Air Conditioner Curb Installation- Flat Roof – Watch Video

Flat roof curb installation for an air conditioner in Connecticut. We serve Pittsburgh, Monroeville, Stamford, Greenwich,  and White Plains, CT.

The Bow Tie Royale 6 Cinema contracted Commercial USA to install an air conditioning unit on the flat roof of 542 Westport Ave., Norwalk, CT. The curb was supplied by the The Heating and Cooling Company located in Norwalk, CT.  Mike Tavolacci marked exactly where the curb would be positioned on the roof.

Here is the Flat Roof Curb Installation process:

The curb in the video below was installed on an EPDM single-ply roof membrane.  We cut the EPDM rubber exactly where the markings were. Then, we removed a 3″ insulation isoboard. Under the the insolation was a 5/8″ gypsum board. After removing the the rubber, insulation, and gypsum board we had to cut through the metal sub roof. The opening through the metal roof was for the intake duct to the A/C unit.

After the opening was made for the duct work, we then placed the curb in position. Because the roof is slightly slanted, one side of the curb had to leveled with boards. After leveling the curb, we anchored the curb down with 4″ screws to the metal sub roof.

After positioning the curb and anchoring it, we could vulcanize (to improve the strength, resiliency, and freedom from stickiness and odor of the entire curb). We installed a EPDM cover tape on the entire curb, and then carefully added the flashing as well to tie it into the existing rubber roof.

[otw_shortcode_content_toggle title=”Flat Roof Curb Installation – Video Transcription” opened=”closed” icon_type=”general foundicon-plus”]Hi I’m Erik from Commercial Roof USA And today they called us to do this commercial roof It’s an EPDM roof and they called us because they need us to flash a 10 ton A/C unit Now this needs more than just flashing done This roof is unleveled so were gonna have to level it you can see there the bubble is off a little bit So um what we are gonna do is were gonna level it first Then on the inside there where you can see the orange marker uh we’re gonna cut the vent the vent or the intake vent and then were gonna have to flash the whole thing and uh the way we do it is a is a double step process where we flash on the inside and on the outside so they’ll never have a leak again And I’ll be showing you every step of the way This is how to flash a 10 ton A/C unit Alright well we’ve installed the ah curb and we vulcanized the unit here and uh we’ve installed this tarp on here so that when the HVAC people are ready they can just put the unit down on top This is how you install and vulcanize a curb[/otw_shortcode_content_toggle]

Flat Roof Curb Installation Steps:

  1. Make sure all the measurements are correct and the location is properly marked.
  2. Prep surface area by removing all debris and water.
Flat roof curb installation on a rubber roof
Make sure the surface is free of water and debris

3.  Cut the rubber and insulation away to expose the metal sub roof. Before cutting through the metal roof, make sure there are no electrical wires or any other objects that could get damaged during the cutting process.

Preparing the roof to cut a hole through the metal
Remove the rubber roof material and insulation to expose the metal sub roof.

4. The metal sub roof. This is what it looks like under all the insulation and the EPDM rubber. The metal roof. Use a metal reciprocating saw to cut the section out.

Caution!

Extreme caution must be taken during steps 3 and 4 because there could be electrical wires under the metal roof. In this case a drop ceiling hanger wire was attached to the the metal so we were fortunate enough to remove it without disturbing the drop ceiling.

Metal roof exposed under the rubber membrane and insulation
The metal roof had to be cut with a reciprocating saw.

5. Placing curb into position and ensuring it is level

Important!

Since the roof was slightly slanted, we had to lift the curb by 5/8″ on one side to get it level. It is important to have it absolutely level; if it is not level, the bearings will wear of faster on the A/C unit.

Placing the curb in position to be flashed
After removing the roofing material and cutting open the intake access area, we could place the curb in place.

6. Leveling the curb.

Important!

The roof is slightly slanted and it was necessary to level the curb before we started to install the flashing.  We used 5/8″ wood strips under the one end of the curb. After getting it level we secured the curb to the roof with 4″ screws that held is into place.

Air conditioner curb leveling
This air conditioner curb had to be leveled before we could flash it in.

7. Vulcanizing and flashing the air conditioner curb.

Important!

Once the curb was leveled we covered the entire outside of the curb with EPDM cover tape. To flash the curb in, it is necessary to clean the surface very well. We used lacquer thinners and rags to remove all the oxidation form the surface where we needed to adhere the new EPDM cover tape.

After the cleaning, we brushed primer to the surface and waited for it to dry. After a touch dry test, we installed the cover tape and flashed the entire unit in.

Curb-flashing-installation
It is essential to clean the surface form old oxidation before installing the flashing.

8. Installing the flashing.

In the case of a EPDM roof, it is necessary to use compatible material to do the flashing. In this case we used EPDM cover tape. It is very important to use a roller to roll the cover tape so it can propely adhere to the EPDM rubber.

Cover tape being rolled out.
It is important to roll out every inch of the cover tape to get a secure bond to the EPDM rubber roof.

9. Cover the curb with a tarp.

Noteworthy

It is difficult to coordinate two different trade crews to complete a A/C unit installment on the same day, but if  the A/C contractor marks out where the curb will be installed and leaves the curb on the roof, we can then notify them when curbing has been completed and is ready for the A/C installation.

Covering a A/C curb with a tarp awaiting for unit installation
After installing the curb we cover it with a tarp. The A/C contractor can schedule a time to install the unit.

10. The proper material for the right job

IMPORTANT!

Whenever there is curb to be installed or flashing that needs to be done, it is important to use compatible materials. On an EPDM roof, only EPDM materials and be used. The same principle applies to a Modified Torch Down roof; only Modified Bitumen materials should be used. Sometimes, we find that this principle is not practiced by other roofing contractors.  In the images below we are flashing a curb with Modified Bitumen Membrane Torch Down material.

Flashin curb with Modified Bitumen Membrane
Flashing the curb with Modified Bitumen Membrane

The image image below is also a Modified Bitumen Membrane curb installation. It is essential that a special tar be used to try and seal any flashing, but it should be used very sparingly. Installing a curb is a very important and should only done by professionals.

Curb-flashing-Modified-bitumen
When the curb is installed on a Modified Bitumen Roof, it’s important to use the same material to do the flashing.

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