Conference 7.286::home_work

    Why are you not more concerned with the floor acting like a heatsink?
    
    Steve

                As for the slab acting as a heat sink - It will. It will 
        also give back a lot of what is put in. I can say this from 
        everyday experience, I live in a house which is heated in just 
        such a manner (except that the source of the heat is the oil 
        burner).
                
                The heat thus given off is a very even and steady heat 
        (I like it). There are some problems though. In the spring and 
        fall, when temeratures are going up and down like a yo-yo, the 
        thermal time lag of the slab is a big problem (the lag is about 
        8 hours at first, dropping to about 2-4 during the winter). This 
        also precludes the efficient use of a setback thermostat to save 
        energy.
                
                 In fact, if I know that the temperature is going to 
        drop a lot that night (20+ degrees or so), I will kick the heat 
        on manually to ge the head start so that the house will not drop 
        too much before the slab catches up. This is especially true on 
        a sunny day when the heat won't run at all much after 9:00AM 
        because of the solar heating (just what's coming in the 
        windows). This allows the slab to cool a significant amount, so 
        if the house temp is to stay relatively constant, you need to 
        anticipate the need by about 2-4 hours.
                
                One other problem with this kind of heat is the fact 
        that you have to be careful what kind of floor covering you put 
        down. A wall to wall carpet that insulates too well can slow the 
        heat transfer down even more.
                
                /s/     Bob

    About 12-18 months back Fine Homebuilding had a big article on radiant
    heat floors. It included diagrams of pipe layout, curves, equations
    etc. If you cant find the magazine send me mail and Ill try to find
    it and copy the article.
    
    I would NOT use the sand and 2x4's. Its guaranteed to rot. The idea
    of adding on a top layer to hold the pipe is fine, if you can stand
    the loss of headroom, but why not lay the pipe and pour a couple
    inches of new concrete over the old.
    
    I would add 2" of rigid insulation on the OUTSIDE of the basement
    wall. Its a bit of a hassle to dig down all the way around but I
    think well worth it. Note by insulating the outside the concrete
    walls become part of the internal thermal mass and hold additional
    heat. I designed and built a house in Maine using insulation outside
    the foundation wall with a sand and brick floor. I did not add the
    pipes. It has been amazingly successful. With just the sun thru
    lots of south facing windows the floor remains comfortably warm.
    
    Good Luck!

I really wonder how useful all this is going to be coonsidering that you have 
no insulation under the slab.  The earth under the floor stays at a pretty 
constant 50�.  I would think that a _lot_ of your heat is going to go into 
heating the surrounding ground.  If you have the headroom to do it, you would 
probably be better off putting an inch or two of insulation down, then putting 
in your piping and pouring a slab around it.  With a 3" slab, that would be 
about a total of 5", and it seems that you have that much room.  You would have 
less thermal mass, but the mass that you have would be isolated from the ground 
underneath, and I think you'd have a much more efficient heating system.

Paul

	I'm a relative un-handy type of guy and regularly come to this
	conference for help and understanding.  Current problem:

	I have a wood threshold which is to go in the doorway between
	two rooms.  Both of these rooms have carpet (foam padded) over
	concrete slabs.  How do I attach this oak threshold to the
	concrete floor nicely (and hopefully, relatively easily)?  I
	have little idea on how to penetrate the concrete slab with
	something that will hold the threshold in place without 
	a) looking bad (i.e., looking like I did it on my own) and
	b) coming loose in the near future.

	Handyfolks of the world - some help?  Please?

						Pete (Unhandy Dan)

    

Go with construction adhesive, which has been spoken about in several notes
recently.  You can clamp the threshold to the floor while the adhesive sets by 
wedging 2x4s between the floor joists above and the threshold.  

Paul

    Adhesive, yes.  Just a couple of beads the length of the threshold
    should do it.  You probably don't even need to clamp it; just step
    on it to mash down the adhesive, and let it set.
    
    Steve

    Our plumbing is beginning to act strange.  Sometimes when more than
    one thing is draining at once (use the bathroom sink when the tub
    is draining or toilet is flushing), water will stand in the sink
    or bubbles and gurgles will come from the sink.  A few times we
    ended up with water on the floor, I think it is coming from beneath
    the sink (although I can't see that point, its under the base of
    the cabinet).
    
    This problem comes and goes, so its hard to tell if using Liquid
    Plumber in the sink is helping or not.  The house is on a slab,
    so we can't see what's going on underneath.
    
    Does this sound like:
      		Time to call a plumber?
    		Impending septic problems?
     		Something we can fix?

    Sounds like your drain vents are not vented. When plumbing is installed
    they re-vent the vents on all drains to prevent this.
    
