Tapered Roofing System

A tapered roof system is where the slope or ‘pitch’ of the roof is formed by the insulation where the roof is flat, to allow water to drain off. Tapered polyisocyanurate roof insulation or tapered iso for short, is made from the same ridge foam material that normal polyiso roof insulation is made from. Regular iso board comes in flat sheets and in several different thicknesses to include tapered. It can be a complexed process to slope a flat roof using this system, especially where 3 sides come together. But there’s a mathematical formula, or method to the madness, as we like to call it, that brings all the pieces in place which ever flat roof configuration we calculate.

For example, here’s a bit of math within a tapered system. Tapered polyiso is sold in 4’ x 4’ pieces or panels that change thicknesses over 4’ distance. The amount of the change in thickness in each panel is a 1/4” per foot. This means that for every foot of distance the iso get 1/4 “thicker. There are 3 types of sloped panels made.

X panel measures 1/2” to 1 1/2 “in thickness

Y Panel measure 1 1/2” to 2 1/2 “in thickness

Z Panel measure 2 1/2 to 3 1/2 in thickness

Then for example an X panel begins at 1/2” thickness and increases a 1/4” in thickness every foot. Since the piece of iso is 4’ long, the thickness increase will be equal to 1/4” times 4 or a rise of 1” over the 4’ distance ( 1/2  to 1 /12” )Flat roofers can then arrange the sloped insulation to move water towards roof drains, scuppers, or gutters.

At this 1/4″ slope per foot, there are only so many panels available that can reach a distance of 12′. If your flat roof is larger, the next section can utilize the same set of panels after installing a 3″ flat panel, one that you put those same panels on top of. This means the next 12′ after the first 24′ would need two 3″ flat panels under the next set of slopping panels.

Now picture this, some homes have 2 and 3 sides of shingles coming to a flat roof. Each side where the shingles meet the flat the slope needs to run in the same downward slopping direction. This means that for a 3 sided roof the tapper will move to the center while still sloped to the 4th side and off the roof. This is where the madness comes in, but thankfully there’s math involved to every inch. Don’t worry, we have you covered and can handle any configuration your roof brings us.

There’s a 15 to 20 year warrantee to CertainTeed tapered iso systems.

Call us for a free quote and more information. (727) 518-7663 or send us an email: info@augustoroofing.com