Slab Advice

Tom R

I'm going to be doing a patio slab for a regular customer in the next week or so, - - it'll be 9' X 18', - - right up against the back of the house, - - running (longways) parrallel to the house.

It'll be 2" of 3/4" crushed stone, then 4" of 3500# concrete with a metal control/key joint across the middle, - - effectively making two 9' X 9' slabs, - - that can be poured simultaneously. I'll provide a slope away from the house of 1/4" per foot.

Along the foundation wall I plan on using (what I call) 'zip-strip' foam, - - so after it's done I can peel off the top of the strip and fill it back in with self-leveling caulk.

So here's the question, - - should the slab be 'tied-in' to the foundation wall with 're-bar shorts' or should it just be allowed to 'float'??

I would think just let it float, - - but want to make sure that's the right way . . .

Appreciate any and all input . . .

I'm in central Jersey.

6stringmason

I would let it float. Sounds like you have it pretty well put together. I use that same type of exp joint as well for alot of things.

__________________
Kamps Masonry & Concrete Countertop Design Green Bay, WI
920-680-3195
Visit our website @
http://www.concretecountertopsdesign.com/

Tom R

Thanks 6,

Yeah, I would think 'tying it in' could possible CAUSE a problem down the road . . .

But yet I have heard some say it's better, - - or even recommended.

6stringmason

Ive heard the same thing about both as well. My thinking is that if you tie and have some heaving during the winter it could possibly mess things up. I dont see any problems with not tieing it in. Possible seperation between slab and foundation if you get heaving but nothing structural. You wont have to worry about cracking the or ruining the foundation.

You could also always put down a few inches of sand on your base.

__________________
Kamps Masonry & Concrete Countertop Design Green Bay, WI
920-680-3195
Visit our website @
http://www.concretecountertopsdesign.com/

maj

I like to dowel slabs to whatever it is they are abutting. I have seen too many garage approaches & sidewalks that have settled or pulled away. Usually because of the overdig. Maybe you don't have that on this project Tom? (overdig, I mean)

I will epoxy #4 rebar every 2', then tie a bar perpendicular out about 1'.
Right or wrong, I've not seen any problems since I started doing it this way. Maybe if they did it here,http://www.contractortalk.com/showpo...34&postcount=1, this wouldn't have happened.

__________________
The views expressed in this post are merely opinions of named poster and in no way shall be deemed meaningful by members of the herd. By no means does anything posted by named poster mean a damn thing for anyone else partaking in this thread.

Tom R

Thanks maj,

No, no overdig scenario, - - but interesting point about the 'pulling away' possiblity . . .

As far as that porch that Ron's talking about, - - sounds like it was a combination of loose fill and no wire or re-bar that may have caused that . . .

Tom R

Here's what I would view as a possible 'pitfall' of tying in . . .

Where it's tied in is the 'warm' side of the slab (against the house) . . .

The outside edges are all 'cold' (subject to frost heave) . . .

If the outside edge and the side were to 'heave', - - and the house edge were to 'stay', - - seems something would have to give . . .

Also, - - maybe a potential problem of causing a 'reverse-slope' after several years of the outside edge heaving and not going back down as far each time . . .

Just thinking aloud here . . .

Anyone??


P.S. Oh, just saw your post (#4) after I wrote this, 6string.

Tom R

You mean just sand, or both sand and the stone??

For what, - - curling prevention, maybe??

Glasshousebltr

Tom....just be sure to tie up any rogue goats.

Bob

__________________
Bob

6stringmason

I guess sand isnt really a must. I just use it since it helps with drainage and reduces the chances of getting a frost heave in my neck of the woods. Its not needed, just something I have always done since I was a grunt and still do today.

__________________
Kamps Masonry & Concrete Countertop Design Green Bay, WI
920-680-3195
Visit our website @
http://www.concretecountertopsdesign.com/

joasis

I know it is different up north..we don't have frost heave in Oklahoma...but I'm with maj, we would pin it..only I don't epoxy, I angle the pins alternating and tie a bar out.

__________________

maj

Hey, THAT'S a good idea, why haven't I thought of that!!!!
I hate messing with epoxy!!! Thanks Jay, I'm going to angle 'em from now on...

__________________
The views expressed in this post are merely opinions of named poster and in no way shall be deemed meaningful by members of the herd. By no means does anything posted by named poster mean a damn thing for anyone else partaking in this thread.

Tom R

Never heard of that angling 'angle', - - that's a good one.

jmic

If I might throw 2 cents in I'd prefer the 3/4" stone ( about 4" ) under the slab for drainage and added protection from frost. I might be mistaken but Tom do you get much frost down in Jersey ? Or very minimal?

__________________
___"Remember You Never Get A Second Chance To Make A First Impression"______________________
Joe

Tom R

We get a good amount, I guess, - - our 'frost-line' depth is actually 2', - - so our footing depth requirement is 3' . . .

2" of stone is pretty 'standard' around here, - - at least for those of us who even 'put it', - - most guys will just dig the 4" and lay the slab right in.

What's your frost-line there??

And what's your opinion on 'tying-in' to the foundation wall??

I'm still undecided, - - good points from both sides . . .

Glasshousebltr

I'd let her float Tom. It may prevent movement problems down the road.

In fact, just did one.....a floating.

Bob

__________________
Bob

Tom R

Thanks, Bob . . .

Now, - - we are talking about SLABS, and not EX-WIVES, right??

Glasshousebltr

I'm pretty sure not a one of those brauds would float.

Bob

__________________
Bob

tkle

Doweling through the expansion joint(as compared to a control joint)defeats the purpose of the expansion joint.More so with the use of epoxy.There would be no slippage to allow any expansion.You also create a place for water to enter creating a rust problem,leaving possible voids in the slab.That said,I usually don't put expansion against the foundation as long as the slab isn't locked in and has a place to move.If there is a frost heavage problem in you're area,I would consider doweling.I know when I worked in Lake Tahoe we never doweled any exposed slabs and never had a problem.Just pay attention to your base as advised.A good base will allow water expansion under the slab as jmic pointed out.

jmic

Tom,
We use 42" for frost protection. As Maj pointed out I would pin it if overdig was an issue, but I gather what you're doing the site has had many years to settle, so I would think it has good compaction. I vote let her float.

__________________
___"Remember You Never Get A Second Chance To Make A First Impression"______________________
Joe