code apply if its called a loft?  Personally i believe the 2nd floor porch solves the problem of egress during fire  and moving furniture.  However, the issue with accidents is an issue, especially if its rented and their is a liability issue.

heres some images of bathroom under stairs.

https://www.google.com/search?q=bathroom+under+stairs&biw=897&bih=920&tbm=isch&tbo=u&source=univ&sa=X&sqi=2&ved=0CBwQsARqFQoTCLi_w5zq5cgCFUKgPgodT-IG2g

[NathanS]

If you are subject to the IRC I don't think there is any way around a big set of stairs. It's too bad, I think a small 1 1/2 story with loft and a ladder up to the sleeping area would be a great design. I think they have code accepted spiral stairs, those might be the smallest.

The other thing to consider is where to put all your utilities (upstairs might not be a bad option).


About the 16 or 20 foot span - you might want to read this:

http://seaoo.org/downloads/Presentations_CONF/seaoo_2012_conference___woeste___design_of_wood_floors_to_mitigate_floor_vibration_problems.pdf

Span tables for floor joists don't consider bouncy floors.

[MountainDon]

Codes are available online in the original non-ammended IRC form.  Start here.   Look at Chapter 3 .. planning. There is a section regarding bathrooms.  One on egress requirements with stairways being section R311.7   I would advise you check with the local building code/permit authirities to see what code your area has adopted. There may be changes, additions, etc. to what I linked to.

There is an illustrated guide available on stairways.  It used to be free, don't know if it still is. You should have a look at stairways.org.


If you want to consider a spiral I would recommend finding someplace with a spiral so you can check them out. I have an aversion to spiral stairs; have friends with them and I find them inconvenient to use. Personal thing.

[ken henry]

i have no interest in spiral.  they can have dual purpose as both stairs and as artwork, but as stairs they can be rather difficult to use, especially if the radius is small.

As for the issue with bouncy floors.  First, I'm willing to make compromises, especially if its just some noise, but will it get worse over time?  also could it lead to creases, cracks in ceilings or flooring?  I know its risky depending on improvised solutions, but what if 2 inches of spray foam is added to the underneath of the floor? it would dampen sound as well.

EDIT: i looked over some of the prices and designs of spirals on the Home Depot site.  Some seem pretty nice for the price and foot print is small.  If the wash-dryer is kept up stairs so clothes don't need to be carried, it might work.  Again, the 2nd floor porch could be used for egress during emergency or getting large furniture in-out.

[MountainDon]

Exterior stairs to the second floor porch?

[ken henry]

>>Exterior stairs to the second floor porch?

definitely a possiblity.  they would have to be covered unless the material is weather resistent.  it would help solve some of the egress problem, even is spiral is used inside.  If there is a basement i would like to have its entrance from the outside, even if its enclosed in a porch.  that way the floor plan doesn't change if the basement is or isn't installed.


I looked over the plans on the site and found 3 variations of the 16ft wide model with 2 floor porch:

16x16

16x20

16x28

[flyingvan]

If you're sacrificing porch space for stairs, why not just put interior stairs where part of the porch is?  You could still have your 16 X 20 footprint.  Have them go out in the porch area, turn at a landing then return---you'd gain some nifty secured storage underneath the bottom run, and some interior closet space/entertainment center on the interior under the top run

[NathanS]

As for the issue with bouncy floors.  First, I'm willing to make compromises, especially if its just some noise, but will it get worse over time?  also could it lead to creases, cracks in ceilings or flooring?  I know its risky depending on improvised solutions, but what if 2 inches of spray foam is added to the underneath of the floor? it would dampen sound as well.

I didn't mean to dissuade you, there is nothing wrong with a 16 or 20 foot joist span. It's actually not the noise that people complain about, it's that spans of 15+ feet can produce a certain vibration frequency that is very annoying to most people. You don't need spray foam or anything like that. The general advice is to design using 40+ psf span tables to determine what size you need, then step the depth of the joist up by one size, and glue and screw the subfloor on. Then you should be fine.

[ken henry]

I found a site that shows some framing costs for 16ft vs 20ft.  Basically it seems pretty much the mcmansion trap on a smaller scale.  the 20ft is cheaper than 16ft on sq ft basis just due to volume - surface area.  The funny thing is I would like to live in a smaller house, but the 20ft, wouldn't be much smaller than what i have now, especially if there is a basement like i have now.

[Don_P]

NathanS, you got some 'splainin to do. Nobody knows that stuff  .
I took Dr Woeste's seminar and wrote those equations into a simple calc;
http://timbertoolbox.com/Calcs/floorfreq.htm

[hpinson]

Trying the calculator. What is "Modulus of Elasticity (million PSI)"?  Not familiar with that.

[MountainDon]

You can find modulus of elasticity for wood products in a few places and I don't have my bookmarks on this device.  BUT if you go to the AWC joist span calculator you can pull that and other data for different species from the calc results. There is a link to the AWC calc on the Home page for the forum.  Click Home in the menubar and look to lower right on the page that opens.  You would need to pick the species and run a spancalc on something to get that. There may slight differences in some of the technical data depending on lumber/timber size.

[NathanS]

NathanS, you got some 'splainin to do. Nobody knows that stuff  .
I took Dr Woeste's seminar and wrote those equations into a simple calc;
http://timbertoolbox.com/Calcs/floorfreq.htm

Awesome calculator.

[Don_P]

Modulus of elasticity, E, is stiffness.  Or, a rubber band is strong but is not stiff. Knowing about and accounting for material stiffness is an important part of design. This is not a strength value, it is how deflection, sag, is determined. In this calc E is used to determine the vibration frequency of the joist... it's figuring out what note the floor is playing. The human body apparently also uses the 7-10 hz frequency band that he is calling annoying in a floor.

One way Woeste explains to work the problem without using these equations is to use the regular deflection calcs and design long spans for a maximum of 1/2" deflection rather than L/360... other engineers suggest a max deflection of 3/4". Those seemingly minor deflection differences can make fairly large beam size changes on long spans.

The AWC spancalc is a good source for E numbers, do not check the wet service or incised checkboxes and the numbers will be right out of the "Supplement" to the NDS, the real reference.

Generally, the vibration problems this is talking about happen on longer spans of light floors. Mass is also sometimes a solution, usually as a fix rather than by design. Double the 133 lb load in the calc's example and it drops just below the annoying frequency band. Going that route, go back to the load calcs and make sure they still pass, that doesn't work as well if the joist breaks. We had one 24' trussed floor that was annoying, a second layer of really well screwed and offset subfloor fixed it. There was not enough mass to account for the change but the second layer of flooring really improved the T beam created by the joist and subfloor. I think that helped the overall stiffness enough to make the difference.

As an aside, the way a lumber grading machine works is, the lumber is passed through the machine flatways and passes over 2 lower rolls with an upper roller centered between. The upper roller is applying load and measuring deflection. Before that batch is run, they break 100 samples and adjust the computer algorithm that correlates stiffness to bending strength for that particular batch of lumber... so there is a variable correlation between stiffness and strength. At the back end of the machine stands a grader who then visually checks the lumber behind the machine. He's looking for the opposite of the rubber band, boards that are stiff but not strong.