Author Topic: Issues with building man cave in backyard  (Read 2404 times)

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Offline JohnJ

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Issues with building man cave in backyard
« on: February 22, 2012, 11:24:29 AM »
I sent this email to John Raabe and he suggested I share it in case any of you are thinking of doing this seemingly easy task in the backyard . . .


Hi John,

My project was to build a structure that would tie to my existing deck.  I was thinking 24 x 16 feet.  Thanks to Forum comments and what I’ve read there, I’ve gotten some information from the county which I thought you might find interesting.

1)  If the structure does not attach to the house then no building code applies.  The only thing that does apply is a permit to ensure it is set back far enough from the property lines.

2)  There is no legal requirement applying to foundations but they recommend an 18-24” footer, minimum of 6” thick (8” preferred) that is built beneath the 18’ frostline.  So, in other words, I’m digging a 26” deep trench, 18-24” wide.  But my question is WHY . . . why is that recommended?

                a)  The first answer was “stability.”  So I asked, “are you a saying pier and block system is NOT stable? 

                “Oh, no, no . . . it’s fine too . . . “

                That left me pretty confused.  So I drilled down deeper to see what they meant by “stability.”

                b)  Frost heaving was one issue.  But then I asked if the gravel system would be “good enough” and again the answer was “probably so.”  We do get freezes here but not long ones.  He also said ANY foundation would move regardless of what it was.

                c)  Wind picking up the house.  But I asked if the floor being bolted to the piers and building something around the house to prevent wind from getting underneath wouldn’t prevent that.  Again the answer was “probably so.”

                d)  Prevent animals from getting under the house and protecting pipes from the cold.    But wouldn’t building something around the house prevent that?  Again the answer was “probably so.”

                e)  Earthquakes?  Not really an issue around here.

So, in the end, there’s this amorphous idea called “stability” which is highly desirable but which seems very hard to describe.   To me, it honestly seems to come down to whatever is legal . . . where legal does not always equate to “acceptable given local conditions.”  In my case, block and pier are both legal and acceptable.

3)  The real problem with adding on, I’m finding, is the location of existing utilities . . . drain lines, septic tanks, drainage field, underground electrical lines and water lines.  Our home sits on a lot that was carved out of the side of a mountain.  Flat space is at a premium.  I thought the septic was far down hill.  But according to the man I spoke with, the tank is probably sitting in my back yard, around ten feet from the house.  He said building something on top of utilities IS NOT a good idea.

I’m getting someone to come out and locate exact locations, but . . . after a lot of exploration, it looks like I’m back where I started.  I first need to find a suitable space and then find the plan to match it. 

Frustrating . . . but it’s been a valuable learning experience so far.

John

Offline umtallguy

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Re: Issues with building man cave in backyard
« Reply #1 on: February 22, 2012, 12:21:32 PM »
your town may have a septic plan of your house on file with the tank location... otherwise, wait for spring to soften the ground, get a piece of rebar and go probing.

Offline Squirl

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Re: Issues with building man cave in backyard
« Reply #2 on: February 22, 2012, 03:13:11 PM »
Sorry I did not get a chance to respond to any of your other questions so far.  I saw you had a few. 

1. Cool, building codes are still good practices to follow, but it is nice not having someone look over your shoulder.
2. 6" thick is more than enough for a light frame single story building.  If you go with 8" and you want to add a second story or someone else may then you have that option.  These guidelines for best practices are pulled out from the American Concrete Institute 318.  It is like a guidebook on best practices and requirements for light frame construction.

a.) One of the biggest differences is stability.  It is not a question of is one good or one bad, it is a question of is one O.K. and one better.  Of almost all foundation types, one of the ones that is most likely to have stability or shifting problems is a pier foundation.  Any foundation if constructed improperly can shift. With foundations the deeper and heavier the better.  Also, nobody knows what kind of soil you have.  Houses are heavy.  People load them up with storage and stuff.  They hold tens of thousands of pounds, between the weight of the material, the stuff in them, and the snow on the roof, and many times those loads aren't distributed evenly.  Then you add in sideways forces of the wind, you can have a lot of weight centralized on a very small area of the ground with the pier.  That is one of the main purposes of a full footing is the most assurance that all that weight is distributed over a large enough surface of the ground that can handle it.

