|Posted on Friday, January 12, 2001 - 05:04 pm: ||
My wife and I had our yr. 1903 home in Philadelphia re-roofed in new slate (so much was broken). Actually, the contractor had trouble finishing the job and then he caused a $250,000 casualty loss from starting a fire.
Anyway, we would like to ask questions that are related to dispute with this contractor, and their surety bonding company who guaranteed the roofing contract, concerning broken slate on the rear of our roof (they walked all over it).
Q1: As a percentage of total slates, what number of broken slates, or in any event ones considered needing replacement, should be considered normal and/or acceptable on a brand new slate roof?
Q2: As a percentage of total slates, what number of broken slates, or in any event ones considered needing replacement, might a roof face have before it might be considered to need re-roofing?
Q3: If a home owner had a smooth slate surface and entered into a contract for a slate roof replacement, wouldn't a prudent person reasonably expect a smooth slate surface instead of a textured one? Our contractor failed to grade the slate in order to save labor costs.
Q4: If the order was for 3/16ths" slate, knowing that slate is hand-cut and that each will be unique, what variance in thickness of slates should cause a competent slate roofer to reject too-thin or too-thick slates - if not hidden on dormer sides or other places where it would not matter?
Q5: What effect would it have if the roofer,
for sake of additional protection, had laid ice and storm shield under virtually all of the roof's slate?
Philip V. Hoad
|Posted on Saturday, January 13, 2001 - 02:51 pm: ||
To "Anonymous Residential",
Firstly let me state that this response is based upon not having actually viewed your slate roof, so there may be other circumstances and conditions that I am not aware of at this time.
1. Wastage allowed when ordering and installing a new slate roof is normally in the region of 5%. Wastage levels of 10% and higher are generally unacceptable and may be indicative of inferior stone. The accepted standard for roofing slate can be obtained from ASTM C406. Testing of roofing slate may also be performed in accordance with ASTM to establish quality levels. Three levels have been established within these standards - S1, S2 and S3.
2. The decision to replace an old slate roof is based upon many factors, including but not limited to the following;
- Age of the roof and condition of the deck and structure
- Condition of slate material and possible option of salvage of some of the existing material and subsequent relaying
- Condition of slate fasteners
- Condition of sheet metal flashings and associated complexity of the roof
3. The texture of roofing slate varies according to the quarry and colour of the material selected. Some colours from some quarries are much smoother than others and vice-versa.
4. Standard and good practice when installing a slate roof is to thoroughly grade and sort the roofing slate PRIOR to installation. This requires that the material be sorted and graded into three basic thicknesses - HEAVIES, MEDIUMS AND THINS. The heavies are used to the eave areas, mediums to the main body and thins towards the ridge or top of the roof. This practice is often not performed by roofing contractors in North America, but in Europe it is very much accepted practice by skilled and trained master slaters. This grading and sorting is very important to providing a sound and long term slate roof. The subsequent foot traffic on your newly installed slate roof which resulted in many broken slates was most probably because the slate was not properly graded and sorted by your roofing contractor !
5. Roofing slate is NOT gauged like flooring - and is available in thickness ranges, starting at 3/16" - 1/4", 1/4" - 3/8", 3/8" - 1/2" etc. Roofing slate is "split" from a block (usually by hand using a chisel and mallet) to provide the natural riven finish. Slate should be rejected prior to installation if it is broken, cracked or defective in some other way (such as pyrite inclusions or excessive irregularities on the surface). It should also NOT be laid if they have been "holed" incorrectly (ie. at the thick end of the slate, when they should always be holed at the thin end of the slate). If this is not done, then slates that are laid on a roof will not be correctly and properly supported by the ones underneath. This same principle will apply to incorrectly graded and sorted slate. There is no need to reject a thin slate unless the above applies OR it is obviously well below the prescribed thickness of 3/16" making it too "brittle" to use.
6. Slate roofing like many trades should only be performed by skilled, trained and certified personnel. All too often, this is not the case because clients and consultants always seem to decide based on the bottom line - PRICE, often to the exclusion of experience and training. A "contractor prequalification" can be applied to the tendering process which will ensure only suitably qualified contractors are able to submit bids.
7. The use of Ice and Watershield over an entire roof is often a poor excuse for poor quality workmanship and material. Furthermore, in many circumstances it may prevent the "building envelope" from functioning correctly. A properly installed slate roof does NOT require this material over it's entirety, although in areas of snow it is advisable to have it installed at eaves, valleys and other critical roof junctions and penetrations. However, sufficient roof slope and the correct slate headlap is required for the installation of roofing slate at all times.
|Posted on Monday, February 12, 2001 - 09:38 pm: ||
I am in the process of purchasing a home built in 1929 located in Sussex County, NJ. The slate roof is random with many sizes and thicknesses. Repair work has been done by the previous owner, but the roof needs work. From discussions with the previous roofing contractor and my own research (The Slate Roof Bible)I believe the slates are from various locations. Some are red, green, grey, etc. Thickness range from 3/16 to over 1". Widths are from 6" to over 2'. Quite a few slates are face nailed, have holes, or are broken.
