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Q: Flat Roof vs. Angled Roof ( Answered 4 out of 5 stars,   0 Comments )
Subject: Flat Roof vs. Angled Roof
Category: Family and Home > Home
Asked by: buckman-ga
List Price: $3.00
Posted: 01 Sep 2002 14:29 PDT
Expires: 01 Oct 2002 14:29 PDT
Question ID: 60740
I am building a house and desire a flat roof. What is the cost comparison and  
longevity/drainage to an agled roof? The roof will be flat with 3 foot walls
surrounding it. Would the flat roof have to slop down to a central drainage 
point? How would it hold up in extensive snows and rain?

Request for Question Clarification by actualwolf-ga on 02 Sep 2002 07:11 PDT
To answer  your  question appropriately we will need a lot more
information.  For example.  What materials will you be constructing
your roof out of?  Do you hae an outside limit for square feet?  It
also depends on the angle of the angled  roof.  Etc.

Request for Question Clarification by knowledge_seeker-ga on 02 Sep 2002 07:52 PDT
...and whether or not you're dealing with a dry climate, rainy climate
or snow cover ...


Clarification of Question by buckman-ga on 02 Sep 2002 08:27 PDT
The house will be castle style. It willbe built on the border of NH and ME
and will have to stand up to all 4 seasons. Actual square footage is a 
little over 1900 sq ft with cathedral ceilings throughout. 2 X 8 will serve as
roof framing.

Request for Question Clarification by seedy-ga on 02 Sep 2002 16:55 PDT
Dear Buckman:

There is no simple answer to your question.  I am somewhat confused as
to your having catherdral ceilings throughout but a "flat" roof on
top. Will you have false ceiling above the catherdral inside ceiling??

Following is a comment which I made on an earlier question regarding
flat roofing material.  I live in Nashua, NH.

"Adding my two cents from personal experience.  Our home in NH has
cathedral ceilings throughout.  The house was built about 40 years
ago. I describe it as looking like a McDonald's stand to people trying
to find it. I'll assume your house,s finished ceiling (tongue and
groove finished boards) is the bottom of the room deck over the
support beams as ours is.  While you report that your home has a steep
roof angle, our home was built with shallow roof angles exacerbating
the problem with ice dams and proper drainage.  I tried the metal
flashing, roof edge heater wires, and going out after every storm to
try to rake the roof(rapidly gave up on this option).  Each of the
"fixes" lasted a winter or two (we've lived there for 32 years now)
but eventually failed.  About 10 years ago, I sprung for a single
menbrane roof over 1 1/2" insulation board.  Voila!!  Not one problem
ever since. BUT...the problem now is that, in a rain storm, it sounds
like we're living in a tin roof house in Hawaii. If you go the single
membrane roof route, be sure to get the contractor to figure out a way
to break up the rainfall to it doesn't require you to retreat to the
basement during a rain storm."

If you could give one more clarification, I'm sure we can put an
answer together for you.  If you are determined to have a flat roof,
you will need some slope to get to drainage particularly if you are
surrounding the roof with a 3 ft wall...A good example of this type of
construction is the Sheraton Tara at Exit 1 at Spit Brook Road in
Nashua, NH.


Clarification of Question by buckman-ga on 04 Sep 2002 14:48 PDT

Thanks for the help. Here's more info...

I do plan to have a false ceiling between the ceiling and the roof.
I was planning on having the roof slope from all sides to a drain in
the middle of the roof. Been looking at using EPDM as my roofing 
material. Do you think this will prevent the problems you experienced?
Subject: Re: Flat Roof vs. Angled Roof
Answered By: seedy-ga on 04 Sep 2002 21:32 PDT
Rated:4 out of 5 stars

I decided to collect the question revenue....

EPDM is a film made from Ethylene/propylene/diene/terpolymer.  It is
excellent for aging, water resistance, and water vapor transmission.
You may wish to read the article from the following source which makes
a stong case for heat welding on TPO's

The three films that are commonly used are PVC, EDPM, and TPO's.  You
should consult with your roofing bidders as to which system will do
the best job for you on your building design.

As for the center drain, I think that is a mistake.  (remember that I
am not a roofing expert so I bear no responsibility to the performance
of your roof...only the selected roofer can give you the best
consulting available)  Where you place your drain should be
determined, in my opinion, as to where you are going to get hte most
sunlight.  A drain in the middle of the roof that is not going to get
sunlight at the end of the winter will keep snow and water on your
roof for too long.  I have a white roof with edge drains formed by a
slight roof pitch. Of course, I don't have a parapet nor do I have a
false ceiling above my catherdral pitches.  Having the drains come
over the edge does result in icicles during the melting/freezing
cycles but I would worry about the snow/ice/water load if your drain
area was not in a place that would allow you to take maximum advantage
of the freeze thaw cycles.

I have  1 1/2" of fesco board insulation under the single membrane
roof layer. (my membrane layer is from Firestone)

Remember, Buckman, the most important decision is the selection of the
roofer. I had my roof put on over 12 years ago. After a storm this
past winter, a tree limb fell on the roof and put a hole through the
membrane. My wife and I were leaving at 7:00am the next morning on a
five week trip. I called the roofer from the airport before boarding
the plane. He was at the house later in the day and installed a patch
and charged me $75 for the work.  To say I was pleased, is an

One problem I have had, is I did some renovation on the house after
the single membrane was put down.  The same roofer applied the single
membrane to the newly renovated section of the house using the same
film from the same supplier.  The color matched at first but after
about 8 years is beginning to show a difference in the shade of white.
 Fortunatly, it is not visible from easy sightlines but only one angle
approaching the house from the back.

OK....I don't know if I have given you enough information to help with
your decisions. If you feel you need clarification on the information
I have supplied, please don't hesitate to request it. Thank you for
using Google Answers for this interesting construction question.


Search on Google:  Firestone + roofing
Search on Google:  EDPM + definition
buckman-ga rated this answer:4 out of 5 stars

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