What do I specify when I go out for bids?
2,200 sq. ft. crawl space with a grade to floor height ranging between 4′ at one end and about 10′ at the other. A full basement is not in the budget, but it would make for some really useful storage space.
So, I would like to put in what some on this forum have called a ‘rat slab’, i.e. a thin layer of cheap cement.
The grade has about a 1′ in 10′ slope.
I’m not expecting anything more than a garden rake finish, some cracking is inevitable, and no structural strength required.
In my mind, this means they strip off the topsoil when they do the grade work for the rest of the foundation, put down a vapor barrier, and pour a couple of inches of cheap cement. Is that really what I ask for?
Replies
You still have topsoil in a crawl space?
Is this house already built?
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Ground graded smooth, otherwise you won't get any kind of a consistent slab thickness. 1" thick slab will be a waste of money.
Install some kind of drainage system at the low point so that if the crawl does leak, the water has a way to get out. Floor drain, or better still both floor drain and several sections of perforated pipe below the slab. A drain tail that exits to daylight is required.
If required, don't forget the termite treatment before placing the vapor barrier.
6 mil poly vapor barrier with no voids. You may even want to run it up the walls some and glue it to the walls - if so, use black poly.
2 1/2" slab thickness of 2500 PSI mix, bull floated but not finished. Use concrete rather than cement.
Exactly the information I was looking for
THANKS!
My opinion... a rough, raked out rat slab will be worse than dirt. Have them float it out at least a little bit.
I might disagree with half of what he said depending on conditions - got any answers for me?
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Think about that slope for a minute.Now try placing crete on a plastic VB.Even with low slump, most of it will be at the bottom while you end up with only a stain on the plastic at the top.
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That slope is stopping me from commenting.SamT
Anyone who doesn't take truth seriously in small matters cannot be trusted in large ones either. [Einstein] Tks, BossHogg.
I'm still a waiting to see if he is going to tell us if that is the natural slope on an unbuilt site full of topsoil or not.I'm thinking that somebody who needs to specify for bid how to do a rat slab is trying to GC his own build but lacks a LOT of experience stillThen there is the "Can't afford a full basement" - but The only way I can imagine ending up with a slope like that inside a foundation is if it is ledge, but he has topsoil there...Something is screwy here.
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In my mind, this means they strip off the topsoil when they do the grade work for the rest of the foundation, put down a vapor barrier, and pour a couple of inches of cheap cement. Is that really what I ask for?
"This is a process, not an event."--Sphere
And I'm a legitimate certifiable Tool Whore.--Dieselpig
I saw that.
So you agree?It is hard to have a discourse with the guy. He says he has exactly what he wants now, right or wrong. He read my request for info and ignores it...
All we can do is wish him luck.
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Gotta love the cut-and-run posters. I think he got the answer he was looking for.
My guess is he's GCing his own place and doesn't know what to tell the excavator or foundation guy.
Mark's advice sounded ok to me, except for the slippery vapor barrier, and if it's on ledge I'd throw in some radon venting. I don't know how big an issue that is outside of Maine.
I'm curious--what else would you disagree with on the given advice?
