Commercial Flat Roof Repair – Hot Tar with Gravel Roofs
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 start to crack. The stone aggregate hides these cracks, so it is not easy to spot them.
The downfall of these roofs was:
- Difficult to find a leak among the stones
- They get brittle over the years and start to crack
- Repairing such a roof is almost a nightmare
- More expensive than a rubber roof to install
- Life expectancy is less than that of rubber roofs
- 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 will be followed.
There are two ways to deal with such a roof when it is time to replace it.
- Rake the stone evenly and remove debris.
- Install 1/2″ fiberboard over the stone.
- Install a base paper.
- Install new metal edging
- Install a rubber membrane.
Second Choice (as the pictures show below)
- Remove the existing tar and gravel.
- Clean the roof and flashing.
- Install a base paper over the plywood.
- Install rubber membrane.
These videos show the process of removing an old asphalt roof and installing a Two Ply rubber roof
2nd Video – Installing Fiberboard and Base Sheet
3rd Video – Completion of Installing and repairing a commercial roof
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 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 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 3 – Commercial Flat Roof Repair 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.
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
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 a positive water drainage.
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 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 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.
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.
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 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 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.
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.
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 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 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!