Author Topic: Foundation for a 20 x 30, 1 & 1/2 story cottage?  (Read 5847 times)

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RonDay

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Foundation for a 20 x 30, 1 & 1/2 story cottage?
« on: August 12, 2006, 07:11:04 PM »
We're in the planning stages for a 20 x 30, probably stretched to 20 x 40, with 12 foot walls to give us more useable space on a full 2nd floor. The location is about 35 miles NW of Bryan/College Station in Central Texas. The area has been undisturbed for a long time, if it ever was, and the soil is very sandy and drains very well. It feels very loamy and is pretty well covered with trees. We'll be doing the soil density "test" outlined in the plans tomorrow just to confirm our general impressions.

Typical of many here, my wife and I will be doing as much of the work as we can, most of it by ourselves. We want some form of a pier, or post, and beam foundation. At first we thought about pouring piers using the cardboard tube forms. This would allow us to pour as many as we could handle at a time. However, while exploring some of the individual project sites a couple of days ago I noticed that, for a smaller structure, someone had used pre-cast post supports for 4 x 4s and precast pads. Unfortunately I can't reference the site because I can't re-locate it! However, if we could use these pre-cast post supports for our place it would be much easier and probably cheaper, too. Practically, there is no frost line here since the air temps go below 32 maybe two or three days a year, if that often.

At Home Depot today, they had no idea what I was asking about and the only pre-cast post supports they had were for decks. So..., can we use these pre-casts for a place as large as we're planning, and if so, where can we find them? If we can use them, and can get them, how can we mechanically tie the pre-cast pad to the pre-cast support and then the 4 x 4 to the support? Or do we just use big anchors screwed into the ground and tie them to the rim joists?

If we can swing the cost we're thinking of using SIPs. Even if we end up stick building the walls (and foaming them ourselves) we'll probably use SIPs for the roof since the second floor ceiling will be the underside of the roof. Our goal is to have this up and liveable before it gets hot again next summer. We moved in March to be close enough to the property to work more often. Our June electric bill was $370 and we haven't seen July's yet, so we have a lot of motivation to get this done. The sooner we start, etc. Regardless of rather we use SIPs or stick build the underlying structure will be the same.

BTW, there is going to be a "Renewable Energy Roundup and Green Living Fair" (http://www.theroundup.org/) in Fredericksburg, NW of San Antonio, September 22-24. I'm sure we'll be able to get some comparative cost info on the SIPs, and a lot of other info, there. We went last year and it's worth the effort if you're close enough to make it.

Ideas/suggestions are greatly appreciated.

TIA,
Ron

jraabe

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Re: Foundation for a 20 x 30, 1 & 1/2 story cottag
« Reply #1 on: August 20, 2006, 02:22:56 PM »
I think you are remembering the precast deck blocks that can be used for the lightweight post and pier Little Houses. These are not available in all parts of the country but the plans include information for making your own.

However, you will want a much more heavy duty foundation for the 1-1/2 story plan. Use the post and pier foundation plan on Sheet 1A of that planset as it is designed for this house and the footings can be properly sized for the local soil characteristics.
« Last Edit: August 20, 2006, 02:26:32 PM by jraabe »


RonDay

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Re: Foundation for a 20 x 30, 1 & 1/2 story cottag
« Reply #2 on: August 22, 2006, 05:37:10 PM »
Thanks, John. That makes sense. We've decided to build the larger version of the Little House to get us moved onto the property ASAP. Was thinking about making it 16 x 24 rather than 14 x 24, and using 2 x 6s in the walls and for roof joists (for a shed roof), then foaming both the walls and roof joists before doing the interior sheathing. Is increasing the sides the extra 2 feet a problem?

Building this smaller place first should get us on the property before next summer and we won't have another summer of outrageous electric bills.

Ron

jraabe

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Re: Foundation for a 20 x 30, 1 & 1/2 story cottag
« Reply #3 on: August 23, 2006, 07:16:57 AM »
You do need to resize the joists and rafters and floor beams for the wider loads. It is easier to extend the length and stick to 14' wide. I know some folks have just taken the simple 14x24 Little House plan and upsized the floor joists to 2x10s and built it 16' wide. If you are on good solid soil without a heavy snow load it would probably be fine. However, I am not saying this is the way it should be done.

There is a 16' wide studio house with post and pier foundation on sheet 3 of the Victoria Cottage plans. It is more tightly engineered for a simple 16' wide building and does not have the cantilevered floor joists.

RonDay

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Re: Foundation for a 20 x 30, 1 & 1/2 story cottag
« Reply #4 on: August 24, 2006, 06:58:03 AM »
Going longer vs. wider makes a lot of sense. We'll look at that, and the other options you suggest. This first place is a stop gap to get on the property ASAP. We'll probably start on the story and a half almost immediately. The cabin will be used as a craft cottage/guest house once we get the larger place built.

One thing we don't have to worry about is a frost line. The area we're in, roughly 120 miles NW of Houston, rarely sees air temps below freezing. We tend to worry more about dealing with the heat. It looks like this year will rank at least 10th on the list of summers with days officially above 100 degrees.

That was the primary reason I asked about using 2 x 6 in the walls. If we go 14 wide with 2 x 6 walls, should we upsize the floor joists to 2 x 10s? The cost difference should be negligible.

Thanks again,
Ron


jraabe

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Re: Foundation for a 20 x 30, 1 & 1/2 story cottag
« Reply #5 on: August 24, 2006, 07:08:40 AM »
The 2x6 wall (24" o/c) is a good idea for better insulation but doesn't add any load to the floor system so no changes are needed when doing this for the Little House or Builders Cottage plans. This is true of any stock plan... sometimes you need to check that the thicker wall doesn't throw off some critical dimenstion such as a bathtub alcove.

 

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