"This is a process, not an event."--Sphere
And I'm a legitimate certifiable Tool Whore.--Dieselpig
Like I said, it depends on the answers this OP never provided.But assuming we are right and this excavation has not even started yet, I would explain that it will only cost another two nickles or dimes to excavate enough that he can have a full basement someday if he wants it, unless he is on ledge. Then he can still do a rat slab but it owuld cost but another quarter to have a real floor. He seems to have assumed that he can't afford a full basement, but the few facts he gives are contrary to that.The size of house in SF and the slope he indicates shows this house to be about 40x60 or more likely, 36x66. Pretty good size, wouldn't you say?So he can afford some space down there. The slope would afford a fine walkout basement. The extra appraised value would more than make up for the cost of creating the rough shaped space.OTOH, if this is on ledge, then he needs a drainage plane under this rat slab, or maybe no rat slab at all, since there is already rock there. He would only need to use a pressure washer to clean it, but he might need to plan for drainage and radon removal. That would place the plastic VB in a different laoction in tha plan.i'm not picking on Mark I think it was. I'm just suggesting that since the OP only gave half the necessary info to get a decent answer, the answer he took away with him was not worth much. Not because Mark was wrong, but becuase it was based in part on assumptions and was generic information. Good genericly, but maybe not specificly
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Sometimes work gets in the way of life.We have a construction loan and are working on the foundation drawings. The next step after that is permits.The house is 33x70 - to fit within a boundary of some very large live oak trees.We looked very long and hard at a partial basement - The budget was just not there for it. The concrete retaining walls are ~$10 per sq. ft., and a full basement would have required a lot more concrete.The house is going on the part of the yard with the least amount of top soil. I lack a WHOLE lot of experience. But I'm trying to make up for it with stubborness.The foundation is a stepped pier and beam foundation and I just got the foundation engineer to replace some of the concrete walls with cripple walls.No, I do not know what to tell the excavator or the foundation guy, that's why I've been asking lots of questions.No Radon in this area - but lots and lots of termites. I will have a professional come in with Termidor and I will come in afterwards and treat with Boracare.If you can't put the concrete on the plastic, what is the answer?
Paul,
You can put concrete on plastic.( I think there are better underslab moisture barriers than plastic personally)
I think what the issue here with the concrete poured directly on plastic was the slope of the ground under the plastic, not with the plastic itself..
Most of the time any area that may conceivably be used , or would have a slab of any kind put on it is cut to a flat grade by the excavator. Then a gravel bed is spread out and levelled. Then the concrete. Exception noted for ramps, driveways etc. in terms of flat or level grade. "Rat Slab" is a generic term that has come to mean a relativly rough finshed slab that is either temporary in nature, or as in your case simply to seal an earthen floor without regards to the finish being smooth . If I recall correctly from earlier threads then you are looking at someday maybe finishing a portion of the basement are, but not all of it. Your excavator (after he sees the site and prints ) should be able to guide you in terms of how much of the basement he can safely cut to level without impacting bearing of the building. Certainly your engineer can do that for you anyway. What I understand is that you want a partial area of the crawl/basement area to be covered with a slab . Is that correct?
The hope was to cover the whole 2,230 sq. ft. with the rat slab.The HVAC equipment and water heater will be in the crawl space. I had not planned on anything level except under the water heater.There will be a full size door as an entry way, but no stairs or other openings. The crawl space will be insulated and conditioned.
OK, I misunderstood.
So I will ask why even bother with the rat slab?
Level the area for the utilities , level a walk way that area and just pour those.
I am not at all familiar with a pier stepped foundation with crawl space so I'm a bit blind on this.But I can say fairly certain that it would cost no more to excavate the rest of that space to make potential someday for a full basement than it will cost to pour a 3" slab in there.
So My choice would be to dig all that soil out when the digging is happening..Then if money is way too tight, pour the slab later.The reason you can't pour on THAT plastic as described earlier is that plastic is slippery when wet. A pitch like that will let it slide right off. There are other moistop products that are tougher and that have a bit of a weave, and are not so slippery. but you would still want no more than half that slope. Since you need the slope smooth more oir less to pour, it is relly easier for most equipment guys to smooth it flat than to smooth it sloped, depending...
There are other ways to do it too, such as gunite, but you are talking budget...So to get a lower slope that you can pour onto and expect it to stay you have to dig more soil out anyways.Unless when you comment on topsoil means you have ledge (bedrock?) close to surface, that changes things too.BTW, a stepped footing foundation is harder to do and thus more expensive than a straight one, except for cost of the crete itself.
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The beams are only going about a foot below the surface in many places. More than a partial basement would require digging into rock, since it isn't very far down to limestone on the up hill side.I realize that the stepped foundation is more expensive than a straight one - however, a straight one would add a lot of rock digging, and make the concrete wall around the crawl space about 10' high and we are talking about 200 linear feet of wall. Right now, the tallest wall is 4', and most of it is 3-1/2' tall. Six foot high of concrete x 200 linear feet x $10 a sq. ft. is an extra $12,000, and an additional $5 to $20K of excavation. A stepped foundation is a bargain by comparison.
