tooltime

Hello,
My house is a single story ranch style, with basement, and I am planning add an addition to the back. My rough ideas are an 8’d x 12’ w to be used as a laundry /mud room type of area. I am hoping this to be a temporary addition ( approximately 1 year) to get enough money saved for a much larger addition, so keeping costs minimal, doing as much as I can myself is my key goal. I have ability, just not so much the know-how of some of the finer things contractors know.
Some questions I have in regard to this particular project are:
How to layout/and cut to make these 2 roofs fit together properly?
I have no idea about pitch, but it is not very steep.
What do I need to do with the underside of the addition?
It will be raised approximately 2’ off the ground, frame/joists of 2x6 pt, with ¾ OSB Sub Flooring covered by some self stick vinyl tiles.
With plans of a bigger, better, permanent addition, there will be a slab poured so I am also concerned about the poured concrete footings on this temporary structure.
Here is a rough sketch, addition being yellow:

I am sure more questions will arise, and I thank you for your assistance.

Square Eye

1. Are you using 2x6 or 2x4s for rafters? Pick one and put a block of scrap on the top plate. The scrap needs to be the width of the 2x4 or the 2x6 minus the depth of the bird's mouth. So, you will need to rip an inch or so off and put the block on top of the top plate at the edge of the wall. Take another scrap of the same width as the rafters with you onto the roof. Lay your rafter material on the block with the overhang you want and the other end on the roof. Now lay the scrap on the roof against the rafter and trace the angle you will cut along the top of the scrap. Now, go to the wall's top plate where the block is and make a plumb, vertical line from the outside wall up across the rafter. Then mark the depth of your bird's mouth by measuring up from the bottom. Square this mark with the plumb line marked earlier. After you cut it, don't nail it down!! This is your pattern. Trace it exactly on all of the rest of the rafters. Nail them down first and watch your fit. If you have to adjust them you can cut them one at a time.

2. Insulate it with R-19 and fasten hardware cloth (1/4" square weave) under it with staples.

3. Pour the footings 12" below the surface level of the floor that you will pour. Then when you do pour the floor, you can leave the footers there and forget them.

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tooltime

Awesome! Thanks Square Eye!

#1 Looks a tad complicated by reading it, but I am sure it will all make perfect sense when actually doing it

#2 You’re talking about the underside correct? R19/Hardware cloth under the floor joists.
I’m guessing you mean faced insulation, with the face towards the ground?
No Plastic sheathing of any sort? Figuring being off the ground that high should reduce the chance of moisture problems.

I have not made up my mind to insulate this addition or not…since I am hoping it will be a temporary structure. Most likely will because I think the cost will be minimal. But if I choose not to, will hardware cloth be sufficient? (to keep pests out from under the joists)

I know I originally stated it would be approximately 2’ off the ground, which it may very will be, but I have been entertaining the thought of dropping it down a little to have a higher ceiling in the room.

#3 Will there be any code issues with the hole being empty (form the ground level, down 12” to the concrete footing)?
Will I have to worry about water pooling or otherwise effect the PT posts?


I thought I was reading about span distance regarding 2x’s in this forum.
Would I be able to go with just 2 sets of footings (2x = house, 2 footings spaced roughly 4’ apart) by using 2”x6”x12” or should I go even bigger (8”, 10”, 12”)?

Even though this is “supposed” to be a temporary structure, I want to build it properly.

*Edit: Another Sketch

Square Eye

If you drop the floor closer to the ground, lay plastic on the ground and turn the paper side of the insulation up to the floor. The hardware cloth will keep the mice and the cats out. You will be able to spray it for bugs right through the hardware cloth.

Fill in around the posts with dirt after you pour the footers. The same way you would build a deck. The PT posts should be ground contact rated.

2x8s or 2x10s would span the 8' distance fine. Use the 2x10s if you dance a lot. Deffinitely use the 2x10s if you span the 12' direction. Most contractors would span the 8' direction. The floor would be much stronger. Add a post in the center of that 12' outside wall and it will add even more strength.

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tooltime

GReat, thank you for the assistance, Square Eye, I think I pretty much have it understood now.

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If you want it done right, guess you gotta do it yourself. :D