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Roofing Questions & Answers


The following are questions and answers that we have found common from many of our visitors and members.  We will continue to list them here as the list grows.  If you do not find your question(s) answered here, please go to the Ask the Pros section and direct your question to the appropriate person.

HOW DO I SEAL WHERE A FLAT ROOF MEETS A SLOPED ROOF?
WOOD DECKING AND VENTING
WHAT PROBLEMS DO I LOOK FOR ON THE FLAT ROOFED BUILDING I'M BUYING?
HOW DO I BUILD A CRICKET BEHIND MY CHIMNEY?
HOW DO I ROOF OVER A HOLE MADE FROM REMOVING A SKYLIGHT?
HOW MANY LAYERS OF SHINGLES CAN I HAVE?
I HAVE A LEAK, BUT I'M UNSURE IF IT'S MY CHIMNEY. WHAT CAN I DO?
WHAT'S THE DIFFERENCE BETWEEN 25 AND 30 YEAR SHINGLES?
WOULD AN OVERLAY INSTEAD OF A TEAR-OFF BE A REASONABLE APPROACH?
WILL A METAL ROOF AFFECT MY ENERGY BILL?
HOW MUCH VENTILATION DO I NEED?
WHAT CAUSES ICICLES ALONG THE EAVES AND WHAT CAN BE DONE ABOUT IT?
CONSTRUCTION ON A CONDOMINIUM COMPLEX
ANOTHER VENTING QUESTION
VENTILATION OVER STEEL DECKING WHILE USING ADHESIVES
I HAVE HORIZONTAL CRACKS IN MY SHINGLES. SHOULD I REPAIR?

 

HOW DO I SEAL WHERE A FLAT ROOF MEETS A SLOPED ROOF?
CONTRIBUTOR WRITES:
What is the best way to seal the joint where a flat (patio) roof meets the house (sloped) roof? I had to replace water damaged plywood on my patio's roof and I had to remove the existing shingles (asphalt) back about one foot. Also, what is the best way to apply rolled roofing to my patio roof? Thanks in advance for the help! -M. P.

RESPONSE:
I'll try to help you as best I can. To properly seal at the flat-to-slope roof area, you need to remove the first five courses of shingles. You then install the roll roofing up to the bottom edge of the sixth row of shingles. I'm not sure how much you want to spend, but you'll want at least a base sheet and a cap sheet on the flat roof. Nail the base sheet to the deck and then install the cap sheet with cold-applied adhesive at the rate of approximately 2 gallons per 100 square feet. There's a special broom that you'll buy to apply the adhesive. Further instructions should be on the can of adhesive. Start at the low end of the roof and work your way up so that water runs over the laps and not against them. Next reinstall the 5 rows of shingles.
NOTES:
(1). If allowed to run, the adhesive can drip between the seams of the plywood and onto whatever is below the roof. It's very difficult to remove from things without making a mess.
(2). The bottom course of shingles should be about 6" away from the flat roof. Try not to go any lower than that.
-E.J. Sandquist, RoofHelp.com
CONTRIBUTOR WRITES:
EJ, Thanks for the advice and help! -M.P.

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WOOD DECKING AND VENTING
CONTRIBUTOR WRITES:
Hi, I am about to start on a reroofing project at my cottage. The roof is about 400 sq.ft. and has a 2 1/2 in 12 slope. It is an existing wood deck made up of 2" X 6" X 1 1/2" and is about 40 years old and appears to be in good shape viewing it from the inside of the building. It has a cathederal ceiling (under side of roof deck)with no insulation or vapour barrier. I figure that I have two ways to do the job, Plan 1 is my preference. PLAN #1 Remove the existing roll roofing down to the wood deck. Lay down 6 mil vapour barrier. Strap roof deck with 2x2 lumber 2 feet apart. Install 1" thick deckmate insulation between lumber. Nail 5/8" plywood over top. Apply two layers of 15 pound felt. Apply 25 year shingles. The problem I have here is ventilation. I have no way of installing eve vents. I can install a ridge vent though. Question - would it be practical to intall small mushroom type vents near the edge of the roof in each of the 2' wide insulated spaces venting up to a ridge vent. PLAN #2 Remove the existing roll roofing down to the deck. Cover existing deck with 1/2" plywood to provide additional support to the deck and smooth out any cupping that may have occured in the wood 2 x 6 deck. Lay down two layers of 15 pound felt on top of the plywood. Install 25 year shingles. Install a drop ceiling inside creating a attic and insulate and vent the space above the ceiling. Are both solutions practicle? What is your opinion? How would you approach the job? Thanks for your time. -Bill

