Replies

1. 
   rez | Aug 15, 2009 01:31pm | #1

   Greetings cutawooda,

   This post, in response to your question, will bump the thread through the 'recent discussion' listing again which will increase it's viewing.

   Perhaps it will catch someone's attention that can help you with advice.

   Cheers

   94969.19  In the beginning there was Breaktime...

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2. 
   SamT | Aug 15, 2009 05:41pm | #2

   Depend$. What level of $quality$ are you looking for? how much time does the concrete have before you need to be on it?

   For enough $$$ and time it can be smooth, level and crack free for the next 100 years.

   In any case, you'll have to use a pea gravel aggregate since you only have 1 1/2" to work with.

   Assuming the existing has no settling/heaving issues.

   Wham! Bam! Get-er-done, broom finish, be framing tomorrow: Pressure wash existing, pour a 3" slump. Probably work fine for 10-20 years. Maybe longer. Will still show some tiny shrinkage cracks. Pre-pin the framing to the existing all the way around.

   Garunteed shrinkage crack-free, steel trowel finish, frame two weeks after pour: Sandblast existing, saturate existing with 2 days before pour, day before pour; cover with small guage galvinized chain link fencing, weave edges together with same guage galv' wire, leave 1 1/2" around edge clear, pin to existing with powder actuated nailers. Rewet existing that night. Day of pour; surface dry, lightly dust existing with cement, or substitute cement adhesive, (your concrete man will know.) Pour with 1" slump.

   Finish. Don't allow to dry, but only lightly mist, DO NOT WET, wet the soil outside the slab, cover with visqueen, sealing the edges to surrounding wet soil and house. Wait two weeks before removing visqueen.

   Perfect for acid staining.

   If you protect the visqueen so you can walk and work on it, wait two days then start framing, etc.

   You'll need to discuss FL and FF with your concrete man.

   Let $$$ be your guide.

   SamT

3. 
   Matt | Aug 15, 2009 10:53pm | #3

   Does the existing have footers under it?    Maybe they don't have inspections where you live...

   I think I'd might want to use poly between the two for 2 reasons - 1) to isolate the two so they could move somewhat independantly - you know the new is gonna shrink during the first day or 2, where as the old probably isn't changing much, and 2) I guess you don't know if there is poly under the old... Building a enclosed structure on a concrete slab with no poly is a bad thing...

4. 
   ponytl | Aug 16, 2009 01:28am | #4

   this is worth what ya pay for it...

   I'd put down 1/4 blue foam like you see under replacement siding... might require a few dabs of liquid nails to hold it flat... this will isolate it and form a thermal break from your existing slab and whatever issues it has..

   the 1.5" is fine... I cast 1.5" concrete countertops and we pick up 10ft ones flat with no steel in them and they don't crack...

   i'd order small rock vs pea... pea is round has no bite and makes concrete weaker...

   I would order 5000lb mix... a 5" slump would be fine for me... it won't kill you working it...

   I would put in flat wire... the wire that comes in sheets vs rolls... chances are it'll end up at the bottom anyway... but try to get it centered... if you can't get the wire i wouldn't worry about it... I think you'd be fine without it...

   I assume the concrete will be the finish floor? hard steel trowel... even machine trowel... keep it covered and damp as long as you can... I'd even consider stamping it if it was mine...

   p

5. 
   mrfixitusa | Aug 16, 2009 06:32am | #5

   we just remodeled a house that had a concrete patio

   it was a four inch thick concrete patio

   It had cracked really bad

   a large crack right across the middle of the patio

   We had a guy take it out

   When we got it out we found another 4 inch concrete patio below it!!!!

   We assumed the top one cracked because it was just too much weight

   But we were just guessing

   We really don't know what caused the problems

1. 
   Matt | Aug 16, 2009 01:43pm | #6

   A few Qs:

   1) Was the bottom patio cracked badly as the top one was?  If so was there a large crack in the same place as the top one?

   2) Was there anything between the top and the bottom patio?

1. 
   mrfixitusa | Aug 16, 2009 03:02pm | #7

   I'm sorry but I don't know about the bottom slab And no, there was nothing in between the two slabsWe had a laborer remove everything by hand and looking back that was a mistakeIt was just too slow to have a guy breaking up concrete by hand and then carrying it off by handWe were walking in and out of the back door on a daily basis and we were walking across broken up uneven concrete and it was a bad dealSomeone could twist their knee or ankle

1. 
   brownbagg | Aug 16, 2009 05:25pm | #8

   if a bottom slab has a crack, the top slab will always crack in same area. The movement of bottom magnified into top. we alway remove existing concrete because we dont know what type soils, soil compaction, footers under the slab.