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Commercial Flat Roof Repair – Hot-Tar Gravel Roofs

A very detailed video on how to install a Torch Down Rubber roof over Tar and Gravel

Commercial flat roof repair with the old Hot Tar and Gravel on it. These roofs have come a long way, but time has come where they are not repairable any longer. Over the years the hot tar becomes brittle and starts to crack. The stone aggregate hides these cracks, so it is not easy to spot them.

The downfall of the Tar and Gravel roofs were:

  1. Difficult to find a leak in the stones
  2. They get brittle over the years and start to crack
  3. Repairing such a roof is almost a nightmare
  4. More expensive than a rubber roof to install
  5. Life expectancy is less than that of rubber roofs
  6. More costly to repair than rubber roofs

The following suggestions are equally good. It is how the flashing and other obstacles are on the roof that will determine what method to follow.

There are two ways to deal with such a roof when it is time to replace it.

First Choice

  1. Rake the stone evenly and remove debris.
  2. Install 1/2″ fiberboard over the stone.
  3. Install a base paper.
  4. Install new metal edging
  5. Install a rubber membrane.

Second Choice (as the pictures show below)

  1. Remove the existing tar and gravel.
  2. Clean the roof and flashing.
  3. Install a base paper over the plywood.
  4. Install a rubber membrane.

These videos show the process of removing an old asphalt roof and installing a Two-Ply Rubber Membrane Roof

Removing the old Tar and Gravel roof to install a new Torch Down Rubber Roof

2nd Video – Installing Fiberboard and Base Sheet

Notice the flashing is cleaned up and a self adhering base is installed

3rd Video – Completion of Installing and repairing a commercial roof

https://youtu.be/MN_A3WLK2Vs
This is what the final product looks like

Steps on Removing an Old Tar and Gravel roof to prepare for a new rubber roof

Step 1 – Removing the old tar and gravel

Tar and Gravel roof is removed to prepare for new rubber roof. The stone was to protect the roof from UV’s. It’s very labor intensive to break up an old roof. The weight of the aggregate adds to the cost of carting the roofing debris away.

Step 1 - Removing the old tar and gravel. Commercial Flat Roof Repair - After stripping the gravel roof, all the preparations need to be done to replace it with a rubber roof.
Removing the old Tar and Gravel Roof

Step 2 – Breaking up the old roof

It takes a lot of energy to strip and remove an old gravel roof. Many dumpster loads are necessary for removing the aggregate.

Labor intensive – all the people involved

A top view of stripping a roof. A lot of hands make light work but also costly.
It’s one of the time-consuming parts of the roof – drains and skylights and air conditioners. All of the flashings have to be cleaned and prepared

Step 2 - Breaking up the old roof. Commercial Flat roof repair - removing old roofing material takes a lot of effort. After lifting and breaking the old roofing up, it is thrown into a dumpster.
It is super labor intensive to remove any old roof before installing a new rubber roof
It took many people to strip this flat roof in Greenwich. Care must be taken not to ruin the flashing around the drains and skylights.
The cost is more than double than that of installing over an existing roof

Step 3 – Repairing and Replacing old drains

The drains on a roof affect the cost of redoing a roof. It is always a battle between replacing or reusing the existing drain.

Re-using a drain avoid the plumbing cost and the installation of a new drain. The problem sometimes is that the old cast iron drains have so much tar build up and some of them are cracked, meaning it will cost more to repair them than replacing them. Drains are the more expensive and time-consuming part of a roof installation on a commercial roof.

Using Torch heat to melt the old tar to make the necessary repairs to be able to use the old drains again.

Step 3 - Repairing or Replacing old roof drains Commercial Roof repair - All tar and old roofing material must be removed to be able to install the new rubber roof. Using Torches to clean drains
Over the years the cast iron leaf filters got stuck due to tar leaking toward the drains. By heating them up, they can made unstuck
If everything else fails, just kick the drain. After melting the tar around the strainer, we were able to remove the strainer.
See the smoke? We use a propane torch to melt the tar

Commercial Flat roof – Drain Repair

As the images indicate, while preparing the roof, someone is repairing and preparing the drains for the new rubber roof installation.

The location of a drain is critical on a roof. Watch this video on Flat Roof Drains Location

It is really the biggest issue on a roof. For the installer and for the home owner. The roof surface is already clean and ready for a new rubber roof but the drains are still been worked on.
The preparation to install a new rubber roof takes a lot of time. Drains are the most time consuming objects to get clean and ready

Step 4 – Roof Levels

Finally, the roof is stripped and cleaned. Some areas of the roof were lower than the drains. We installed 1/2″ fiberboard to build the roof up. Some places we had to build it up as much as three inches. Flat roofs are not completely level and can cause water ponding if caution is not taken.

It is important to check the roof levels before installation. It is common that the drains are not positioned correctly for water flow. This where the roof has to be built-up in areas to create positive water drainage.

Step 4 - leveling the roof to cause positive water flow.
After all the preparation is done, then layers of fiber board is used to slant the roof towards the drain

Step 5 – Removing and Repairing Skylights

Since the levels of the roof were too low, we had to lift the skylights also about 3 inches.

After making sure the levels are right, we then fasten the fiber board with long screws and big washers to the plywood. It is best to use a laser leveler over long distances to get an accurate level. Once a rubber roof installation is complete, there is no turning back to make corrections.

