Making my own plans - 16' x 24' Gambrel Style 2 Story

[TxBxSx]

So here's the scoop. I am getting ready to start clearing a half acre I bought. There is an old trailer there now and I want to build a small but nice guest house at the back of the property. I have lots a good ideas, but Im not totally confident that I can execute them properly when it comes down to the details. I need a little direction!

I am working  on making my own plans now using Solidworks, But I am not certain on things like what type of materials should be used where and what are common/good practices.

Here is where I'm at so far, THE FLOOR. I am planning on doing my own pillar and beam foundation, but am not sure what I should use for the beams/floor joist and how far apart to set the concrete pillars. I have been told I can use 2x6's on 8" centers for the floor joists, but would like a second opinion. And for the concrete, I live on the north side of the Houston area, and from what I can tell of the soil it is very sandy and loose up top.

I think I have provided what info I can, but if there is something I'm missing let me know. Here are some pics of what I have done with the floor. 2x6's doubled up for beams around the perimeter, and one beam down the center. Joists are also 2x6 on 8" centers, and I was thinking I could use osb tongue and grove  for the subfloor. Pick away!

[UK4X4]

I started much like you with an idea in my head- but not the technical knowledge to carry it out,

i bought a set of the plans from here and studied them- then asked lots of questions from the people here as my original plot had access problems - but my second one had minimum size...

So the plans I recieved are my reference for the technical parts / detail

I have learnt from the site how to calculate beam spans and trace loads, I'm on design 6-ish right now after finding out the latest plot also has earth movement issues

I bought framing plumbing and electrical books as recomended on the site, as being a brit this woody construction is new to me- blue you guy's changed all the wire colors !

if your in a building code area - you'll also be busy looking up relavent tomes.

for your size building - I think there's a set on here which will give you all the standard construction - but think its a normal gabel roof- you'd need to research the gambrel- but at least it will get you to roof level in one simple and relatively reasonable action.

Once I got the basics of span's etc and the calculations required I then looked for software and found I-level Forte.

I'm able to use that now to design my bits not covered by the original plans- and also check it manually as well.

Without the manual knowledge I would not be able to properly use the software-

the last thing i want is bouncey floors and the snow collapsing the roof.

There are many well documented builds here and very knowledgable people who have helped me get to where I am today.

Nope not a nail fired in anger yet- but I'm confident design 6 will function as planned !

do searches for

Built up beam
Joist span
pier placement

there have been quite a few worked examples

ie

http://countryplans.com/smf/index.php?topic=10511.msg149025#new

[MushCreek]

Your floor framing should be prescriptive, which means there are existing tables that you can easily look up the proposed span, load, joist size, etc. without having to calculate anything. I've never heard of going 8" centers; the closest is usually 12". Look up 'framing span tables' or something like that to find the tables.

For gambrel designs, check out barnplans.com. I used their very reasonable plans for my 28' X 48' barn. They use a simple truss design which results in an open gable area. They have sizes from sheds on up. If nothing else, you can get inspiration there.

[TxBxSx]

Your floor framing should be prescriptive, which means there are existing tables that you can easily look up the proposed span, load, joist size, etc. without having to calculate anything. I've never heard of going 8" centers; the closest is usually 12". Look up 'framing span tables' or something like that to find the tables.

For gambrel designs, check out barnplans.com. I used their very reasonable plans for my 28' X 48' barn. They use a simple truss design which results in an open gable area. They have sizes from sheds on up. If nothing else, you can get inspiration there.

Awesome, I found this...

http://www.decks.com/deckbuilding/Beam_Span_Chart_Table

and if I'm reading this correctly, I CAN use 2x6's using southern yellow pine as long as my post spacing is less than or equal to 5'. With that being said, I think I would rather step up to 2x10's so I could cut the amount of posts in half, and reduce the amount of concrete work. The idea of 2x6's came about trying to cut cost, but if I'm doubling the amount of concrete it seems like it could be more expensive.

I will be doing my walls next. I am considering doing shed dormers on either side since there will be a full second level in the house to maximize head room up there. I will get a basic config drawn up and post it so that if there is anything wrong with it, i'll know before pulling the trigger.

[Squirl]

Decks have VERY different loading requirements than 2 story houses.
Southern yellow pine is usually only pressure treated and not the best quality wood to use.

You are asking enough information to well... fill a book.

You could try this one.
http://www.amazon.com/exec/obidos/ASIN/1580114431/countryplanscom

It is great. $13 before you go building something for $20,000.
I'm sure there are plenty of public libraries that would carry a similar framing book
It should cover all the basics of sizing, spacing, and how to fit everything together.

[MountainDon]

If you have decided on the floorplan, the layout, rather than worrying about how to frame the floor your attention should go to the roof design. How will that gambrel roof be designed? How will the upper segment of the gamrbrel rafter be tied to the second one; the second being the one that attaches to the sidewall? What is going to restrain the horizontal outwards force of each rafter? Will they be factory made trusses? Will they be engineered self built trusses as in the ones I have seen in the link Mushcreek posted? Will there be a main ridge beam at the top and a couple of other beams where the roof angle changes; something like a timber frame? The answers to those questions will influence the side and end wall design. Those in turn will affect the foundation design. And foundation design depends a lot on soil conditions.

[Don_P]

I've been playing around with it a bit, just one way to do it;


The main floor girders are supported on 2x treated nailed to the 6x6 posts, the top of the posts are notched to accept the 2nd floor rim. The full height posts are braced by the wall sheathing. The upper roof is tied as a level ceiling the lower pitch is tied by the 2nd floor joists. The pitches are 30 and 60 degrees, the upper ceiling is 7'8".

[TxBxSx]

I bought the book listed by squirl above. I'm confident that this will provide a wealth of knowledge, seeing as how I've learned plenty just in the first 20 pages.

The illustration above is almost identical of the ideas I've had swirling around in my head.

[TxBxSx]

So I have been doing alot of homework and decided to rework the floor framing. Based on some info read in a framing book I have been reading, and a number of floor joist and beam span tables, I have decided to go with 2x10's. The beams will be built up using 2x10s to make 6x10 beams supported every 6' with concrete posts. The joists will be 2x10's on 24" centers which is said to be able to span up to 13', but I will only be taking them about 8'.

Using all pressure treated 2x10x8's @ about $6 a piece, brings in a total of a little over 300$ before tax. Sounds like a nice start

It really seams to be overkill, but this is what I have read and it is after all the base and foundation. If this fails then the rest is all a waste as well! Better safe than sorry.



I will be working on the walls and roof design next. I need to do some more reading, but I think I will be doing 2x6 studs on 24" centers rather than 2x4's  on 16" centers.

[MushCreek]

Don, your dwg is similar to how I did my barn roof. I got the plans from barnplans, but couldn't get the framers to go that route(?) They insisted their way was cheaper. Whatever. We built the 4 walls and the loft deck. Then we built vertical walls set in from the edge to be plumb under the roof pitch transition. We put small trusses on top for the upper cord, and then conventionally framed the lower cord w/ 2X6's. This way, I have plumb walls to work with upstairs. I like to think the triangle they form strengthens the roof. If I ever finish the loft (doubtful) they'll make huge closets. They are just big enough that I can walk back there without turning sideways or ducking. Here is an internal view of my loft, with the detail in question on the left.