Do purlins get damaged and need to be replaced when stapled cedar shingles are removed

We are replacing a cedar roof installed in 1993.

Standing in the attic you can see the purlins and the undersides of the shingles. The purlins are 7" o.c. (not 7.5).

The spacing of the existing purlins is driving the decision about the size of the exposure, and the choice of shingle.

But I have a question.

The roofers in 1993 used very long staples not nails. These staples go entirely through the purlins and protrude about an inch from the underside.

Are these purlins going to get damaged during removal of the old shingles, to the degree that they will need to be replaced in any case?

Will this be an opportunity to change the spacing and change the shingle exposure?

If the purlins are standard 1" x 4" there should be minimal damage from tear off.

You should look for a roofer that can explain this stuff to you in such away that you understand and trust him.

It’s important that you trust your roofer to do his job without you second guessing him all the time.

Keep looking until you find that roofer.

All the information you need is in that link that Don put up in the other thread.

Alot of the staples will probably get driven down as well, thats fine and nothing to worry about

I prefer knowledge over trust. I’ve talked to six roofing companies all with good regional reputations.

When it comes to technical matters, they have disagreed on quite a few things. The reasons they give are always “we have found that this works best”.

– whether passive or mechanical ventilation would be the better choice.
– whether under-shingle intake vents (in the absence of soffits) are necessary or recommended
– whether hip vents are needed in a passive-ventilation scenario on a hip with a cathedral ceiling below it (no attic)
– the maximum reveal allowed for the cedar shingles (of the same size, apples-to-apples) given the pitch of my roof
– whether copper valleys should be used or avoided
– whether there should be a weather-shield under the first few courses
– whether there should be an interleave of felt paper between the courses

In all cases, we’re talking about not having any CDX decking, just nailing the shingles to the purlins.

So you have skip sheathing, you still need to decide whether you would like shingles or shakes.

Cedar shingles don’t have interlayment (felt between courses) cedar shakes do have interlayment, this is one of the main differences between the 2.

Shakes usually have a larger exposure 7" - 10" is common in my area.

Shakes are usually handsplit to give a rough textured appearance.

With cedar shakes the felt interlayment is really the waterproofing part of the roof.

Cedar shingles are machine cut from clear cedar, these are typically installed with a 5" - 7 1/2" exposure.

Cedar shingles do not have felt interlayment and when installed have a more uniform finished look to them.

Copper is the ideal metal for flashing and valleys for cedar roofs, the copper helps in keeping the roof free of moss & algae in addition to superior weathering and aesthetic appeal.

With a skip sheathing deck ventilation really isn’t much of an issue because air will flow through the roof assembly to some extent, additional ventilation certainly won’t hurt.

As stated earlier you first need to choose what type of cedar roof you would like, you will not get any straight answers until you do that.

Why did the original roof only last 1/2 as long as it should?

Your last question is exactly the question I’m asking and exactly the reason I’m trying to get additional information now :slight_smile:

I had asked the original roofers back in 1993 to give me a shingle that could support a 7" reveal. I wasn’t paying too much attention back then, being overly busy with my own business at that time, and did not do any reading prior to making the decision. And the roofing company was chosen by the contractor who was putting an addition on the house, over the garage. He recommended them, and the contractor had a good reputation in our town.

The roofer used 18" perfections 3/8 thick, which partly explains the roof’s lack of longevity. They also did not install any intake ventilation, just a ridge vent, so I don’t think we have a well-functioning passive air flow. That also took some years off its life. They used staples, not stainless steel, and when I inspect them, I see that many of them are too deeply driven, cracking the shingles, and many are too shallowly driven, so that when someone walks on the roof, the shingle above the proud staple gets cracked underfoot. And the trees around the house have nearly doubled in height in the past 20 years, so that what used to be in sun is now in shade, and doesn’t dry off as fast as it used to, and the shingles are mossy. All of these factors contributed to the shortened longevity.

