Possible leak or condensation in new addition

We've just had our first couple weeks of below-freezing temps and about 8" of snow this winter here in Seattle, and I'm having some water issues with an addition we started this summer and are still trying to complete.

The addition extends 20' from the back of our house. The first 5' has a drop ceiling with trusses, and the remaining 15' is vaulted with 2x12 rafters. The rafters are unvented and filled with R-38 fiberglass. The trussed area is insulated with R-30 fiberglass plus some cellulose blown in on top, and has two roof vents and eave vents (five 2-1/2" holes drilled into the blocking between the truss tails on each side).

The main problem is a leak above one window in the trussed area. The water appears to be accumulating under the eave and then following the moisture barrier (behind the siding) into the window opening. The secondary problem is visible moisture under the eaves around the house.

I'm assuming this is a condensation issue because:

1) We've had several hard rains and no leaks since putting the roof on four months ago.

2) The problem didn't appear until we got freezing temps recently.

3) A large part of the attic was very poorly insulated until after we had the low temps (I had some electrical to finish, so I put off blowing in the insulation -- we blew in 30 bags of insulation the day after we first noticed the leak).

At this point, I'm pretty confused about what to do. I think I need to increase the size of the eave vents, even though the attic no longer feels warm since being insulated. I've checked several times over the past couple weeks and can't see any sign of moisture in the attic -- just outside under the eaves. And the moisture under the eaves is not consistent -- it's on some parts of both the existing and new roofs, but not everywhere.

Could my leak be due to condensation that froze before I insulated, and now it's melting? Should I be concerned about the water under the eaves?

Sorry for the long post, but I'm trying to be as complete as possible. Thanks in advance for your advice!

Here's a photo of the addition roof this summer before adding the ridge cap and finishing the skylights:


Here's a photo showing the melting snow. The leak is above the window to the right of the slider.


Here's a photo of the water coming down apparently from the vents to the window. I'm installing the gutters today, and I'll prime the eaves as soon as they dry out.

 

it`s called an ice and water back up,check that the area under that valley/fascia are properly sealed and waterproofed--snow makes things leak that don`t in a simple rain,---you should also have ventilation in the ceilings to relieve built up heat (CODE),OR YOU WILL END UP WITH MAJOR PROBLEMS down the road

 

An ice dam makes sense. I guess I just thought it would take more snow to see problems. We shouldn't have any more snow for a while, but lots of rain. I'll keep my eye on it to see if the eaves dry out.

I looked into the eave vents last night and could see a little condensation on the decking a few inches in, so I'm pretty sure we have inadequate air intake in the trussed area of the addition (the photo with the round vents). I'll be opening that up completely between the trusses today. I think code is 1 sq ft vent per 150 sq ft attic space, and this should give us twice that.

This summer, our inspector said we could either vent the cathedral ceiling or simply fill it in completely with insulation (which we did with R38 fiberglass). I don't have leaks or visible signs of moisture in the cathedral ceiling yet, but I'm concerned we made a colossal mistake by not venting it or using closed-cell foam, and problems are right around the corner.

Is there something I can use to check for moisture in the cathedral ceiling? If so, what is an acceptable range of moisture?

Again, thanks for the information. It's hard to get a decent night's sleep while this is going on. =|

 

"Ice damming" could be the entire cause of this problem, that's a minimally sloped roof for shingle installation, there has been been no mention of waterproof shingle underlayment (WSU) installed at the eaves, and you could expect that snow melted by heat inboard of the roof-wall junction would then freeze and dam as it ran over the open, unheated wide overhang at the eaves, which is pretty much the prescription for ice damming:



However... I spend all winter looking at this sort of problem and I'm not 100% convinced... or at least 100% convinced it's 100% of the cause - the setup just does not look quite right to me to produce all the water we are seeing at the vent holes in the soffit, and I'd also suggest looking at another variable: air infiltration into the attic - what factors what could be raising the relative humidity in the attic?