OK, see this is the info I was after with my line of questioning. First time there has been more than a bare hint that there was rock ledge in the way. There may still be details I am not seeing from here, but with ledge there, I don't see any need for a rat slab or we also call it a mud slab. Just cleaning the dirt off the ledge exposes rock that pretty much does the same thing.Maybe I have a mental blank here and you can educate me.The soil you say is maybe 3-4 feet deep at the uphil side. So you will dig holesfor piers down to the ledge and a trench along tops of them. Is this all trench form and no wood or metal forms?then with this grade beam in place you build a concrete wall atop that
Is that to be CMUs or re-inforced, formed concrete?So the inside of this area is the dirt you speak of that has to be dragged down closer to level to get crete to stay on it. Once that is out of the way, the piers are exposed....This is where I really get lost.It is so much easier and better to my mind and way of thinking to just dig it out to ledge in the first place and place the footers right directly on ledgeNow too, there is something strange about the figures you are working with.
What I ddescribe does not necessarily mean adding that 6' of wall height all the way around. You already said you have that att he deep end, so this shouls only be about 60% of the way around - again, be aptient with me since I'm in the blind both about site and your local methods in Texas hill country - so the amt of crete would be much less.Then, the price for it - I am on an island and crete is expensive here, but we figure slightly over $250/yd placed in forms for footers or walls formed. It costs no more to form an 8' wall than a 5' wall, labour-wise. So the only cost is the extra crete.But let's say I was pouring enough extra wall at my local rate to do the amt you say you would need, it would cost me about an extra $7500. In my concept though, you would only need half as much crete extra and that would cost no more for labour so it might be an extra $2500 rather than the $12000 you thought.So I ask myself what is missing in this?I put myself in th e place of a crete guy in you l;ocation talking to you and start scratching my head.
First thing I say is "This guy is not sure what he is doing here ($$) and this stem wall is stepped ($$) and it is short so my labour per foot has to be higher ($$) and maybe this is far out of town($$) so I better quote high enough to cover my butt for all this unigue work"If that is what we are looking at, it might explain the high price. Maybe the guys there rarely do poured concrete walls for residences so the only ones with wall forms are the commercial guys. That would make him more expensive. Or the guy is quoting high to help defray the cost of buying forms...
I don't know but the dollars you are dealing with is definitely up there.Then the excavator. Half a day for a trench pour dig vs two days for a full dig?Let's be generous and think 16hrs at $150. Double that in caase it is particularly slow. Five grand sounds like tops.
I have never paid twenty grand to excavate a cellar let alone an EXTRA 20K !So there is my thinking, maybe an extra $7500 for excavate and extra wall to end up with deeper space and no rat slab - ledge rock instead - versus $3500 for crete and labour to place a rat slab inside the space you first described.But you end up with more space and a more solid wall foundation. Another option for consideration would be using CMUs for the walls if that is the locally dominant type used. Then you can drop the price possibly.
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You might want to read through this thread: http://forums.taunton.com/tp-breaktime/messages?msg=87719.1
Other aspects of the foundation are discussed.
The (4) 2x14's have been replaced with a 5x14 gluelam. One of those is 10' long, the others are all 8', so should be reasonable for the framers to work with. The floor joists are 2x12's. According to the span tables, the engineer appears to be aiming for L480 worst case, so I'm pretty happy with what I have of his current design.
