Bo Don't Know Roofing

Simon

Gentlemen,

Your advice is always a plus and I could use a little simple help on the proceedure for making a tight-as-a-drum flat roof. A good friend of mine offered me the job and even offered to help out, but I've never actually done one of these flat rubber roof jobbies.
I agreed to take the job, but I'm not entirely sure what my materials list is gonna look like and I want to do a good job for my friend. So I need adhesive, big sheet o' rubber (the roof is perhaps 30' x 10'), flashing and appropriate fasteners...and a book for improving spelling. All these things are within my grasp, but I want to look like I know what I'm doing when I go to meet my friend. Also I know this roof has been a problem in the past so I'm assuming the sub-roof is going to sub-suck. Any tips on how to make my job easier and more durable??

Grumpy

Well flat roofing can be very scientific. Let me tell you about an estimate I sent out today: We will tear off the roof, then install 2" ISO insulation and 1/2" fiber board. We will install 2 layers of 33# base sheet then we will TORCH apply a layer of smooth modified bitumen. Over this we will torch apply a layer of granulated cap sheet modified bitumen.

If you've never used a torch before be very careful. You may be better off using mop down modified bitumen.

The manufacturer would warrant my spec for 20 years, and do an NDL warranty if I were a registered contractor. NDL means No Dollar Limit. In these cases the manufacturer warrants their material AND your labor!

Rubber? Do you mean modified or EPDM?

Teetorbilt

Grumpy. I have a flat roof over my FL roon, what is your opinion of installing Grace over it?
My aunt once lived on Bayshore drive, her husband was Walter Stenhouse, architect. Just curious as to whether you had heard of him.

Grumpy

I've never put Grace on a flat roof. I know one other person here did it and said they have zero problems. If you do put grace make sure it doesn't come in contact with your roofing membrane. Perhaps a layer of ISO insulation or fiberboard between the grace and membrane.

Never heard of him. I live in a shoe box. I dont even know where bay shore drive is, unless you mean lake shore drive.

Teetorbilt

Grumpy, need some clarification. I thought Grace WAS a membrane. My ignorance is really showing now! I just want a bulletproof roof that I will never have to worry about again.
Lake Shore drive was the place, only there as a youngster back in the 50's. They were divorced in the 60's and my aunt moved to Sarasota, FL. I was just always curious as to what happened to Uncle Walley, he was quite successful.

Simon

Well my ignorance is showing too. When I say rubber, I'm not sure if I should be talking modified or EPDM. I'm not sure what is modified or what EPDM stands for. School me, my friend, I could use it. I've checked out the roof and the flashing will be a pain because someone has gooped silicone or caulk or something black and fowl so thickly it will be hard to remove. The rubber sheet I was looking at is simply sold at Menard's and is a solid sheet of 14 ml if I'm not mistaken. I'll certainly replace the fiber board but I don't know if I'll have the 2" for ISO. There is a door that opens to the flat roof from the second story that I think causes more trouble than it's worth, but 2" above what is there will get in the way. No deck to concern myself with, but they may get some bright ideas if the roof is solid. The sucker ought to be insulated though, as these Michigan winters can be a pain. I think my man has been shoveling snow off the roof thus causing more damage. Is there more advice for care of the roof? I'm assuming that if I do a bang up job no shoveling will be required. I should go with two layers of cover? Seems solid, I like it! Tell me more!! I have no experience with a torch outside of copper plumbing but I like fire! How do we use it without singing "The roof, the roof, the roof is on fire"? Heh, I love this biz. Thanks fellas.

Grumpy

Teetor ice shield is a sloiped roofing underlayment membrane. The membrane I was generically referring to was the low slope roofing membrane. Ie: TPO, Mod Bit, EPDM. A double layer of modified bitumen, with a granulated cap sheet will last you a pretty good ammount of time. YOu get a 20-year warranty from the manufacturer in most cases. This is the best your ever going to get for a flat roof.

SImon, Modified bitumen is basically asphalt that has been modified with plastic or rubber. It comes in two forms SBS and APP. I won't get into all the technical details because there are many. It is probably the most common material used on residential or small flat roofs and is sometimes called rubber. EPDM is a true rubber, it looks and feels like a roll of bicycle inner tube. EPDM is more common on large flat roofs like factories and arenas, but I've seen it a few times on residential roofs too.

If you NEED to remove snow from the roof use a push broom.

If you havent used a roof torch before purchase the "glue" grade modified bitumen. Also called cold. I prefer the torch but there's no chance of burning your building down with the glue.

Grumpy

One last thing. It's not likley at all that Menards will have EPDM. EPDM is a specialty roofing material.

Simon

Thanks, Grump, I always like to turn to the experts. I'll poke around to find a good place to find the mod. bitumen of the cold variety. I appreciate the advice and I'm sure my friend will too. Once it stops thundering and raining around here I'll be getting into the gig. Y'all stay dry now, y'hear?

Unregistered

Check for prpoper insulation i Live in minnesota and have done quite a few flat roofs and i prefer EPDM Rubber Membrane 45 mil. One of the most common problems here with flat roofs is in the winter. If it only leaks in the winter there is an insulation problem i Have seen up to an inch of ice build up on the underside of the roof boards do to condensation. i always have added more than the traditional 1/2 inch fiber board i normally go with a 1.5 inch ISO board than the 1/2 inch fiberboard. 1 inch ISO board will give an r-value of about 8 Fiberboard gives you a r value of 1. Roofs should have an r38 most flats have 6-8 inches of blown in or loose fill which gives an r20 - 24. also take in to consideration if you use the ISO and someone walks on it it is a fairy soft material you may want to cover it with a 1/2 inch plywood then 1/2 inch fiberboard before you apply the roofing material. you will need 2 1/2 to 3 inch screws and 3 inch plates to install the additional Iso Board / plywood / fiberboard.. Glue down the epdm to fiberboard the ISO board can be used but it takes time to make sure you get no bubles or wrinkles. IT is much easier to glue to fiberboard.

Grumpy

Insulation is typical under most flat roofs. We usually use the 1 1/2" ISO also. Sometimes home owners dont want to pay the upcharge but we always push, but it's their choice.

jmorgan

Our Grace Ice & Water Shield is regularly used as a vapor barrier under BURs and single ply roofing. This is a VB not a roof. We do not recommend GIWS at slopes less the the roof covering's manufacturer. Sometimes this is quite low sloped. EPDM can be laid over GIWS. You cannot "stick" GIWS to EPDM, however. There is asphalt in GIWS and asphalt and EPDM are not compatable. The asphalt is in the GIWS adhesive. The plastic top sheet of GIWS is compatable with EPDM. In low sloped GIWS applications, more care is needed in placing the fasteners. Get them in clean, straight and just snug.
Jim