It looks like the roof on our 1890's Victorian is shot and we need to replace it this summer. It will be a complete tear off (2 existing layers of asphalt shingles). Although the existing 1" sheathing looks good with only small gaps between the boards, we will probably do new plywood over the entire roof anyway just to be sure the new shingles have a good hold on something. The roof is a 12/12 pitch with multiple valleys and ridges.
I'd like to do something different than the standard architectural shingle but need to stay with asphalt shingle (no slate, no cedar shake) because of the cost. So, I'm looking at Grand Manor and Carriage House line of shingles from Certainteed. Has anyone used these? Has anyone used both at the same time to make a pattern? Grand Manor has a square bottom and Carriage House is scalloped, so I was thinking of 4 rows of each repeating up the roof. They appear to be a very heavy shingle and I'm worried they are a difficult to work with - for example, they require an open valley because they are so thick/heavy that the do not bend well. I'm also worried about the weight - 425 lbs per square, which is almost double standard shingle weight. There is no way I'm doing this myself and I found a roofer who seems willing to use them and do the pattern, but I don't know if he has ever used these particular shingles before.
With the extra weight of the sheeting, heavy shingles may be too much for your rafters. You may want to consult an engineer. If you are in a snow climate, you may really create a weight issue.
My initial rough guess was it should be ok since we currently have two layers of standard 3 tab shingles up there (so probably about 400 lbs per square up there now) and the new shingles will be 425 lbs. But then add more for new plywood + snow load (yes, I am in Northeast PA - so we do get a good amount of snow) and it might be too much. Good point. I guess a structural engineer would be able to do the computations and give a yes/no answer.
I would look into an engineer because we live in Nebraska and I worked at a college with an old building that needed new shingles. They wanted to put shakes on it because that was original in 1888. Only problem was, they were too heavy for the roof so they had to install I-beams to support the extra weight. Don't want this to happen to you.
I'd have to check our records (I'm being lazy) but I think we used GAF Camelot "Antique Slate" (which is similar to CertainTeed's Grand Manor) on the main roof (9/12 & 12/12 pitches) and CertainTeed Carriage House (maybe "Gatehouse Slate") on the tower 17?/12 pitch).
We considered doing a pattern, similar to what you describe, but opted out because each style has slightly different overlap requirements (because of Carriage House's beveled corners) and there'd be some mismatch of the alternating seams from one row to the adjacent. Also, there's a slight thickness difference between the two which could impact both appearance and the warranty (what little that actually matters).
Our roofer had extensive experience with both GAF's and CertainTeed's Luxury shingles (thanks to the multi-million dollar homes on Long Island) so we took his advice about the possibility but difficulty (there was also a small added labour charge for doing a pattern because of the care required).
The GAF Camelot was less expensive than the CertainTeed Grand Manor but has a very similar look, and (I think) is lighter (though not a factor for us).
Note: The fine print of the warranties reveal they're fairly worthless so don't let that be a deciding factor in your decision. The warranties appraises the annually depreciated cost of the shingle (not incl. labour) based on it's its stated effective life in order to assign replacement value. The manufacturer will determine whether or not failure was caused, in whole or part, by "faulty" installation and decrease the replacement value accordingly. Check the installation instructions and don't deviate from them....get them into your roofing contract.
One note about the pattern: If you search "images" of slate/cedar roofs, which combine square with scalloped, you may find most tend to have 3-5 rows of square, from the ridge, with 3-5 scalloped, then 5-10 square, then 2-5 scalloped.... I think such a pattern makes the scalloped look more delicate, an accent, and more visually appealing. IMO.
I also agree with the other comments about checking the weight load. However, a 12/12 tends to have fewer problems (concerns) than post-traditional 9/12s.
Balloon construction was very common 80-125 years ago because the trees were old and they could cut long lengths at the saw mills. This construction style had a flaw in it that building would twist with the wind. No cross bracing. Floor joists were attached to the long studs with nails. Not a lot of strength, but much cheaper to build.
Yeah, I'm not surprised about he "cheaper to build" part - even though our house is "Queen Anne" style, it is really just a modest / average middle class Victorian. Nothing overly ornate or fancy. I knew it was balloon framed (found that out when I was running wires in the walls), but I always assumed there should be some sort of exterior bracing or sheathing over the studs. The structural guy didn't think the lack of bracing impacted the roof weight load too much and I guess if it lasted 100+ years like this without twisting, then it is probably ok.
I am just a homeowner with no experience regarding roofing. However, we used Certainteed Carriage House in our c.1880 Eastlake. We had up 4 layers of roofing, including original cedar shingles. We had to plywood the entire roof too. It looks great and the company that installed them did not consider it was an issue with weight. Did I mention 12x12 pitch and a tower? Anyway, good quality and we are pleased with the result. If you like I can send you a picture. Just email me. Best of luck!
I had another structural engineer come out to look at the roof and her initial response was that it should probably be ok. However, after looking further, she started mentioning something about collar ties. It appears the roof rafters are about 24" on center and my ceiling joists are less - maybe 16", so they don't always line up and in some cases the roof rafter is not attached to a ceiling joist (I hope I'm explaining this correctly). And when they are next to each other attached, they are just nailed.
The firm is going to run some calcs and get back to me with an answer.
She was also surprised that the house had to exterior sheathing and said my wood siding was probably adding strength to the walls and if I ever remove it, I would need to add exterior plywood.
Just a follow up on the roof project...
I received the report from the second structural engineer and she did recommend adding new 2x6s alongside any existing roof rafter that exceeded 13' 9" in the central pryamid section of the roof. So, we need to re-enforce 7 roof rafters in the center and re-enforce the one cracked rafter in the back. The longest 2x6 is 16' 9". I'm going to use LVLs. I ordered the lumber but my roofer is going to do the work.
At this point we are just waiting for all materials to arrive so we can finally begin the new roof! Should be soon. I can't wait.