Old flat roof


#1

I obtained an apt building with a flat roof in 1999 which had leaks to start with. It continues to find new entry points into the ceilings even with multiple patch jobs. I am contemplating which style new roof system to use (single ply vs built up vs epdm). It most likely be a complete tear off.
The water pools about 2-3 inches and sits for days or weeks. I’m considering a TPO (Everguard by GAF), but, am concerned with the “no-pitch” problem. The warranty also seems very difficult to maintain to keep it in force. Any suggestions? BTW I’m in the St Louis area if that helps. Here are a couple of pics…



#2

A built up roof ( BUR ), Sarnifil, or APP modified system.
Find a local commercial outfit.


#3

what kind of roof “sandwich” layers etc. is presently there? What kind of deck design do you have in mind?
I don’t have TPO but its supposed to be a good and cheaper substitute for PVC membrane.


#4

Ranger88,
I don’t know what the current layers are. To me it looks like a layer or two of the same type of material 3 tab shingles are made from (asphalt?) and then topped with some sort of fibrous membrane.
The decking underneath is plywood, which would stay the same.
So far, I have talked to 2 companies. One suggested tear off, replace bad wood, lay down insulation, and finish with GAF Everguard.
The other recommended tear off, replace wood, then Tamko awaplan 170.
Here is a pic of a failed patch that might give you an idea of what is presently there
http://i57.photobucket.com/albums/g236/fotofan_2006/120-2090_IMG.jpg


#5

From what I hear TPO can still carry the factory warranty even with no positive drainage. Sounds pretty confident dealings to me. A BUR is a system thats worked for a long time. Made lots of people happy. I would say the installer is more important than the material.


#6

Hi,

I hope you are not having the company who did that patch bid the roof.


#7

whats under the decking? fibreglass batts? If so, it could get thrashed with debris during tearoff.
Ventilation? I suspect you could have yet another unvented stinker like mine. What caused the ponds? It could be more than bad decking, the structure could need repair. Many roofers are quite lazy when it comes to redecking and especially structural repair. Study the whole “sandwich” -from top membrane down to the ceiling. A tearoff gives you a unique opportunity to fix the entire roof/insulation/structure design, if needed. It will be alot tougher or impossible to correct some defects later on.


#8

In your second set of photos I still can’t quite make out what kind of roof is installed, but the patch material looks to be GAF Rubberoid (modified bitumen). The original roof almost looks like an old Owens Corning membrane, but I’ve got to assume it is not, and that it is also a modified bitumen roofing membrane. More photos would help if it means anything, but since you are already planning to tear off I don’t see the purpose.

Anyway, I noticed you have some raised edges along the roof perimeter in some areas, and that there are some scuppers that I assume drain into conductor heads and downspouts. Assuming there is no existing roof board insulation, and the original roof was installed overtop a base sheet that was mechanically fastened to the plywood roof deck, this is what I would do:

  1. Remove existing roof system.

  2. Replace deteriorated/damaged plywood decking at a specified unit cost per square foot. Minimum 1/2 sheet plywood replacement where wood is to be replaced.

  3. Install new tapered roof insulation.

  4. Widen scuppers where feasible.

  5. Install new roof system.

Now, what type of roof system you select and how you install the insulation is totally up to you. You could install a base sheet and mop tapered insulation with asphalt. If you did this, it would only make sense to continue using asphalt on the project. Another option is to fasten the base sheet and adhere the insulation with a cold adhesive, or even a spray adhesive like Insta-stik. You could also loose lay the insulation and install a roof system like EPDM, but it would require ballast, and I would not recommend going that route. Me, I’d probably go with a tapered polyiso board (not cheap, but will help a lot with heating and A/C) fastened to the roof deck, and then either a totally adhered or mechanically fastened TPO (you can do this with EverGuard), or a cold-applied modified bitumen like Performance Roof Systems (Derbigum). I’d probably go with the TPO if it were my building, since you would get a good product for a reasonable price, AND future repair costs typically will be lower than with most asphalt based roofs.


#9

if you are considering a tear off…then go for the most for your dollar and that would be a recovery board + modified roofing membrane system of your choosing


#10

naturally you will need additonal cricketting to provide positive waterflow toward existing drains…this is an ideal project for modified membrane roofing


#11

Please explain to me how that is “getting the most for their dollar?” They will still have ponding issues no matter how many crickets are installed. The roof needs tapered insulation to promote positive drainage; crickets aren’t going to be enough without the tapered insulation. Add that to the fact that mod. bit. manufacturer’s aren’t going to warrant the ponded areas, and recovery board makes little sense.