Are there kitchen or bathroom exhaust fans or clothes dryers venting into the attic? Are there poorly insulated scuttles or pulldown stairs which are allowing large quantities of moist warm air from the inhabited portion of the structure into the attic? Is there a vapor barrier on the conditioned side of the attic floor under the insulation? Are there large numbers of "can lights" lacking their air seal gaskets in the ceiling below? Are there other openings such as chimney chases conducting conditioned air into the attic?

In my experience these factors can add enough moisture to an attic to defeat the "required" amount of ventilation.


Fig. 1


Fig. 2

In both of these examples infiltrating or injected warm moist air from the living space below air has raised the relative humidity to the point where frost is forming on the underside of much of the sheathing, from which it dripping down onto the insulation.

Typically, I would do it IR scan of the ceiling to see if I can detect evidence of imperfections in the insulation and/or moisture in the ceiling assembly. If I saw anything that looks suspicious the next step would be to take moisture readings with something like a Tramex (a type of meter that senses moisture level a short distance below the surface of the drywall).

If you suspect water in a cathedral ceiling in areas such as eave or within the insulation nearer the sheathing side of the roof the only way I know of to reliably determine moisture levels is to drill small holes and insert two probes which are insulated along their length and sense moisture levels only at their tips:


Fig. 3

this requires to 1/8 inch holes about an inch apart, I carry a small tube of quick drying spackle to fill them in afterward.

By taking readings at various depths as you push the probes through the insulation you can obtain a moisture profile of the wall or ceiling assembly, for example in many cases you can determine approximately where the dew point is located within the wall at the time of inspection.

 

It's an Ice Dam. But, are the shingle tips/tops clipped off vetically, starting at the last of each shingle's exposure? Along the valley cut?

Check to see if they come to a point/ If the tops end at a point, you'll get leaks.

 

This (shown for open and closed valleys)?

 

The problem seems to be caused by damming -- but not ice. I cleaned out a bunch of leaves and other debris from the valleys today, and also discovered that we did not do our valleys correctly. We rolled felt down the valley, then put a 24" 'W' valley on top of that, then put felt and shingles over the flashing up to about 2" away from the middle ridge in the flashing. This only happened on the addition side -- on the existing roof we slid the flashing between the felt and shingles.

Putting the felt over the flashing allowed the water to run right onto the decking when it got dammed up from the debris.

This weekend, I plan to loosen the shingles near the valley and put the felt under the flashing. Can one of you guys tell me the best way to use metal W flashing with tabbed shingles? Also, what's the best way to seal up the area near the eaves at the bottom of the valley, given that the addition roof is about 1 foot higher than the other? I already feel like a bonehead for messing this up, and I'd like to do it right the second time. =)

I used some leftover W flashing to extend the valley over the eave, and this seems to be preventing water from working its way into the window where it was leaking before. However, I can't figure out where the water further out under the eaves is coming from. The snow is gone, and it's raining tonight. The gutters have solid covers tucked under the shingles, so the water on the fascia must be coming in under somehow. Here is what the eaves look like:





It's a 3:12 roof with 30# paper overlapped 19". The shingles have a 5" reveal, as directed by the manufacturer for low-slope roofs. The decking is plywood over the 2' eaves, then transitions to OSB over the rest of the roof, with a small expansion gap between all sheets. I'm getting water under the eaves about 6 ft from the valley on one side of the addition roof, but not the other.

 

OK.. that makes it a lot clearer what's happening.

These are several things that likely need to be changed, but first, lets make sure we understand where we are at the moment.

I understand it, this is the current valley as currently flashed:



the "felt" is a water resistant underlayment (WRU) such #15 or #30 shingle underlayment, and these is no waterproof shingle underlayment (WSU) ("such as Grace ""Ice and Water Shield") anywhere at the valley or along the eaves?