b.)On the gravel system, probably so, is also maybe not.  A full footing below the frost line the answer is yes. Done.  Gravel foundations depend heavily on drainage, slope, and soil conditions. I have heavy clay around me.  A hole with gravel and no drainage ditch would be a pond with gravel. The piers would quickly shift and sink.

c.) On the wind, probably so, is also maybe not.  Even if the wind doesn't carry you to Oz, it could tilt the foundation.  Expensive fix.  I am not from your area.  I believe Tennessee has these things called tornados and high wind events, which are rare in NY.  If this is even a possibility of an issue for you, I would look into the high wind framing guides.  They are free at the AWC website.

d.)  Skirting will help, but you will most likely have to insulate any piping.

e.) cool.

3. Building over a septic tank or drain field would be a complete disaster and is illegal in most septic regulations.


The foundation is the first thing you start with and the last piece designed in a house.  It depends on the structure above it, work you want to put in, site conditions, looks, money, risk assessments, longevity of the structure, amount invested, resale expectations, local market conditions, etc...

On the financial side, by the time you skirt and build the pier foundation it will cost you close to the same amount.  The full footing will require more work.

Offline JohnJ

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Re: Issues with building man cave in backyard
« Reply #3 on: February 22, 2012, 04:40:29 PM »
Squirl, than you for your description of "stability."  Explains a lot.

Being naturally lazy and totally inxperienced, I'm drawn to the pier foundation.  But I'm going to research the cost of hiring a small backhoe, cost of cement and blocks. 

If backhoe is too expensive then I suppose I can quit my gym and break out the pick and shovel for exercise.

Thanks again

Offline Squirl

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Re: Issues with building man cave in backyard
« Reply #4 on: February 23, 2012, 06:37:05 AM »
I will explain my feelings on pier vs. block a little better.  I have explained the nuances of the "stability" factors.

One of the ways I approached it was risk and long term investment.  Even though this building is considered a shed for code enforcement purposes, my understanding is it is attached to a deck that is attached to your primary residence.  As far as asset and investment purposes for the long term value of your property I take that into consideration.

18" is pretty shallow and depending upon the soil can be accomplished in many ways.  Trencher/ tractor with plow, there are even walk behind loaders that can do a lot of that, even if you aren't willing to do it by hand, a full sized backhoe may not be necessary.  My estimate would be $1300-$1500 in materials for a full perimeter footing and concrete block wall.

On the pier design, I would not recommend the use of deck blocks for a long term structure.  By the time you add in the rebar and concrete for those footings, the good Simpson connectors, the 4x6 or 6x6 ground contact rated pt posts, the double to triple girders (depending on spacing), the straps and post connectors to connect the girders to the posts, the pt cross bracing, and the ground contact rated pt plywood skirting, you are looking at as close to $1000 or more. It does require less digging which can be brutal.

If you just did the outside load bearing walls as concrete block and skirted the other two sides, it would probably be cheaper.  The simple answer is because concrete is cheaper, longer lasting, and more stable per square foot than pressure treated wood.  It just takes a lot more labor.

I weighed these factors when building my house. What if I need to sell it, borrow against it, live in it when I’m decrepit? $500 and more labor wasn’t worth it in my calculations.

BTW how do I know?
http://countryplans.com/smf/index.php?topic=7305.msg102818#msg102818

I did a 12x8 tiny little shed with piers, gravel, deck blocks and drainage.  It shifted in the first year.  You don’t see everyone putting their failures on the internet.  I don't care because it is just a shed in the woods as a temporary structure until I get a larger more permanent structure.  Speed was more important to me than stability and longevity.  I will probably move it and make it into a chicken coop.

Offline Squirl

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Re: Issues with building man cave in backyard
« Reply #5 on: February 23, 2012, 06:57:57 AM »
2)  There is no legal requirement applying to foundations but they recommend an 18-24” footer, minimum of 6” thick (8” preferred) that is built beneath the 18’ frostline.  So, in other words, I’m digging a 26” deep trench, 18-24” wide.  But my question is WHY . . . why is that recommended?

