Question on How to Build Your Own House

Discussion in 'Homesteading Questions' started by angus, Nov 21, 2005.

  1. angus

    angus Somewhere in Oklahoma

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    Do you just absolutely *have to* build a sub-floor for your house??? I mean are there any structural ( or other ) reasons why you *must* do this ???

    We have a dream to build a Passive Solar house. We don't have tons of money so we need to be careful how much we spend. I figure one method would be to use the Thermal Mass of the foundation. Wouldn't have to build a sub-floor, and as long as we insulate the foundation, it might do a respectable job of providing alternative heating during the winter.

    Of course we would have to calculate window, surface area and take into account all the other details that we need to think about when building passive solar.

    We wouldn't install any flooring of any kind on the first floor. So I just don't see any need to have a sub-floor ...

    Is this OK or am I just completely off my nut ???


    Thanks So Very Much !!!
     
  2. farminghandyman

    farminghandyman Well-Known Member Supporter

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    pour a concrete slab for the first floor,

    a sub floor is the structural floor in a wood floor construction, as most finish floors have not the strength,

    if your using a wood floor system, you usally have joists, and then a "ply wood" type sub flooring, and over that you put the finish floor, (carpet, tile, finish wood flooring).

    now if your discussing putting "sleepers" down, usually 2x4 on edge over a concrete slab, and then the sub floor and a finish floor, (this is usually done for comfort, as concrete is usually tiring to walk on and stand on),
    it is not needed as there are many, many, homes that have been built with concrete slabs as the main floor.

    yes insulate the foundation or the outer edge of the slab,
     

  3. JAK

    JAK Well-Known Member

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    Do you just absolutely *have to* build a sub-floor for your house??? I mean are there any structural ( or other ) reasons why you *must* do this ???
    - If you have a conventional concrete foundation then the subfloor of the main floor often needs to be either diagonal tongue and groove lumber or tongue and groove plywood in order to strengthen the foundation walls.
    - If you have a second floor the ceiling of the main floor can be the floor of the second floor. Tongue and groove pine finished on both sides for example. Technically this is the subfloor. You always have a subfloor, you don't always need to cover it.
    - In Canada at least, you cannot have a concrete floor supported by wooden floor joists. You can have a thin concrete slurry or float like they use with radiant heating on top of your wooden subloor. Ceramic tiles word also. Wood that is a dark colour will also absorb heat, but if you have most of you glazing on a floor above a basement you will want to circulate the heat down to the basement. This is sort of getting into active solar but can still be done practically.

    We have a dream to build a Passive Solar house. We don't have tons of money so we need to be careful how much we spend. I figure one method would be to use the Thermal Mass of the foundation. Wouldn't have to build a sub-floor, and as long as we insulate the foundation, it might do a respectable job of providing alternative heating during the winter.
    - OK. So you are talking about the basement floor. It does not need to be covered. You should insulate the foundation walls on the outside and parge over that. You should also insulate under the slab if you intend to use its thermal mass. What is going to heat up this subfloor? Ideally you might have a walkout basement with lots of sun shining in in the wintertime. Alternatively you can have radiant heating in the floor. You can tile over this, or use a simple woodstain and tile it later maybe. In summer you can cool the floor by using it to preheat the water going to the hot water tank. Works through the same heat exchanger that heats it in the winter. Or you can just have a woodstove in the basement and add the radiant heating later since it is usually in a float of special cement on top of the actual slab.

    Of course we would have to calculate window, surface area and take into account all the other details that we need to think about when building passive solar.
    - The best way to do passive solar is to have a nice view to the south, that you want to see anyway, or a integrated sunroom or greenhouse that you want to use anyway. Glass is expensive so it should have more than one reason for being. Also, it is both practical and sufficient to have vertical glazing for your passive solar. As long as it faces due south it will not get too much sun in the summer, and you will get an extra bounce off a snowy field or lake in winter. For area, if in winter you get 2 kwh/m2 per day that works out to the equivalent of a 1500watt heater running 6 hours a day for every 50 square feet of window. That can add up, but you will want some way of adding shutters at night to bump the R-value by about 5 from R3 to R8. To avoid overheating it is usually best to have concrete that capture heat directly or is at least uncovered in the same room, and to have something like wood heat for the coldest days and days without sunshine. If your house is reasonably tight and well insulated and has a long wall facing South, it should be both practical and sufficient to have only 50% of that south faced glazed.

    We wouldn't install any flooring of any kind on the first floor. So I just don't see any need to have a sub-floor ...
    - That right. Except for the floor that ties the top of the foundation together like the lid of a shoebox.

    Is this OK or am I just completely off my nut ???
    - This is OK, and if you are like the rest of us you are also completely off your nut. :p

    Thanks So Very Much !!!
    - Your welcome. :)

    Here is a map of the average solar insolation for a Vertical South facing window:
    http://rredc.nrel.gov/solar/old_data/nsrdb/redbook/atlas/serve.cgi
    http://rredc.nrel.gov/solar/old_data/nsrdb/redbook/atlas/

    Don't forget solar hot water heating. If you don't mind it blocking of you windows, like in the laundryroom, it can be inside one of the vertical windows for use all year round. It probably needs about 1 square meter of exposure, or about 10 square feet. Good do-it-yourself project.