RESPONSE:
Hi Bill. PLAN #1 - If you have a cathedral ceiling, then the bottom side of the deck is already ventilated. The idea behind roof ventilation is to get fresh air circulating to the underside of the deck. The general use of doors, windows, etc. will take care of that for you. Roof ventilation products are used to ventilate attic spaces (a.k.a. roof spaces) where there is dead air such as between a suspended ceiling and a roof deck. If you go with this plan, you will need some ventilation for the underside of the 5/8" plywood. This can be done by the ridge vent that you mention for use as an exhaust vent, and a specially made edge material with holes cut into it for use as an intake vent. (The mushroom vents you mention would work but they would sure be noticeable.) The specially made edge material would then need to be countered by a drip edge material to help keep rain out. See the attached drawing.<picture> You could then nail 2 plies of #15 felt over that and then install the shingles. You'll need the two plies in order to get a shingle warranty. Check with the shingle manufacturer to be sure about this. Screw the 2 by 2's to the rafters with screws long enough for 1" thread penetration of the existing 2 by 6 decking. PLAN #2 - Scratch this one. You can't encapsulate decking like that or it will warp severely. The drop ceiling is a good idea, though. ALTERNATE PLAN #3 - Remove existing roofing. Install 2 layers of #15 felt underlayment using 1" simplex nails, plasti-cap are preferred. Install new shingles using 1.25" nails. If you are really interested in insulating the roof, go to http://www.firestonebpco.com/marketin/intro.htm and check out their nailbase insulation. Simply screw it down to the rafters and put your roof on top of it. Much simpler than doing PLAN #1. This is what I would do. You will have to have special drip edge material made for use as intake ventilation. Let me know if you have any further questions. Thank you for visiting RoofHelp.com -E. J. Sandquist, RoofHelp.com

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WHAT PROBLEMS DO I LOOK FOR ON THE FLAT ROOFED BUILDING I'M BUYING?
CONTRIBUTOR WRITES:
I'm buying a building in Chicago that has a flat roof. The building was built in 1927. The current tenants have not reported any leaks, but I want to have it checked out because the 70 year old woman I'm buying it from can't remember when it was last re-surfaced. I'm buying it "as is" so I did not have it inspected by a certified inspector. I'm sure a building contractor will tell me I need a new roof. What kinds of things should I look be aware of? How often does a flat roof need to be re-surfaced? It is currently a black roof. My dad says a silver roof last much longer. Is he right? There is an attached garage with a flat roof. I can see where the coating is pulling away from the building, so I'm sure this will need to be replaced. What kinds of things do I want to have included in a quote from a building contractor. Is a flat roof like a shingled roof -- do you need to strip off all the layers after a number of applications? Your web site has helped with some questions. Thanks for your advice on these. -R. K.

RESPONSE:
I will help you as best I can without seeing the roof.

Maintenance is the key to long-term performance of flat roofs (or any roof). Depending on the conditions, flat roofs should be resurfaced every five to ten years. Five on the average if a flat roof ponds water. If there is a slight slope and the roof drains well, it's usually about every ten years.

Your dad is correct. A silver roof will last longer because it reflects the sun's rays. UV rays are the most damaging element to a roof. A good type of coating would be a "fibered aluminum coating". It is available from most all roofing supply warehouses and often from hardware stores or the local home improvement warehouse. If you plan on applying a coating, simply follow the directions. The average amount that is needed is 1.5 gallons for every 100 square feet. The roof will need to be clean before it is applied. This usually involves scrubbing some areas.

Just because the coating is pulling away from the building on the garage doesn't mean that the roof is no longer in good shape. It may simply need to be recoated with some asphalt emulsion. This you can do yourself. Again, simply follow the instructions. For some detailed information on coatings and emulsions, contact your local roofing products retailer.

Here are some things that you may want to watch for. Look at the penetrations - pipes, vents, etc. - this is the first place where deterioration will start to show. What you'll want to watch for are cracks. Surface cracks, a.k.a. "crazing", are not a real big deal. You'll want to check for cracks that you can stick a pocket knife blade into. The reason this is bad is because of freeze-thaw. Water gets into the crack, freezes, and splits it wider. This is a big problem up north where you live.