    	-Steve-
    

    Re .0
    
    Sounds like the same problem we had the first 2 years in our house
    (also a slab ranch in No. Framingham).  I'm assuming it is clean
    water that ended up on your floor.  In our case it was seeping out
    from under the toilet.  The problem was diagnosed as root balls
    in the drain pipes between the house and the street (town sewer).
    Rotor-Rooter said it was a 2 man job since they have to run their
    gizmo down from the roof...first time was costly (over $200.00).
    The next sping when the same problem arose my husband served as
    the 2nd man which saved quite a bit on the bill (approx. half if
    I recall).  So far so good - no problems this past spring.
    
    Evelyn

    We have not had our septic tank pumped in the 3 years we've lived
    in the house.  Its a pretty safe bet that the previous owner didn't
    do it in the 5 years he was there either (since he didn't mow the
    lawn, shovel the driveway, or fix the roof in that time!)
    
    I have read other notes here about septic systems, with mixed advice
    on pumping.  It sounds like a good thing to try, anyway.
    
    Does it sound like that could be the problem?

    When our tank needed pumping, we found that if you didn't use a
    lot of water at a time, things would drain fine.  However, if you
    used quite a bit, the water would back up in the soil pipe and come
    out the lowest drain (the one for the washing machine in the basement).
    Kind of messy if the straw that broke the camel's back is someone
    flushing a toilet.
    	Anyway, we called a pumping outfit, and after finding the tank
    (that's another story), he was able to use a pole poked into the
    to of the tank to gauge how high the sludge was.  Pumping the tank
    fixed the problem for us.  A septic tank is normally quite full,
    but it should be full mostly of water.  If it's full of sludge,
    call the man with the truck.  Good luck.....
    

    re .4
    
    You means you have a septic tank and you use Liquid Plumber?  You're
    killing your system.  Don't put chemicals down your plumbing.  Use
    a snake.
    

    On the advice of a phd chemist, we add yeast to our septic system
    one a month, to improve the decompositon process. 
    re .-1, could you elaborate on the stricture against Liquid Plumber?

    Bacterial action helps break down some of the solids in the septic
    tank.  If you put chemicals down the drain that kill or inhibit
    bacteria, the solids will accumulate faster and you will be forced
    to pump out more often.  Liquid plumber, Drano, some dyes, etc should
    be avoided.
    
    /Dave

    For further education on your septic system, do a DIR/KEYWORD=SEWAGE.
    I believe note 832 has some useful information about do's and don'ts.
    
    Elaine

 How does under-slab insulation work without getting squashed? I have seen only
one picture of under-slab insulation where sand was put down, then unidentified
insulation, then a plastic vapor barrier, then rebar which overlapped onto the
footings, then concrete. I understand that the footings will support the edges
of the slab but that the middle would float on the insulation. Is this the case?
What keeps the insulation from being compressed? Even if it is relatively stiff,
can it support the weight?

 Here is what the diagram looked like:	# concrete
					x insulation
					= slab
					| expansion filler material
  x##                                                                  ##x 
  x##                                                                  ##x 
  x##|================================================================|##xx
 xx##|================================================================|##xx
 x######xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx#####x
 x######x                                                           x#####x
                                                                              
 Kind regards,
-Tom Rezucha

    Did you ever step on one of those foam insulating panels? It held
    you up, right? Didn't crush under your foot, as long as it was flat
    on the floor and your foot was flat on it.
    
    Now consider the weight of a piece of concrete, the shape of your
    foot and 4-6" thick. Weighs quite a bit less than you, eh?
    
    I imagine that a support column, or anything else that concentrates
    a weight on a small area, would have to be firmly anchored in the
    earth under the slab. But the slab itself should pose no problem.
    In fact, you should be able to get away with a bunch of inverted
    styrofoam cups placed side by side (though I wouldn't be of a mind
    to try it).
    

>    Did you ever step on one of those foam insulating panels? It held
>    you up, right? Didn't crush under your foot, as long as it was flat
>    on the floor and your foot was flat on it.
    
Yes, very true.  I also installed the panels in my water bed.  Two years later
when I moved, the one inch foam was about .25 inch.  I assume that over time it
can crush, maybe the warmth from the bed helped?

Is there a report or warrenty on the long term effects of loading on any of the
foam sheets?

    r .11
    
    Was it the white bead foam that was put under your mattress or the
    blue solid foam. I'm sure the white stuff would tend to crush under
    the mattress but the blue stuff wouldn't crush that much!!??
    The white bead stuff is garbage and isn't worth much.
    

    
    	There is probably a valuable cushioning effect too, i.e. the
    ground under the slab will continue to settle for a long time and
    the foam, as well as the usual sand and gravel, will take up some
    of the irregularities that develop and thereby minimize crackin
    of the slab.