I'm still waiting to see the detail sheet though, and the devil is in the details.
piers down to rock (or refusal as the foundation engineer calls it)On top of the piers, formed grade beam walls (at least 12" thick), reinforced concrete, in wood forms, 3' to 4' high, stepped, with 2x6 cripple wall from the top of the grade beam wall to the bottom of the floor. The cripple wall varies in height between about 1' and 6'.The rock is about 4' down at the top end and about 7' down at the bottom end of the slope.at least 99% of the houses done in this area are slab on grade. Everybody (but me) brings in enough fill to level the lot - the good contractors compact it.In this area, the expansive clay soil starts to become a real issue when you talk about retaining walls. Big footers, lots of steel required, etc... With balanced fill on both sides of the walls, except for 33' at the garage end, I get away from most of those problems. Digging out the crawl space would lead to a LOT of those problems.Your $250 a yard for formed walls is right at the $10 a square foot that I am told is standard in this area. I don't know what is standard in your area, but in mine, any concrete wall with unbalanced fill is going to be 12" to 18" thick due to the expansive clay soils.
Just to reiterate what we know. All cut and paste follows.
The house is 33x70
2,200 sq. ft. crawl space with a grade to floor height ranging between 4' at one end and about 10' at the other.
The grade has about a 1' in 10' slope.
[The two above para's do not compute. ST]
The [bed]rock is about 4' down at the top end and about 7' down at the bottom end of the slope. [2:10 slope]
The foundation is a stepped pier and beam foundation
The beams are only going about a foot below the surface in many places.
On top of the piers, formed grade beam walls (at least 12" thick), reinforced concrete, in wood forms, 3' to 4' high, stepped
The HVAC equipment and water heater will be in the crawl space. I had not planned on anything level except under the water heater.
There will be a full size door as an entry way, but no stairs or other openings. The crawl space will be insulated and conditionedSamT
Anyone who doesn't take truth seriously in small matters cannot be trusted in large ones either. [Einstein] Tks, BossHogg.
Since budget is of high concern, why not go to a pier and bond beam foundation vice pier and grade beam?
This would save (1'x2'x200') 26yds concrete @ $4000. It would also eliminate all the pony wall$ up to the floor, all the extra foundation $teps and all ek$cavating.
No VB or rat $lab. Insulate under subfloor instead of foundation walls.
Floating slab and conventional framed mechanical room.
You could color coat the piers or put latice around the area.
Later, it would be real easy to shovel out a flat area, put in a locked block retaining wall and pour a small slab for storage space.
Oh, a bond beam is a floating beam the ties the tops of the piers together. It does not need to rest on soil. Typically around 18" deep and as wide as the pier diameter.SamT
Anyone who doesn't take truth seriously in small matters cannot be trusted in large ones either. [Einstein] Tks, BossHogg.
Budget is always a concern. I really appreciate the suggestion, but I am having trouble following it.
If the grade is 10' below the level of the floor - I only see three possibilities.
1. a LOT of fill dirt - not the right answer for this lot
2. 10' concrete wall - expensive
3. concrete wall and cripple wall.
So, what am I do dense to see?
The problem with insulating under the subfloor instead of at the crawl space walls is now all my duct work is in unconditioned space.
The house has a brick exterior from the gradebeam all the way to the rafters, so just piers supporting the house is not going to work.
That did give me another idea though. Would it make sense to turn the stepped pier and beam foundation into a stepped floating slab - like the garage but with steps a thinner slab and a lot less steel in the floor?
Not to try to re-enginmeer this foundation but just for information purposes. I am curious why the design isn't for a simple inverted "T" foundation. We also have expansive clay soils here and yet use it all the time on engineered foundations. (Soils bearing assumed at 2500 PSF.) Why the grade beams, and piers?
And here even with unbalanced fill the engineers will design a re-bar placement and tie the floor system to the tops of the walls so as to allow us to pour an 8" wall most of the time. I have done dozens of 50ft. or so long walls 8-10' tall at 8" thick and sitting on a relatively small footing.
Actually sometimes it is a cost saver to pour the slab as it acts as a compression member to hold the bsae of the poured walls in place. Just asking ?'s here.
Edited 3/30/2007 11:37 am by dovetail97128
Paul - there is another data point that you may not have considered.
You mentioned expansive clay soils. When you backfill with enough gravel, this problem goes away.
