New drain holes

Arthur C · 09-17-2009, 12:17 PM

I have my flat roof redone recently. The new drain holes I have now are the round holes at the side wall jointed by a pipe down to the drain pipes outside of the house. The roofers told me these drain holes are better than the old ones i used to have: a square hole and box container inside drain the water down to the drain pipe. I like to know others' opinions. Thank you.

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**Scott Patterson** · 09-17-2009, 12:24 PM

Originally Posted by Arthur C

I have my flat roof redone recently. The new drain holes I have now are the round holes at the side wall jointed by a pipe down to the drain pipes outside of the house. The roofers told me these drain holes are better than the old ones i used to have: a square hole and box container inside drain the water down to the drain pipe. I like to know others' opinions. Thank you.

I have never seen roof drains like that. It looks like they have no flashing around the hole/pipe and that it has been sealed with roofing tax. I can see them becoming clogged easily and allowing water to pool.

The old type drain that you described is a time proven type of roof drain. They work and can handle a great deal of water. With the drain that you have I can not see them handling a great deal of water.

I can see other problems with the roof in the pictures.

It might be worth your time and money to invest in an inspection by a third party home inspector who is familiar with flat roofs.

**Rick Hurst** · 09-17-2009, 12:49 PM

I guess your dad never pulled you aside as a child and had the father / son talk about buying a home with a flat roof.

rick

**Jerry Peck** · 09-17-2009, 01:07 PM

If your code is like the widely accepted IRC down here in the states, those drains are:
- 1) too small
- 2) too high
- 3) no overflow drains

(underlining and bold are mine)
- R903.4 Roof drainage. Unless roofs are sloped to drain over roof edges, roof drains shall be installed at each low point of the roof. Where required for roof drainage, scuppers shall be placed level with the roof surface in a wall or parapet. The scupper shall be located as determined by the roof slope and contributing roof area.
- - R903.4.1 Overflow drains and scuppers. Where roof drains are required, overflow drains having the same size as the roof drains shall be installed with the inlet flow line located 2 inches (51 mm) above the low point of the roof, or overflow scuppers having three times the size of the roof drains and having a minimum opening height of 4 inches (102 mm) shall be installed in the adjacent parapet walls with the inlet flow located 2 inches (51 mm) above the low point of the roof served. The installation and sizing of overflow drains, leaders and conductors shall comply with the International Plumbing Code.
- - - Overflow drains shall discharge to an approved location and shall not be connected to roof drain lines.

From the IPC.
- 1101.7 Roof design. Roofs shall be designed for the maximum possible depth of water that will pond thereon as determined by the relative levels of roof deck and overflow weirs, scuppers, edges or serviceable drains in combination with the deflected structural elements. In determining the maximum possible depth of water, all primary roof drainage means shall be assumed to be blocked.

- 1107.1 Secondary drainage required. Secondary (emergency) roof drains or scuppers shall be provided where the roof perimeter construction extends above the roof in such a manner that water will be entrapped if the primary drains allow buildup for any reason.
-1107.2 Separate systems required. Secondary roof drain systems shall have the end point of discharge separate from the primary system. Discharge shall be above grade, in a location that would normally be observed by the building occupants or maintenance personnel.
- 1107.3 Sizing of secondary drains. Secondary (emergency) roof drain systems shall be sized in accordance with Section 1106 based on the rainfall rate for which the primary system is sized in Tables 1106.2, 1106.3 and 1106.6. Scuppers shall be sized to prevent the depth of ponding water from exceeding that for which the roof was designed as determined by Section 1101.7. Scuppers shall not have an opening dimension of less than 4 inches (102 mm). The flow through the primary system shall not be considered when sizing the secondary roof drain system.

Note that those holes through the walls are "scuppers", with a minimum dimension of 4 inches.

Section 1106 for sizing of the drains does not address BC, however, the northern part of the states nearest BC is the state of Washington and would require a 3" horizontal pipe and opening (a 3" pipe is about 3-1/2" in diameter) for up to 3,288 sq ft of roof area at 1/8" per foot slope; or for up to 4,640 sq ft roof area at 1/4" per foot roof slope.

Not that this is superseded by the 4" minimum dimension for scuppers.

**Markus Keller** · 09-17-2009, 06:24 PM

I would have to say the roofer is full of BS. Those have to be some of the worst drain holes I've ever seen. As Scott mentioned, there do not appear to be any control joints or term bars used on those holes beyond a bunch of 'goop'. Holes are exactly what you have, not drains. Scuppers or Zurn drains are not cheap, at least not around here. Did you go with the lowest bid?
It also looks like you'll get 1-2" of water pooling before it goes out the drain.
I would guess you'll see signs of leaks after the 1st winter.
Beyond that, the seams do not look detailed very well. Also, is that a framed or brick parapet wall? Could they have used any fewer screws to fasten the metal cladding? Looks to be a screw about every 4'+. With that few screws I would be worried about panels detaching in the mid term.
Can't tell for sure but it looks like it might be a rock impregnated material, which to the best of my knowledge does not get coated. If it isn't, and is more of a standard A or B grade bitumen type you should check warranty info. Most modified roll roofing sold around here requires coating for warranty to stay in effect.
Good luck