Isn't it ironic considering
the importance of the need for a flat roof to protect the entire
building, it's contents and occupants from water damage that
most flat roofs have been the depository of the cheapest and
lowest quality types of building materials known to man! It's
normal to see tar, tar paper, tar soaked fabric, loose foam
sheets and latex, (water soluble), coatings on flat roofs with
poor or no effective drainage. This puts a heavy burden of
performance on those low quality materials, with all of their
seams and weak points. Now, top all of this mess with a layer of
ballast stones to make it impossible to find the leaks! Is it
any wonder that flat roofs are notoriously plagued with leaking
problems even if these types of low quality roofing materials,
with excellent drainage, are "installed correctly", and often
they aren't?
Normally, flat roofs consist of concrete, steel, or wood
substrates, heavily contaminated with tar combined with layers
of loosely fitted tar paper. The tar paper usually has turned up
edges and corners; it is warped and puckered, sun and heat
damaged, and has protruding high points, irregularities, random
seams, raised patches, tar deposits, stone ballast, etc.
Flat roof owners must realize that it is not practical or cost
effective to apply a high quality, permanent RoofMasterUsa.com roofing
system directly on these types of low quality materials. If
installed upon a flat, clean surface the amount of RoofMasterUsa.comproducts required to seal the same size roof surface could be
ten times less than what would be required if installed upon a
rough, irregular, contaminated surface. Also, the bond to the
old low quality roofing products can only be poor and temporary
at best.
The flat roof owner should consider the following options;
OPTION #1 (often not practical)
Remove and strip all of the old roof materials down to the
original substrate, (concrete or wood), and remove all residual
tar contaminates and install a new RoofMasterUsa.com directly on
the clean base substrate.
Disadvantages
Often it is extremely difficult or next to impossible to
completely remove all traces of tar "film" bond breaking
contaminates from the original substrate after removing the
loose tar paper layers.
If there are large areas of tar contaminated surface on the
original substrate no high quality systems such as XXXXXX can be
used.
The building is left vulnerable to rain damage during the
stripping, cleaning and re-coat process.
Expense of removal cost, labor and debris disposal.
Option #2 (Preferred Method of Flat Roof Transformation)
Before starting, remove all loose ballast stones. Install a new
3/4" tongue and groove plywood substrate directly over the
existing flat roofing materials. If the existing underlying roof
substrate is wood, it is extremely easy to nail down new plywood
over all or a portion of the old roofing materials. This can be
done a little at a time or all at once at the option of the
contractor or building owner. Large, poorly fitted or
excessively wide seams may be quickly filled, sealed and bonded
using LRB/TAV mixtures. If the flat roof has no parapet walls
install new drip edge and seal the drip edge and all flashing,
mechanicals and vent pipes with LRB/TAV mixtures instead of tar.
 Flat
Roof Plywood Decks
Prime all joints, seams, cracks, holes and around physicals with
Permaflex
Install 2" fiberglass joint tape by brushing or rolling it into
the wet Permaflex on all joints
Caulk/fill using 3/4" LRB/TAV bead brushed or smoothed (as per
above sketch.)
Apply a base coat Permaflex over roof @ 240 sq ft gal
Apply LRB with catalyst membrane @ 50 sq ft gal
Apply surface coat AR or Permaflex-AL @ 240 sq ft gal
20 yr roof-
prime/seal joints & around mechanicals using Permaflex & LRB/TAV,
apply 2 coats Permaflex @ 240 sq ft gal per coat (AR-base coat,
AL-surface coat)
Lifetime roof-
prime/seal joints & around mechanicals using Permaflex & LRB/TAV,
apply base coat Permaflex @ 240 sq ft gal,
apply LRB membrane @ 40 sq ft gal,
apply surface coat Permaflex @ 240 sq ft gal.
Metal Roof-
2 coats Permaflex (base coat AR, surface coat-AL)
using the LRB/TAV to fill/seal joints & around mechanicals
If parapet walls are also covered with old materials simply
strip them to expose an area of vertical substrate below the
wall cap which is not contaminated with tar or cover all
contaminated vertical surfaces with plywood. Terminate the
vertical plywood at a point on the vertical wall which is not
contaminated with tar or other sealers. Prime the area and apply
LRB/TAV mixture to completely bond and seal this point. (SEE
Figure 1)
It i s
easy to attach the bottom of the new vertical plywood to the new
horizontal plywood by installing securely nailed 2"X4" "L
Corners" continuously under the plywood at all parapet wall
perimeters. This provides a nice raise in grade to direct water
from this crucial potential leaking point seam at the base of
the parapet wall. It is not necessary that the vertical
terminations be attached securely with nails or other mechanical
fasteners. Often only a few fasteners, clamps or even weights
are required at this point to temporarily hold the plywood tight
to the wall until the LRB/TAV mixture is installed and cured.
The LRB/TAV mixtures will secure the top of this new plywood
wall completely and more securely than nails due to the
extremely strong adhesive properties of the products.
To prevent water damage to the new plywood substrate all that is
required is that Permaflex primer and LRB/TAV mixtures, (used on
joints and seams), are applied at least 45 minutes before a rain
to prevent droplet damage to the newly applied products.
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