If this were my house I would do what I could to have the excavator dig something square, flat and easy to form - spend the money on rock removal rather than the labor on complicated formwork - and get a basement for a similar price.
Of course if this were my house, I'd use ICFs too, and everything would be in conditioned space.
Best wishes on your project.
Treat every person you meet like you will know them the rest of your life - you just might!
I strongly suspect that digging down 6 feet into a limestone ledge is not something I want to pay for. I'm sure it would be a lot easier to form, but I doubt that it would be cost effective. Before you hit 6' into the limestone, the soil test report claims it has gone from medium hard to very hard.
The crawl space will be insulated and in conditioned space.
I've read and studied the ICF's a lot. My personal opinion is that they are an answer looking for the right question. I think there are cheaper ways to solve the issues that ICF's excel at. But, that is another thread alltogether.
Everything I do on this house that is non-conventional in this area is another headache and battle. Some of them, such as the pier and beam foundation, I am willing to do battle. Where I can, I'm keeping the construction as conventional as possible and still end up with the house I want.
I gotta agree with Piffin on this one. Dig out the dirt, leave the ledge, make as much usable flat space as can cost effectively be done at this time. Do it that way because, expensive as it is now, it'll be vastly more expensive to do after the house is built.
Look around the rest of the plans and budget for stuff you can put off and finish after you've moved in. Maybe live with one bathroom to start with, and do the rest later?
-- J.S.
I really don't see the value added. No matter what I do, it is still going to be a crawl space. So the appraisal value will change very little if any.
I will still have a lot more conditioned storage space than what I need.
Maybe your limestone is different from ours. Around here, if you want a basement, you bust rocks. And the rock man comes, leaves that afternoon, and the bill isn't all that outrageous - something like $2K/day If you are blasting an entire house into rock, thats a different story.
If you don't want a basement, skip it. But don't skip it if you are afraid of expansive clay (use gravel) or only "strongly suspect" busting the ledge costs more than the labor of building custom forms.
The guys with the 9' aluminum forms come, set up and pour the same day when the footer is level - thats conventional for MD.
I built one house for my family, and regretted every compromise I made. Regrets stink. The second house I have done almost everything I wanted to - so I'll counsel others to be certain before they build - may you get exactly what you want in your house...
Treat every person you meet like you will know them the rest of your life - you just might!
What are common and accepted construction methods in one area aren't necessarily the best approaches for other parts of the country.
Making comprimises sucks, but if the OP said 99% of the houses are slab on grade what does that leave? Maybe 3/4% for crawl spaces and another 1/4% for basements? What are his chances of getting a good basement contractor? So in his case, not having a basement isn't necessarily a comprimise - it's might well be the smart thing to do. As far as I'm concerned, he is already going to have a (CS) house that is more comfortable to live in than 99% of the houses in his area.
Now let's talk about building a tsunami proof beach house in Western Maryland :-)
As an aside, I think you are grossly underestimating the expence of going from a CS to a basement in his situation. Further, from a resale standpoint do people there even want a basement? For that mater, it sounds like he doesn't want a basement. BTW - I don't want a basement either...
points taken.
I have seen many, many homeowners get less than they wanted b/c they didn't do the research, then live with the regrets. I was just pushing him to consider all the options, with all the facts in place, not guesswork.
The rat slab, the form work, the engineer's "solutions" all smell like someones trying too hard, and not exploring the options. Its hard to tell over the internet, but the advice is free too.
Tsunami proof - I found out about ICFs the week after cowering with my family in the basement while tornadoes tore up the neighborhood. I am more attracted to the energy savings, but my wife likes the security - and she's stopped having tornado dreams...
As an aside, my basement is 2,000 s.f. of untaxable living space.Treat every person you meet like you will know them the rest of your life - you just might!
LOL, untaxed does not mean untaxable
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shhh...
Big Brother is coming!