If you get a quote from a contractor, ask him what it will take to prolong the life of your roof. If he says that you can't, then simply tell him that you do not have the money to install a new roof and you need something done. If he insists that there is nothing that he can do and that you need a new roof, then he may be correct. However, you want to ascertain this by talking to three different contractors.

Building code in all states that I've worked (37) states you can only have two roofs on a building before removal is necessary. If you have more than one roof on your house, then they'll have to be removed to comply with building code. You can determine this by making a quick call to the city building office. Ask for the building code enforcement department. They are usually quite helpful.

I hope that I've been able to help you. Unfortunately, not seeing the roof has me at quite a disadvantage. If you should have any questions, or if you should need clarification on some of this information, please don't hesitate to contact me.

Thank you for visiting RoofHelp.com
E. J. Sandquist
RoofHelp.com

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HOW DO I BUILD A CRICKET BEHIND MY CHIMNEY?
CONTRIBUTOR WRITES:
The roof is galv. metal 9 on 12 pitch with a chimney at the eave downslope -- not on the gable end but on the side of the house -- thus, downslope, I think. The severe pitch of the roof forces the rainwater to slam into the chimney. There is a 8" flashing we put in, but it doesn't work very well. It's been leaking for several years in severe, heavy rains. The width of the chimney is also part of the problem, it's approx. 6' wide from local limestone construction. Looks like we need to build a cricket. I can figure the dimensions but I don't see where the flashing goes betwen the new cricket and the old roof. Precisely, from the new ridge beam of the cricket connected to the old roof passed the edge of the chimney. Thanks for any help you can provide. -J. D.

RESPONSE:
I have been looking for some details from metal manufacturers that would help you with your problem but have been unable to locate any. I recommend that you visit the National Roofing Contractor's Association's (NRCA) web site and order the NRCA Steep Roofing Manual, Fourth Edition which can be found at http://www.nrca.net/services/publications/tech.asp. NRCA has a metal roofing manual but it does not address crickets, so don't order it. The steep roofing manual and a little common sense will give you the answers you need. Cost is currently $75. In response to your questions regarding the flashing, these will also be addressed in the manual; and should you have any questions about the information, I will try to answer them. Unfortunately, I cannot send a copy of the details you need because it is all copywritten. I do feel that the manual will help you and I recommend it. If I can be further assistance, please let me know. E.J. Sandquist, RoofHelp.com

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HOW DO I ROOF OVER A HOLE MADE FROM REMOVING A SKYLIGHT?
CONTRIBUTOR WRITES:
Hello, I live in Casper, Wyoming and am having trouble with a leaky roof. The previous owners built an addition onto the house and did a poor job on the roof. The roof is a flat roof (built-up tar with gravel). There is a skylight in the middle that constantly leaks. We never use the skylight so I would like to take it out. After taking out the skylight how should I re-cover the hole? Thanks! C. D.

RESPONSE:
Skylights are a big problem. If you don't know anything about doing patch work to tar & gravel roofs, I strongly advise that you contact a roofing contractor. It's not difficult, but you do need to know something about it. After removing the skylight, you'll want to cover the hole with decking material. Use the same kind of decking that is on the rest of the roof. My guess is it's probably 1/2" CDX plywood (CDX simply means it's rated for exterior use). I have to tell you that all professional roofing organizations recommend that the plywood be replaced in whole sheets only. What I mean is, don't just cut a piece to fit, you need to replace the entire piece. It has to do with maintaining the structural integrity of the roof. Now comes the roofing part. I really can't help you here without actually seeing the project. I can give you some tips, though. (1). Your tie-in with the existing roof should be at least 12" in width. (2). You should prime the existing roof with asphalt primer which available at most hardware stores. (3). You can use Cold Process materials which will make it easier if you do it yourself. (4). There are references available to help you. Please visit http://www.roofhelp.com/library.htm -E.J. Sandquist, RoofHelp.com
CONTRIBUTOR WRITES:
Thanks for your help, it is much appreciated. -C. D.

