| Author | Message | ||
     Benjamin (Benjamin) New member Username: Benjamin Post Number: 8 Registered: 01-2013 |
The water that runs off of cedar dissolves coppers protective patina. This action drastically reduces it's life span. Would be better off with PAC clad ,kynar. Iron oxide behaves in a similar fashion. Oh, I almost forgot to mention that felt is not a roofing material. | ||
| Cpaulin (Cpaulin) Member Username: Cpaulin Post Number: 25 Registered: 08-2006 |
Good grief.. | ||
| Steveb (Steveb) New member Username: Steveb Post Number: 7 Registered: 09-2012 |
Yeah Joe, I'd seen that discussion. Good idea to increase the head lap. Another thing you might want try is to do what we do when we lay shakes and that is to install an interlayment of 30# twice the weather exposure up slope..or even with that same head lap. We use 18" strips by cutting the rolls in half with a wormdrive, then its woven into either the 18" or 24" shakes, extending the headlap on two levels. It could even be more if you were to keep the rolls at 36 inches. There would be some extra cost and labor but the beauty is that the felt acts as out lines. We simply adjust the whole facet like a story pole so we hit the ridge. I've done many roofs with felts set in cement. That was the norm in New England when I learned the trade in the 70s. Canadians also have been doing this for as long as I remember. The only difference is we kept going up slope until we passed the warm line by dropping each row of felt to a 17" exposure...double coverage fashion. The deck was still clean enough to get up on for installation. Those felt will last a long long time. When we pull off the shakes roofs most are between 30 to 50 years old and the felt interlay looks like it was put on yesterday, because it is buried so far up inside the roof system. The other issue of course is the batten under the undereave. Personally I'd put something under it with spacing like under barrel tile and then keep the waterproofing on the top level. I know you have your own copper profile that you sometimes use to get the cant on the slate right..that's a good design. Some .060 or even .045 EPDM rubber membrane might accomplish the same thing. You'd have a grommet anywhere you drove a nail. Neither the rubber or the cemented felt are glued to the deck so it can be removed by anyone down the road and neither one is going to breath so its a toss up. I doubt the rubber would deteriorate in 100 years if the sun doesn't see it. You could partially glue the rubber just to hold it there I suppose. I included a couple shots to show you what I'm talking about.   | ||
| Steveb (Steveb) New member Username: Steveb Post Number: 6 Registered: 09-2012 |
Same up here. First period colonial which was first thatched and that didn't work so they switched over to local shingles cut with a horse and spokeshave. Then came the Federal and Greek Revival periods...again wood, but not necessarily cedar...probably not. Finally the Victorian period and these house are still mostly slate around here. Some of them have been trashed of course, but most are Monsons so they are still fine. You are right in that the underlayments which 9 times of 10 around here are red rosin paper...no felt unless they had been worked on during the interim over the last 50 years, and many have. The rosin is nothing but dust now, but my guess is these roofs still had their share of leaks behind the tower sections. Again this is a heat issue and those roofs were not heated to the extent they are today so there wouldn't have been the degree of ice we have now. Most of these houses now are condos for the white collars who got sick of Boston. Insulation was blown in, clapboards replaced and efficient heating systems along with ac ducts on every level. All this changes the way these houses run. Now the barns are a different story and we have many. We never see copper fasteners because nobody used them but they did have real hot dipped nails and that's what I see most of. Also there are a number that have small headed nails of the same zinc bath. The heads seem to be around 5 to 7mm. We're losing a lot of nail heads, especially where the roofs sag away from the chimneys. The stone is fine but eventually many will need to be taken apart and put back down again. Some can afford it (the churches) but most families can't. So here comes the 20 year cycle till the end of time. The Vermont sea greens don't fair as well near the ocean but the unfading purple, mottled purple and unfading greens look very good, and of course red from NY. I'm not sure why but we got some seriously bad Pennsylvania ribbon slate sent up here and its like soft mica now. This is mostly found on the prep schools. I'll check out the link but I've probably seen it already. | ||
| Joe (Joe) Moderator Username: Joe Post Number: 726 Registered: 07-2006 |
