Some building owners are surprised to discover their new roof costs less than anticipated. Cold process, fluid applied reinforced roof systems can be eligible for “warranty renewal” or extension, for an additional ten (10) years, at reduced cost. The asphalt emulsion and polyester reinforcement beneath the reflective white surfacing is left unchanged. New white surfacing is reapplied after correcting surface defects. Waterways and drains are reinforced with polyester fabric and acrylic surfacing.

This particular roof has excellent roof slope, good drainage, and two (2) plies of polyester reinforcement fabric set in cold processed asphalt emulsion during the original application, hence it was an ideal candidate for resurfacing.

Main low slope roof areas, as well as small lower level front sections were included in the scope of the Work.

Loose sections, sump drains, pipe flashings,and waterways were repaired and reinforced with polyester fabric, prior to resurfacing.

Roof preparation includes power washing to remove surface contaminants, and provide a clean surface to facilitate proper adhesion of new materials.

Drain sumps are considered “waterways.” Polyester reinforcement fabric and acrylic surfacing is extended beneath the clamping rings into the drain bowls.

Appropriate protection is used to avoid over spray on to adjoining surfaces, such as this stucco wall. Notice in the distance, the metal coping joints at the wall tops were also reinforced and sealed.

Surfacing is applied in two passes using cross directions for complete coverage. It is essential that correct material quantities are applied. A slightly textured “eggshell” surface appearance should be visible on completion.

PVC-KEE single ply roofing membrane was selected as a lightweight upgrade to this large, low rise, single tenant, office building in Ventura County, California. Office environments have a very low tolerance for roof leaks compared to retail or commercial/industrial properties. We were able to deliver the completed Project significantly under budget. (See our Commercial Roofing page for cost and quality control specifics.)

The building had recently completed a “sale-leaseback” to a major financial institutional tenant. The new owner wanted a minimum maintenance, energy efficient, long term roofing solution. They had budgeted for replacement, and we were able to include a fully adhered new roofing membrane installed directly over the existing emulsion/acrylic surface, including a twenty year full value, no dollar limit, manufacturer backed warranty. The specified membrane has a successful in service field history of over thirty five years.

Original construction dated from 1981, thirty-three (33) years prior. At the twenty year mark in 2001, a cold process emulsion system overlay with a ten (10) year warranty, including one ply of polyester reinforcement and acrylic surfacing, was installed over the existing “built up” cap sheet roof . Now at thirteen (13) years, defects and leaks were present.

While the old acrylic surfacing had lifted in “ponding” areas, the polyester fabric installed toward the uppermost portion of the old asphalt emulsion provided a “biting” surface to assist in creating a physical bond, so while the surfacing had weathered and worn, the roofing material Manufacturer approved installation of the new fully adhered membrane directly over the primed, old surface.

The roof surface was cleaned, then a water based primer applied, to enhance adhesion “tack” strength, and bind residual surface contaminants.

3M CR-20 two component, low rise, adhesive foam was used to adhere the membrane in the “field” or main roof area.

A substantial amount of polyester “fleece” is adhered to the back of the membrane. The backing on each roll is destructively tested for adhesion prior to leaving the Manufacturer’s plant.

Solvent based adhesive assures complete bonding of the smooth membrane to vertical surfaces, yet was incompatible with water based acrylic surfacing. The lower portion of existing roofing on the wall was removed, and new membrane fully adhered to the concrete substrate, with the upper edge receiving butyl tape compression seal behind mechanically fastened metal also incorporating a quarter inch sealant ledge.

The original upper level roof was installed over lightweight insulating concrete with a light gauge vented steel deck. Fully adhering the new single ply membrane was the best option for securement.

Modified Membrane APP “Cool Roof” Installed

Seven (7) primary roof design solutions were implemented:

1. Install new underlayment over the old aggregate surface,
2. Replace metal coping cap with integral weatherstripping for glass curtain wall,
3. Insure perimeter wind uplift resistance at upper level,
4. Provide slip resistant roof surface for window washing equipment on the Sixth Floor,
5. Fabricate correct Unistrut mounts for cell tower cabling,
6. Cure Second Floor roof leaks at curtain wall base flashing,
7. Develop effective and economical “pitch pocket” details.

Aggregate surface was vacuumed and defects repaired prior to installation of underlayment.

 Mechanically fastened cement fiber board (above) on the upper level served as a base for heat welded APP modified membranes. To meet budget constraints, 3/8″ thickness was used on the inaccessible upper level and 1/2″ on the main roof area and parapet walls.

Old repairs fastening to the existing walls were ineffective. They simply pulled out of the thin gypsum wall board beneath.

Pitch pocket bases received a layer of smooth and granulated modified membrane. Acrylic flashing cement reinforced with polyester fabric was applied from the penetration extending down over the sides.

 The new “Cool Roof” Title 24 approved membrane was fully adhered over Securock fastened directly to wall supports under the existing substrate. Continue reading →

We provided the Owner with seven (7) possible choices to meet their criteria of a twenty (20) year roof system with proven performance, installed by seasoned applicators, while meeting stringent budget requirements. They selected the all acrylic fabric reinforced system applied over the existing single layer three ply built up cap sheet roofing. This roof has a highly reflective white surface which reduces surface and interior building temperatures to save energy and extend weathering life.