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The house has a brick exterior from the gradebeam all the way to the rafters,
Never mind what I said.SamT
Anyone who doesn't take truth seriously in small matters cannot be trusted in large ones either. [Einstein] Tks, BossHogg.
The house / garage is one big rectangle 33' x 99' - all under one big hip roof. The garage is at the high end of the pad with the garage doors near grade level.
The garage, and the breezeway between the house and the garage, is slab on fill. The house is pier and beam.
On this 99' length, the total drop in grade is 9' 11".
In the crawl space area, the grade is between 4' and 5' below the finished floor elevation at the top end and ~ 10' at the bottom end. - average grade ~ 6/70 In some places it a little less, some more, after grading, I expect the maximum slope to be about 1' for every 10'.
Rock is ~8' below the finished floor elevation at the top end and ~17' at the bottom end. grade of the rock is a little steeper at ~9/70
The garage slab has perimeter and interior grade beams 12" thick, 24" from bottom of beam to top of slab, all supported on 12" piers going down to bedrock.
The house foundation is 12" thick gradebeams supported by 12" piers going down to bedrock. The gradebeams are stepped and are between 3' and 4' tall, with 2x6 cripple walls from the top of the grade beam to the floor.
On this 99' length, the total drop in grade is 9' 11".
Rock is ~8' below the finished floor elevation at the top end and ~17' at the bottom end. grade of the rock is a little steeper at ~9/70
First a little clarification, what your engineer is calling a "Grade Beam" would be more familiar to us as a footing on piers. We have a company here in Mid Mo that does the same thing, but they use 6" piers and only go down 6' to 18' depending on soil conditions. No bedrock.
You already have at least 7'6" clear between rough floor framing and bedrock. By removing 2'-3' of limestone at the top end and 1' of soil at the bottom, you will have a flat bottom for the footing with piers going down to bedrockwhere needed. You may have to overdig the bottom some to get rid of the topsoil over the mineral earth.
Topsoil is soil with organic material in it. Mineral earth is soil (sand, gravel, clay, whatever,) without organic material. Undistrubed Soil is mineral earth that has not been disturbed in the last 200 years. Or thereabouts(|:>)
Topsoil is only on topfew inches, it does not go all the way down to rock. You must remove topsopil from under concrete. You must remove Disturbed Soil under footings. You do not have to expose the rock except where it would intrude into the plane of the footing.
The excavation to give you a full walkout is a minimal addition to what you already have to do. You can even leave the rock sticking out of the floor in that area and pour the walls there right on the limestone, using the rock itself as a footing. Pour a stem wall around it, backfill with engineered soil and slab over it. Put your mechanicals up there.
BTW, that rafter tall brick exterior is the most expensive part of your foundation.SamT
Anyone who doesn't take truth seriously in small matters cannot be trusted in large ones either. [Einstein] Tks, BossHogg.
In this part of the country, brick is about $1 a sq. ft. more than Hardi Plank, and it is a lot easier to find decent brick layers than it is to find somebody that knows how to install Hardi Plank right. Only the very cheapest of homes do not have full brick exteriors. The expensive homes are more likely to be stone.
It is very hard to find a PE that has any experience at all in crawl spaces, much less basements. The one I found is well past retirement age. And that means that any residential basement design that I get is going to be a CYA design that would be extremely expensive to build. Without experience, their only choice is to add more steel and concrete.
Foundations in general and basements in particular have a very poor reputation in this area. It is quite likely that a basement would be a liability instead of an asset were I to try and sell the place. People like crawl spaces, but they are certain that any basement in this part of the country, unless it is a multi-million dollar job, will eventually leak. I do not intend to sell, but this is a huge investment and must be treated like one - just in case.
One of my earlier designs for this house had a partial walk out basement. I tried to make it work, but the house was a lot bigger than the two of us needed and the mortgage was more than my wife and I were willing to sigh up for.
So - back to the original question - what do I ask for to get a cost effective rat slab?
Edited 3/31/2007 10:45 am ET by paul42
A rat slab is a thin wash of poor cheap concrete spread over a space to keep rats and other vermin from tunneling up. It's only 1" - 2" thick and usually is not finished in any way, just left like it flows out of the chute.