We might be living in the house for 10-15 more years. When it comes time to sell, I want to be able to tell the buyers they have a good 10 years left on the roof. So here’s my plan for a 25+ year roof, despite the tree-shade.

** The shingles in worst shape are the bottom courses, which stay wettest longest. I need to make sure they can breathe, whatever we decide to do in terms of ventilation.**

“tapersawn shakes” 7/8 butt thickness nailed with stainless steel ringhshank 4d nails. “sawn shake” is a contradiction in terms, since shakes are split and shingles are sawn. But it’s not my terminology in any case. It’s what the producers are calling their thicker sawn royals, 5/8, 6/8, 7/8 butt.

I want super-duper ventilation without sacrificing aesthetics. Contemplating these options:

a) a single mechanical exhaust fan coupled with under-shingle intake vents at the drip-edge; no ridge vent; no hip vents, or
b) ridge vents, hip vents, and under-shingle intake-vents or this Marco design or this one from GAF at the drip edge for a passive system (we don’t have overhanging eave/soffit)

c) option b) with the addition of a product like this nailed onto the purlins, to expose more of that 4" shingle underside to the air and possibly increase the natural passive upflow of air towards the ridge (this product has both wall and roof applications)

d) tearing out the purlins and reinstalling them at 5-1/2" spacing and using 5/8 or 7/8 tapersawns with a smaller 5-1/2 reveal

e) installing CDX decking on top of the existing purlins and then CedarBreather underlayment between the decking and the shingles, and dropping down to a 5-1/2 " reveal

Options d) and e) add significantly to the cost, in both labor and materials.

CEDAR-SAVER
Some sort of metal stripping (copper or zinc) placed every few courses to discourage moss growth.

Your original roof should have used 24" shingles to achieve 3 ply coverage if you wanted a 7" exposure.

A thicker butt will cost more and last longer usually.

A minimum of hot dipped galvanized nails or staples should be used, stainless is ideal.

We get a bit of snow here in Michigan so I always do a triple starter course.

If you want super duper ventilation you will get that with power vents but you will still need an intake, you have no soffits at all?

What you choose for intake vents will depend on what you have to work with.

Skip sheathing is ideal for cedar shingles/shakes, you don’t need any of the aftermarket cedar breathing products they are for solid decking.

Your roof is currently set up for a 7" exposure so it will be most cost effective to retain that exposure and use the right shingles this time.

The metal stripping is something we do here.

We use a 4" wide copper strip that is hemmed and it is installed every 8’ - 10’ up the roof and at the peaks/ridges.

The more copper on your cedar roof the better it will be, the copper kills the moss & algae.

If a cedar roof is done correctly with the proper materials they will last 50+ yrs but they are frequently shortcutted because the expense of doing it correctly is significant.

People like to save money by using the wrong fasteners, they try to substitute thin aluminum for copper, forego cedar breather on solid decks, etc.

We don’t have any soffits, just the fascia board. It is done in a decorative cedar half-circle pattern, so I would rather not tear it off and replace it with a fascia vent. Under-shingle intake vent seems best aesthetically.

Is the hemming of the stripping to give it some rigidity, or does the hem serve another purpose?

Hemming makes the strips a bit stiffer so that they don’t curl and deform and it gives a cleaner edge.

I leave 1 1/2" - 2" of the strip exposed.

The thinner materials like zinc strips get bent by the wind.

Are royals available in different thicknesses? Is it possible to get a true 24" shingle (not a tapersawn shake) in a 5/8 thickness?

The reason I ask, is that “tapersawn shake” dimensions are nominal, according to the Cedar Bureau’s rating system. A 24" tapersawn shake can be actually only 22 inches long, and then felt must be interlaid. I’m having a hard time understanding how the cedar breathes when it is sitting on felt.

Very impressed with your knowledge of cedar roofs axiom. They are one of the few roofs I have never installed in my life. Would love to work for you on one just to learn a few things