Low Slope Roofing
From Open Source Ecology
About
- Puncture Resistance - RPE is 3x more resistant than EPDM - [1]
- This video says you need an underlayment with EPDM, but not with RPE. [2]. EPDM folds better around corners. Vid says 1/2 the weight and 3x the puncture resistance - making it a great choice [3]
- However, RPE is weeps small amounts of water, it is not exactly water tight. See BTL Liners feedback below.
SBS
- SBS peel and stick - [4]. 3 ply. 10,000 sf in 160 hours, or 500 sf in 8 hours. Buy at Menards - [5]. 120 mil thick. 3 layers? Or can we do 1 layer + ballast? More info from another manufacturer - [6]
- Note - if it is multiple ply (2 or 3) - it is effectively like doing 2-3 roofs instead of one with EPDM. Proper termination detail still needs to be done at fascia and Bargeboard
- SBS Installation Video
EPDM
- Seam tape - $1/ft [7]
- Seam kit - $3/ft [8]
- Exterior seaming kit - $6/ft [9]
- EPDM - $1.2/sf [10]
- Seam primer [11]
Landfill Liner
Outdoor Carpet
- 50 cents/sf [12]. 7 year outdoor warranty - [13]
Feedback
- MJ - Is EPDM also more durable than polyethylene - when compared in a buried application? I am seeing manufacturer reports of 40 year lifetime for polyethylene when not exposed to sunlight. Does EPDM exceed on this performance metric?
- Half Off Ponds - Pond_Liner#30_Mil_LLDPE - 1/9/23. Yes, EPDM is going to be much more durable than the LLDPE liner. We typically say that the LLDPE polyethylene liner will last about 5 years while the EPDM should last 25 years plus depending on the application. Obviously the LLDPE can last much longer than 5 years but it would have to be an application where it is not being walked on and not near anything sharp since it is very easy to puncture. I personally have never heard of the LLDPE liner lasting anywhere near 40 years, potentially that was someone using an HDPE(high density) polyethylene liner and more durable than our LLDPE(low level density). If you plan on using this for the roof of a house then I would recommend only using EPDM.
- If RPE good for primary roofing membranes?
- BTL Liners - The short answer is no, we don't recommend reinforced polyethylene (RPE) as primary roofing membranes. One of the main technical reasons is the possibility of the liner "weeping" or allowing water vapor to creep through the membrane potentially creating a moisture layer between the roof and liner. Due to the "molecular space" created when inserting a reinforcing scrim between the coatings, water vapor can work its way into the liner albeit in miniscule amounts. Another main contributing factor is an RPE will grow and shrink depending on temperature and most roofs don't have that sort of tolerance. The other products you mentioned above are non-reinforced allowing for a tighter molecular structure that prevents vapor transmission. We now carry a product (RPEL 30) that has a thicker top coating on it to prevent the vapor transmission but you would still have the stretching and shrinking issue in a tight fit scenario. I hope this helps to answer your questions but please let me know if there's anything else I can help you with. v/r. Jim Nicholson, VP Product Development/Customer Relations. BTL Inc. 920-779-0306 jim@btlliners.com.
- MJ - Thank you for the feedback regarding RPE. Would the same stretching/shrinking issue also apply to non-reinforced polyethylene? Regarding HDPE or LLDPE liners - say at the 45 mil thickness - would it be feasible to use a roofing system with 4 layers consisting of tarpaper - liner - tarpaper - gravel ballast? The design specification is to achieve long life via UV protection, and added puncture protection with the tar paper. Does anyone in the industry do this? If not, what are the drawbacks of such a design for a single-sheet roof of 16 foot width? Ie, we would have no penetrations at the top of the roof. The advantage we are looking for is longevity, puncture resistance, 1/3 less weight, and lower cost all in one compared to the standard primary roofing membranes such as PVC, TPO, and EPDM.
- Jim at BTL Liners - Jim Nicholson is quite helpful - 'You're not going to run into the same shrinking/stretching problem with a non-reinforced material since it's the scrim inside the reinforcement that is the cause. I'm not familiar with tar paper properties so I can't speak to those type questions and have limited knowledge of standard roofing practices. That all being said, realistically if you were to use the RPEL 30 material ($0.59/sq ft + freight) with a vapor barrier underneath for added moisture protection you would achieve what you are looking for as long as the liner wasn't pulled super tight and anchored. The shrinkage actually occurs in HOT weather and the material relaxes in cold, so a cold weather application would be safer. We do have many clients that use the material in this way successfully for out- buildings and such (all with sloped roofs), it's just not backed by the manufacturer or officially recommended and nor is it warranted. Hope this helps to shed some light on your questions. Let me know if I can be of further assistance.'
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