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HOW MANY LAYERS OF SHINGLES CAN I HAVE?
CONTRIBUTOR WRITES:
Could you advise how many layers of shingles could a roof take? When a contractor repairs/installs a roof, should he peel off the old layers or add on new layers of shingles? Presently, our roof has 4-5 layers and it is leaking. Our contractor told us that he would just install a new layer of shingles. Thank you. -S. in New York City

RESPONSE:
For your information, it is illegal to have more than two layers of roofing on your roof. My advice would be to remove all layers as there may be damage to the roof deck and this should be taken care of. The damage I refer to will probably be dry rot, which is: "Wood rot caused by certain fungi. Dry rot can result from condensation build-up, roof leaks that go untended, or from other problems. Dry rot will not remain localized. It can spread and damage any lumber touching the affected area." If you do not wish to remove all layers, then remove everything but the bottom layer and install a new layer over that. Please note that the bottom layer is liable to be extremely brittle and in very poor condition and may not make a suitable underlayment for the new roof. Your roofer should be able to tell you. If I can be of further assistance, please let me know. -E.J. Sandquist, RoofHelp.com
CONTRIBUTOR WRITES:
Thank you very much for your response. We will be in a better position to deal with our contractor. -S

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I HAVE A LEAK, BUT I'M UNSURE IF IT'S MY CHIMNEY. WHAT CAN I DO?
CONTRIBUTOR WRITES:
Dear RH, My chimney leaks into the basement around the outside of its casing. At first, we thought rain was coming down the inside, but there is some staining now around the outside of the chimney when I look up at it by the furnace. I checked the rooftop and sealed around the chimney and flashing with a couple tubes of tar but it seemed to have had no effect. I guess my next step will be to borrow a ladder and check inside the attic for staining. The house is a 20 yr old bungalow in Saskatoon, Saskatchewan, Canada and the chimney is the type which is known for giving problems. I inspect it frequently in the winter and haven't had any trouble yet. Thanks, RCR

RESPONSE:
I have been doing some thinking with regard to your problem and have consulted some friends of mine who live up in cold weather country such as yours. The first thing that needs to be done is to find the source of the problem - whether it's coming from the roof, the flashings, or the chimney. I recommend doing this by water testing the chimney. You'll want to start from the low side and go up the roof. You do this because if you start on the high side (or upslope side) of the chimney, then it will be unclear if the leak is coming from the upper side, the sides, or the lower side of the chimney. Conversely, if you start on the low slope end with your water testing and it leaks, then you know it has to be the low slope end because you haven't run water on the sides or top yet. (1) Start at the low end of the chimney and run water on the roof for about twenty minutes. Keep the water off of the chimney. Run water only on the roof around the base of the chimney on the low slope side. Check for leaks inside the house or in the attic if it's accessible. If leaks occur, then you know there is a problem with the flashings or roofing materials on the low end of the chimney. If no leaks occur, make note of it and go to the next step. (2) Next, water test the sides. Run water along the sides of the chimney. First one side and then the other. Each for about twenty minutes. Be sure to keep water away from the upper side.   (3) If no leaks occur on the low end or on the sides, water test the upslope side of the chimney for about twenty minutes. If at any time during the above water testing procedure you detect a leak, immediately stop testing. These leak areas will need to be repaired by a roofer, or yourself, before you continue water testing. If no leak occurs after water testing, you will then need to test the watertight integrity of the masonry on your chimney. Do this by running water about a third of a meter (12 inches) up the chimney for about twenty minutes at a time, one side at a time. Keep going up until a leak occurs. If a leak is sourced in this manner, mark the side where you suspect the leak to be coming from, and contact a mason to tuck-point the chimney. I hope this information helps.

Please contact me if I can be of further assistance.

Thank you for visiting RoofHelp.com.

Sincerely, E.J. Sandquist
RoofHelp.com

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WHAT'S THE DIFFERENCE BETWEEN 25 AND 30 YEAR SHINGLES?
CONTRIBUTOR WRITES:
Dear Roofhelp, Could you please explain the difference between 25 year and 30 year in laminated architectural type shingles? Thanks, MK

RESPONSE:
Shingles are referred to as "25 Year" and "30 Year" because of the manufacturer's warranty. The difference in the two is the thickness which corresponds to the weight of the shingle. 25 year shingles are generally between 240 and 265 pounds per 100 square feet while 30 year shingles weigh between 265 and 300 pounds per 100 square feet. -E.J. Sandquist, RoofHelp.com

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WOULD AN OVERLAY INSTEAD OF A TEAR-OFF BE A REASONABLE APPROACH?
CONTRIBUTOR WRITES:

Our leaking roof currently has three layers of asphalt shingles on it. One of the contractors we asked to bid on the replacement job suggested removing only the uppermost layer of shingles and replacing them with new, high-quality shingles; his thinking was that we should spend the money on enhancing the shingle quality rather than on removing the lower layers. We've never heard of this approach -- is it a reasonable one? Thanks for your help. -A. A.

