laying flagstone over rubber membrane


  #1  
Old 11-10-09, 04:38 PM
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laying flagstone over rubber membrane

I would appreciate any imput what-so-ever on the following process!

There is an existing concrete mezzanine above a garage the contactors would like a flagstone patio on. This property is in Central Ontario snowbelt region!

Here is the process suggested for an October/November project!

1. waterproof rubber membrane placed over entire area - including 2 drains for water runoff from roof with no eavestrough. (by general contractor)
2. 3" pins drilled thru membrane into concrete (with epoxy on each) approx every 16" (by general contractor)
3. a washer on top of membrane - wire lathe laid over it - 2 more washers then a nut to hold it together. (by general)
4. 1/2 to 3/4" of pin remains exposed on top - trimmed off excess with hand grinder. (by general)
5. stone mason lays flagstone on mortor bed on top of lathe.
6. contractor (not stone mason) completes joints but does not seal around the edge where stone meets walls of house.

It is later said that the stones all popped - not in the spring but throughout the following summer!

Any imput on where this process went wrong?
 
  #2  
Old 11-11-09, 06:12 AM
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Originally Posted by mvine View Post
I would appreciate any imput what-so-ever on the following process!

There is an existing concrete mezzanine above a garage the contactors would like a flagstone patio on. This property is in Central Ontario snowbelt region!

Here is the process suggested for an October/November project!

1. waterproof rubber membrane placed over entire area - including 2 drains for water runoff from roof with no eavestrough. (by general contractor)
2. 3" pins drilled thru membrane into concrete (with epoxy on each) approx every 16" (by general contractor)

What are the pins for?

3. a washer on top of membrane - wire lathe laid over it - 2 more washers then a nut to hold it together. (by general)

What is the nut attached to? Pins threaded?

4. 1/2 to 3/4" of pin remains exposed on top - trimmed off excess with hand grinder. (by general)
5. stone mason lays flagstone on mortor bed on top of lathe.
6. contractor (not stone mason) completes joints but does not seal around the edge where stone meets walls of house.

It is later said that the stones all popped - not in the spring but throughout the following summer!

Any imput on where this process went wrong?
Central Ontario weather is different from what we experience in central Virginia, but we still go through freeze/thaw cycles.
Not knowing the size or placement of the pins, I would guess that expansion and contraction of the pins perhaps is the culprit.This is really a wild guess though! Why was this process with the pins and the washers used? You have so many variables in this, structural concrete deck, membrane, pins, lath, and flagstone that controlling expansion and contraction in this conglomerate approaches rocket science!
Good luck with this.
 
  #3  
Old 11-11-09, 10:26 AM
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Thanks for your reply!

The pins are used to hold the lath in place! Where you would normally screw or nail the lath on every 8" or so - they drilled into the concrete and fixed in these 3" pins approximately every 16".

Yes the pin is threaded - the end in the concrete is like a tapcon end and the other end in threaded.

How would you have done this?
 
  #4  
Old 11-11-09, 11:34 AM
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I never would have penetrated the membrane! I think a setting bed on top of the membrane would be a better option, providing the structural integrity of the underlying structure was not compromised. Personally I think that one needs to be real cautious when combining items with differing thermal proprieties, IE the pins move (expand and contract) different that the concrete slabs that they penetrate. This movement would need to be addressed in the design component of the project. There may very well be problems with the existing construction that dictated the use of the pins. Was an architect or engineer involved in this project?
 
  #5  
Old 11-11-09, 12:03 PM
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Yes - there are many people involved!
Thank-you for your reply!
This is actually an existing issue that is in progress of being settled in court.
My husband is the stone masons who was hired to simply lay the flagstone on a mezzanine. The job was started by my husband in October of last year and he was stopped during the first day. They (the general, a holding company, a renovation company) decided to lay wire lathe on top with the process I described in my first post and have him lay the stone on this instead of directly on the membrane. To make a long story short they are maintaining that the stone all popped due to improper laying of the stone - not in the spring when we were there to take the pictures but in mid-summer this year. They believe that none of the stone (popping) is due to the prep before the stone was laid but was due to improper laying of the stone by my husband. He didn't even do the joints never mine sealing or grouting between the stone and the walls.
Thanks for your replys - I mush appreciate it!
 
 

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