# how do you feel about insulation on a concrete substrate?



## Grumpy

How do you feel about polyiso insulation on a concrete substrate? necessary or waste of money? 

I'm bidding a job on a 12 story. I came up with my own spec since none was provided. I bid 1/2" HD ISO coverboard set in low rise adhesive then fully adhered atop that. 

Now the customer is requesting R20. My personal opinion is that it's not necessary. There is no insulation now in the core cut, and in my limited experience these roof types seldom ever are insulated.

I was hoping someone with more experience could shed some light. Thanks.


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## 1985gt

Depends on what kind of concrete deck. The flexcore decks can condensate. Is the customer trying to get LEED credits? Although R20 is low for that.

R20 is 3.25 ISO, I say give them the price put the money in the pocket. Same install since its only one layer.

Poured concrete only has a R value of 0.08 per inch. I know it use to be common practice just to mop on the deck but now a days you know thats totally unexceptionable.


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## Grumpy

Actually I've always been told not to exceed ISO by 2" so I was figuring 2 layer. Hmmm maybe I'll give them a price for both since I alredy told them it would be 2 layer. 

I'm not so sure flex core was used 80 years ago? Yes the deck was mopped when originally built.


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## shazapple

I'm not sure why it wouldn't get insulated? Any concrete deck around here has a mopped vapour barrier, insulation, fiberboard, and membrane. R20 can be done in one layer, although 2 is preferred.


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## 1985gt

Versico doesnt like you moping anything over 2.? iso They make bigger and you can screw it down. Im just not sure on the adhesives though I would venture to guess they would stick with the 2" or less iso and do it in multi layers.

As far as the deck goes can you see the underside? 80 years ago they did some weird things but I doubt flex core or pre-cast Ts were around. probably a poured in place ugh think about it pouring concrete 12 storys up back in the 1930's? no thanks.


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## Grumpy

It was a field rep who said "It's allowable but not adviseable" Wasn't versico.

Plus I don't "mop" anything. he mentioned something about thicker insulation being prone to cupping or something over time.

Can't see the underside everythign is finished beneath, I asked. Maybe possible some where but they didn't know or didn't want to show.


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## 1985gt

moping and adhesive's would be the same thing, and yeah thats what I understand too that the thicker the more cup prone. if its screwed down less chance of it popping up. If you wanted to mop we still have a couple of kettles we would sale you. Even give you free training :laughing:.


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## Grumpy

Mopping is mopping, adhesive is adhesive IMO. The two are mutually exclusive and not the same in my book. If someone says to me "mop the insulation" the first thing i think of is hot mop with asphalt. After all no "mop" is used in the application of insulation adhesives. 

I wouldn't take a kettle if it were free. I've never liked hot work, ever. Even decided to phase out the torch this year. No more torch work period, last year we did it on request. Next year we will remove it from our policy. If a job HAS to be modified, I'll install SA only. 


As for screwing, I'd not ever consider screwing a concrete deck. Predrilling all those holes? Fug dat!


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## shazapple

I agree with Grumpy, mop and adhesive are not the same. We mop everything though, so kettles are alive and well here (Concrete deck, mopped 2-ply, mopped insulation, mopped fiberboard, mopped base sheet, torched cap). 

That being said, we do use adhesive as well (same procedure as above, but replace 'mop' with 'adhere') although only when the building has to be occupied during the re-roof (I guess people don't like the smell of the kettle, go figure!)


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## 1985gt

I know they are completely different except they dont have a mechanical attachment that screws and plates do. Thats why they only allow the 2" of insulation per layer.

Hot work is the best IMHO, its kind of like asphalt shingles and slate, where single plys would be the shingles and a BUR would be the slates. That should stir so stuff up.

Mopping ISO is about 100 times faster then using adhesives. FWIW.

SA modified? :thumbdown: wont see me putting that on anything but a porch or a small addition. I cant see someone using that on a 1,000sq warehouse.

Screwing in to concrete does suck but our guys actually got use to it, they hate it but meh.

Nothing and I mean nothing is better then the smell of hot asphalt in the morning, I have no idea why all these people complain about the smell.


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## Grumpy

GT said: Mopping ISO is about 100 times faster then using adhesives. FWIW.

Man I have to whole heartedly disagree. But I hate hot and will disagree with anyone who likes it  Seriously though, how cna it be faster if you are adding one full time worker to the mix to get to the job early, start up the kettle, keep the kettle at optimum levels all day, shut down, etc... Adhesives go fast, especially on big open spaces, and I am talking about using the hand held manual applicator too. I couldn't imagine how fast it'd go with an applicator cart. 


