# Re-roofing using torch down over tar and gravel



## Lucky (Mar 11, 2006)

I have a duplex w/ tar and gravel roof. I've been told to sweep off gravel and use 2 layers of underlayment then apply the torch down?? My roof has a slight pitch to it 2 in 12 I think. It also has 2" of insullation over the living areas. I sure would like to avoid the cost and mess of a complete tearoff. Any info. would be appreciated.

Lucky


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## River Rat Dad (Feb 18, 2006)

If you just have the one layer of BUR, after you sweep and spud the gravel screw a layer of 1" fiber board over the mess to smooth it out


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## Lucky (Mar 11, 2006)

*Thanx for info.*

I think I'll go ahead and strip off all the old roofing, the expense of sheeting kills my idea. Lucky


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## Teetorbilt (Feb 12, 2004)

The last one of these that I did (1974) tearoff was the ONLY recommended procedure. I should have backed up my '68 Chevelle SS 396 a little further, had to have a repaint.


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## Alan Hughes (Mar 1, 2006)

Lucky said:


> I think I'll go ahead and strip off all the old roofing, the expense of sheeting kills my idea. Lucky


screwing down timlok fiberboard is cheap compared to a tearoff and disposal.

I'd screw down the fiberboard and fully adhere 60mil epdm. 

Epdm last much longer than torchdown and you don't have fire being applied to your property.:furious:


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## AaronB. (Oct 6, 2004)

Alan Hughes said:


> screwing down timlok fiberboard is cheap compared to a tearoff and disposal.
> 
> I'd screw down the fiberboard and fully adhere 60mil epdm.
> 
> Epdm last much longer than torchdown and you don't have fire being applied to your property.:furious:



We have 16 year old torchdown that is good as the day it was installed. It was nmaintained, though.


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## Grumpy (Oct 8, 2003)

EPDM adhered to fiberboard? I read somewhere it's not a good idea unless the rooof layers are well ventilated because EPDM will create condensation and fiberboard is a sponge.

I am always a fan of tear off. When I can not tear off what's there I try to go liquid applied. Face it, you don't want to tear off if you are cheap and liquid applied is a cheap method of roofing.


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## AaronB. (Oct 6, 2004)

I still dont buy into that, Grumpy. In ordder for the EPDM to cause condensation on the underside of the sheet, Moist air would have to hit the underside of the sheet. I thnk thermal bridging may cause condensation, and the PVC/TPO guys blame it on the EPDM.


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## red_cedar (Mar 30, 2005)

I dont buy into that either. The fiberboard then becomes the underside, insulating the sheet.( fully adhered.)
I just put down some fiberboard today over some Grace ice and water shield and am going to adhere the EPDM to the fiberboard to it tomorrow.
When I built the roof structure, I allowed the underside of the decking to get vented as well. 
Problems, not on my watch.


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## Grumpy (Oct 8, 2003)

Warm air holds moisture. Fiberboard is not a good insulator at all, thus will allow warm air in contact with the epdm. 

Red, why grace AND epdm? That confuses me.


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## AaronB. (Oct 6, 2004)

Grumpy said:


> Warm air holds moisture. Fiberboard is not a good insulator at all, thus will allow warm air in contact with the epdm.


On top of the sheet. What are you thinkin, dude?


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## Alan Hughes (Mar 1, 2006)

I glue a lot of epdm right to plywood and haven't had a problem yet.

Low slope additions, esp on doublewides, epdm is the ticket.


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## red_cedar (Mar 30, 2005)

Ice and water for no problems ever. thats how I sold the job. Wouldnt have been the first time I put ice and water under a low slope roof. 
personaly, I believe better on the low slope than on steep slope applications.
Except along gutter edges.

Warm moist air is in contact with almost everthing. aka: humidity. The fiber board provides a backer/seperator., not so much of an insulator of which fiberboard has almost none. But it is insulating the EPDM ( bottom side) from direct real temperatures.
I do not believe that the fiber board will hold enough moisture to adversely affect applications. All things being done correctly.


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## Alan Hughes (Mar 1, 2006)

Fiberboard really is next to nothing stuff. :laughing:


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## red_cedar (Mar 30, 2005)

Alan Hughes said:


> Fiberboard really is next to nothing stuff. :laughing:


Adhering directly to the decking is pretty much an amatuer application.
When your deck moves over time, and we know it will, your EPDM will be stressed and possibly rupture/tear.
My understanding is fiber board or another board, acts as a buffer from the structual movement.
Double wides are just a big trailer... Low end roofing applications.


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## AaronB. (Oct 6, 2004)

I use fiberboard to separate systems, provide a smooth flat surface, separate the roof deck from the roof covering, separate ISO from the heat of our hot applications, provide a tight grip for hot asphalt base plies, but not for insultaing purposes. 

Why anyone would want to adhere to a roof deck is beyond me.


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## Grumpy (Oct 8, 2003)

AaronB. said:


> On top of the sheet. What are you thinkin, dude?


Under the sheeet as well. What are you thinking? Hot air rises. 

I don't want to argue with opinions... and I am not the one to do the testing but I have to adhere to industry standards and manufacturer recomendations. After all who knows better than the company who makes the product?


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## AaronB. (Oct 6, 2004)

Where did you hear that at? I remember MIke H saying it, but how does the hot air get to the bottom of the sheeet through the vapor retarder and fiberboard?


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## red_cedar (Mar 30, 2005)

OK, just for conversation, say warm moist air travels to the underside of the membrane, thru the fiber board. Which, lets say happens naturaly. Would not the drier air times ( Winter ) draw out the moisture. Moisture, is not always drawn up.
I still dont believe this is a problem when things are done correctly and is being over thought.


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## Grumpy (Oct 8, 2003)

Seldom do I see vapor retarder speced. Infact correct me if I am wrong but vapor barrier is not part of an EPDM spec, it is part of a BUR spec. Fiberboard has little to no R value and anything can pass though it. As you know it's basically shredded and pressed cardboard.


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