If this is correct, please post a close up showing that roof intersection head on and from the side for about 2' on either side of the valley, taken form an angle such that we can see the exposed edge of the sheathing if visible or the drip edge if installed, and how the metal flashing, fascia and guttering are detailed at the bottom of the valley.

Also, take a look here: Shingle Underlayments,, here Grace Ice and Water Shield.

Don't know about your area, but here in Chicago - especially on a lower-slope shingled roof like that - WSU is installed in the valley and overlapping the same installed as eave protection, drip edge is required, and the WSU is often wrapped down over the fascia,



sometimes, with additional flashing installed over it.

 

First, let me just say how much I appreciate your detailed responses and willingness to help. This experience has been pretty demoralizing, but reading your posts gives me confidence that I can fix the problem I created.

Your valley diagram is correct. There is no WSU or drip edge in place on either the old or new roofs. We don't get a lot of snow or really low temperatures here in Seattle, and I've never seen anything resembling WSU when I drive by new homes being roofed -- but I could be mistaken. For what it's worth, I couldn't find anything like that at Home Depot, either.

I have to run some errands right now, but I'll post the photos you requested, as well as a simple diagram of the roofs, a little later today.

 

Typically, in a low slope application shingle manufactures require two layers of felt underlayment with a 19" lap or one layer of waterproof shingle underlayment over the entire field(s) of the roof. Around here roofers routinely apply WSU under every valley and at a minimum over the first 36" at the eaves, and the building departments require drip edging.

You many not get "a lot" of snow, but you clearly can get enough to cause you "a lot" of problems!

 

We used Owens Corning Oakridge shingles. If I'm reading the installation instructions correctly, they recommend a single layer of underlayment (they don't specify waterproof or not) with a 19" overlap on most of the roof and an extra layer at the eaves. I think we doubled up the felt at the eaves, but I can't remember for sure.

Regardless of their instructions, I can see now in hindsight that it would be advantageous to use WSU on the entire roof. Likewise, adding a drip edge would help. It seems that about half the homes in my neighborhood have drip edges, and I have no idea if it's currently required by code here. I imagine the inspector will tell me when he comes for the final inspection.

You sure are right about incorrectly doing the roof causing a lot of problems. Since we still have about five months of the rainy season ahead of us, I'm anxious to get this corrected ASAP.

Rather than clutter up this post with a bunch of photos, I posted a diagram and some photos here. If I didn't get the shots you asked for, just let me know, and I'll post 'em on that site. I'm expecting to have to remove the bottom 36" or so of shingles, allow the eave to dry out, then install WSU, drip edge, etc before reinstalling the shingles. Then I'll do something similar for the valleys.

Would you recommend sticking with the metal W flashing, or should I get rid of it and just do a shingle valley? Any tips you have for this kind of rework (removing/replacing existing shingles) would be greatly appreciated.

Thanks again, and I hope you're having a great weekend!

 

Hi,

Those pictures are very useful - wife and I are checking out the new blu-ray player this evening, but I'll tomorrow morning.

 

Ahh, nice. I'm thinking of getting the LG that supports Netflix Instant Play to complement our 52" Sony Bravia. Have a good night!

 

I have to work today and tomorrow, but I'll comment as I have a chance.

1) Your first difficulty is that Owens Corning's installation instructions are difficult to interpret accurately unless you know the relevant building codes, which are not directly referenced in the instructions. And even then you don't know what's required in your community unless you know which code provisions have been adopted by your AHJ.

For example Fig 1 calls for "Specialty Eave Flashing" "where required" - which would leave a homeowner to suppose this is some unique requirement for special situations.

In fact the instructions are referencing the International Residential Code (IRC) (905.2.7.1, to be specific), which is the building code adopted most everywhere in North America.

Here's a annotated version of your instructions, formatted as I would present it in an inspection report for a property where I had observed the required eave protection was not installed:


Fig. 1

If the 2003 or later IRC is adopted in you community, unless the eave line protection is specifically excluded, the "Specialty Eave Flashing" is a requirement if the average January temperature is 24F or lower, and obviously a very good idea in any case if you are located somewhere it snows (see below).

