Frequently Asked Questions

What is a Plumbing Vent Flashing ?

According to Wikipedia: Flashing refers to thin pieces of impervious material installed to prevent the passage of water into a structure from a joint or as part of a weather resistant barrier (WRB) system. In modern buildings, flashing is intended to decrease water penetration at objects such as chimneys, vent pipes, walls, windows and door openings to make buildings more durable and to reduce indoor mold problems. Metal flashing materials include lead, aluminum, copper, stainless steel, zinc alloy, and other materials.
Basically, it’s the part that covers the plumbing vent pipe to keep the water out of the building.

Around the country, plumbing vent flashings are given different names: Pipe boot, Vent boot, Pipe flange, Roof Jack, Stink pipe boot. On our web site we use the names vent flange and vent flashing.

What are the advantages of purchasing an F.J. Moore plumbing vent flashing?

Our 2 part plumbing vent flashing encloses the entire vent pipe above the roof. We do not use rubber seals. A rubber seal will crack with age and may allow water to enter the attic – this can cause mold and mildew issues in a building.

Our product was patented in 1918 and our design remains superior to all others in the marketplace.

Our galvanized or painted steel, with a lead top, is usually good for the life of the roof. When installed properly, we guarantee it for 10 years.

Since 1972, F.J. Moore has offered the Olson top for PVC pipe. The Olson top is usually good for the life of the roof. When installed properly, we guarantee it for 10 years. Learn more about Olson Tops

Also, the Olson top seems to be critter resistant Critter Problem ?

How does an F. J. Moore plumbing vent flashing work?

The base of our vent flashing is adjustable to the roof’s pitch. The base flashing rotates under a row of shingles, above the vent, to provide water drainage. The top cylinder slides over the base cylinder and attaches to the top of the plumbing vent pipe. As the roof expands and contracts, the base rises and falls with the roof. The top, attached to the vent pipe, stays stationary. This design allows the roof to flex, with the temperature changes, without compromising the seal at the pipe.

Why is a rubber seal flashing inferior to the F.J. Moore design?

A rubber seal dries out and becomes brittle when exposed to temperature extremes and the sun’s UV rays. The roof expands and contracts, causing the rubber seal to slide up and down the vent pipe. As the rubber ages, movement of the roof causes the rubber to crack and allow moisture to enter the attic. Most new homes use rubber seal vent flashings for cost savings. Most re-roofs, in Minnesota and the surrounding states, use the F.J. Moore frost resistant plumbing vent flashing simply because it is a superior product and it has a longer life span.

Is the F.J. Moore plumbing vent flashing worth the cost ?

Our vent flashing retails for about twice the cost of a rubber seal vent flashing. With about two per roof, this is a tiny increase in the thousands of dollars involved in an overall roof replacement.

If you factor in:

  • The time savings (easy installation)
  • Our written 10 year guarantee (when properly installed)
  • Peace of mind (no water allowed to enter the attic to cause mold and mildew)

Then, we’re confident the answer is YES!

Painted vent flashings cost slightly more, for the materials, but they cover the stark white plumbing pipe sticking out above the shingles. Choosing a color, to complement the roof, provides a more finished look along with our superior design features.

Are F.J. Moore plumbing vent flashings difficult to install or retrofit over existing rubber seal vent flashings?

Refer to our detailed printable installation instructions found on the How to Order and Install page.As our vent flashings require no removal of the existing old rubber seal vent flashing (some trimming may be required), no removal of shingles and no sealing with tar, they are not difficult to install.

How do I measure the inside dimension of the plumbing vent pipe?

Most plumbing vent pipes are made of PVC plastic, cast iron or copper. Place a good steel ruler across the top of the plumbing vent pipe. Measure from the inside edge, of one side, directly across to the opposite inside edge. This measurement will be your inside vent pipe diameter.

All standard residential plumbing vent pipes are 1.5”, 2”, 3”, 4”, 5” or 6” diameter. Should you require a flashing, for a non-standard application, please contact us directly.

How do I know if I need a standard or high pitch vent flashing?

Refer to our detailed instructions, for Measuring the Pitch or Slope of the Roof on the How to Order and Install page.

Standard vent flashings adjust to fit 1/12 to 11/12 pitched roofs. High pitch vent flashings adjust to fit 5/12 to 15/12 pitched roofs. If the roof pitch is 11/12 or more, a high pitch flashing is necessary.

Do you make vent flashings not shown on the catalog pages?

Yes, we welcome custom orders. Please contact us directly with your request.

Where can I buy F.J. Moore vent flashings locally ?

Please refer to our Where To Buy page for a list of some of the companies that sell our products. Call ahead to see if the items you want are in stock. Business’s offering our vent flashings, over the counter, are primarily located in the 5 state upper Midwest area (MN, WI, IA, ND, SD). We are constantly working towards national distribution. Contractors and wholesalers – call us direct at 1-800-658-2331

What is the CVV Code on a Credit Card ?

Card Verification Value (CVV) is the authentication code procedure used by credit card companies to fight fraudulent internet transactions. The cardholder enters the CVV number at the time of the order to verify the card is on hand, instead of actually presenting the card in person. The CVV code is three or four numbers used to validate the information embossed on the card, but not part of the card number itself. The back of Visa and MasterCards contain the 16 digit account number followed by the CVV/CVC code. Some banks only show the last four digits of the account number followed by the code. For your protection we require the 3 or 4 digit code on the back of your credit card. Your online ordering information is protected by Secure Socket Layer (SSL) technology certified by a digital certificate. Please see the SSL discussion in our Privacy Notice, left hand column of our Catalog pages.


F.J. Moore Manufacturing
500 Washington Street West
Cannon Falls, Minnesota 55009

(800) 658-2331
Fax (507) 263-4439