There is enough water added to make it self leveling, so it won't work on any slope. It is extremely rough as there is no finish applied. It is too delicate to see any but the most occasional traffic, like once in 20 years when you finally have to repair some plumbing.
This is why nobody here can help you. A rat slab can't work for you.
I haven't done one in years, but the callout at that time was "Rat slab, 1" x 3 sack." That meant a 1" thick wash of concrete that had 3 "sacks" of cement per yard of concrete.SamT
Anyone who doesn't take truth seriously in small matters cannot be trusted in large ones either. [Einstein] Tks, BossHogg.
I figure around 20 yards of concrete at about 3" thick. In your part of the world, will $4k get me anything useful out of that?
I believe that concrete is in the neighborhood of $85 a yard around here, and labor is fairly cheap.
That crawl space is ideal for storage, and I expect it to get used for that. Just about any kind of floor will be better than a plastic vapor barrier - any other suggestions?
>> Just about any kind of floor will be better than a plastic vapor barrier - any other suggestions <<
Tu-Tuff. It's a hybrid poly that costs maybe 3 times as much as regular poly - but it lives up to it's name. I've never seen it in a store - only have ordered it via phone. Google for it. Also, there are other products for this purpose. I think you said it would be a sealed crawl space. JLC had a good article some time ago on them.
$4K isn't much.
Can you do any physical work yourself?
Can you let Time work for you, or do you need this storage space soon?SamT
Anyone who doesn't take truth seriously in small matters cannot be trusted in large ones either. [Einstein] Tks, BossHogg.
Yesterday evening, I was hit by the internet's biggest enemy - the backhoe. My sattelite internet connection (only option other than dial up at current residence) was disabled at the Wyoming uplink side. But back again this morning.
I haven't gotten the foundation design from the engineer yet so I can go for permits, so yes there is time.
The physical work I can do myself is limited more by time than anything else. My wife and I gave up watching TV a few years ago - not enough hours in the day.
I will be doing a lot of the duct work, low voltage wiring, and probably the house wrap and wall insulation myself. So, I have to set some practical limit to what else I am willing to take on.
I am very interested in whatever you are thinking though.
During construction have the crawl space area, at least the bottome section, leveled in terraces.
After you get your CoO, use lock block to build retaining walls, then dry lay 3" -4" sack 'crete over visqueen, using a garden roller to compact it.
After compaction, lightly mist the dry concrete until it's been wetted to an inch or so depth. Then bull float it to the finish you want and let set for 24 hrs. After 24 hours wet the surface thouroughly and keep it wet/damp for 2 weeks. Work in no more than 10' long sections. You can do a section a day, a section a week, or a section whenever you get a Round Tuit.
Since it will crack between sections, you may want to round over the edges with a curb trowel.
This technique has very few time constraints, mostly only as you first begin to mist. From that time until you have the finish you want, you can't stop. As long as you keep the sack crete dry, you can lay it on the visqueen over as long a time as it takes.
fer instinks; Take three weekends to get 40 sacks (80sqft x 3") down there, the following weekend lay the dry 'crete out and roller it down. 2 weeks later, wet and finish. As long as it stays dry! Even high humidity counts as damp. watch the weather.
SamT
Anyone who doesn't take truth seriously in small matters cannot be trusted in large ones either. [Einstein] Tks, BossHogg.
Hunh??
How do you keep from ending up with a very un-homogeneous slab...all rock in one place, all cream in another?
How do you get anything other than a homogenous mix?
In fact the main difficulty, the one that prevents this from being suitable for fine finishing, is getting the rock to push down into the cream. It takes a heavy float to do that.
The reason for using a fine mist to wet it is to prevent washing all the rocks clean. even so, it will be an exposed agregate finish. Although the aggregate will be finer and in plane with the finished surface and not all "bumpy" like normal exposed aggregate.SamT
Anyone who doesn't take truth seriously in small matters cannot be trusted in large ones either. [Einstein] Tks, BossHogg.