 

RESPONSE:
Yes, it's reasonable. First off let me tell you that I have worked in 42 of the 50 states. In every state, more than two layers of roofing is illegal. So you will have to remove two layers of shingles before you can install another one. Secondly, let me state that on average, shingles last about 3/4 of their service life. Here is a cost analysis example. Let's say 20 year shingles will last around 15 years. Maybe they cost around $120 per roof square installed (1 roof square = 100 sq. ft.). That means they cost around $8 per square per year - $120 per square divided by 15 equals 8. 30 year shingles may last 22 years. Let's say they cost around $150 per square installed on average. These will cost $6.82 per year. In the above scenario, the thirty year shingles are obviously the better deal. This will not be the case in all situations because there are many factors which affect the quality of a new roof - material quality, deck quality, ventilation, geographical location - to name a few. Of all these, I firmly believe that quality of workmanship has the greatest effect. Roofers who take the small amount of extra time needed to do a job right will generally have the longest lasting roofs. Please view the section of RoofHelp.com "Choosing a Contractor" before you contract your roof to be done. Thank you for visiting RoofHelp.com. -E.J. Sandquist, RoofHelp.com

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WILL A METAL ROOF AFFECT MY ENERGY BILL?
CONTRIBUTOR WRITES:
I recently had my roof redone using metal. Some of my friends state that it will get extremely hot in the summer. Is this true? If so, is there something I can do to alleviate the heat? Thanks for the help. -T. M.

RESPONSE:
There are conflicting opinions about this in the roofing industry, so I'll give you mine. I don't think you have anything to worry about. Metal is a great conductor, so as fast as your metal roof heats up in the morning, it's going to cool down that quickly in the evening. Some people argue that the problem is not the metal heating up, it's all below-roof components, such as the roof deck, air space in the attic, ductwork, etc. I agree that these items will stay heated longer in the evening after the roof cools down, but they'll also stay cooler longer in the morning after the roof heats up. When talking to people with metal roofs, they all seemed pleased with them and have reported no significant changes in their monthly energy bill. One thing that would really help is to ensure that your attic is properly ventilated, visit http://www.roofhelp.com/ventilation_main.htm. Please let me know if you have any further questions and thank you for visiting RoofHelp.com. -E.J. Sandquist, RoofHelp.com

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HOW MUCH VENTILATION DO I NEED?
CONTRIBUTOR WRITES:
I have a 2800 square foot house with an average slope and I want to install the right vents the next time I reroof. What type of ventilation and how much do you recommend? Many thanks for any help you can provide. -T.R.

RESPONSE:

Proper attic/roofspace ventilation will help with energy efficiency, help reduce ice damming, and also help prolong the life of your roof. The amount of ventilation needed is easy to figure. Industry standard is that for every 300 square feet of attic space, you need one square foot of intake ventilation and one square foot of exhaust ventilation. An even better way to do it is to run continuous soffit ventilation (intake) and continuous ridge ventilation (exhaust). For more information, visit http://www.roofhelp.com/ventilation_main.htm. -E.J. Sandquist, RoofHelp.com

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WHAT CAUSES ICICLES ALONG THE EAVES AND WHAT CAN BE DONE ABOUT IT?
CONTRIBUTOR WRITES:
A client of our's is faced with a roofing problem, and we were looking for the reason...   She has an asphalt shingled roof, which is sloped (although I am not sure of the slope amount). Her problem is that she is getting a great number of large icicles forming along her eavestrough line. She is concerned that her roof will begin to leak, or that she is losing heat from her home. Should she replace the roof, or the insulation, or both? What extra damage can be caused by the icicles? Will she be able to wait until spring? -A.K.T.