As for the underlayment required, there is "disagreement" the roofing industry about what constitutes adequate underlayment under fiberglass mat laminated shingles.

Owens Corning's instructions for low-slope applications for your product specify one layer of conventional underlayment with a 19 inch overlap.

However the CertainTeed Shingle Applicator's Manual for Laminated Shingles instructions for low-slope applications specifies two layers of conventional underlayment or a single layer of WSU under some of there laminated shingle products, requiress WSU under some others, and "strongly recommends" WSU is areas "whenever there is a possibility" of ice buildup:


Fig. 2

As the design, materials and construction of both company's products are more similar than they are different, you have to wonder why they specify different minimum underlayment requirements for low slope roofs.

In any case in my area industry best practice is adhere to stricter standards, and often simply use WSU on the entire roof.

Still, for starters, it's necessary to know what's required, at a minimum, by code at your property.

We start by referring to the manufacturer's installation instructions, the first line of which is "Before installing this product, check local building codes for their roofing requirements".

Seattle's are on line at: Seattle Building Code

Locating the relevant section, we find the following table is provided:


Fig. 3

Seattle has an average January temperature of 40.9F, so yours is a low slope roof (if it's 4/12 or less) it requires a minimum of two layers of conventional underlayment or one layer of WSU, but does not require eave protection.

Building code, however, "is the absolute lowest standard to which you are legally allowed to build something" .

I also note that temperatures as low as 0F are experienced in Seattle, so eave protection while not required to prevent ice dams would IMO be a "good idea" (and "strongly recommended" by major manufacturers such as CertainTeed) in your situation.

(To be continued)

 

Thanks for the link to the Seattle codes. I don't know why the building department doesn't provide that when issuing homeowners with permits.

The code refers to a low-slope roof as "< 2:12" in a few places. Is our 3:12 roof "mid-slope," or does the roofing industry generally consider anything less than 4:12 "low-slope?"

If I'm understanding 1507.2.8 correctly, we installed the underlayment per code. That is, 36" wide sheets overlapped 19", where the 19" overlap effectively creates a double layer of felt over the entire roof. I've been in the attic looking for signs of moisture many times over the past several weeks while troubleshooting my leak, and everything looks totally dry. I wish we had put WSU on the entire roof this summer, but I don't think I have the energy to it now. =|

However, I clearly have a problem at the eaves/valleys, and I definitely need WSU and drip edge in those areas, regardless of the code. We have 24" eaves, so it looks like I need to remove at least 48" of shingles and felt, install the eave drip edge, WeatherLock (overlap 6" butt joins and 3" edge joins), felt and shingles, in that order.

In the valleys, I'll put a strip of WeatherLock down (running it over the WeatherLock at the eaves), then the felt, flashing and shingles. We currently only have about 3-4" of flashing exposed, which seems to make it easer for debris to get stuck on the shingle edges and dam up. Should I cut the shingles back further to reveal more of the flashing?

Edit: It looks like our local Home Depot sells GAF WeatherWatch. I'm assuming this is an acceptable WSU. It looks like we've got a 2-day break from the rain at the end of this week with temps in the high 40's, so I'm going to try to knock this out then.

 

2) The roof intersections shown below need to be reworked, normally a kick-out flashing would be required at the intersection of the fascia of the upper roof and the field of the lower roof, but IMO runoff is too to be great effectively controlled in this manner. some sort of more comprehensive flashing solution is needed to protect the areas receiving the runoff and the fascia beside it.