This is a common misunderstanding about frost depth. 18" is the bottom of the footing requirement, not 18" then 6" of footing.  Depending upon soil bearing capacity, most light frame footings can be 12" wide for 2-3 story wood construction.  What they recommend is better, but not even required under modern building codes.  You should be fine just adhering to code.
http://publicecodes.citation.com/icod/irc/2009/icod_irc_2009_4_sec003.htm?bu2=undefined

Offline umtallguy

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Re: Issues with building man cave in backyard
« Reply #6 on: February 23, 2012, 10:26:16 AM »
I do not think he has stated where he is building. Footing vary hugely, you lucky southern folks only have to think about little things. Up in the north we can have 60" plus which just hurts the wallet.

Offline MountainDon

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Re: Issues with building man cave in backyard
« Reply #7 on: February 23, 2012, 10:42:41 AM »
Some place in eastern TN I believe.
Just because something has been done and has not failed, doesn’t mean it is good design.

If you didn't have the time or money to do it right in the first place, when will you get the time and money to fix it?

Offline JohnJ

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Re: Issues with building man cave in backyard
« Reply #8 on: February 23, 2012, 10:56:55 AM »
Thanks again for the great info.  Yes, eastern Tennessee, about 25 miles from Virginia line.  It's on a mountain that had a spot graded out for a house and a bit of yard.

TN has a service where you call and they notify utilities that you're planning to dig.  They mark all lines for free within 72 hrs.  You're on your own with septic but the contractor who marks for the utility companies finds those for a fee.  Bottom line, I'll know by Monday exactly where NOT to dig.

Re-sale is a non-issue because I am establishing a family homestead here into perpetuity and will come back and haunt any child or great-grandchild who tries to sell any of it.  But . . . based on your sound reasoning and recommendations I will go with a perimeter foundation. 

I’ve shifted my original location to avoid all possible utilities.  I believe I can fit a 24 x 16 building in the new spot.  I’m visualizing a 384 sq ft open space with only walls in the corner to separate the bathroom.  Minimal kitchen . . . maybe a hot plate, microwave and small frig.  A complete second story or two lofts would work and is only for storage.  John Raabe recommended gable roof as easier than flat sloping roof.  No basement.  Two doors.  A few windows but not overkill.  Nothing extravagant anywhere; this is a plain structure to work and relax in.

I want to do it for $10K or under.

What plan would you recommend?  (Little House or Builder’s Cottage?)

Thank you

Offline Squirl

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Re: Issues with building man cave in backyard
« Reply #9 on: February 23, 2012, 11:26:02 AM »
I'll let someone else recommend the plan.  I am doing a 20x30 single story.  It costs a little more per square foot because of it being single story and not taking advantage of the sunk cost of the roof and foundation, but I hate stairs.

It may depend on when the house was built if the septic system is on file.  It is not uncommon in code areas for that to be on file with the local jurisdiction.  This way if a neighbor wants to put in a well, house, or septic system, they know how far away they legally have to be from yours.
As an example my septic drain field is 15 ft from the property line.  If the next owner wants to put in a well or house, it has to be 200 or 50 ft respectively from my drain field, so it limits their property.  The drawing is in my septic permit file with the building department.

Offline umtallguy

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Re: Issues with building man cave in backyard
« Reply #10 on: February 23, 2012, 02:33:47 PM »
one of the threads on here had something similar, the guy who was building a vineyard it Texas made a studio, cant remember which thread it was

Offline CjAl

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Re: Issues with building man cave in backyard
« Reply #11 on: March 06, 2012, 11:40:59 AM »
I do not think he has stated where he is building. Footing vary hugely, you lucky southern folks only have to think about little things. Up in the north we can have 60" plus which just hurts the wallet.
i will dig your foundation if you come hurricanr/tornado proof my house. [cool]

Offline muldoon

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Re: Issues with building man cave in backyard
« Reply #12 on: March 06, 2012, 12:58:50 PM »
one of the threads on here had something similar, the guy who was building a vineyard it Texas made a studio, cant remember which thread it was

I'm pretty sure your talking about phalynx, his thread has his main house and then his man-cave building that starts like 15 pages in. 

http://countryplans.com/smf/index.php?topic=2525.0