The average roof we work on is about 100 years old. No matter what underlayment was used at installation, it has not been effective for decades. That's why we don't rely on underlayment when doing new installations. We now install eaves with 5 inches of headlap on slate roofs and we do install a beefed up underlayment, but don't know how long it will last. Video: http://www.youtube.com/watch?v=pIh-Q6JwMbQ&feature=share&list=PLCAFA8B61D36361D8 | ||
| Steveb (Steveb) New member Username: Steveb Post Number: 5 Registered: 09-2012 |
That's a good way to take care of it. A curb and some good soldered hems can help immensely. One thing about slate which can make it fair better than other roof materials is the fact it is smooth, and a lot more likely to relieve itself of the ice and debris both on top and underneath. With cedar shakes this is not the case so we have to be a lot more careful with the design aspects. All the math and individual specifications are all well and good but you can build two identical houses side by side and one will have issues and the other will not; this is usually because of the individual hands on every corner but sometimes its the luck of the draw too. Where I live the wind is so fierce that we often can't get away with minimum or even the more accepted requirements. I've been witness to water penetrating 3" stucco walls, beach sand findings its way through cracks, crevices and venting and filling livings rooms up with a foot of sand. It can be brutal here; add a snow storm to that and the phone rings off the hook. Certain areas get it every single time; I can almost guess the street numbers at this point. Last year in Newburyport, Mass the bottom 3 or 4 rows of Monson slate and in some cases the entire soffit box were torn right off the houses that faced the ocean; I've never been witness to anything like that in my life as a roofer....street after street covered with copper hip cap, pieces of slate and piles of asphalt everywhere. Of course this was a straight on 90 mph hit! Sometimes I wish I were inland. We have to protect ourselves and stand behind our warranties both...there's no getting around that one. Beefed up underlayment secured with cap nails under roofs, walls and cornice areas will remain the norm here I'm afraid. | ||
| Joe (Joe) Moderator Username: Joe Post Number: 724 Registered: 07-2006 |
I had ice damming 6 feet up one of my 4:12 roofs last year (it's on my own house - upper steeper roofs drain onto this low sloped roof). The slates didn't leak (we had already installed a copper snow apron), but a bottom corner flashing on a skylight did, six feet up the roof. I'm going to reslate the roof with extra headlap and replace the skylights with raised curbs and soldered flashings. | ||
| Steveb (Steveb) New member Username: Steveb Post Number: 4 Registered: 09-2012 |
Hi Joe, I'm Steve Balsavage dba Precision Shingling Co. out of South Hampton, NH. Its a pleasure to meet you, even if its electronically. I also live in a house now that's about 40 years old and it was set up the same way. I bought it about 5 years ago with a leaking roof which gave me some bargaining power. Being primarily a red cedar shingle and shake roofer I put up CCA treated red cedar shakes in a Dutch Weave style. a lot of the pitches are slow on this building, as low as 3/12 so I had to beef up the deck. Its plywood, not boards, so there was major delamination involved. Prior to this I lived in a 300 year old colonial with the only insulation being corncobs and pine needles. That's what they did back then..scrape up the forest floor and stuff it in. I had major problems on the rear of that place so I finally broke down and threw up some panels. the problem went away. The winter of two years ago was springing leaks everywhere, including the old slate homes and institutional buildings. I had one customer who had a cake of ice that just sat at the end of a lead coated valley pans I put in a few years back. The ice melt jumped the internal hem and took down a wall. I would have wished there was a good underlayment under there. At the time I just stepped back the slate, put the pans in and reassembled the slate. I see a lot of guys around here covering the whole house with ice and water. On new work along the ocean this is the norm..roofs and walls just like a Christmas package. It does bother me to see guys covering the older board homes with Grace because they are just going to rot the place top down. All I can do is control my own work. One item I've seen mentioned a lot in here the discussion of treating the first 3 feet of the roof, whether it be the addition of standing seam copper panels, smash lock or beefed up underlayments. There's a little more to it than that; there's no magic number when it comes to ice dams. What ever is used as a treatment should extend up slope to a point 2 lf. inside the warm line of the building. If you were to draw an imaginary line straight up from the interior wall you'd hit the back of the frozen ice; from that point forward you'll get ponding which is why I suggest the extra couple feet covered above that. A little extra wouldn't hurt either. What should happen is the warmed up ponding water should separate the ice from the roof eventually helped along by the sun. This is one of the reasons why the folks in Vermont cover there houses with tin panels (or seagreen slate). Those buildings are all sieves. We don't fair much better down here. That's my 2 1/2 cents anyway. I enjoyed your book, especially the pictures and history of the mines. | ||
