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hart
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# Posted: 4 Jan 2011 00:50
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I am long winded, please forgive me.
I am new as I was searching ideas and came across this forum the other month.
Little bit of background information- I want to build a place out of pocket on my grandfather's farm (he is getting up in the years and now seems like a good time to LIVE there).
Roughly speaking, I was shooting for a 20x30 structure.
Question- Foundation/flooring/Im cheap
My first idea was to simply pour a concert pad as a floor (I am on a tight budget) despite all the livability drawbacks.
However I am swaying in the wind and leaning towards building my own joists and laying t&g osb on top, IF I can find a small sawmill (there are a few Amish mills in the area) that will break me a deal on the lumber.
That said, which type of foundation would you recommend? The 'pier' system looks the cheapest BUT I am concerned about the inlet water pipe freezing during an Ohio winter.
My other thought (if I do go with joists and not a pad) is to use concrete block around the entire perimeter, then also in the middle for support (this idea seems a little bit more pricey, time does not concern as much as price).
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hart
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# Posted: 4 Jan 2011 01:01
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Oh, I forgot to mention, I will be using a backhoe onsite anyways so digging is not a big issue (grandfathers backhoe).
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fooboo
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# Posted: 4 Jan 2011 04:06
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In Ohio, piers are going to be cheaper than a slab.
You can borrow some tips from the mobile home industry to prevent frozen pipes. Mobile homes are similar to cabins built on piers because of the unheated exposed crawlspace.
There are several things you can do to prevent frozen pipes. First is to have skirting to keep the wind out of your crawlspace. Second is to use thick pipe insulation, and third is to use electrical heat tape that has a thermostat built in to the tape. If you get the kind with the thermostat, it won't run all the time. There is some basic info on heat tape at URL
Those three things should be enough to keep your pipes thawed out. If you get a freak storm that pushes down the temps to 20 below, you can always turn on your faucets and let a little water trickle out to prevent freeze up on the few occasions this might happen.
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toyota_mdt_tech
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# Posted: 4 Jan 2011 09:17
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With a backhoe on hand, I'd just do a dig out then a footing/stemwall. Easier to keep varmints out, warmer underneath and can access it to plumb etc later. I went this route, easier and cost was about the same, but less labor than holes and sonic tubes, then piers.
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hart.
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# Posted: 4 Jan 2011 21:00
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Thanks for the ideas and link fooboo.
toyota_mdt_tech - I have not looked up the price for a pier system but was surprised to find how much the steam wall would cost (which wasnt horrible).
How many blocks should a person use? I was thinking only 2 high. One in the ground on poured concrete then another ontop that.
Is that too low?
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toyota_mdt_tech
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# Posted: 4 Jan 2011 23:07
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Code will require a minimum of 18" of crawlspace. This is the shallowest it can go. More room will just make life easier on you. With my footing/stemwall, I have a full 3 feet.
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fasenuff
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# Posted: 5 Jan 2011 08:29
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While a block foundation may be a bit cheaper you might check how much it would cost to pour the walls in solid concrete. Ir would make things simpler and easier in many ways and the cost may not be too far off.
One block in the ground and one one top would only give you 8" of crawl space or 16" if you dig out the whole interior area. While you may be able to crawl in a space of 16" working there is a bear some times. It will cost you more now but later you will be glad you put in the extra space. My ground slopes and I have 2' on the short side but 4' on the tall side. The tall side I use for under cabin storage and is where my water tank will be installed come spring. I also built a storage area for shovels and other tools into the tall side.
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hart
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# Posted: 5 Jan 2011 22:08
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There is no zoning at all to worry about.
I certainly agree you should have a house a little high so you can get under it! So some digging and another round of blocks might be in order.
Fasenuff- A grandparent wanted me to simply pour the foundation as well so I checked costs- doesn't look like I cant afford it :(
I do love the idea of storage under there though, I am going to be running off an Ag well which has NO storage at all (the old farm house had no running water for many years, my first time staying at my grandfather's was an experience-had to pull water out of a shallow spring with a bucket).
