BCAB #1026 - Roofing, Section 9.27
September 27, 1988
Re: Roofing, Section 9.27
With reference to your letter of July 27, 1988, regarding the application of Section 9.27. The roof in question consists of cedar shakes terminating in a back gutter formed behind the eaves fascia.
There is a general question of principle, which should be clarified before dealing with the specific questions raised. Article 184.108.40.206. of Section 9.27. states that "Roofs shall be protected with roofing, including flashing, installed to shed rain effectively and prevent water due to ice damming from entering the roof". As stated in an earlier appeal, we regard this as a performance requirement expected from the roof, and it does not necessitate every detail being included. The Code provisions merely indicate, in general terms, minimum steps that are considered necessary to achieve this performance, from a limited range of conventional materials. We would also emphasize that flashing is clearly a part of the roofing.
To deal with your specific questions:
- In the design under review we regard the roof as extending to, and including, the flashing shown over the eaves fascia. From this point water leaves the roof, usually to be collected by a separate eaves gutter. If the water is collected in a gutter formed within the roof, then water leaves the roof when it is discharged from the roof drain. A gutter formed within the roof is no different to a valley or other design feature, and the location is irrelevant. It may well be located behind the fascia as in this case, or at an intersection of different roof slopes well within the area of the roof. Thus the gutter in question clearly falls within the jurisdiction of the Code.
- We assume that this question relates to the choice of materials used to form the gutter, but would point out that there is no clear distinction between roofing and flashing. There is no reason why similar materials cannot be used for both purposes provided that the installation methods accommodate anything for a specific use, to provide the general performance requirement indicated earlier. We would assume the choice to remain with the designer, subject to approval of material and installation by the authority having jurisdiction. We note from the information submitted that the manufacturer of the gutter membrane states that it is incorrectly installed even for roofing. As indicated below, a gutter is a more severe condition.
- This question is partly answered above, but requires further elaboration. The Code provides minimum slopes for various types of roofing, in Table 9.27.3.A.; it further gives installation methods which it considers will ensure acceptable performance at these minimum slopes. There are no minimum slopes given for gutters, and this becomes a separate issue. Ideally every gutter should be laid to a fall, but this may not always be feasible, although a gutter should certainly not trap water. The Code is not specific on material selection for gutters formed within the area of a roof, and as these are locations which receive a concentrated discharge of water it must be assumed that they require a much higher standard than sloped roofs, both for materials and installation. It is not necessary for a shallow pitch gutter to be formed in metal, there is no reason why suitable membranes cannot be used, but the selection and method of installation must provide for the increased risk at such a location.
- This appears to be directed towards upgrading the gutter indicated on the sketch submitted. While it would undoubtedly be possible to bed sheet lead in a suitable asphaltic compound over the existing felts, there is a problem. The felts shown form both the gutter and flashing, which could be acceptable except that they already contravene the principle in Article 220.127.116.11. which requires that they extend up the roof slope for a distance not less than one and a half times the single exposure. For this the shingle reference means a rigid unit and would include shakes or tiles. If our opinion is of any assistance, we do not consider the height requirement to be critical in this specific instance, as the upper edge of the gutter membrane is shown as extending to a reasonable extent above the top of the fascia flashing, and the portion of the membrane located beneath the bottom shakes is protected from the action of weather. The installation of the sheet lead would, however, be critical.
- We consider the existing drain detail to be questionable in any event. It is unfortunate that the Code does not address electrolytic corrosion, but it should be reasonable for specialists to have some knowledge of such properties. There is already a good possibility for corrosion of the aluminum downpipe, immediately below the discharge of the copper drain. If the gutter is lined with lead the possibility would also exist for corrosion of the lead from the copper, but we regard the risk as low, certainly far less than that presently existing.
- Eave protection is required under the provisions of Subsection 9.27.5., and we are unable to ascertain from the details whether or not the installation complies with these requirements. There would seem to be a difference between what is referred to in the Code as "eave protection" and the term as used in your enclosures.
- Our difficulty with the eave protection is the impossibility of determining, from the details, whether it extends up the roof sufficiently to comply with Article 18.104.22.168. A bead of caulking as suggested would not change this position.
- The Code does not require eave protection at the hips, but again this seems to be a terminology misunderstanding.
- This question still appears to be directed at eave protection, but Article 22.214.171.124., as pointed out earlier, has much wider implications; a direct answer is therefore impossible.
J.C. Currie, Chairman