| Joe (Joe) Moderator Username: Joe Post Number: 721 Registered: 07-2006 |
When I built my house 33 years ago, I designed it so that all of the roof spaces are used as bedrooms. I stuffed fiberglass between the rafters, installed a plastic vapor barrier interior to the insulation, sheathed the roof with rough-sawn boards, 1" thick (mixed hardwoods), covered that with 30 lb.felt, then slated over it. This is similar to the traditional old-fashioned roof designs except for the insulation and the vapor barrier (the vapor barrier is critical). I added no other ventilation methods (no vented ridge or soffit vents). I have never had a problem with this design. The roof breathes. There is no plywood or peel and stick to prevent air transpiration through the sheathing boards and out. The vapor barrier (heavy mil plastic) prevents moisture from entering the roof from the interior warm air. | ||
| Steveb (Steveb) New member Username: Steveb Post Number: 1 Registered: 09-2012 |
Hello All, I'm new to this forum; I've read a few comments/questions here and I'm especially interested in both Peter's and Philadelphia Architect's questions/comments concerning ventilation. I'd address your comments directly but I'm not sure how to do that here. In general, being a roofer/consultant for 30+ years and dealing with severe weather conditions on the coast north of Boston, I would never consider using the smart vent or anything like it in the field of the roof. Add a gutter to that and you are really asking for it. It wouldn't matter if the roof were slate or an entirely different material. There are ways to cheat air into cavities and I would consider most of them to be jury rigs. Its really just a question of mechanics. One of you mentioned putting bat insulation up against roof boards and no, you don't want to do that. These attics were part of the little balance these houses had back at a time when furnaces weren't the norm. I'm guessing these houses are at least that old. So if the top floor under the slates is going to be turned into a living space then there has to be some serious thought put into it. Insulation is number one when a furnace is involved and ventilation under the roof would fall under that by a good amount. You also have to consider what exactly you are venting. A ridge vent without a soffit vent will work in reverse and siphon moisture in from the outside. I realize you see a lot of buildings with just a ridge vent or pan vents mounted in the field minus the soffits down below but they aren't relieving the house of moisture; the opposite would be true. Instead there is more of a vacuum going on. You need a 60/40 ratio minimum with the soffit being that first number to push air under the sheathing. The "proper vent" styrofoam chutes that so many use in a cathedral setup don't work well either because you aren't relieving the whole bay, rafter to rafter. In essence you want that roof to operate as if it were detached from the building...which is tough to do. If you can accomplish that then there will be no rot cycle and no ice damming. The temperature would be a constant on all surfaces. As for the soffits, there are some tricks. A lot of 300 year old colonials have had their sheathing boards lopped off. This was commonly done a few hundred years back. Almost all of them looked like barns originally with vertical boards hanging off and no real facia at all. Technically they WERE barns...barns with a chimney. A house should have provisions for air exchange but I still see some pretty dysfunctional designs around, even being built today. One fix is to install an extended drip edge and figure out a way to cut slots up high enough into the wall to get under the roof deck; I've even had to add supports to the ends of the rafters and cut a mouth into the ends of the boards to sneak air in there. The real answer is usually to put on a double roof deck which I've been involved with many times, but with slate you are adding to that already heavy 7 or 8 pounds per foot dead load, not to mention the snow load if there is one. In this day and age I would certainly stay with some sort of ISO/closed cell insulation, ridgid or blown in because there wouldn't be an R at all, bats are not efficient and can only hold the heat back for so long. I also don't like the idea of blowing the foam so its attached to the underside of the sheathing..especially a good native lumber sheathing. If I saw a few pictures I might be able to help one or both of you. I realize I'm just touching on some general points here for the time being. Anyone remember Hicks vent?? :-) Yup, all these new ideas work great until we discover they don't work at all. | ||