I am curious, do you have anything supporting the center of the structure? I was figuring on laying blocks the length of the building in the center to help support the joists (I was guessing 2x8 or 2x10 every 20in, would be enough?).
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toyota_mdt_tech
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# Posted: 5 Jan 2011 23:30 - Edited by: toyota_mdt_tech
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Floor Joist 16" OC, 2X8 is fine up to about 12 feet. How long is the span? If its longer, you can support it in the middle and add a few pier pads. Decking, use 3/4 or 1" tongue and groove, glued and nailed.
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fooboo
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# Posted: 5 Jan 2011 23:41
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The 20x30 plans over at countryplans.com call for 2x12 full span joists that span the entire 20' width. Piers are spaced 7'6" apart and there are 5 piers along each 20' side and one pier in the middle of each gable end, for a total of 12 piers. There are no center piers in the middle of the cabin.
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hart
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# Posted: 6 Jan 2011 00:31
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toyota_mdt_tech
I am thinking about 20x30.
Had figured on laying a foundation and block down the middle as well (or maybe just some here and there down the middle) then tossing a beam down to support the joists where they met (in the middle). Did not know how much to overlap the joists when they meet as I would have to bolt them (or use a mess of 6d nails).
So maybe narrower oc specs and keep them 2x8s!
I have not picked a sawmill yet, but I am planning on using ungraded lumber from a small mill.
I will have to check to see how much engineered joists are, maybe it would be cheaper to go with fooboo's idea and simply buy the modern joists and leave them unsupported.
Now that I think of it I find it funny, as a side hobby my grandfather use to build a house and sell it every now and then, up to about ten years ago. He would drop the trees and take them to a small mill, then build completely with his own lumber. I pass the last house he built quite often, it just resold for over 250k, the lumber wouldn't even meet most communities code lol (though its likely better).
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fasenuff
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# Posted: 6 Jan 2011 08:49 - Edited by: fasenuff
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My cabin is 12x14 and I have 9 6x6 posts on deck blocks under it. They are placed 3 down each side and 3 down the middle. At the corners they attach to the 2x8 joists and have 2x6 running under the joists supporting them. Same thing down the middle. The floor is very solid and has no give at all. No bounce when you walk on it. The entire posts, peir blocks, and joists only cost about $250.00. The soil here is very rocky and I am on a hillside so drainage is good.
As far as overlap on the joists, the more the merier but a couple feet would work. However if your building ever settles a larger overlap will help prevent the sharp bulge in the middle you can get. If you do go with a 20x30 use 12' joists and support in center.
It would be easier to lay block piers in the center with wood beams spanning them.
http://www.awc.org/calculators/span/calc/timbercalcstyle.asp
The above link is very usefull for helping decide which floor joists to use. Hope this will help you a bit. I know it can be hard to decide which way to go with so many options to do things. The floor supports everything else and what you do there can make such a difference in how everything else turns out. My look on it is if you can, over build the floor. The more solid it is the more solid everything else will be. If you have to cut costs somewhere don't do it on the floor and foundation.
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toyota_mdt_tech
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# Posted: 8 Jan 2011 12:45
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Quoting: hart toyota_mdt_tech I am thinking about 20x30.
OK, you can run a huge quad 2X8 the 30 foot length down the center w ith pier pads supporting it along that way, maybe ever 4 to 6 feet, then run your 2X8's every 16" across it (get them in 12 foot) and they can overlap over the quad 2X8 by 4 feet. Bolting can be spendy, an air nailer, some 16D and shoot them in multiple times would make this plenty solid. Foundation/floor is one item that is nearly impossible to change later, so you are better off overbuilding it. Keep the span at 16" for ease if insulation. If you go bigger than 2X8, then you will find 9 foot tall siding wont quite cover the rim joist.
