Little House Plans Modified to 16x28...

[ajbremer]

01/01/11 Happy New Year: Oklahoma, USA

A few days ago I purchased the 'Little House Plans' but I wanted to increase its size to 16x28 so I became a member here and I also ordered the '3D Home Architect 3.0' software on eBay.

I'm starting to spend hours reading this forum (a great help) but I might be getting confused. We don't plan on doing any modifications to our plans except windows and doors (I need to keep it simple). That being said, I've read here on the forum that what that means is that I'm basically only doing 'more of the same' so I don't need any special plans.

What me and my wife want to build is very identical to the Nash home presented on one of the links here at countryplans. I believe they took the little house plans and simply extended them to 16x28 with no major changes (just did 'more of the same'). The 'Nash' home is here:

http://www.countryplans.com/nash.html

My question is this: Since we want to build a 16x28 Nash look alike, did I do right by ordering the 'Little House Plans' and then downloading the 16x28 modification templates presented here - I don't need to buy anymore plans? (I think I saw where the main section of the 'Victoria's Cottage' is pretty identical to someone building the modified 16x28 Little House. But now that I look at the Victoria, I see that it's a second story as opposed to a loft?

I hope I'm on the right track - any comments?

[MountainDon]

Virtually any plan can be lengthened without the need to make any changes to material sizes. You simply build it longer doing "more of the same".

Making a structure wider than what is in the plans is different. Changes may be required in the foundation, the floor joists, ceiling joists and rafters. Those changes are fairly easy to calculate though.

It sounds like you have found the first of the changes, the foundation plan that John released for a 16 foot wide. You may have also found where we've discussed the problem with scaling up of a little house design. This doesn't work well especially in the area of the cantilevered floor joists.

Depending on type of soil the method Hal used can work. He was fortunate in having well drained clay free soil and he took time to construct well drained gravel "boxes" for his piers to sit on. Others who have chosen pier foundations have not been so fortunate and have encountered lateral movement. In some instances this may have been exacerbated by improper or non existent bracing, huge seasonal chnages in water content of the soil and/or other factors.

There is a calculator available online for sizing the joists and rafters.
http://www.awc.org/calculators/span/calc/timbercalcstyle.asp
or
http://www.awc.org/calculators/span/reversecalc/reversecalc.asp

These can help in making the correct choices for lumber.
Examples of code-prescribed deflection limits and live load values for use with the calculator are:
   * Living room floors L/360 & 40 psf
   * Bedrooms and habitable attic floors L/360 & 30 psf
   * Attic floors with limited storage L/240 & 10 psf.
   * Rafters  L/240

My 15.75x30 is more or less an expanded and modified little house plan.

[ajbremer]

Thank you Don, all your information is excellent. I must make it known that I am just a beginner in the world of house building. I'm only a little beyond knowing the difference between a joist and a rafter! I've built a few walls in my house before and have done some minor stuff but I don't go too much further than that. I have a few questions:

When you say, "cantilevered floor joists": does that simply mean where the width of the sub-floor goes beyond the house walls?

As far as my soil is concerned, I believe I also have well drained, clay free soil. You know what would be cool, if some high tech. soil dude made a youtube video showing someone shoveling into different types of soil and explaining the content, draining properties, etc. That makes me wonder: you know how you can take your water to places to get it tested? Well, can a person take a small shovel full of dirt and get it tested?

You talked about making the correct choices for lumber. I just need to be concerned about the deflection and load values and not about the different kinds/types of lumber such as pine, cedar, fir, cotton wood, etc. correct? All my 2x's are pine - right?

Last thing: your calculated examples say: L/360 & 40 psf, L/240 & 10 psf. I don't know what the 'L' stands for and I think the psf is pounds per square foot? I don't have to worry about regulations or codes where I'm building but I do want a strong floor both in the loft and on the 1st floor. I'm hoping that I don't have to worry too much about doing calculations as long as I follow the 16x28 plans.

I hope I haven't bugged you too much Don - I appreciate your patience with us newbies.

[MountainDon]

You talked about making the correct choices for lumber. I just need to be concerned about the deflection and load values and not about the different kinds/types of lumber such as pine, cedar, fir, cotton wood, etc. correct? All my 2x's are pine - right?

The amount of permitted deflection, load AND the lumber type are all needed. The commonly used and available species can vary around the country. Here in NM we generally can choose between Douglas Fir, Hem-Fir and general purpose SPF (Spruce-Pine-Fir) Fir is not the same as Douglas Fir, common abbreviation DF. Southern Pine (southern yellow pine) is what you'll find in some places. Etc. Etc.

So when trying out different things with the calculator you should check what is available to you. Lowe's and Home depot websites are set up to indicate inventory by Zip Code.

Lumber Grade: what you find will generally be a #2 grade. Sometimes for a wide span it may be necessary to order a higher grade like Select. Stronger and more expensive. Decreasing the floor joist spacing can make up for lesser grades or smaller sizes. I think using the calculator and changing one variable at a time is educational.