| Tim_dittmar (Tim_dittmar) Senior Member Username: Tim_dittmar Post Number: 52 Registered: 05-2008 |
Coachmike- you've browsed the generalized information, say? To be specific requires a lot of interaction and probably on site... One picture is worth a thousand... I'm in NW CT right now(Mom's house) with plans to go back to NC in just a few days. Can discuss with you plans to see your problem as I pass by- check my cred's at slate roof consultant site(SRCA) and call 910 540-5294 if you wish to pursue this idea at some length- alt contact is slateconsultant@yahoo.com | ||
| Coachmike (Coachmike) New member Username: Coachmike Post Number: 1 Registered: 07-2009 |
I'm a homeowner of a 189 y.o. stone farmhouse in northeast Pennsylvania. My slate roof appears to have been nailed to lathe strips of some kind 3/4" off of tongue and groove underlayment. The prior homeowner put 6" fiberglass roll insulation tight in between the rafters of the attic flush against the inside of the tongue and groove. The insulation deteriorated so badly I had to remove it, uncovering a lot of moisture stains and traces of mildew. I want to continue to use the attic as living space but don't know how to insulate without creating further moisture damage to the tongue and groove and potentially reducing the life of the slate, which has begun to flake. I see comments about air barriers and moisture barriers, but am unclear about them. If there is no ridge vent and no soffit venting, where is the air circulating from (do I leave a space near the floor?) and where does it go? I'm not confident with the contractors I've consulted in the area. I'm getting conflicting advise, and this 7 yr. renovation has become such a financial drain because of incompetent contractors. I want to redo the attic right the first time. Any clarification of insulating the attic ceiling under a slate roof so the attic can be usable space will be very much appreciated. | ||
| Matt (Matt) New member Username: Matt Post Number: 1 Registered: 05-2009 |
Hi, I was wondering if I could get a few names of peter low slate underlay products. We use a product called Slatex, but I was wondering what other products are available. Thanks Matt | ||
| philadelphia architect |
I am an architect working on a building which has a 100 year-old slate roof in great shape. I am trying to figure out how to ventilate an existng slate roof. The Attic under the roof will become a mechanical space which requires that the roof insulation be placed in the rafters instead of at the floor of the attic (the mechnical space must be nominally heated). The existing ridge cap is copper with decorative balls at the ends. I was thinking of lifting it and installing a new copper ventilating cap. The 1x3 T&G deck would be cut to make a slot on each side of the ridge beam. There is no existing eave venting and no easy opportunity to add it, as the building has concealed gutters and an elaborate wood fascia. Any suggestions? | ||
| Peter |
Hi, Have you considered using an insulation board fixed to the underside of the rafters, that would maintain the heat inside the attic space while at the same time preventing condensation on the back of the roof covering. I don't know if you have access to Glidevale vents (or similar) they can be fitted in place of the slate, providing a through flow of ventilation above the insulation board between the rafters. You could install more vents at the ridge or install the new copper vented ridge as you described. Depending on the amount of space you have under the rafters it may be possible to cross lath the rafters inside before fitting the insulation. That would allow a better dispersion of the air and could mean less vents are required. Kind Regards, Peter Crawley, M.I.o.R. www.crawleyroofing.com | ||
| philadelphia architect |
Thanks very much for the ideas. I looked at the Glidevale vents and at the DCI SmartVent (http://www.dciproducts.com/html/smartvent_other.htm). If the roofing contractor can install the Smartvent under the existing first row of shingles, it will be completely hidden - a great solution. Do you think a roofer can retroactively install this product under old slates? Has anyone had experience with this product? | ||
| Barry Smith |
A course or two (or 3) would have to be removed and then reinstalled with longer nails over the smart vent material. | ||
| Peter |
I have removed slates and installed Glidevale vents with very little if any difficulty. I have no experience with Smartvent it appears to have been designed for shingles as opposed to slates but I only took a quick look at their site. It would be possible to manufacture a vent similar to the Glidevale on site using copper and some fine mesh to prevent insects getting into the roof space. Depending on the height of the building and the type of gutters you could most likely fit them in the second course of slates without them being seen from the ground. Kind Regards, Peter Crawley, M.I.o.R. www.crawleyroofing.com | ||