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MtnDon
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# Posted: 8 Jan 2011 21:53 - Edited by: MtnDon
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hart, the AWC calculator fasenuff referenced above is a great reference tool. The entire 20 foot span works without a center beam using 2x12 select structural Douglas Fir. There are other species that will span the 20 ft wide as well. Sometimes it is more cost/work effective to order the more pricey lumber for joists than it is to dig and pour a proper footing, install a row of piers and install a third beam down the center.
If the decision is made to go with a center beam though, there is no need to overlap the joists at the center by measurements involving feet. The IRC 2006, for example, calls for a minimum overlap of 3 inches. That's all. Three inch overlap and the use of a minimum of three 10D face nails. Joists may also be spliced, that is butt jointed, end to end, over the beam. The IRC calls for a minimum of 1.5" of joist bearing on the beam. So you could butt the joists ends, centered, over a 4' wide beam (3 1/2 inch true measure) and secure them with a one foot length of 2x that is the same as the joist (2x12 joist; 2x12 splice) That would be scabbed onto the side where the joists meet. Use three 10D nails into each joist, six total in the splice.
Joists that overlap over a beam or are spliced over a beam also should have solid blocking (bridging) applied where the joists pass over the beam. Not X blocking, but solid. Generally distances between bridging and/or rim joists should be 8 feet maximum.
If you use 92 5/8 std studs, two 2x top plates, a single 2x bottom plate, 3/4 inch sub floor sheathing on 2x12 joists you can still use 9 foot wall sheathing panels and only be short 1 1/8 inches of coverage at the bottom edge of the joists. That is not a big deal and much stronger than using the normal 8 foot tall wall sheathing panels where the panels do not extend down and lap over the joists.
If you are using ungraded lumber all the recommendations from the AWC or any other calculator or chart/table is null and void. Grading is part science and part an "art".
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hart.280
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# Posted: 8 Jan 2011 22:39
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fasenuff- I am very new at this so please bear with me. For the block piers would I dig a little, pour concrete, then lay block ontop? If so, How deep would you go with the concrete, I wouldn't think it would be supporting nearly as much as the outside....
Toyota_mdt_tech- Wont the overlap be 2 ft? Sorry, you lost me there.
And thanks to all.
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fasenuff
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# Posted: 9 Jan 2011 06:25
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A lot depends on the type of soil you have. If it is a soft soil where settling could happen or the ground could heave from freezing then you would wand to dig deeper and possibly pour a wider footing. Where I am the ground is very solid and rocky so all I had to do was dig the top few inches of organic material away and use pier blocks. But if you have soft soil I would recommend digging down below the local freeze point and pouring a pad at least 12"x12" and putting piers on that. Again a lot depends on your soil type.
This is one of those things where you can get a lot of opinions on how to do it but ask local builders what the local freeze depth is and how they put in piers. That more than anything will let you know how you need to go about it. What worked for me here may not work for you there. If you do not know any builders go down to the local coffee shop and chat up some of the old timers. They will know.
MtnDon is correct, in a perfect world if your footings and peirs never settle an 1 1/2" overlap would work. But myself I am not comfortable with that. But if it did settle anywhere the overlap area is where you would notice it. 2' on each side of the center point will give you more area to fasten the joists together and strengthen them. I myself would prefer that. But let's face it, to get boards long enough to make sure you have an 1 1/2 overlap you will need boards over 10' long. Next stanfard lenght is 12'. Don' cut them just overlap the difference. Sure most 10' boards are longer than 10' but not a consistant amount over 1 1/2".
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MtnDon
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# Posted: 9 Jan 2011 12:37
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I'd like to add that if a foundation is done correctly there is little expectation that the structure sitting on it will ever need adjusting. That said I know there are foundations that are improperly done and cause problems. Not just owner built but in some cases I've seen here one's that contractors built. But it can be done right in such a manner that the chances of movement will be negligible. It does seem that I see a good number of foundations that would be classed as less than optimum.