    In summary, it is most practical to scale the passive solar so that it provides all you solar hot water in the 8 warmest months, all of your heat in the 4 shoulder months, and half of your heat in the 4 coldest months. 100 square feet of vertical southern exposure per 1000 square feet of floor area should be enough. Double pane glass and shutters are key. Supplementary heat for the coldest darkest days will allow you to get more out of the windows you have without overheating on warm days. Go solar.
     
  4. TnAndy

    TnAndy Well-Known Member Supporter

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    JAK,

    You and Angus are talking apples and oranges. As farminghandyman said, pour a concrete slab for the first floor. This is done all the time in more southern climates. My own house is a combination of slab and wood joist over full basement on the first floor.....would have gone wood over full basement all the way, but hit too much rock.

    Building on a slab is far cheaper than a conventional wood joist with subfloor also.....in addition to being thermally more efficient if you insulate it properly.
     
  5. MississippiSlim

    MississippiSlim Well-Known Member

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    I don't guess I hav ever seen a floor built over a cement slab.....In fact the new "en vogue" thing around here is scored concrete stained to looklike some type of stone/marble/etc. My only warning...It is LOUD! Seems that noise just carries terribly withour carpet or something to muffle it. I built my own house and built raised foundation (piers) with joists and OSB then covered that with White Pine shelving board to which I applied a polyurethane finish. We are very proud of the way it turned out and it ended up costing about .65 cents a square foot for the white pine but it has gone up I think since then.
     
  6. MississippiSlim

    MississippiSlim Well-Known Member

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    I don't see how this can be cheaper... a slab would have cost quite a bit more (65$ a yard concrete, wire, rebar, form work, dirt work, etc.) than what I paid for the materials for my raised foundation (I compared cost). Plus, I have a crawl space
     
  7. TnAndy

    TnAndy Well-Known Member Supporter

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    Add up the wood framing PLUS the cost of your crawl space. You'll find it's more.
     
  8. jeffreyc256

    jeffreyc256 Well-Known Member

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    Check out www.ourcoolhouse.com

    A subfloor is typically done to get the structure built then apply finishes at one time. Stained, colored and patterned concrete floors are an example of concrete without subfloor concept. Post and beam or joist construction with 1x or 2x flooring direct to studs is an example using wood construction. Typically subfloors allow installation of smaller pieces of more expensive material to be applied without having to worry about nail or fastener placement.

    I am designing a log cabin that will have 2x6 T&G Voint bottom and square edge top for the loft space. You get a ceiling and floor in one application.
     
  9. Blu3duk

    Blu3duk Well-Known Member

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    you probably have studied up on passive design and some folks probably havent... anyhow I just today got the current catalog from Lindsay Books and they have a new listing for $25 detailing a passive solar house [have not read the book but they dont have "junk" books for sale] it is the Number 2081 in the catalog The Passive Solar House by Jammes Kachardorian. It may be some use to folks thinking about building that type of structure. I did not find it listed yet on the website.

    I think most of the other posts answered your question.... bout a subfloor...

    William
     
  10. JAK

    JAK Well-Known Member

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    I am on a slab. I am on a rock ledge so I am built right on a slab. No crawlspace or anything just a hint of a concrete perimeter wall. It's not that cold either and in summer its never too hot. It was built 43 years ago. Hot air ducts run around the perimeter under the slab, but I don't know if they are insulated. I might insulated around the perimeter someday, if only down 2 feet or out 2 feet if I hit the ledge.

    When we moved in we pulled up old wall to wall carpet. There is no sub-floor. Just a concrete slab. Very hard and it was impossible to nail into so we screwed. I didn't really want to. We covered about 500 sq.ft in terra cotta ceramic tile, directly on the slab. The rest was 900 sq.ft of hardwood floor built on 1x3 strapping that was screwed into the concrete. I would rather have gone with ceramic tile everywhere, but I have had no trouble with the hardwood so far, but it does bother me a bit when we spill milk or something like that.

    I am still not entirely sure what you mean by subfloor, but I would say that it would be best not to put wood over or under concrete. I think the best think over concrete is to leave it as is or cover it with ceramic tile.
     
  11. papaw

    papaw Well-Known Member

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    Slim,
    Would you post a picture of this floor? I'd like to see the way it turned out.
     
  12. MELOC

    MELOC Master Of My Domain

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    insulate the concrete floor and foundation? what? huh? how ?

    if i were building new, i would have a concrete slab with hot water heat. i think the best treatment afterward would be something thin like carpet or hard wood flooring (even though wood is an insulator, if it is thin and in direct contact it will transfer heat).

    if i already had a slab i would consider installing the tubing on it and using the special concrete...then treat as desired.

    if i did not want to use the floor heating, i would consider the sleeper idea. having a space in the floor is great for retro-fitting all the little projects that get overlooked initially. it is a good place to run plumbing, electrical and data wire or who knows what 5 years down the road.
     