    I was describing a problem I've got with my front porch to a
    friend the other day, and he responded:  mudjacking. 
    
    Have any of you ever heard of this and have comments about its
    legitimacy as a method for leveling and/or supporting sinking
    foundations or slabs? 
    
    Here is how it was described to me:  say you've got a slab that is
    sinking on one side.  These guys come out with a truck and some
    long hoses, drill holes in the slab, insert the hoses, force air
    to clear an area under the part to be supported, then shoot a
    slurry under the slab, raising it to the proper level and
    providing ongoing support beneath. 
    
    This method eliminates the need to dig out, jack up, pour
    supports, and lower.  It is all done from within the confines of
    the area being raised.  It is presumably clean. 
    
    There are actually outfits listed in the Yellow Pages under
    mudjacking (in the Colorado Springs phone book).  I plan to call
    one of them to come out to give an estimate (and a better
    explanation of what they do) and it helps to know a little
    something about the technique before talking to them. 
    
    So, any knowledge?  Comments, yea or nay?
    
    Sid

    	"Mudjacking" is a legitamate profession. I have read several
    articles on the process and your descrpition is pretty close. Some
    processes just inject pressurized mud to lift the object and others
    find it easier to jack up the object mechanically and inject the
    mud afterwards. It isn't inexpensive but compared to the alternative's 
    it is considered economical.
    
    Glenn

    Couldn't find any info on this. Does anyone know how thick a slab
    of concrete (8x8) I would need to place a hot tub (SPA), whose
    approx weight would be 3800lbs (full w/4 adults) at approx. 350
    gals of water. I wish to lay a slab of concrete to set it on..
    but I'm not sure as to how thick it should be....thanks...

    Your slab should be 6" thick using #4000 mix with 1/2" rebar on
    a 12" matrix.  
    
    You should also have 4 to 6 inches of 1 1/2" crushed stone for a
    stabilizer
    

    I aunts house in arkansas has a slab for a front walk and hall
    entrence.  the house is over 50 years old and she does not won't
    to change the appearence of the house.
    
    The problem is that the drought has caused the slab to tilt so that
    water on the outside portion now runs into the house due to the slab
    tilting that way.
    
   1) I suggested they cut the outside portion off with a concrete saw,
    chisel and possible sledge.
   2)  seal the face left on the house.
   3)  tilt the outside portion so that water runs away from the house.
   4)  then fill the crack up with hydrolic cement.
    
   would this be an effective method of resolving the problem?  she
    needs to do something soom because the water is wicking up the lath
    & plaster of the hall and making it drop off. 

    They had a sidewalk here at DEC cxo that did about the same thing
    I believe they used something called mud jacking to level it out
    again. It looked like they just pumped concrete under the old slab
    under force to level it up. Anyone know more about this?
    
    -j

    Splitting the slab in two as described in the base note might solve
    the current problem of water seepage, but it doesn't solve the real
    problem: How to stop the sinking of the slab.  Chances are you'd
    be spending money and time for the half-way fix and later on you'll
    be spending more to solve the big problem. This sounds like you
    should consider professionals... jockying slabs isn't a do it yourself
    job unless you have some heavy equipment.                
    
    Mud Jacking (I've seen it done, but did'nt know what it was called
    until I read .1) sounds like a possible solution. I watched a crew
    work on a sinking slab that was the floor of an enclosed porch.
    They dig a narrow tunnel from outside the porch under the slab about
    5 feet long and "seemed" to raise the slab and the addition by
    forcing the concrete under the slab through a long pipe. 
    
    If you can't raise the slab, but you can stop the sinking... would
    it be possible to apply a skim coat of cement to the interior section
    of the slab to raise it above the exterior?
    
    							* MAC *

    Hello,
    	Getting ready to pour concrete walk along the side
    	of our house...I guess they call that area a "dog run"???
    	Anyway, its nothin but weeds right now....
    	
    	My question(s):
    	
    	1)When pouring do I need an Expansion Joint between the 
    	  new concrete and the foundation of the house, or can I pour
    	  right up against the foundation without any joint at all ?

    	2)The dog Run or walk along the side will be 6ft wide
    	  by 46ft long and 4" deep, how many joints do I need within
    	  that 46ft long walk and what kind ?
    
    	3)If using permenant wood joints...do I need to soak the
    	  redwood joints with sealer or water seal and will this 
    	  warp the wood ?
    
    	Hopefully these questions haven't been asked already in the
    	notes conference. I did a search by title for concrete and looked
    	around but didn't see anything about concrete joints, I know
   	there is more than one (1) way to joint concrete. Any help
    	would be appreciated.
    							Thanks,
    							Jeremy 

    I recently did a very similar project along the side of my home.
    
