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TOPIC: Roof Design and Waterproofing

Roof Design and Waterproofing 30 Mar 2005 23:00 #28848

What is the main purpose of a theatre roof having a "parapit" design on the sides?

Is there a better way to seal a roof, other than "torching and melting" that rubberized material?

Thanks....
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Re: Roof Design and Waterproofing 31 Mar 2005 03:05 #28849

  • outaframe
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The parapet walls are usually aesthetic but also provide a place to terminate and seal the sides of the roof where it doesn't drain toward the sides, but rather to the rear... And they keep the building from looking like an aircraft hangar or a factory building...

There are any number of commercial roofing systems which have come on the market in recent years: cold process applied roll rubber, heat sealed rubber composition, turned flange metal, mineral fibered, etc... The heat sealed rubber composition you mention is amoung the better ones...

[This message has been edited by outaframe (edited March 31, 2005).]

[This message has been edited by outaframe (edited March 31, 2005).]
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Re: Roof Design and Waterproofing 31 Mar 2005 08:59 #28850

  • jimor
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Many city building codes require a parapet wall around the roof of flat or nearly flat roofed buidings for safety's sake, there is more presumption that someone may be upon that roof for some reason and become likely to fall off the edge, as has happened in many cases. This stems all the way from the Bible, where at Deuteronomy 22:8 the ancient Israelites were commanded to put a parapet around their roofs for safety's sake.

Parapets obviated gutters, as on pitched roofs, but then necessitated either scuppers which drained through holes in the parapet, or roof drains which usually had a raised, pierced dome shape to prevent clogging, though usually through the years they became clogged anyway since no one thought to go upon the roof every year to inspect and clean them out. This is the reason that so many theatres had drastic roof leaks where the stagehouse wall joined the auditorium roof. The drains were not cleared and then the pooled rain water penetrated the roof and poured in on the organ chambers or the proscenium.

Not all cities permitted scuppers especially on taller buildings since they could allow a considerable amount of rain water to spill down upon pedestrians on the sidewalk below, possibly causing injury.

The best way to really 'seal' a roof is to build a "super-roof" above it that is pitched and will therefore spill the rain off the building BEFORE it has a chance to pool and penetrate the roofing membrane. Such is not cheap, but in the long run, the best preventative. It is done by opening the caps to the steel columns in the walls and attaching at least seven foot high aluminum or similar column extensions rated to hold the weight of a new roof of aluminum sheets over the existing flat roof (as well as wind load), such that a man could walk upon the flat roof with enough head clearance that the new aluminum structure would clear him. Such aluminum roof sheets would shed the rain to the sides if the city allows such, and thereby keep the original flat roof essentially dry during a rain. The sides of such a new raised, pitched roof would best be made of pierced aluminum sheets that would prevent the entry of goodly amounts of rain, as well as birds and wind blown debris. It may not be the prettiest way to prevent roof leaks (depending upon how it is handled) but it is the best bet in the long run. Remember how you know a roof is leaking: by looking up at the inaccessable auditorium ceiling and noticing the expensive damage to paint and decor up there which sometimes requires the skills of a restorationist to restore at many times the cost of merely resealing the roof -- if one can find all the point(s) of leakage. This double pronged method of avoiding roof leaks (the original flat roof toped by a new pitched roof that no one walks upon) may be the only real long term protection, though not cheap. This "Super (as in 'Above')-roof" is the province of an architect, not a roofing contractor. Note that the aluminum sheets are NOT sealed to each other like shingles so as to allow for considerable expension and contraction, and therefore a small amount of rain is still expected to come upon the flat roof, which is why it still must be resealed after so many years and its drains, if any, kept clear of debris. In heavy snow load areas, the aluminum will be heavier and more costly and local regulations will restrict the pitch and disposal or fall area of any snow load. Your architect should be familiar with such.
Jim R. (new E-mail: This e-mail address is being protected from spambots. You need JavaScript enabled to view it ) member: www.HistoricTheatres.org
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Re: Roof Design and Waterproofing 31 Mar 2005 10:14 #28851

  • muviebuf
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A rubber roof is generally not recommended when you have a parpit wall with roof drains. The black rubber becomes very slippery when wet and when the snow begins to melt it slides into the corners overwhelming the roof drains often refreezing and blocking the drains. Better to use neoprene stuff like Tamko's Awaplan 170.
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Re: Roof Design and Waterproofing 03 Apr 2005 11:24 #28852

I also noticed during the last big rain, water is settled in the areas near the drains and looks to have formed a depression. I scooped out a sediment laying on the bottom and it looks like it needs to be re-pitched. Is this done by laying that rubberized material and melting it on that surface. Its only in 4 isolated spots...
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Re: Roof Design and Waterproofing 03 Apr 2005 16:20 #28853

  • outaframe
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The material I am familiar with can be built up in multiple layers and will bond to itself... The old existing material would need to be cleaned carefully to remove all dirt and surface oxidation to insure a good bond to the new repairs...
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Re: Roof Design and Waterproofing 03 Apr 2005 19:32 #28854

  • Mike
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we have a large central drain in the misddle of our 60 x 160 foot flat roof with no edges except the false front. One time it got clogged and leaking because of leaves. I went up and felt like I was in Dr. Strangelove wading into the middle of the 1'deep ponmd with a plunger! Yee-haw. It took a steamer to open it up as tar had gotten down the drain. 9 years later: it is working poerfect even in a flood like this weekend but we do clean the leaves every fall.

Downtowns and other spots often want all that roof-rain water to go into "Storm water" drains. Imagine if every building in a downtown spilled the rain onto the street. Things would be a lot wetter.

Michael Hurley
Impresario
Michael Hurley
Impresario
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Re: Roof Design and Waterproofing 04 Apr 2005 11:56 #28855

  • jimor
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Mike makes reference to rain falling down from tall buildings, and that cities usually wanted such to drain into storm drains, and that is accomplished where legal by means of receivers at the tops of downspouts that convey the water on the OUTSIDE of the buildngs down to the piping below the grade line. That is the most probable way of containing the water falling from the pitched aluminum 'Super-roofs' I advocate in my post above. Modern gutters along the edge of such a roof would be of the shielded type to prevent wind-blown debris from entering them, and the water would be conveyed to downspouts OUTSIDE the building, rather then the drain pipes (from roof drains) which are INSIDE the building that serve the roof drains, but which often leak through the years. Obviously, if a pipe or downspout is to clog, it is best that it be OUTSIDE the walls so as to have its leaks be noticed out there and not from damage to the interior.

The irony is that in many cities with combined storm and sanitary sewers, there is a great push on to empty those downspouts down upon the street's gutters where it is hoped that such will eventually be connected to new, storm water only collection which does not go through treatment plants where it can overload them. The trouble with this scenario, is that it has been found that the runoff from the surface into gutters and thence to storm sewers can be more toxic than that of the usual biological content in the sanitary sewers! So now experts are saying that ALL liquid effluents should go to the waste water treatment plants in order to preserve the environment. This may make your rain water control plans difficult to plan! Best Wishes!
Jim R. (new E-mail: This e-mail address is being protected from spambots. You need JavaScript enabled to view it ) member: www.HistoricTheatres.org
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Re: Roof Design and Waterproofing 28 Nov 2011 16:15 #37479

  • dataman19
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Wouldn't the new spray foam roof coatings be best.

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they are sealed with an acrylic sealer, and are white....
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And best of all - while they are sprayed on they can be sloped to make the water go where you want it to go..
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Just my take... (I have used torch down - it's light grey)..
...
Dave
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