Question: With such a variance in slate types and sizes, what would be a logical material purchase for repairs? I wish to purchase a few squares now.
|Posted on Wednesday, September 05, 2001 - 03:39 pm: ||
I have a House in lancaster county Pennsylvania with a old slate roof. The roof age is at least 100 years.It has minor rain leaks that can be repaired. The roof faces the direction that all the snow and thunderstorms and come from. The
heavy winds that are gusting 60 mps all winter
long drive the snow and rain into the attic, where
small piles of snow accumulate. No wind no problem! If I repair the roof with 30 pound felt
under the slate will this trap moisture and rot the roof or am I better off with the snow in the attic?
|Posted on Wednesday, September 05, 2001 - 05:27 pm: ||
You should be able to keep the snow out of your attic without having to install felt under your slate. Try to determine exactly where the snow is entering and then focus on repairing that spot or area only. I doubt that it's blowing under the slates - it's probably something that needs repaired (flashing, fascia, slates, etc., but not due to lack of felt).
|Posted on Wednesday, September 19, 2001 - 11:00 am: ||
We have a 1919 frame house with slate roof that had several leaks. The roof has three 25'-wide dormers with less pitch than the rest, thus ice can build up and fall from the dormer to the roof over the first floor. A local roofer repaired several areas of flashing defects and about 15 broken tiles with the few left over from original construction.
Where can I obtain more slate tiles? Our material appears to be grey/green rather than dark black, and is in the 3/16"-1/4" thickness range. We are located in southeastern Massachussetts, and so far have come up dry on suppliers.
Also, do you recommend installing ice dams on the whole roof?
|Posted on Wednesday, September 19, 2001 - 07:17 pm: ||
You should have no problem finding replacement slates to match in Mass. You have to know exactly what size they are (eg. 12"x22"), what shape (square corners? rounded?), and what type of slate (Vermont unfading green? "sea green"?). Have you tried the directory on this site? It lists roofing contractors state by state, and surely one in MA near you will have what you're looking for.
Lower slope shed roof dormers can be hell on the roofs below during a bad ice year, such as last winter. You may want to install snow gusrds on the dormer roof to prevent ice avalanches and damage below. A good snow guard to use is Berger Brothers stainless steel snowguards that simply slide up under the slate and hook on an existing nail. Berger is listed at the front of the Slate Roof Bible.
|Posted on Monday, April 15, 2002 - 01:04 pm: ||
I have a 70-year old row-house unit with slate in the front of my unit. I can see on my 2nd floor ceiling big water stain. I had two roofers over to check on the cause of the leak.
A little history of the leak. When I discovered water stain on the ceiling about 5 years ago, our contractor put a new flat roof on. Then about the same time, another roofer put tar on the valley to temporarily fix the leak where bucketful of water was going from the top right hand corner of the 2nd floor window into the house, which was approximately where the valley ends. The previous home owner also had tar put on many slates.
This 1st roofer says water is most likely coming in from areas where the flat roof meets the slate roof. He says the previous roofer should have taken out the slates where they meet the flat roof and put the slates back after the flat roof was properly installed. He thinks the leak comes from the inproperly handled join between the slate and flat roofs. He says he would hose the roof to test the leak. He also says that slates along the area which gets more sun is in bad shape and needs to be replaced. So is the valley and the slates around it.
The problem is, the 1st roofer is busy and can't be sure when he has time for our repair. He says he recommends replacing 70-75% of the slates to be sure the job is done right and will build scarfolding for this job instead of using the hook ladder.
Then I have another roofer over suggesting the use of rubber slate. He says that today's rubber slate looks just like real slate. He says tar should never be used to fix the valley or on the slates. He also recommends replacing the entire slate roof with new rubber roof.
I've read about the rubber slate exchanges on this board. My question is - how can you be sure where the leak is coming from and how much of the slates that need repair? Thanks.
Dino the diligent
|Posted on Monday, April 22, 2002 - 12:39 pm: ||
A water hose, access to the attic/rafters, and a lot of diligence and patience. This is true for all the roof leaks that I've fixed on all types of roofs, and only recently, slate. I start applying water at the bottom of the pitch and work up, looking for leaks as I go. A helper in the attic/house helps. I use a "thump on the roof" method when I see water enter. The helper on the roof marks the point where water is flowing. (Those cheap two way radios are great for this.)Leacks can be tricky sometimes. Water may enter at one point but exit into the house further down. This is why access to the rafters is important.