The other systems that were considered but not chosen, in part due to higher installation cost were: single ply PVC-KEE mechanically fastened with an alternate for fully adhered, a competitive acrylic fluid applied product, four ply asphalt built up roof, and APP polymer modified roof retrofit or with removal of the old roof.

Once the selection was made we prepared written Specifications for the installation, screened contractor references, conducted the on site pre-bid job walk and obtained three competitive bids.

Following a pre-construction meeting to review the Specifications with the project superintendent, work began and we performed quality control inspections at regular intervals.

The system was applied in four (4) stages. After cleaning and preparation, polyester reinforcement fabric was embedded in four gallons per hundred square feet (aka roofing “square”), followed by three additional applications of finish surfacing.

The foundation coat differs from the finish coat is several aspects. Apart from lack of UV (ultraviolet) and dirt release compounds, the foundation coat includes a surface which retains its adhesive tack even when dry to resist ponded water and improve adhesion of the finish layers.

When Santa Ana winds deposited a layer of dirt over this surface, it was cleaned with water and a stiff bristle broom then a new layer of foundation coat applied to re establish the adhesive surface.

Here are some photographs which illustrate the progress of the project.

The roof is being power washed to remove surface contaminants.

Local ordinances permitted this type of “grey water” discharge though some municipalities differ.

Here you can see the clean surface on the left compared with accumulated surface dirt on the right in the process of being cleaned.

Because all rain water striking the roof surface is directed to drains, the old roofing at the drains was removed, a mechanically fastened base sheet installed, followed by a smooth mid ply APP polyester reinforced modified membrane, and a granular surfaced finish membrane. Look closely and you can see the line where the old roof was removed, as well as the drain pipes from the upper level that empty into these drains.

Here one of the workers is “brooming in” the polyester fabric to insure full adhesion with no wrinkles in the foundation coat. The base coating is applied at four gallons per square with the fabric absorbing three gallons.

Note the tan color to differentiate from the finish white surface applied later, to help visually confirm full coverage.

Some of those side parapet walls are seven (7) to ten (10) feet in height.

With this system, polyester fabric was installed over all wall surfaces as well as in the main “field” area of the roof.

Here you can see the first layer of the roof being applied with the application of acrylic base material, embedding polyester reinforcement fabric, and brooming in for full adhesion with no voids.

When this dries,  the roof is waterproof. The next three (3) layers protect this foundation layer from the elements over time.

A second layer of polyester reinforcement was applied in all waterways at the base of the walls, around drains and extending out to areas that may hold water temporarily in heavy rains, and also an additional layer in front of equipment where service personnel will create foot traffic during maintenance and filter changes.

Here is a photograph showing three (3) sections of the completed roof area.

There are two adjacent spaces separated by the parapet wall in the center as well as one of the upper level roofs.

Flat Roof Materials Solutions – Need A Flat Roof? – How Do You Decide?

It’s easy to be confused when evaluating roofing material solutions for the flat or low slope roof. By understanding something about the source, benefits and drawbacks of each type of material, you can make a choice better suited to your needs and sift through the often confusing stack of proposals.

Manufacturers place their own proprietary names on their roofing materials to promote them. To compare and understand what is being offered, let’s begin with the basic categories of commercial low slope or flat roofing systems.

Single Ply Roofing and Multiple Plies

We will look at TPO, PVC, BUR, modified, cold process and EPDM.

Continue reading →

Roofs are actually designed to shed water, so all the rain water striking the roof surface winds up at the drains. This is why it is so important to make sure roof drain screens are clear and allow free flow.

Water weighs over eight pounds per gallon, so ponding water can allow weight to accumulate quickly which can lead to subsidence with increasing volumes of water gathering during subsequent rain.

Most commercial roof designs include an overflow drain as a safety valve. These are often a raised scupper drain outlet, or a second sump drain with a collar surround to prevent the water level from rising above that height. Still, it is best to avoid the height of standing water prior to reaching the over flow.

Drains are frequently located in the corner of the roof area and form a natural place for wind blown debris to collect, so be sure to have the roof drains cleared annually as part of routine maintenance, and definitely check the dome strainers for blockage prior to large rain events.

You probably don’t want to think about pipe flashings, and if they are installed properly can be worry free. Wherever you have a pipe penetrating the roof deck there is potential for water entry because the opening in the deck forms a direct path to the interior of the building. If you have any dynamic deck deflection from wind loading, foot traffic or equipment installations, additional stresses are placed on the flashing and seal.

Each different roofing material has different requirements for pipe flashings and there are some alternates within material groups. Cost is often a design consideration and better devices are available at additional cost. For example Chem Curb makes a versatile, excellent urethane based fluid applied sealant poured within a fixed enclosure “the curb” that works well with a variety of systems and is especially useful when pipes are clustered with limited spacing.

The illustration on the left above shows a lead pipe flashing. These are also very durable installations, albeit at somewhat higher cost. These flashings last because the lead is bent over the upper pipe opening, and the field flashing portion of the lead deforms less that the typical light gauge sheet metal during temperature change.

Various other configuration are determined by the material manufacturer. With single ply membranes, pre formed boots are common. They are often cut to size on site, and terminated with compatible sealant and a band clamp.

It is helpful to understand the chemistry of the sealants used. Higher polymer content with less filler is always helpful and varies between manufacturers.

When using asphalt based built up roofing we always recommend polymer modified sealants rather than the standard cut back asphalt mastics.

Feel free to call us with your design, specification, quality control or bid and budget questions.