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Flat Roof in Los Angeles – New Construction

This is by far the best Flat Roof Installation.

My (new construction) flat roof has the following characteristics:

Flat Roof installation by owner in Los Angeles spec sheet

  1. Located in Los Angeles
  2. Small – about 700 sqft
  3. Has a parapet, partially from concrete partially from wood (see pictures)
  4. No penetrating pipes, vents, windows or equipment on the horizontal roof surface
  5. The roof is insulated with closed cell polyurethane spray
  6. The roof has proper slopes (crickets) for drainage with 3 scuppers with overflow protection on each
  7. The sheathing over the last layer of plywood is 1/2″ fiber cement as fire protection since the structure is in a high fire zone area
  8. I was originally planning to use 1 ply roof from FiberTite but decided against it after I realized it was very proprietary and had a hard time getting an installer
  9. I am planning to use torched down Modified Bitumen from CertainTeed in 3 layer configuration
    • 1st (base) layer using Flintlastic APP/FG Base T, attached with roofing nails
    • 2nd (mid) layer Flintlastic APP/Poly STA, torched down
    • 3rd (top) layer Flintlastic APP/Poly GTA-FR Coolstar (Fire Rated and Title 24 compliant), Torched Down
  10. I have an experienced roofer to do the torch down process
  11. Parapet will be properly sealed, waterproofed with a Bitchutain Membrane and will have sheet metal flashing to completely protect from any chance of water penetration
  12. The Titanium UDL currently showing is just temporary protection and will be discarded before the new roof is installed
  13. What is the best way to protect the roof from foot traffic if it used as a deck?

See material from CertainTeed attached in case you are not familiar with the specific material/product.   I would appreciate very much any recommendations for making the roof better and last longer.

My opinion on the 3 Ply Roofing System

I don’t think this will make the roof better by installing an additional cap sheet. I think the best way is to install a Modified Bitumen Self-adhering base and a ceramic granular surface cap sheet.

The added membrane in between could make it difficult around corners and scuppers.

I am not against this method, I just think it’s unnecessary.

Recommendations for improving what’s already a very good flat roof system

After looking at the images you send me, I am very surprised to what length you have gone to make sure you do everything right.

The only concerned I had were 2 things:

  1. How the walls would be covered
  2. The size of the scuppers

I didn’t understand what you meant by “Parapet will be properly sealed, waterproofed with a bitchutain membrane”.

My suggestion is to apply a thin layer of Karnak 81 Trowel grade Modified Bitumen Adhesive to the wall and then install the APP cap sheet. What this means is to continue the roof membrane up the walls. I will try and make a quick illustration of what I mean.

I also notice a Eucalyptus and a pine tree nearby. The leaves of those trees are small and so the scuppers should be fine. Pine tree needles tend to accumulate and block scuppers rapidly. Make sure you have easy access to the scuppers.

With this type of roof installation, there is no better way. The only problem I might foresee is how the roof technician attaches the rubber membrane to the scuppers.

We have developed a technique that has proven to be our lifesaver when attaching the torch down membrane to metal or to the parapet walls.

The only tar to ever use with APP Modified Bitumen membranes

The Tar shown in the above image is the only way to attach an MB Torch Down membrane to metal or to walls.

Here is how we do it:

  1. Prepare the surface that needs to have the membrane attach too. Dry dust free
  2. Smear liberally the tar to the surface
  3. Turn membrane facing back side up – torch burn the plastic on the back
  4. Apply membrane to the tar surface and work out the trapped air so the tar squeezes out from the edges.

This was a secret we kept for 30 years – good luck

Check this article on a Rubber Roof Installation

Our Secret Revealed for the first time

The tar above is the secret to guarantee a material bond between the rubber membrane and the metal flashing

Illustration of the parapet wall and torch down roofing membrane

This is what I suggest to do on the walls. The best way is to continue with the same cap sheet onto the walls so it is all part of the roof.

For extra protection against foot traffic, depending on how much foot traffic is expected, furniture and other objects that could be placed on top, I suggested to install a composite type of deck on top. leaving room around the scuppers for easy access.

Illustration of installing a torch down membrane on a wall making transition to roof

This is a Flat Roof in Los Angeles under New Construction. One of the better roofs I have seen.

Flat Roof in Los Angeles - New Construction

Temporary Roofing makes for added cost

Added expense to cover the roof with a temporary plastic till the proper membrane could be installed. Maybe when planning new construction, the roof should have been thought out before the start of the construction and completed first before the inside was being done.

A temporary cover over roof - amazing well done

Insulation under the roof deck

Insulation before the roof deck was installed with closed cell polyurethane spray. Excellent work and thorough work.

These were images sent in by the owner.

We see a problem with this setup. From our experience, the insulation will cause moist to be trapped under the plywood causing the plywood to rot.

Insulation before the roof deck was installed with closed cell polyurethane spray

Plywood deck installed after insulation

Flat Roof Los Angeles - 1/2" plywood deck installed

Scupper holes look small

The holes through the wall in the image look small for a scupper.

Flat-roof-Los-Angeles---Scupper-holes-prepped-in-wall

Scupper looks good

In this image, it appears the scupper hole was increased. But again this could be the wood part of the parapet wall. The concrete wall scupper hole looked very small

Flat-Roof-Los-Angeles-Scupper-Installed

Flat-Roof-Los-Angeles-titanium-UDL

Amazing to have a temporary cover installed. But it shows that the owner is not concerned about little extra costs to do the job right.

Flat-Roof-Los-Angeles-titanium-udl

This is a really pretty scene for a flat roof in Los Angeles.

Thanks to the person that send these images. It appears he is doing a fantastic job on the roof. I hope to get some other images in stages when the roof is installed.

Flat-Roof-Los-Angeles-pretty-scene

Fire Protection in Los Angeles

Cement board is installed over the plywood to give it the extra protection against fire. Especially in the Los Angeles area, this is a needed layer of protection.

Flat roof Los Angeles - Fire protected cement board is installed over plywood

Nice job!

This looks like a very well planned thought out roofing job. It all depends on the roofing technician on how well he does his job as how long this roof will last. A three-ply system will last indefinitely. It’s overkill by far.

The best roofing system bar none.

What about the outside of the parapet walls for fire protection?
CertainTeed low-Slope Roof product Selection guide
Base Sheet by Certainteed – 1 st layer
CertainTeed 3 ply system – 2  ply
Final Cap Sheet – with the ceramic surface for UV protection

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