  13. OneWheelBiting

    OneWheelBiting Redneck Hippy

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    Build with logs. Use either a pillar system and a sub-floor or go with a footer and block wall followed by a sub-floor. Don't get to wierd. Think resale value and future mantaince. I would go Eastern Red Cedar Logs, and a full poured basement. use 4500 psi fibre-force concrete it is higher then most but the cracks others get you won't. Also tie your own rebar it is simple. Set your own forms, and do your own dirt work. use either a T300 bobcat with digging teeth or go with the older 900 series units. A man can do his dirt work in a day and most of the time less. Rock is no biggie for the big bobcats. I use to dig basements in highschool with a old 800 series for extra cash. I got a 450 Case track loader I can send a boy over if your close for pretty cheap.
     
  14. MississippiSlim

    MississippiSlim Well-Known Member

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    I am at work offshore now but when I get back home afer Thanksgiving I will post some pics. We were really pleased. It is not a super tough floor...if you drag stuff across it it will leave scratches but we like it and it was cheaper than any wood flooring around plus we can sand til our hearts content if we refinish and not have to worry about anything.
     
  15. cc-rider

    cc-rider Baroness of TisaWee Farm Supporter

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    I absolutely LOVE your floors! Now that they are done and you've lived there....would you change anything about them? Staining process? Grout lines? (Did it work.... have they cracked? I thought the purpose of the sawed lines was to keep the cement from cracking).

    By the way, you probably used "tiger tape" from the quilting section. It is used so that a quilter can make very uniform stitches. You might have been able to use pinstripe tape from an auto store, too. It comes in various widths. Might have been cheaper. :)

    Anyway.....Loved it! Hope to try it on my OWN home someday.
     
  16. TNHermit

    TNHermit Well-Known Member Supporter

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    Concrete floors aren't a problem till you've walked on them for 30 years or so and you can hardly get up in the morning. Real real hard on the old joints.

    Kinda tuff when you got to fix waterlines or your heat ducts rust out. Built hundreds of them for HUD
     
  17. cc-rider

    cc-rider Baroness of TisaWee Farm Supporter

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    I want to have a walk-out basement and use the cement floors (and lots of south windows), but would have wooden floors on the 2nd and 3rd levels.

    Can I just run all my lines in the interior walls and OTHER floors? I can't imagine that there is ANYTHING that would HAVE to go through/in the basement floor.
     
  18. Tio Ed

    Tio Ed Active Member

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    Nothing absolutely *has* to go through the foundation if you design it to go elsewhere, eh? That said, you'll need to keep elevation for your toilets in mind - you have to have the proper amount of fall for your 3" waste line to work properly. Unless you want to have your toilet mounted higher than your floor (always a sure giveaway for lazy or amateur plumbing work) so the waste line can go through the wall, you'll want to at least run the line at a downward angle through the edge of the slab (meaning you'll have to locate your toilet on an outside wall). We had to do this at our place and have photos documenting it on our website.

    We live directly on our slab, BTW, and will second the earlier comment about it being hard on the joints. On the plus side, it is marvelously cool during our hot Texas summers, doesn't hold dog and cat hair like carpeting and has no grooves like wooden flooring for grit to build up in. We use area rugs during the winter months for the bathroom and bedrooms and will probably be doing some extensive staining and stenciling this coming year.

    If we lived in a colder climate, I would have installed hot water heating tubes in the slab. The Romans perfected the idea and it worked well for their villas as it produces an even, radiant heat that works so much better than forced-air heating systems.

    We've designed and built our own place, which makes extensive use of concrete's thermal mass properties. Gory details, unflattering photographs, true confessions, bad puns and a lot of useful info on DIY construction at:

    http://www.texasmusicforge.com/gimmeshelter.html

    if you're curious and want to do a drive-by.

    Best of luck,

    Tio Ed
    Austin, Texas
    El Rey de Sweat Equity
     
  19. cc-rider

    cc-rider Baroness of TisaWee Farm Supporter

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    Yeah, I'm trying to figure out the toilet/septic line thing. The septic tank is in now.... I need to figure out where to site the house now! Of course, since, I'm doing a walk-out basement, and the toilet will be on the floor above that, I should be WELL higher than the septic system. (If you figure the septic system is even lower than the basement). I need to draw it all out so I can get it straight in my head.

    Yes, Tio Ed, I looked at much of your site. Wish I lived closer and could visit and "pick your brains". I think I'm going to use the dry-stack for the basement.
     
  20. TNHermit

    TNHermit Well-Known Member Supporter

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    If you use a block wall you should backfill with stone or sand about 3 ft away. If you use dirt it will push the walls in over time. Can't tell you howmany block walls I've seen with crack running around about half way up. You should brace it well and fill about 2-3 ft at a time. Best to backfill block after you get floor joist on top and floor poured. Putting the floor joist in can be a hassle with the hole around. But since your doing a walkout you can do everything from inside pretty easy.
    Don't forget your tile. I would put a double row. One at the bottom and one at frost line. plus one down from each window well.

    Just my experience
    Dave