I don't know what the 'L' stands for and I think the psf is pounds per square foot?

Yes, PSF is pounds per sq ft.   more on L and deflection in next post

[MountainDon]

Deflection:  Rather than go into a long post about how it is calculated let's just say that for most floors is the calculated deflection should be no greater than L/360. For a ceramic tile floor this is important to prevent cracking. For a natural stone floor the deflection should be less; L/720.

A floor that calculates out to L/240 deflects more than a floor that is L/360.


For tile and stone floors there is another calculator at http://www.johnbridge.com/vbulletin/deflecto.pl The results between it and the AWC differ slightly 



Cantilever:  yes that is the amount of overhang at the joist end. The 14 wide little house has something like 2 feet. When widening to 16 feet that can not be increased and should actually be made less. That's why the 16x28 foundation supplement has the beams out under the side walls.

You may have read that it is fine to cantilever a joist by the amount of the depth of the joist. That does not require any special calculations. EG: if a 2x10 is used as a floor joist the end of the joist can extend 9.25 inches, the actual depth of the 2x10.

[MountainDon]

Soil:  Someplace John outlines how to do a rough soil test yourself. Sorry just off hand I forget where or if it is included with plans or maybe is on the PlanHelp site. I'll look later or maybe John will see this. Or someone else.

[Don_P]

The "L" is span, or Length of the joist or rafter between supports. One way to think about it is if we were limited to L/360 and had a joist 360 inches long, it would be allowed to sag under full design load as much as 1". We don't use 30' joists! So breaking that down to think about it in a real world way if we had a 16' span (192") and wanted to limit deflection to floor code minimum we would figure 192/360=.533". A joist that just passes is allowed to sag about 1/2" under full load in 16'. Since a roof isn't as critical as a floor it is allowed to flex more under load.

Soils;
John has a good thread on using the web soil survey, in a quick look I failed to find it, hopefully someone has it bookmarked;
http://websoilsurvey.nrcs.usda.gov/
Your local ASCS or soil conservation office can give you local info as well.

This post helps describe soil types the way the building code refers to them;
http://countryplans.com/smf/index.php?topic=8861.0

From that info you can look in chapter 3 of the building code, find the basic 2 letter soil classification and it will give allowable bearing strength.

[MountainDon]

ajbremer, also FYI... as you look at and use the calculators I wanted to be sure you are aware that span refers to the unsupported length. To clarify, If a joist sits on two parallel beams and there is a distance of 14 feet between the beams, that is the span. The amount of the joist on the beam is not included in the span. You will notice the AWC calc supplies a "minimum bearing length" with the result. That is the minimum amount of each end that should be resting on the beam.


I notice you are associated with a website about machinists software. I would think if you are at ease with that you should be able to handle this stuff. It's just new and different; the same way I'd feel about preparing to machining metals. I did some of that long ago.

[ajbremer]

Ok, thanks Don. I'm trying to take my time and understand it all and I"m very much looking forward to receiving the plans for the 'Little House' and even more so, I'm excited about getting that software and actually seeing the stuff. I went to Walmart today and then I was going to go to Lowe's to look at some pier and beam supplies but they were closed because of new years day.

I'm really good about making videos for youtube and I plan on documenting my project through every step.

I really appreciate all the people like yourself here, all the knowledge that this board has to offer. What a great way to learn! Thank you for your help...

al
Allan Bremer

[John Raabe]

Simple soil test:

• Does it drain? Did a hole down to footing depth. Keep pouring several buckets of water in until the soil is fully saturated. Fill the hole up to the top with water and see if it will drain in 15 minutes or less.
• Does it have expansive clay? Dig out some of the saturated soil at the bottom of the above hole. Is it slippery when you rub two fingers together or is it gritty? If you pack it into a jar and mark the top of the soil level and then put it in the freezer, does it expand as it freezes?

If it fails the first test and turns out to be expansive, then you are likely to have foundation problems, especially with shallow pier foundations.

If you do a basement or crawlspace foundation (PT wood or concrete) AND it is properly waterproofed with the footings at or below frost level AND you put in footing drains and backfill with drainage material such as crushed rock, THEN you can likely build a solid foundation even in poor soil. That is why this is the default foundation type that most inspectors want you to build.

If you soil drains well and is not expansive then you have little chance of frost heave no matter what type of foundation you build. You have more options.

PS - I will be best to wait until you've had some time with the plans, the booklet that comes with it, and have laid out your new 16' wide floor plan since lots of things will become clearer as you do this work. Also, be sure to get a couple of good building books if this will be a first big building project - see (especially the first two) http://www.countryplans.com/books.html

[ajbremer]

Thanks for the information about the soil testing John. I'm going to dig a test hole and see what I come up with. I'll do a video of it too.

It's in the low teens here in mid-Oklahoma this morning - so I'm just trying to stay inside with my coffee.  I plan on doing soil tests tomorrow on my day off. I'll look at those books you mention and continue with my learning process. Be blessed!