Fig 1 Runoff at roof intersections. You can see that this area was wet even before the additional water runoff from the new roof above


Fig. 2 Roof surface damaged by uncontrolled run-off

At this intersection


Fig 3

if that's HardiTrim it needs a 2 inch hold back and a treated cut edge:


Fig 4

and at a minimum there should be properly constructed step flashing behind the fascia,transitioning to a kick-out flashing, and it would be very good idea to have the vertical-horizontal transition below it covered with a continuous sheet of WSU:


Fig. 5

as given the fact that debris collects here and holds water against the roof membrane and the amount of runoff flowing over this area that might be the only way to guarantee a water tight junction at this location.

Even better, IMO, would a a continuous flashing system that addressed all these problems, something along the lines of:


Fig. 6

which I know may look a bit odd at first sight, but is often the best way to permanently solve such problems.

(to be continued)

 

Fig. 1 Low-slope defined

I tell clients a composition shingle roof with slope of less than 4/12 is not a "low-slope" roof, it's an "aggravating condition", that is one which makes almost any roofing problem worse - as the slope is reduced below 4/12 you become increasingly dependent on the underlayments, flashings, and water control and removal systems, rather than the shingles, to provide the water-seal, and detailing of these systems becomes increasingly important.

I'm outta' here for today, but you are now headed in the right direction - sorry you have to do all this additional work - I'll have a few more comments tomorrow.

In the meantime take a close look here Leak Protection: Roofing/Gutter/Soffit/Fascia Protection for a description of how we detail eaves here in Chicago to prevent ice dams (these are the roofers who do the work at my own buildings) - you may not have to go this far, but it will give you an idea of the general approach.

Also, tinner666 and others may have their own ideas as to how to best solve your problems; I'm a pretty good property inspector, but my knowledge is limited to the Chicago climate, and I'll never understand this stuff as well as a really good roofer.

 

Here's a link to one I did about 8-10 years back. Not sure when. Photo Album Account Logon

Browse down to 'Low Slope Shingles'. Just under 3/12. Elks. 4" exposure. Called their rep and after discussion, I 'Dutch-lapped' them 6". No butt joints. We've had torrential rains, 14" of snow and never a leak. No metal flashing to my recollection. Just I&W, and the Elks.

The GC I do work for wanted it on his house, so I did it. I don't like shingles that low, but it can work. Took almost 40% more shingles.

I wouldn't have an exposed valley on your roof. The purpose of metal under a weaved valley is to make a smooth 'field' area for the shingles. If water gets to it, a leak has occurred and it WILL show up somewhere.

On the same link, go to 'Multi-Valley Pitch Puzzle'. It all had metal and I&W under it and was leaking. I alternated hidden and exposed metal when I repaired it about 10 years ago.

 

Michael T. is explaining things much better than I can. You can cruise my albums for photos, and I can answer questions about them.
I'm not much on explanations, even on my sites, but I can 'show' cause and effect.

 

I guess I'm not exactly sure what a Dutch lap is. We installed the shingles according to the Owens Corning instructions. That is, we butt joined the shingles in each course, we had a 5" reveal between courses, and the butt joins were offset 6-1/2" between courses.

Would you recommend I do a weave or closed-cut valley, and should I shingle over the W flashing or yank it out?

Here's something odd: We had a little snow last night, and I noticed this morning that it melted from the eaves before it melted from the roof. Just the opposite of an ice dam.

 

Dutch Weave- No butt joints. At 4" exposure instead of the standard 5-5/8", the headlap was 13" instead of 2" standard.
The shingles lapped each other 6" side to side. If both ends were double thick, I removed the upper layer on the lower one. No set pattern of left to right. Just random based on thickness of shingle ends. Builder insisted and since it was HIS house, not a client's I did it. No leaks.
I would never be able to explain to you what to watch out for.
Not for the faint of heart to install. There are pitfalls in every technique.


As for the 'W' valley. Worthless in the expanse of roof on each side is equal. I'd remove and fully weave. No joints within 12" of valley center. If a shingle is going to end within that zone, you need to add a 12",18", or other sized piece in between it and the one before it. WITH CLOSE ATTENTION TO THE JOINT AND NAIL PATTERN BELOW IT! And THEN ABOVE IT TOO!


