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Old_school (Old_school)
Senior Member
Username: Old_school

Post Number: 345
Registered: 01-2009
Posted on Tuesday, December 29, 2009 - 09:14 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

The guys said it better than I could.
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Joe (Joe)
Senior Member
Username: Joe

Post Number: 488
Registered: 07-2006
Posted on Tuesday, December 29, 2009 - 12:47 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

Rihpc: Your architect doesn't know what he's talking about. He's way out of line. His contention that "the industry standard states that a slate roof requiring 20% repair or greater should have total roof replacement," is incorrect. What if a tree falls on one side of a hip roof (4-sided) and damages that side. Does the entire roof have to be replaced? No. The 20% recommendation is derived partly from an over-generalization published in the Slate Book by Stearns et. al.,page 151,where they state, "When evaluating a slate roof that is 70 years old or more, keep in mind that all flashings will need to be replaced. If this means disturbing more than 25% of the slate on the project,it will probably be more cost effective to replace the entire roof."

What they don't say is that you can replace the flashings - all of them - on a slate roof with little disturbance to the rest of the roof. You only have to remove the slates that cover the flashings, then re-install the same slates in the same place they originally were.

The 20% recommendation is further complicated by Jeffrey S. Levine's Preservation Brief 29: The Repair, Replacement & Maintenance of Historic Slate Roofs, which states, "If 20% or more of the slates on a roof or roof slope are broken, cracked, missing, or sliding out of position, it is usually less expensive to replace the roof than to execute individual repairs."

Again, this is an over-generalization that is misleading. Unfortunately, architects, engineers and roofing contractors, among others, have latched on to this recommendation without understanding the bigger picture. An example of which would be the hip roof I mentioned earlier.

These recommendations were meant to pertain to soft PA slate roofs nearing the end of their lives. Hard slate roofs with 20% or 25% damage can simply be repaired.

Failing metal on slate roofs is common, the replacement of which is the basis of the slate roof restoration trade. Replacing worn out flashings is routine and not a sign of deteriorated substructure. If there is some wood damage, repair it.

Hard slate roofs from 1935 are half way through their lives. What kills them is misinformation from architects, engineers and roofing contractors, among others. You will find that the restoration of a hard slate roof will generally cost about 10%-15% of total replacement costs.

I have seen many new slate roofs lately that were installed by contractors who had no business doing slate. These are the same contractors blindly citing the 20% rule because their experience with slate is minimal. As a slate roof consultant, I have had to condemn a number of NEW slate roofs around the U.S. because of gross installation errors - no headlap, for example.

So if you have solid slate roofs in need of repair or restoration, it may be a grave risk to rip them off and replace them based on bad advice.

You can read more about my consulting services here: http://slateroofconsulting.com
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Slate_man (Slate_man)
Senior Member
Username: Slate_man

Post Number: 542
Registered: 01-2007
Posted on Tuesday, December 29, 2009 - 06:25 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

Virginia, I to agree with Ward on this, that the slate could be monson. I has just in Newport RI, looking at a job.

What is the flashing, steel or copper? Do you know if the nails are copper or steel or dipped?
What is the decking 1" or 2" boards, T&G?
What is the headlap onn the slate 2" or 3"?
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Olde_mohawk_masonry__historic_restoration (Olde_mohawk_masonry__historic_restoration)
Senior Member
Username: Olde_mohawk_masonry__historic_restoration

Post Number: 109
Registered: 04-2007
Posted on Monday, December 28, 2009 - 09:34 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

Virginia: My guess is that these institutional structures in Rhode Island have Monson (ME) slate roofs. There is no way replacement is warranted. We are licensed by the RI Contractors' Board and have performed slate roof restorations in the College Hill neighborhood of Providence. I would be pleased to provide you with flashing replacement/slate repair estimates for the buildings in question. You could then present these against the architect/engineer's estimate of cost to replace with asphalt. I bet you'll be pleased with the results. Feel free to contact me directly at 877.622.8973 or Ward@WardHamilton.com to discuss.

www.OldeMohawk.com
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Old_school (Old_school)
Senior Member
Username: Old_school

Post Number: 343
Registered: 01-2009
Posted on Monday, December 28, 2009 - 05:31 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

Photos are of the utmost importance here!!!!

I aggree with you that it is a total waste of a good roof. At 75 years old, those slate roofs may be just getting "broken in" if they were a good grade of slate originally. If there is no indication of leakage in the attic, then "it is not leaking!" How much intelligence does it take to know that?

Sounds like they want to take off a good roof that needs a couple thousand dollars in repairs to last another 40 to 50 years and spend 15 thousand to replace it with a roof that will last 25 years, with luck and then need replacement again. We see it all the time and it makes us angry.

Where are you located?
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Plaughlin1 (Plaughlin1)
Advanced Member
Username: Plaughlin1

Post Number: 42
Registered: 03-2007
Posted on Monday, December 28, 2009 - 03:12 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

I believe you are correct in questioning the assesments.
There is no real magic "blanket number" of years that a slate roof or associated flashings will perform on any said building.
Each and every instance has to be looked at seperatly and a determination made from there.
I have done some goverment contracting and in some instances the amount of back scratching and waste is just sickening.
Do you have any photos you can post?
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Rihpc (Rihpc)
New member
Username: Rihpc

Post Number: 1
Registered: 12-2009
Posted on Monday, December 28, 2009 - 02:28 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

As a staff reviewer for a state government agency, I am charged with protecting historic buildings from inappropriate or harmful work with public funds. My staff and I are often frustrated by architects who contract with the state for slate roof repairs and automatically and predictably recommend asphalt replacement as the most economical solution. One in particluar argues that "the industry standard states that a slate roof requiring 20% repair or greater should have total roof replacement." Is this so, and how does one determine that 20% or greater needs replacement?

I have been out on site and counted a maximum of 15 broken slates on a roof of one of these buildings, with no signs of interior leaking. Out of five buildings in question, only one looks like it really needs total replacement - and not because of the slates, but because it has many dormers with failing flashing. I am getting nowhere with the state on this because the architect keeps claiming that he is acting in the state's best interests to economically address the problem. In most cases, I just don't see that there is a problem, or one that can't be fixed with a repair.

He also claims that failing metals on slate roofs usually indicate that the "substructure" is deteriorated as well and needs to be replaced. Again, I have witnessed no sign of deterioration of the decking from within the attic. Is this also an industry rule-of-thumb, as he claims? Can anyone direct me to a source of these "industry standards" that he is fond of quoting?

The current group of buildings in question date from circa 1935, and are institutional buildings that are residential in scale. However, the same scenario has arisen on several much larger buildings.

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