FWIW, I get what you are saying about hot being the slate and single ply being the shingle, but I think a good PVC roof will last equal as long as a good hot roof side by side. 


I'd rather smell a farm on a hot summer day next to the manure pond than smell hot.


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## SinglePlyGuy

I typically use low-rise/ iso on a concrete deck by choice.... need to have that nice smooth surface for the adhered.

I don't think any manufacturer "requires" it, it may be a township/code requirement tho. I have actually done some jobs where the concrete was nice and smooth and we were able to put down fleeceback pvc directly to it with adhesive and it looks phenomenal and get a 20 year warranty.

If you need to go with R20 go with a 3.5" board in low-rise with beads at 4" spacing. Going over 2" thickness and using 2 boards is to minimize thermal loss at joints- dont know if that is a concern with concrete deck tho.

And hot mopping sucks too :thumbup:


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## 1985gt

Grumpy said:


> GT said: Mopping ISO is about 100 times faster then using adhesives. FWIW.
> 
> Man I have to whole heartedly disagree. But I hate hot and will disagree with anyone who likes it  Seriously though, how cna it be faster if you are adding one full time worker to the mix to get to the job early, start up the kettle, keep the kettle at optimum levels all day, shut down, etc... Adhesives go fast, especially on big open spaces, and I am talking about using the hand held manual applicator too. I couldn't imagine how fast it'd go with an applicator cart.
> 
> 
> FWIW, I get what you are saying about hot being the slate and single ply being the shingle, but I think a good PVC roof will last equal as long as a good hot roof side by side.
> 
> 
> I'd rather smell a farm on a hot summer day next to the manure pond than smell hot.


Out pacing a manual gun would be easy, a cart im not sure about. IT would off set the cost of another person quickly, plus if your doing the single ply route the guy comes up when he's done on the kettle.

There will be a million people with a million different ideas on whats best so we will just agree to disagree.

Oh and if you like to small a farm next to a manure pond on a hot day over asphalt your one sick puppy.





> And hot mopping sucks too


Only people who suck at it say that. :thumbup::laughing:


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## Grumpy

LOL my daughter and I were driving and some driveway guys were using hot on a parking lot to seal the cracks. Yeah not the exact same smell, but she said "Papa, that stinks!" 

I was soooo proud of her!


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## 1985gt

Boo! When I was still in the field my kids loved it when I came home smelling like hot...


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## Grumpy

I'll show you the picture one day of the kettle sitting next to the steel scrap yard. Not even the scrap yard wants anything to do with hot anymore


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## 1985gt

Haha true... some places can be picky


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## SinglePlyGuy

My kettle has some nice trees growing out of it waaaaay back in the yard..... will be a cold day in hell before that thing ever gets used by my crew lol.:laughing:


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## 1985gt

Its a dieing art, and its haters like you who are killing it! :yes:


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## SinglePlyGuy

I was a kettle man in a previous life and am very comfortable admitting that I am a hater today! 

I can still hear it, like yesterday.... " HOTTTTTTTOOOOOOO" being bellowed from the rooftop.... shiver



I also think describing hot mopping as an "art" is quite a stretch - but to each his own!


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## 1985gt

SinglePlyGuy said:


> I was a kettle man in a previous life and am very comfortable admitting that I am a hater today!
> 
> I can still hear it, like yesterday.... " HOTTTTTTTOOOOOOO" being bellowed from the rooftop.... shiver
> 
> 
> 
> I also think describing hot mopping as an "art" is quite a stretch - but to each his own!


You were the kettle man, no wonder you hate it now, constently being yelled at! 

Mopping is an art, kind of like running a torch, you dont just want the average joe doing it. But then again you were just feeding the kettle reading the news paper now werent you. :laughing:


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## SinglePlyGuy

Well of course there was the reading of periodicals....

god i hated that summer.


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## 1985gt

Yeah being the kettle guy is no fun. Its worse then being the sheet metal guy.


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## Grumpy

Sheet metal is fun, there is no such thing as moving fast when doing sheet metal  Think thrice cut once. Yeah baby! I'm no metal wizard but I take to it better than most other aspects of roofing.


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## 1985gt

Sheet metal "can" be fun. If your bending 1,000's of feet of .050 alum its not fun!

I actually got pretty darn good at it, to the point the boss was having me make copper birdbath liners and such. I will admit making some sheet metal stuff is pretty cool. I'm going to make a bird house/windchime in a western theme for my neighbor who's dad passed away. Out of cor 10 of course.

Copper is fun to work with and making different styles of collector heads is fun too. 

bending countless feet of drip edge, gravel stop or cap metal how ever is not fun but a computerized folder makes it oh so much better.


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