Another thought I had - although a concrete contractor might not like the idea - is to use cheap chain link fabric - about $.26 a sq. ft. Fasten it at the top of the slope, stretch it out, and use a fairly low slope concrete.
Works for me.SamT
There are three kinds of people: Predaters, Prey, and Paladins. For the life of me, I can't see why Prey feels safer from predators by disarming and emasculating Paladins.
I like the idea of the terraced sackrete floor.
The price is right, and I think it would be a lot better floor than I was expecting to end up with.
The problem I see is that the crawl space is insulated and conditioned and that the HVAC, water heater, and heat pump water heater are all located in that space.
Maybe there is a technique to solve the dust issue, but everytime I have worked with sackrete, I have large clouds of cement dust, and that is not a good thing inside a house.
I'm statrting to understand how the local differences evolve and impact this now.We have expansive clay too, but deal with it differently. For one thing, the climate here is wetter more consistantly so things don't cycle quite as much. But we use 8" instead of 12" walls. That explains some of the cost difference too in our figures. Then we replace clay outside the walls when we backfill with gravel that drains and use drainage fabrics. Letting the water out of the soil immediately near the walls keeps it from being destructive. The exapansion from freezing is at least as much a concern as the clay moving
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Piffen, Paul started out in January with questions about his house foundation.
I did a search of the threads and found them all but when I tried to cut and paste it here it didn't copy correctly so I deleted my post. Maybe someone else can do the search and post the results. I have tried 4 times now to re-search for the threads and come up empty handed each time.
I think reading all of his questions and the answers from the beginning will help you understand what the problem may be.
You have a good name, BTW;)I guess my parents liked it too.Back to the original Q - for a residence, there is no need to get too detailed with specs for a rat slab. You could say simply "Rat slab in crawlspace - min 3" over VB"
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A one in 10 slope isn't that steep. It will be fine as long the concrete isn't more than about a 4" slump.
Re your comments about only a few more $ for a basement, that is typical in northern climates since you already have to go 3 or 4' below grade for the footers. In southern climates going from a CS to a full basement can nearly double the cost of the foundation since the footers may only need to be 12" deep, or maybe even less. So, you could easily be adding an extra $20,000 to the foundation cost. Even if it is a walk-out, only about 50% of the area can be truly livable. Granted basements in your climate can be cheap square footage, but for what? To me a basement is nothing more than a dark area to store your "stuff".
Normally I would agree, but look art what he said - this slope runs from 4' to ten feet below his sill. By natural slope he already has 3/4 of the space open. So to dig the upper side another five feet at most for half the house at most is no way going to add twenty grand to this foundation space. Now, if you think you want to pour 4" slump slab on plastic, be my guest. Capture it on film though. It would be fun to watch.
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You could say simply "Rat slab in crawlspace - min 3" over VB"That sounds like a good idea, but around here crawlspaces are very uncommon and the term 'rat slab' would not be understood at all. I had a lot of trouble finding an engineer that still does pier and beam foundation design. A lot of them have retired, and there is not enough work of that type to get new ones interested in learning.
>> I had a lot of trouble finding an engineer that still does pier and beam foundation design. <<
What, are they mostly slab on grade these days or what?
So he can afford some space down there. The slope would afford a fine walkout basement. The extra appraised value would more than make up for the cost of creating the rough shaped space.
I was "reading" that, too. Except, I suspicion that what he "can't afford" is more foundation wall, either up or down to the required elevation. And that, because he's locked into some number the foundation man gave him for block or formwork or some such. Or, the footers are poured, but no walls, so, it's "past" the "oh yeah, we could do this for only $$$ more" stage . . .
Given the slope, could almost just spec some 2000psi fibremesh 2-3" slump to go into 24 or 30 square, 2" deep forms--as individual "tiles" might be a lot easier to set on that sloping visqueen . . . Occupational hazard of my occupation not being around (sorry Bubba)