Also note I stated the overlap was 3", not 1 1/2. ! 1/2 was if they were butt spliced. As many beams used are six inch wide or wider the bearing length is virtually always more than the minimum required by codes.
As for using 12 ft and overlapping that much, they could be cut and the cut off used as blocking/bridging saving on the materials cost.
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fasenuff
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# Posted: 9 Jan 2011 13:16
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You are right Don, most houses are built these days using what you stated above. You can get by using the minimums for things like that. Builders trying to save money will use the shortest board length and get by using the minimum overlaps where possible. And I believe what you are saying is the minimums in the book. Could be wrong about that being the minimum. But I do not believe it is the maximum.
I have seen a lot of 50 and 75 year old houses that are still solid in the floor with a larger overlap. And I have seen more than a couple with less overlap with spongy or bowed floors.
Taken from my post above:
The floor supports everything else and what you do there can make such a difference in how everything else turns out. My look on it is if you can, over build the floor. The more solid it is the more solid everything else will be. If you have to cut costs somewhere don't do it on the floor and foundation.
Like I said, it is just my look on it. I would rather have to buy an extra board or two for the blocking than wish I had a couple years down the road. Neither one of us is wrong on this point I feel. But I would rather err on the side of strength. In this day of a life span of the typical house being around 25 to 50 years I myself would rather build it like they did when the typical lifespan was 50 to 75 years.
I always read when you post advice on something Don. I have found you are very knowledgable and have learned a few things from what you have posted. This is one of the very, very rare times I do not agree with it myself. But that is just me.
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MtnDon
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# Posted: 9 Jan 2011 20:22
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Overbuilding is fine, I do it myself, but sometimes overbuilding increases costs with little real benefit. Let me explain how I view this center beam thing. I am not just latching onto what the IRC states.
First of all, in a design with a center beam the two outside beams should be either directly under the outside wall or at most the outside wall should be cantilevered no more than the depth of the joist. (Some designs using continuous one piece joists can safely use a cantilever up to about 2 feet.) Most builds using a center beam will have the two outside beams directly under the outside walls. The outside ends of the floor joists will end over the outside beams and not overhang the beams at all. There will be no uplift force on the joist center overlap or splice in this scenario. The outside beams each support 25% of the weight of the floor assembly and the center beams supports 50% of the weight of the floor materials. The outside beams though, also support the entire weight of the sidewalls. Depending on how the roof and upper floor structure are made the side walls could also support all of the weight of the rest of the structure. If there is an upper floor/ceiling load bearing wall then some of the upper floor load will be transferred to the center floor beam. However the entire weight of the roof assembly will still be on the side walls. This assumes the roof does not use a ridge beam, but uses the more conventional ridge board.
Mainly the center beam is supporting the above mentioned 50% of the weight of the floor materials plus 50% of the weight of the contents of the building. The load is all in the down direction. The solid 2x blocking installed along the overlap (or splice) above the center beam resists any rotating forces, forces that want to twist the joists. The rim joist at the outside also resists any rotational moments.
The outside beam may be a 4x-something, maybe a 6x-something. The outside ends of the floor joists carry more weight than the center beam carries. The weight on the outside end of the floor joist may only be carried by a 3 1/2 inch width. If the floor is built so the rim joist is also over the beam, there is only 2 inches of joist end carrying the weight. And that all works fine. The weight on the center beam is carried safely as well as long as the number of piers and beam size match the load.
Any excess overlap is just that; an excess. It could be used for blocking. It doesn't really do any harm but if there is some sort of movement in the structure that would depend on an extra couple feet of overlap and a few nails the building will likely have some really serious damage anyways.
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hart.280
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# Posted: 17 Jan 2011 04:10
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Wow.
That was a lot of info.
Maybe i will read it a few more times.
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