| Author | Message | ||
     Anonymous |
We are restoring the roof of 100-year-old house. The house is massive and has a huge slate roof to go with it – the slates are tied to intermittent steel angles, the flashing etc. is copper. The slate is in good condition but the copper soffits in particular are terrible, apparently due to ice damns. Our architect insists that, to stop damage from ice damns (we are in Minnesota) we remove the bottom 6 feet of slate at the eaves, where the eaves curl up, and hang plywood between the steel angles, and put on ice and water shield. This is over an area of the soffits we would never know it was leaking until to late. Should we use ice & watershield in this localized area where the damns love to build up, and in our sever climate? We’re concerned about adding these new materials to a system that worked fine for 90 years (the last ten haven’t been pretty). Everybody else we talk to says we are Ludites to resist the miracle that is ice and watershield and are putting our roof at risk…. | ||
| admin |
Ice and water shield is not the answer. It's a short term solution that architects and roofers insist upon because that's all they can come up with. It sounds to me like you have curved eaves and that ice and snow are building up on them in the winter because of the change in slope. I'm not sure I understand the situation entirely -- are you saying that there is no wood under the slate at all? That the slate is wired to metal framing? You may want to consider increasing your head lap at your eaves, which would require taking the slates off and putting them back on with an extra row of slate added. You could also consider installing a strip of copper flashing between each course of slates in the troublesome area (you may even be able to do this without taking off the slate or increasing the headlap and still solve the problem). The use of strips of sheet metal flashing between courses of slate is a common technique used in rounded slated valleys, eyebrow dormers, and other curved areas of slate roofs which can be otherwise hard to keep waterproof, and it's a lot more permanent that the plywood/IWS underlayment approach. | ||
| Anonymous |
We do have curved eaves and the roof structure is composed of steel I beam "rafters" and steel angle purloins. The slate is wired directly to the steel angles with no sheathing at all. The slates have mortar applied to their backs where they are exposed inside the attic. There is some crumbling of mortar at the back side, but only intermittent. The real problems exist in the eaves - and I'm not sure if the slates have mortar there. I have since been informed that the ice dams do the most damage when they slide off the roof and crash into the gutters, bending them out of shape, creating gaps in the flashing and a pathway for water into the eaves. With this new information - my logic tells me they are going after the wrong problem? How do we stop the ice dams from crashing into the gutters? Can snow guards and heat tape solve the problem? The architects are also trying to figure out how to insulate the roof, but they are tripping all over themselves - the roof is incredible complex. Their latest solution is to spray insulation right onto the slate. This also sounds bad to me – they seemed to have forgotten the vapor barrier? Also when you say the ice and water shield solution is “short term” – does it crack? Or deform? What happens to it in twenty years? | ||
| Walter Musson |
Your problems sound complex due to the roofs peculiar constuction techniques.The slide of snow and ice you say are responsible for the gutters being deformed and leakage thus occuring.Are the gutters built into the fascia, soffit constuction or are they free standing?How does the water get into these overhangs?The top edge of the gutters should be below the plane of the roof so cascading snow will slide over the top of them.Yes you could affix snow guards,but without sheathing you're limited to ones that are secured to the slates themselves.This is not the ideal means of attachment.Alpine Snow Guards sells this style as well as Zaleski Snow Guards.Even though insulating the undersides of the slates is not ideal,the new style foams such as CorBond do not need the tradional vapor barriers like fiberglass requires.Future repair work on the roof would become more involved,but it might be an acceptable alternative.You might need to consider the use of some extra sheet copper in those areas that cause the most concern for ice back up. | ||
| admin |
It seems that snow guards (installed above the problem area) would certainly be a consideration in helping to alleviate the gutter damage. Also, regarding insulation, can the roof be left uninsulated and the ceiling be insulated instead? Walter's suggestion to consider installing a copper apron or something of that nature along the eaves might be another good possibility for solving the problems. | ||
| vfrcomp |
Joe, I am about to install a new slate roof over brand new 1" rough sawn lumber and slate on a residence. I went to get the permit and the inspector told me it was a requirement for their township to use I/W sheild on all eaves. Even after I explained the reason why I prohibit its use he still said that I will use it to comply with the ordinance. I got my necessary forms and told him I would be back. I want to find out how to get around this issue and if anyone else has ever heard of such a idiotic rule. Why would I install a 100-year + roof with I/W shield that only carries a 30-year warranty anyway?? It was perfectly clear that after 1 minute of talking to the inspector he has no knowledge of slate roofs in the least. | ||
| admin |
The International Building Code of 2000 states that in areas where the average daily temperature is 25 degrees Fahrenheit or less, a double layer of felt cemented together or a layer of self-adhesive ice shield are required at the eaves. This is, of course, rather stupid, due to the short-lived characteristic of the underlayment in relation to the slate roof. The roof should be fortified at the eaves by increasing the slate headlap if ice damming is likely (which it won't be if the roof is properly insulated). Nevertheless, the point is that the codes should be examined by the builder and not accepted as interpreted by the inspector. Two layers of felt with some roof cement in between is better than buying the self adhesive, granular material, which is slippery and dangerous on a steep roof, if you have to pacify an inspector. Also, do the codes there specify any degree/days? Maybe your locality doesn't have that condition. Have the inspector show you the code as it is written in order to see what wiggle room you have. Joe Jenkins | ||
| admin |
PS: Are you sure you need a permit for this roof installation? | ||
| vfrcomp |
yes it is required by the township for all roof replacement. This job involves removal of shakes, 2-layer asphalt and lath. Install new 1" boards and slate. I told the homeowners (I/W shield) and they completely trust the proven installation methods for slate so with any luck it the final decision might lie with them. They agread with me and also said that inspectors should treat each job for what it is and not what everyone else is doing. | ||
| vfrcomp |
to show it in writing sounds to be the best solution. I have not run into this problem in any other township in this area. The roof is insulated and it is a 9/12. I do not see the ice damming being a problem. I get the feeling that the inspector is both throwing his weight around and has virtually no knowledge of slate roofs. Thanks. |