BTW If you used EG roof nails and nailed in the nail line just above the exposure, they will rot completely away in 6-8 years. You can only use HD roof nails.

 

If you look in the Jackleg album Photo Album Account Logon, You'll recognize the roof in the first batch of pictures. You'll see what DID NOT work on that valley.

 

I just checked, and I see a box of EG roofing nails in my shed, so I'm pretty sure that's what we used (it figures!). If they last 6-8 years, that'll be about the time I need to replace the old roof anyhow, so it wouldn't be the end of the world to just re-roof the entire house at that time. I'll just have to check for attic leaks occasionally in the meantime.

If time and money permitted, I'd be up there redoing everything right now. At this point, though, I just need to do whatever it takes to keep me dry for the next few years.

Here's my plan for this weekend when we're supposed to get a couple dry days:

1) Remove shingles and felt about 5' up from the eaves and 2-3' on either side of the valleys, and remove W flashing

2) Install GAF WeatherWatch 4.5' on the eaves (2.5' past interior wall) and a 3' sheet running down the valleys, overhanging the fascia about 2"

3) Replace felt on eaves and valleys, overlapped in the valleys with an additional 3' sheet rolled down the valley

4) Replace shingles on eaves and valleys, no joints or nails within 12" of the valley center

5) Add flashing at bottom of valleys behind fascia

Can I weave the valleys if the reveal is not the same between the old and new roofs? If not, will a closed valley with trimmed shingle corners and a healthy bead of roofing cement be an acceptable alternative?

 

Just weave away. Note; Lay 1-2 courses on each side to see if they are passing at the bottom edge of the exposure at or near the center of the valley. It WON'T always be exact. And sometimes, in places, you may well have to lay 2 courses on one side together if/when you find the 'passing point' is drifting far from center.

I also sent you a PM. Look at the top right corner of site/page when you're logged in.

 

Gotcha! I'll be sure to take lots of photos so you can see how it turns out. =)

 

Glad to help. Try to incorporate the metal pan Michael mentioned at the bottom of the valley. You hold it in place with cleats. Turn the edges up and reversed on the top and outside edge. Turn the inner edge up against the fascia under the overhang. Bend it only 80-85 degrees for a tight fit. You need a good drip edge to hook it to on the bottom edge. Google "in progress tin roof". You might find some helpful info if it takes you to a Tin roof in Progress. That would show locking to a DE and how cleats work.

 

concerning the insulation in the cathedral area,it`s the right amount ,but you should have air space for venting--only closed cell sprayed foam insulation can be used to entirely fill the rafter cavity,difference is foam seals all(no edges/gaps) ,and the R-value of the foam is much higher(6.5-7 per inch , heat passing thru regular insulation will condensate at the roof sheathing bottom,and cause the plywood to rot/delaminate from it-hence the reason to ventilate the excess heat away

 

This is something that concerns me because it's difficult to know how much of a problem it is until damage has occurred.

We originally planned to vent the cathedral ceiling, but the inspector said we had the option to not vent, as long as we completely filled the space. He didn't say anything about using foam. If I knew then what I know now, I would not have used fiberglass, but what's done is done.

I'm having the roof redone this week, so I might have an opportunity to improve this problem. While the roofing material is off, I could pull up the sheathing, add baffles and eave vents.

We don't get a lot of super cold temperatures here in Seattle. When it did snow recently, I noticed that the snow on our roof over the cathedral ceiling melted no faster than the rest of our house or our neighbors' houses (I don't think anyone else has a cathedral ceiling, and I see no ridge venting on their houses). Does this mean the insulation is doing a sufficient job of preventing heat from reaching the sheathing, and therefore no condensation should occur?

I'm glad you brought this up because it has been bugging me ever since I learned about insulating cathedral ceilings a few weeks ago. I had resigned myself to just wait until a problem occurred because to install foam now would be pretty disruptive. Venting, however, probably wouldn't be too bad considering we're having the roof redone.