| slateworks |
Hi, Yes the Smart vent can be installed under the Roof slate- remove 1 0r 2 rows of slate,Plus your starter course,cut your slot for ventilation (following manufactures guidelines) I would install either Ice & Water Shield or 30# felt paper over the smart vent, install paper to the bottom edge of vent and up under the exposed roof slate as far as possible,If at all possible try to install the felt under the existing felt that's if the felt is in good condition?Re-install roof slate with slate hooks or bib flashings. You could also use this vent at the peak(refer to manufactures reference) you could lift existing copper ridge and the last row of slate, cut your peak for ventilation,Install vent.Re-install slate followed by copper ridge(caulk old nail holes).You will have to use slightly longer nails at peak ect.,drill holes thru slate and copper ridge as needed to re-fasten,also while the peak is cut open mark where the rafters are on the slate slightly below the bottom edge of copper ridge, set your ridge iron then drill holes thru the copper ridge and slate at these marks,install your nails into the rafter,this really helps to keeps nails from lifting out,almost every slate roof we repair that has a ridge iron you can count on repairing nails that have worked loose ... before you remove anything number your slate and copper ridge so you can re-install them in the same order. For the insulation you can install the styrofoam panels that are made to fit in the rafter space to allow airflow,then the proper thickness of insulation followed by your ceiling material.Hope this helps. | ||
| JIlse |
I'm considering the following roof for a timber frame. 2"x8" Car siding as the stuctural deck over the timber purlins, then 10"EPS insulation (fully sealed at joints), then plywood or OSB nail surface (screwed through the EPS to the deck), then normal underlayment (to keep it dry during slate installation), then slate. I don't see a need for ventilation beneath the slate in this case because of the tight EPS layer. Am I missing something regarding the need for ventilation? An alternate, which could be used if ventilation is truly necessary is to install vertical runners then normal horizontal battens but if these aren't necessary it makes the job a lot easier. thanks for the great site by the way!! | ||
| Joe Jenkins |
We try to avoid nailing slate to either plywood or OSB or anything that's not solid wood with a tried and proven longevity. If the slate is going to last a century or two, the wood it's nailed to has to have a suitable reputation for longevity. The last slate we nailed to a timber frame with SIPs we nailed to horizontal 1x4s screwed to the OSB deck over 30 lb felt. We left gaps at the ends of the 1x4s in case water ever penetrated the slate surface (such as from a tree branch falling on the roof and breaking a hole in the slate during a rain storm) so the water would drain out and not pool under the slate. | ||
| JIlse |
Joe, thanks for the advice. I think I will combine the very old and time tested (and Joe recommended)slate/underlayment/green plank deck with the new superinsulated roof substructure consisting of 10" of EPS filled over 2x6 car siding supported by the timberframe purlins. 2x4's will be run vertically over the EPS core and screwed through to the car siding. This will provide a small gap for ventilation as the plank deck dries. I'll lay a sheet of vapor permiable bldg wrap over the EPS and under the 2x4's to keep it dry during construction and a poly vapor barrier between the EPS and the car siding with EPS joints foamed. This is not a SIP roof as there is no plywood or OSB used, the structure comes from the car siding over purlins. | ||
| Peter |
I am currently fitting out my attic to be a finished space. For the last 80 years the slate roof above was sitting on wood slats and 2x6 framing with nothing below. I never noticed any moisture problems prior to performing any work in the attic. The ventilation was great as the old windows in the attic leaked and I was able to see daylight thru the eaves. Last winter 03/04 I insulated with 6" thick batt insulation that fit tight w/in the 2x6 and then screwed 5/8" sheetrock onto the 2x6. The top foot at the ridge I insulated, but left the sheetrock off as I have a light cove their. Recently when looking at the light cove I noticed the paper section of the insulation covered black with mold. I reached in & felt the wood slats and they were damp. No where else did I notice a moisture problem, but the sheetrock may be hiding it. The ridge is tarred over by the prior owner. Would you suspect that the ridge tarring failed and has to be corrected or did I unfortunately trap moisture below the slate by placing the insulation tight to the wood slats? If the 2nd (or both) situations must be corrected, how would you ventilate but properly insulate the attic? | ||