Step 5 - Repairing skylights and repositioning them. Sometimes it is necessary to remove the skylights if the roof has to be raised in that area. The skylight is then reinstalled after the levels are good.
Some skylights does not have flashing but instead just curb. In this case the roofing materials will be cover the curb

Step 6 – Fiberboard used to built-up levels

After making sure the levels are right, we then fasten the fiber board with long screws and big washers to the plywood. Sometimes as much as five layers of fiber board are stacked up on each other to get the right levels

Step 6 - Fiberboard used to built-up levels
We use screws and large washer to secure the fiber board
To fasten the fiber board, special screws and washers are used. We have been installing rubber roofs over 25 years.
The large washer are placed over seams of two adjoining fiber boards

Step 7 – Flashing is the most important part of a roof

When repairing or preparing a commercial flat roof, flashing is the most important part of the roof. There is flashing against the siding, Air Conditioners, Drains, Vents, and other obstacles. It is important not to damage the flashing when removing the old roof.

The most important part of a roof is the flashing. Care must be taken not to damage it while stripping a roof.
Notice the copper flashing behind the siding. Instead of removing the siding, re-installing new flashing, we just cleaned to old

Step 8 – Dumpster – having it close to the roof

It is important to spread a tarp over the grass and plants for protection against all the roofing debris. It also will help with cleaning up later.

We contract a company to provide a dumpster. The dumpster is placed on boards as not to damage the grass or paving surface. It is very important to have the right size dumpster for removing roofing debris. At all cost, the dumpster should be placed as close as possible to the roof so debris can be thrown into it from the roof.

When pitching roofing debris over the side of a roof, it is best to spread a tarp. It makes cleanup much easier. We are the flat roof experts.
By putting a tarp down on the ground, will help with the clean up later on
Step 8 - Dumpster - having it close to the roof. Make sure you get a big enough dumpster to remove all the roofing debris. Always put boards down for the dumpster to stand on to protect the surface.
Dumpsters to haul away all the roofing debris

Step 9 – Preparing a Commercial Flat Roof

While roof technicians are installing the roof, some areas need preparing as in flashing around the air conditioners. Flashing on any commercial roof takes time to prepare or to install.

Step 9 - Preparing a Commercial Flat Roof - Flashing around a air conditioner is always very hard to clean. Care must be taken not to damage the flashing while cleaning the flat roof.
The flashing around the A/C ducts were not there. We had to do extensive preparation to be able to install the new roof

Step 10 – Copper flashing repaired and prepared for rubber roof

This is what the flashing around the air conditioner is supposed to look like when everything is cleaned. All roofing tar and old wood and debris are removed. Many times new flashing must be installed.

Step 10 - Copper flashing repaired and prepared for rubber roof - It is very important to remove all roofing debris and material; around flashing on a flat roof.
This is what it looks like after the old roofing was removed

Step 11 – Installing Base Sheet

After installing the fiberboard and the levels are satisfactory, then it’s time to install a base sheet. This is a self-adhering peel and stick base layer. Very costly and is almost the same price as the rubber membrane itself. But this is the best system for any roof. This system will outlast any other roofing material as in EPDM or TPO.

Step 11 - Installing Base Sheet - After the fiberboard is installed, then a base sheet has to be installed. The peel and stick base sheet is the best for any roofing system.
After leveling the roof so it is pitch towards the drains, we then installed a self-adhering base sheet

The image shows what it looks like after installing a base sheet and before the installation of a Torch Rubber Roof. All the flashing is clean and ready, all the levels are good. The hard part is over, and the drains look new again.

The roof is ready to receive the final rubber roof. Notice that the base sheet is under the flashing. The best rubber roof system is to have a peel and stick base paper with Modified bitumen Torch down rubber installed.
This image shows the base sheet, drains and skylight flashing all ready just before the cap sheet is installed

Step 12 – Installing Rubber Membrane

Running the torch and melting rubber is much nicer than cleaning drains. Preparing and repairing a Commercial Roof for a rubber roof will determine what the final product ends up looking. The ultimate goal is to see an even smooth surface with as little as possible water pooling after rain.

Step 12 - Installing Rubber Membrane - After all the flashing and base sheet is taken care of, it is time to install the rubber membrane. We used white granulated surfaced rubber material.
The start of installing the Torch Down Rubber Roof
This is the best part of installing a flat roof. The hard work is over. All preparations are done. No other roofing system can be as good as this.
I am torching myself a little because the crew was running behind schedule

Step 13 – Torch Down Membrane – Welding the seams

Too much heat and the rubber gets destroyed, too little heat and the seams don’t get welded. You will notice that all our seams are clean. We work with a white granular rubber membrane. The granules are to protect the rubber membrane from the ultraviolets.

It takes time to develop the proper technique when it comes to using a torch. The daily temperature determines how much heat is necessary to weld seams together.

Step 13 - Torch Down Membrane - Welding the seams - A rubber membrane that is torch down have better seems than EPDM that is glued together. attaching the rubber roof to the flashing is very crucial.
The best is always to install the rubber all the way to the outer edge

Step 14 – Final Commercial Roof Repair and Installation

Over the years we have improved the installation technique. I believe we have a superior roof technique that will outlast any other roof system on the market.

Finally – this is what the roof looks like when it’s done. Another Commercial Flat Roof Repair and Installation well done!

Step 14 - Final Commercial Roof Repair and Installation - This is what the roof looks like when it’s done. The rolls are three feet wide and you will notice the seams. The seams are welded together with heat and will not leak.
This is what the roof looks like after everything was done
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