 

Take those pics - I'll be interested in seeing them.

 

Absolutely -- I have a to-do item to take those pics and post them here when the roof is redone.

Both roofers I talked to wanted to do "California cut" valleys instead of woven. The guy who will do the roof is a friend of a diving buddy of mine, and has been roofing since 1979 in this area. He said the Ice & Water Shield is used a lot in eastern Washington and isn't really necessary here, but he'd be happy to put it on if it'd make me sleep better (and I could certainly use some decent sleep).

As I mentioned in my last post, I'm going to look into pulling up the sheathing while we have the cover off and installing some insulation baffles and venting. I don't know if condensation in an unvented cathedral ceiling is a big concern in our climate or not, but now is definitely the right time to make improvements if I'm going to do anything. It helps that we're about to enter a 7-day dry spell, too. =)

I don't understand why the inspector talked us out of venting and then didn't say anything about using foam, etc. Of course, this is the same guy that talked us out of the drain tile, and now I've got water in my crawlspace. =|

 

I believe ALL shingle manufacturers require balanced venting,and overall code is to have continuous venting per a cathedral ceiling,I believe it`s Certainteed that actually has the guideline of totally filling the rafter cavity with closed cell foam as an alternative to venting them(this way no condensation because as you mentioned no interior heat reaches the bottom of the sheathing

 

Well, the roof has been fixed all week, and, of course, we haven't had any rain all week either. We're not supposed to get rain again until next week, but I'm pretty confident we won't see any leaks.

Here's a shot of the decking after the shingles were removed that clearly shows how the water ran down the valley, hit the tips of the shingles and then followed the tops of the shingles across the roof:



There is now ice & water shield on the eaves and valleys, and the valleys are shingled (not flashed). We also moved the tube skylight so it was a couple feet away from the valley. The roofer did California cut valleys instead of woven. I don't expect to have problems with this because the other valleys on our house are done this way and we've had no leaks in 10 years. I'll just be extra diligent about keeping the valleys clean in the fall.

As far as the unvented cathedral ceiling goes, I'm just going to wait until there's a problem to do anything about it. The general consensus with everyone I've talked to around here is that it won't be a problem, and I saw no evidence of moisture on the decking or on the insulation around the can lights when I added the air-tight trim rings. I'll just cross my fingers that 12" of faced insulation is enough to prevent sufficient heat/moisture from reaching the roof and condensing.

 

I want to thank everyone for their very informative and educational posts here. My hat is off to Michael Thomas for his photos and illustrations and his willingness to educate forum members.

I want to add that I was at a loss about what WSU was, but I have always been aware of the need for it. Getting on the right page with nomenclature and acronyms is important.

So, I went looking for the mysterious WSU. I found the following link where none other than Michael Thomas answered my question. http://forum.doityourself.com/roofin...roof-wall.html

For those not in the know, WSU is Waterproof Shingle Underlayment. WRU is Water Resistant Shingle Underlayment.

It is important to recognize that water resistant is not the same as waterproof, which many homeowners learn the hard way after installing greenboard rather than CUB (concrete underlayment board) under tile in showers.

Thanks again everyone for furthering our education.

 

Blacktoe. May I save a couple of those pictures? May I assume the shingle tops weren't clipped to cause those water tracks? It's a typical cause and effect.

I like keeping examples of what did and didn't work on my site and elsewhere for show and tell explanations.

 

Feel free to use my photos for your site (and thanks for asking). You're correct, the tips of the shingles were not clipped. I'll be happy to provide any other photos or information you might want to help someone else make the same mistakes we did. =)

 

I do thank you sir. I appreciate that. I'm also sending you a PM about other pictures. Thanks in advance. Frank

 

I meant "help someone else *from making* the same mistakes we did." =)

 

The roofers here fully understand waterproof shingle underlayment