| Peter |
Hi Peter, The building regulations (Ireland) are very clear on this detail and I think it may apply to the US as it makes sense. There must be a space of two inches between the insulation and the roof covering, in our case the roof covering is deemed to start at the underlay unless the roof is counter battoned as that would keep the slate at least two inches away from the underlay. What may be happening in your roof is the insulation is tight to the slates preventing a through flow of air above the insulation. While insulation does keep the heat in it will be warmer than the outside of the roof, this can lead to condensation within the insulation. You appear to have insulated too tight to the roof covering using 6" insulation in between 6" timbers. I am not sure if there is a cheap way of correcting this, while you can install vent slates, I am not sure you will be able to create enough air flow to correct the points where the insulation actually touches the roof covering. Perhaps if you post your location one of the local contractors can advise you. Kind Regards, Peter Crawley, M.I.o.R. www.crawleyroofing.com | ||
| admin |
You should have installed a "vapor barrier" (i.e. sheet of heavy mill plastic) interior to the insulation, under the dry wall. The vapor barrier must be wrapped around the corners and up under the ridge area, etc., so no air can penetrate through and beyond the insulation. Otherwise, you will have warm air infiltrating beyond your insulation and hitting the cold roof, then condensing moisture. | ||
| brendan |
I have a similar issue to Peter. I have a large open attic space above part of the second floor of my house in Maryland. The roof is slate installed in 1926. The roof of this attic space was insulated with very old fiberboard and blown insulation that had collapsed and fallen apart here and there. I have insulated the floor of this space and closed it with 3/4 plywood and am wondering what to do about the roof. Should I leave it uninsulated, or should I put in baffles and insulate up to the baffles leaving them open at the floor and ridge so some air could travel between floor and ridge between the insulation and the roof deck. There are no soffits so I can't install vents and there is no ridge vent. There is a little window in the gable and this could be left open or closed as needed. It looks like there was no issue over the last 50 years with moisture even though there was this blown insulation against the roof deck. Any advice, or better yet, any recommendations about literature I can read about insulating old roofs? Thanks | ||
| AJose |
I am an architect and using a vented nailable insulation panel on top of an old hardwood sheathing (4.5cm x 15cm). The current space has no insulation and therefore achieving with the panel. I will apply a vapor barrier directly to the sheathing, the panel provides 2.5cm vent space. I am looking for vents appropriate to the installation as other were in this post. At the ridge I am planning on using a typical roll-type ridge vent material and covering it with a cleated copper ridge cap (25cm wide total). I am wondering if the Smartvent type product is really a good idea at a gutter in colder climates. I am in the US and would be concerned about ice-damming with that product. Can anyone address this? I think I am leaning toward using the Glidevale slate type vents. However my concern there is that being made out of poly propelene, the life-span will be less than slate? One last question, and a good one that someone brought up is that the nailable panels I am using are sheathed with plywood. Thus the slates will be installed to plywood. I will pose this question to a manufacturer as well. Note however that the plywood will be an exterior grade treated plywood. I am wondering if I should be greatly concerned or not. All good questions and very thankful for finding this thread! Andrew | ||
| admin |
We installed a slate roof over SIP's last year, but screwed horizontal 1x4's of rough sawn hemlock to the felted, particle board roof deck, then nailed our slates to those. | ||
| Larry Sutherland |
I live in Southwestern Ontario Canada. We are turning the attic into a bedroom for our son. I've put up a styrofoam product - durovent - that allows an inch or so of space between it and the attic rafters to allow air flow. I am putting up batt insulation over the styrofoam but I haven't found any information on which would be better, the 4" that would fit exactly between the rafters as they are or if I should put in 6" which would require adding an extention on the rafter faces so the 6" will fit properly. I will be putting plastic insulation barrier over the insulation in the roof as well as the floor and the knee walls I've added. What would you suggest for the insulation thickness of the rafters. I'd appreciate if you could email and let me know that you've answered so I know when to come back and check. Thanks. | ||