#12

Lefty
ABSOLUTELY NOT! :stuck_out_tongue:
I couldn’t believe he actually expected to get paid for that poor workmanship.


#13

ranger88
My problem is that even when the roof comes off, I’m not sure at that point what I should be telling someone what I need done. The Everguard contractor that I spoke with only addressed needing to replace much of the tarred plywood.
What kind of structure issues are you referring to?
The previous roofer added the “whirlybird” type vents in 2001 when he attempted to patch the roof stating there wasn’t enough ventilation.


#14

Cerberus
I hadn’t thought about asking for specific prices on plywood decking. I appreciate the tip.
Here’s a link to a few more pics if you are interested.
http://s57.photobucket.com/albums/g236/fotofan_2006/
How much do you suggest tapering the roof? The TPO contractor said it can only be done by removing everything currently on the roof and raising it higher. I’m also concerned about shifting or settling of insulation boards over time.
I’m also curious about your opinion of Sarnifil versus Everguard.


#15

Roofing Maven
What is cricketing? I’ve never heard of that term.

To all who have responded:
Thank you very much for your input. This is very unnerving when dealing with subjects I’m not well-informed about.
Any suggestions about picking a **good **roofer? I didn’t do too well on my last attempt.


#16

[quote=“leaky apt”]Cerberus
I hadn’t thought about asking for specific prices on plywood decking. I appreciate the tip.
Here’s a link to a few more pics if you are interested.
http://s57.photobucket.com/albums/g236/fotofan_2006/
How much do you suggest tapering the roof? The TPO contractor said it can only be done by removing everything currently on the roof and raising it higher. I’m also concerned about shifting or settling of insulation boards over time.
I’m also curious about your opinion of Sarnifil versus Everguard.[/quote]

That all depends on how much the roof currently ponds. Based on the photos, I don’t know that you have a serious problem. Take a look at sample warranty’s for any system you consider, and see if they require ponding to be gone in 48 or 72 hours. All the same, I would probably install tapered iso at 1/4-inch per foot, since I don’t believe they make 1/8-inch per foot tapered iso. Install crickets between scuppers, and once again, it looks like you need to enlarge the scuppers. You may also need to add more scuppers, but it is hard to say from the photos.


#17

Those patch jobs are pretty bad… :frowning:
They probably would have worked if the guy had a clue.

Tapered systems are made to fit the particular roof, the roofer you choose will take care of this.
The advantage of tapered insulation is that you can control where the water drains, and you get a bit of added insulation to boot.
It has been a long time since I installed a tapered system ( 10+ yrs ), I doubt they have changed too much since.


#18

looks to me like you have a recover up there now.
just has that roofed over another roof look.
but wheather theres 1 or 2 roofs up there,
i would go with a complete tear off and reroof.
get your self a good 3 ply hot tar fiberglass
roof, with a silver coat on top.

gweedo.


#19

strip it,put tapered isocyanurate insulation,put new drainsleeves repair wood decking as necessary,and then I would recommend IB Roofing systems 80 mil pvc system which would be warranteed even under standing water—the original roof appears to have been modified bitumen,probably U.S. INTEC BRAI-TORCHDOWN?


#20

“My problem is that even when the roof comes off, I’m not sure at that point what I should be telling someone what I need done.”

thats the same position I was in during my leaky apartment roof tearoff - much to my regret.
Do some investigating. Wherever you can, take a peek underneath to see whats going on with the structure. You may have some rotten or bowed rafters - both can cause ponding or worse. Look in the rim joist areas too around the perimeter of the building (from the inside) as that is even more critical for structural soundness. I realize that this could be tough to do if you have drywalled ceilings - get creative. A dropped ceiling, on the other hand, would be easy for taking a peek.

Those whirlybird ventilators might not be enough, how many are there? Are they moving air from inside each apt to the outside? Check your dewpoint status - if, for example, you have an apt. with 50% humidity at 70 deg. you have a potential moisture problem depending on the type of insulation and vapor barrier you have or dont have. Corrections for these types of problems are best made during the tearoff.

Tapered insulation - great stuff but pricey and it takes some skill to install right. My opinion is that its overrated. A flat deck helps alot - getting it flat could require structural correction. IB roofing is warranted even under ponds, in that case you could accept some moderate ponding (say less than 1 inch deep) as long as your structure can handle the weight. What is the size, span and spacing of your rafters?

Its common for many roofers to ignore these issues; they’ll lay new decking over bad rafters or they’ll say that its a carpenters job and be unwilling to do it or do it poorly. All the more reason to know this stuff in advance and not by suprise.