I'm still new at slating but thanks to this forum I'm gaining knowlege at a much faster pace. The exchange if ideas to solve problems is an omnipotent force.
Of course luck does play a role too so,
Good Luck. Dino
|Posted on Thursday, June 06, 2002 - 12:07 pm: ||
I am looking for 40 squares of excellent condition used slate. Does anybody have some peach bottom lying around?
|Posted on Tuesday, July 30, 2002 - 10:17 pm: ||
I live in a 70 year old house in Birmingham, AL with a grey slate roof. I don't know if it is hard or soft but it is intact except for a few slates which have slipped. My question is two fold, first do you know of anyone in this area who is competent to repair slate roofs and second, if we add on to the house, would I be better off replacing the entire roof or just trying to match the slate on the addition. I had been told that these roofs were good for about 75 years but your site has encouraged me that maybe I can salvage it. Thanks in advance.
|Posted on Wednesday, July 31, 2002 - 09:43 am: ||
It's likely that you have a Buckingham roof, but not certain. 75 years for many slate roofs is not a long time. Buckingham slates should last at least 125 years. When you add on your addition, put slate on the addition. There is a contractor directory on this site.
|Posted on Wednesday, July 31, 2002 - 04:21 pm: ||
Take a close look at the slate (if possible). Shiny mica particles in the stone indicate Buckingham. If it is in good shape after 70 years then, in my opinion, with a little maintenance, you could easily be good to go for another 70 years.
If there is evidence of delamination, scaling, powdery surface or what some folks refer to as "the white smile" below the course lines, then it is likely Pennsylvania.
I will email you privately a few names of slate roofers in your area.
|Posted on Wednesday, July 31, 2002 - 08:54 pm: ||
Jerry- there could be numerous questions to pose to you to offer the best all-around, thoughtful advice- would the addition's roof show from the front?- if not tied into the slate roof, then what other materials would you consider?- if a single story addition on your two-story house, then would housepainters be on the new roof to paint the house- in some climates, ice falling from an upper slated roof onto porches, etc does often alot of damage(in many cases, a copper or tin roof is well advised to limit this sort of periodic "disruption")???
Failing to locate a slater/s to have confidence in doesn't have to limit your progress on an addition(measurably, that is)- if a separate roof, one could consider just a fiberglass shingle treatment(to save $$ and postpone details resisting solution?) for now and then re-engage a slate roof later when it feels better in the gut- please don't omit the framing details of strength and preferred decking materials, etc to keep that future option well in hand- your roof sounds relatively asymptomatic- except the, "some have slipped" comment- that could presage a nail-failure, corroding condition but don't panic- it's often not generalized or fatal but attributable to certain tree's sap, etc or shading/chronic dampness of specific areas of a roof or often mostly low and near the eaves- an informed opinion/assessment of these and other factors might be good for planning/budgetary purposes- space is and should be limited here but I'll be happy to further a discussion with you... firstname.lastname@example.org
|Posted on Sunday, March 14, 2004 - 11:28 pm: ||
I have a slate roof that I assume was installed at the time the house was built in 1950. I currently have a leak at the base of a valley and had three roofers look at the roof. The first one obviously did'nt know what he was doing so I won't discuss him. The next two gave two different opinions. One said the slate was Vermont and the best available and should last another 50 years and suggested reworking the valley. The second one said it was not Vermont and the whole roof needed to be replaced. He showed me a couple pieces of slate from my roof and pointed to a powdery substance on the slate which suggested that it was absorbing water. He then showed me a couple pieces that he broke in half rather easily and said this showed that the slate was gone. Finally he said it was Bangor slate and not Vermont because Vermont has lines in it. When I look at the slate it does not appear to have obvious signs of decay and I can walk on the roof without it cracking. Can anyone give me a third opinion? Thanks
|Posted on Monday, March 15, 2004 - 09:45 pm: ||
Bangor is uniform black (or dark gray). Vermont is usually light gray, tan, reddish, purple, and rarely black, but if so, striated black/gray.
Bangor slate after 50 years is still good. It should last at least 75 years, but more likely 90 years or longer. Vermont slate at 50 years is almost always still quite good. Your valley probably needs replaced. Sounds like neither of your roofers knows what he's talking about.
|Posted on Monday, March 15, 2004 - 09:47 pm: ||
On re-reading your message, the roofer who suggested re-working your valley sounds like he is somewhat on the ball.
PS: You should never walk on your slate roof.
|Posted on Tuesday, September 14, 2004 - 10:14 am: ||
I work for a company in the granite business, and we are beggining the process of importing slate roofs from Brazil. So, I would like to know the standard sizes and thickness of the slates roofs used in the USA in general and also the most used kind, and if there is any special especification for the state of Florida. I also tried to call your 1 866 - 641-7141 number to purchase your book, but it was busy (?) I wonder if I got the correct number.
Thanks a lot