| admin |
6" is better in a roof than 4" - most of the heat of the building is lost out the roof. | ||
| Farkas Szilárd |
I would like to get some information about slate roof insulation prices in general in Ireland. I would be glad to get any info. | ||
| Peter |
Hi, There are many different types of slates used here, there are also a number of natural slates, some good some terrible. As our pricing system is different to the USA a square here refers to sq metre as opposed to 10'x10' in the US. A guide cost would be in the region of 150 euro per sqm supplied and fitted. There are many variables to take into consideration such as location, new roof or renewal, number of valleys, hips, chimneys height etc. Kind Regards, Peter Crawley, www.crawleyroofing.com | ||
| Farkas Szilárd |
Hi Peter, Do you mean outside insulation 'cause I'm asking about that. Regards, Sil | ||
| Bob Sullivan |
We are insulation contractors proposing to insulate a house located near The Greenbrier Hotel resort in the southern WV mountains. The house will have a slate roof over 10:12 pitched 2x10 16"o/c framing. The rafter lengths vary up to 30+ feet. I have two questions: 1)Should the framing not be 2x12 to carry the weight of slate? 2) We install an insulating technique that includes sprayed 1/2" to 1 1/4" thick polyurethane foam (thickness depending upon R-value desired) plus slightly compressed conventional glass fiber batts up to 12" thick (again thickness depends upon framing and R-value desired). My concern is that spraying a coat of polyurethane to the underside of the pitch roof, and directly to the underside of the slate itself, may have an adverse effect upon the long term durability of the slates. Thicknesses in this range of sprayed polyurethane are NOT perm rated. Are my concerned well founded or not? | ||
| admin |
What is the thickness of the slate? Is it a standard installation pattern? How long are the free spans on the 2x10 rafters? Can you install a baffle under the slates to prevent the foam from contacting the underside of the roof? | ||
| Bob Sullivan |
At this point the thickness of the slate is not known. Are there critical thicknesses? If so, what are they so we can advise the builder. We assume a "standard" or offset installation pattern. If not, we will come back for more advise. Spans are on the order of 24 feet from eave to ridge with intermediate support at the mid-point. Yes, baffles attached with staples to the wood roofing "strips" (is this correct terminology as opposed to plywood or OSB sheeting?)are possible. | ||
| Joe Jenkins |
The weight of the slate depends on the thickness. Standard thickness is 3/16" to 1/4", which will weigh 700 pounds to the square, approximately (maybe more, depending on the slate variety) when installed using a standard pattern. A 2x10 roof on 16" centers at 10:12 with 12' free spans on the rafters should have no trouble with a standard thickness slate roof installed in a standard pattern. The wood roof decking should be solid boards, not strips. A baffle (styrofoam?) between the rafters should keep the insulation off the underside of the boards and allow the roof adequate ventilation. | ||
| Laurie Farina |
Is there a way to determine the manufacturer of a particular roofing slate? Do they "mark" individual slates, or do you just take the contractor/supplier's word for it? And I realize this may not be the right board for this post, but you have referenced slates in previous postings, so thought I would start here. LOL | ||
| Joe Jenkins (Admin) |
The pallets are marked (or should be) with the source company's name. | ||
| Laurie Farina |
What if it is an installed product and is failing after installation is complete? Is this a "he said, she said" type of situation with regard to the owner believing it is a particular manufacturer and the manufacturer saying it isn't their product or is there a way to actually determine if the product is their's (using individual slates)? | ||
| admin |
That falls under one of the "top 10 mistakes made when installing new slate roofs" (http://www.traditionalroofing.com/TR4_mistakes.html) - lack of contract details. Your installation contract should state exactly what type of slates are to be used. If the manufacturer is saying it isn't their product, who did you ask (salesman, owner, quarrier, all of the above)? What kind of slate is it supposed to be? What does it look like? How is it failing? If the slate is falling apart, it may be one of the other "top 10 mistakes" (i.e. the slate was walked on during installation). If the problem is rust stains, then it's probably a low-grade Spanish slate (see http://www.jenkinsslate.com/thinkingabout.html). Joe Jenkins |
