# TPO tie-in Question



## Hutch

I need some input guys. One of the companies that I do work for just sold a job that I'm not too comfortable with. It's a lay over with TPO going over a BUR with gravel on top. He wants to sweep the rock, screw down 1/2" fiber and mechanically fasten the TPO. No sweat... The kicker is that he had to sell the job in sections due to the client's budget. My problem is coming up with a way to tie-in my TPO to this built-up. Do you guys have any ideas on the best way to tie the two roofs together for more than a couple days? I haven't had to rely on a tie-in for more than a few days with TPO, so any advice would be great. Thanks guys.


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## Grumpy

The only way to do a proper tie in is to divorce the roof into sections. What may happen is a phenomnia known as horizontal water migration. This is what worries me more than the failure at the tie in, I can make sure that is water tight. But the manufacturer won't warrant it unless there is a divorce of the sections.

How can this be done? I put together a CAD to illustrate this for my crew on a job, but I got a new laptop and haven't had a chance to put on autocad yet so I can't send you the pdf at this time, but essentially this was how it is done: Tear up a channel in the roof down to the substrate large enough for the curb, about 4-8" wide. Build up a curb, flash to the existing side of the roof with compatible material, flash on the new side with your new TPO. I would cover with a metal coping. 

This would be water tight and upon my conversation with a few manufacturers reps is totally warrantable. An expansion joint is another method but seperating the roofs and creating a divorce is key to preventing horizontal water migration. 

A 3rd method on non warranted jobs is to adhere and mechanically attach the new roof membrane to the old then seal with cover tape. This will do nothing to stop horizontal water migration if there are multiple layers though.

So what is horizontal water migration? Essentially it is when water leaks from the old side of the roof and travels between layers to the new. Here is the deal, if there is only one layer now and you lay over that layer and water leaks from one side of the building it is very possible the water can travel to the other side. If you build the curb, this in most cases will stop the water travel down to the substrate. The only way the water can get past the curb is if it's a fluted metal deck, unless you do something to fill the flutes. If you don't build the curb the water would get stopped under the end layer at my non warranted break, but if you are putting a 3rd layer, would do nothing to help.


Personally I hate phasing a roof into sections when there is no permenant break. That's like trusting a night seal to last 10 years. It aint gonna happen.


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## 1985gt

The false wall is the way to go. Also if you look in a manufactures manual you will see another way.

http://http://www.versico.com/documents/reslib/vwc13.1.pdf
or
http://http://www.versico.com/documents/reslib/vwc13.2.pdf

I have used this before but prefer the method grumpy listed much more.


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## Hutch

Thanks for the info guys... The false wall definitely sounds like the way to go. Unfortunately, I couldn't open the links that were posted, but that could be because I'm using my cell phone at the moment. Thanks again for the tips.


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## Grumpy

False wall, I like that! We always called it a curb, knowing it's not a curb, but not having a better terminology.


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## Billy Luttrell

It is posts/threads like this that keep me coming here. This is great advise with the curb/false wall.

Totally worth the garbage threads like 10 rules of roof design lol


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## 1985gt

@billy agreed. You will find a number of people with a good knowledge base here. You will also find people who know everything, just ask us we are roofers. :thumbup:


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## Billy Luttrell

1985gt said:


> @billy agreed. You will find a number of people with a good knowledge base here. You will also find people who know everything, just ask us we are roofers. :thumbup:



Ha, indeed! Just a small problem....not everyone here claiming to be a roofer....is an actual roofer!

Here is a little joke for you though....

How many roofers does it take to change a light bulb? 6!

1 to change it and 5 others to watch him and talk/argue about how they could have done it better, quicker, and neater.


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## shazapple

Grumpy is describing a Roof Area Divider
http://docserver.nrca.net:8080/technical/9121.pdf

We often replace a roof in phases, and typically the roof is already divided up using the above method. Some of our inverted roofs are huge and not divided, so it is usual to split it up over a couple of years. The area divider helps with movement and to contain any potential leaks.


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## 1985gt

shazapple said:


> Grumpy is describing a Roof Area Divider
> http://docserver.nrca.net:8080/technical/9121.pdf
> 
> We often replace a roof in phases, and typically the roof is already divided up using the above method. Some of our inverted roofs are huge and not divided, so it is usual to split it up over a couple of years. The area divider helps with movement and to contain any potential leaks.



What's pictured there is almost more of an expansion joint. They are needed for Torch and BUR roofs when they exceed 100-150 or so feet in length or width. With EPDM and TPO this is not needed as the material can take the movement, unlike Modified. 

Divider/false wall accomplish the same thing. But we all agree on the same thing, they make for a heck of a lot cleaner and functional tie in.


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## RalphTheRoofer

Billy Luttrell said:


> Ha, indeed! Just a small problem....not everyone here claiming to be a roofer....is an actual roofer!
> 
> Here is a little joke for you though....
> 
> How many roofers does it take to change a light bulb? 6!
> 
> 1 to change it and 5 others to watch him and talk/argue about how they could have done it better, quicker, and neater.


 
great joke! :thumbup::thumbup:


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