    My suggestions FWIW;
    
    1.  No need to put an expansion joint along the edge of the exisiting
    foundation.  Just pour it right up to it.
    
    2.  I'd recommend expansion joints about every 10' across the length
    of your run.
                                                    
    exisiting foundation
    ------------------------------------------------
           |          |        |         |         |
           |          |        |         |         |<----expansion joints
    ------------------------------------------------
    ^
    |---What is on this side? Fence?  You may or may not need to leave
    in place the 2x4 used to form the concrete.  In my case I had a
    wood fence.  I laid down a 2X4 for the form and left in place.
    Otherwise, concrete would have oosed through to my neihbors side
    and not looked to nice.
                                                          
    As far as I can tell . . .
    Avoiding cracks in concrete seems to be just dumb luck.  I've tried
    a gravel base topped with sand, expansion joints etc., I still get
    cracks.  There are so many variables, the mix, drying time, soil
    conditions, earth quakes it just comes down to  . . . well, luck.
    
    Regards,
    
    Eric
                                                                         
    

    Yo...
    		Eric, thanks for the info on the expansion joints
    	and overall feedback. I didn't realize I'd get such a large
    	turn-out on this topic..Thanks everybody....just kiddin.
    		
    								Jeremy

    How about the proper thickness for a slab to park a car trailer
    (1200 lb) and possibly a car as well (add'l 2200 lbs or 3400 lbs
    total)?  Do I need to use rebar?
    
    Also, it will be located right next to our garage.  Do we need to
    'connect' the new slab to the current garage slab or can they simply
    be butted up to one another?
    
    Dave

    Here in the south the most common thickness is 4".  I have seen
    occaisonal slabs as thick 6".  You probably will not need rebar unless
    you have a slab which is over 12 feet across.  The two slabs can simply
    butt up against each other.  That way when settling occurs, you will
    not have the two slabs battling each other.
    

    
    
    
    	This seems like the best aplace to put this note...
    
    	I'm finishing my basement. This weekend I put down a 7 ft. oak
    	threshold separating two rooms where the floor in one room is
    	slate tile and the other room is carpetting, everything rests on
    	a concrete slab.
    
    	The treshold was 1/2 in. oak. I routerd 1/4 in from underneath half
    	of it so that the treshold over-lapped the slate tile by half it's 
    	width about 2 in. I used liquid nails to affix the treshold to the 
    	cement slab (carpetted room) and to the slate tile.
    	
    	The side that rests on concrete slab adhered beautifully with no
    	gaps and the full strength of 1/2 in oak. However the side over 
    	slate tile has gaps in spots it looks like almost an 1/8 in.
    
    	I'm worried that the threshold may split. I'm planning on shimming
    	it and using some sort of caulking to hide the gap and shims.
    
    	I was thinking of using the grout I used on the tile floor. Is that
    	a good idea or should I by a tube of some special caulking ? 
    
    						Mike
    						----	 

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    What products are available to put in expansion joints? I have a pool
    area that has many expansion joints that are filled with dirt and
    weeds. I've cleaned out about half of them and want to put something
    pliable in place of the dirt.
    
    Jim

Hi,

I'm preparing to pour a concrete patio, actually extend the existing
patio.  The advice I need is:

What kind of expansion joints should I use?

A couple friends suggested I just create the joints using a trowel or
an edger.  If the concrete should crack along these joints I can fill
them in with some sealer or silicon.
Should I do this or use felt, redwood, etc.
What are the advantages, disadvantages of using any of these methods?

Appreciate any help,

Rub�n

	Creating joints with a trowel (which is quite common) will not
	prevent cracks. Rather, it creates a pre-made weak spot for the
	concrete to crack along when it expands and contracts. So, you will
	end up with cracks, hopefully where you put the joints. 

	Using felt or redwood sounds like you'd have to actually make
	separate blocks of concrete. I've never personally seen that done,
	so I can't comment. If this works and doesn't take too much extra
	skill/effot then it sounds like a good idea. 

	Roy

    When I lived in a warmer climate than New England's, we had a new
    concrete driveway poured.  Standard procedure back then (20 years ago)
    was to pour a single slab, come back later with concrete saw, then
    insert some sort of rubbery material.  My parents still live there and
    still no cracks.
    
    Wendy

    In my childhood home town (Dearborn, MI) we had concrete sidewalks and
    streets.   Expansion joints were built in using a heavy thickness of
    some sort of asphalt/tarred felt.  Typically installed inside the wood
    forms before pouring (I think).   Or inserted before the final
    skreeding.
    
    	Dave.