 

RESPONSE:
The problem is a common one called "Ice Damming". Ice dams form when snow continually melts at the roof edge. When snow accumulates on a roof, the heat in the attic will cause it to thaw and the resulting water will run down to the eaves where there is no heat and it will refreeze. This can occur on a daily basis until large icicle form at the eaves. If no protection was installed when the roof was put on, the ice can eventually back up under the shingles and cause leaks. It can also get bad enough to rip the gutters right off of the building. Ice dams can allow moisture to damage attic insulation which reduces the R-value of the insulation and raises the energy bills, they allow water to penetrate wall cavities which can cause paint and plaster to peel and also rust nails, electrical boxes, or any other non-rustproof metal building material located in walls.

There are three good ways to help prevent ice dams or the damage caused by ice dams. Proper ventilation will help maintain the ambient air temperature at the roof level thereby not allowing the snow located on the roof above the living areas of the home to thaw. Heavy attic insulation will help insure that very little heat gets into the attic. The installation of an ice and water protection membrane to the eaves and valleys of the roof which will help prevent damage, but doesn't treat the root of the problem, which is heat loss. Heat tapes are often used as a solution but rarely prove effective.

  • For information on ice and water protection membranes, visit: http://www.roofhelp.com/icedams.htm
  • For information on ventilation, visit: http://www.roofhelp.com/ventilation_main.htm
  • For an excellent article on ice dams written by college instructor, visit: http://www.umass.edu/bmatwt/dams.html

Please let me know if I can be of further assistance. -E.J. Sandquist, RoofHelp.com

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CONSTRUCTION ON A CONDOMINIUM COMPLEX
CONTRIBUTOR WRITES:
Gentlemen, I am the Vice President of a sixty-four unit condominium complex. We are presently engaged in putting reconstruction work to bid. The roofer of our choice is coordinating with other bidders in another phase of the work we are having done. The situation is the joining of the roof and a part of the top-front edge of a stucco finished facia which was damaged by high winds. My question is awkward at best, as I am unfamiliar with the necessary terminology to communicate the problem to you. But, here goes. In sloping our roof to join the front edge of the building , the contractor has suggested layered shingles. This method seems vastly labor -intensive to say the least. Are we being led astray? Are materials available that would work as well or better than what has been recommended to us. We are spending a very large sum on this endeavor. We cannot fail in our effort to make our homes safe again. Please help me if you can, and accept my thanks in advance for  any asistance you can provide. -L.I.

RESPONSE:
Dear Sir, I'm having a hard time visualizing the problem and I'm not sure what "layered" shingles are. My guess is, if the contractor is talking about asphalt composition shingles, then he is referring to laminated, two-piece shingles. I can't see how this would help your problem except to maybe cover it up, somehow. The labor for installing these shingles is the same as it is to install any shingle, so don't worry about added labor costs. If you are willing to give me your location, I might be able to put you in touch with a roofing consultant nearby who can help you out. I would recommend a consultant because of the large amount you are spending on the project. Who knows, the consultant may even be able to save you some money.

Look forward to hearing from you.

E.J. Sandquist
RoofHelp.com

CONTRIBUTOR WRITES:
Dear Mr Sandquist, Thank you for your response to my question. I have taken your advice. I have hired a local roofing consultant who has a very good reputation for working with structural engineers, and construction contractors. You were just the person I needed to consult. Your timely advice was taken seriously. I appreciate the time you took in responding to my inquiry. Thank You.

Sincerely, L.I.

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MORE VENTILATION QUESTIONS
CONTRIBUTOR WRITES:
Great homepage...has helped a lot, but need additional help, suggestions...

I'm in MAss, colonial home, 35x25 foundation with moisture problem in the attic, right above the bathroom...this is a new roof two seasons ago put in this 15yr old home...originally roof only had gable vents, (12x12) NOW, the continuous ridge vent and button soffit vent (2.5") were inserted...27 soffits 16 inch apart on each side of the overhang...

Do I have enough input ventilation according to the 1/300 NFVA code (there is a Kraft face insulation, 6inch and unface across the joist)...

REQ'TS: according to my calculations and your great example...I need 210 sq. in. total on the I/O.....vents where 1/2 of that is soffit input vent... (105sqin)...minimum? ...(.35*25=875/300=2.92*144=420/2=210 )

INSTALLED: I have 840sqin on the ridge..installed....(.35*12*2 ) a cobra vent by GAF...I may need to verify on the roof that it was properly installed with a min of 3/4" clearance of vent on the roof and a 1" cut on both sides of the ridge board in the attic....

For the soffit button I came out with 66sq. in. installed, where 105sq. in. is min code requirement.

3.14*(1.25) sq= 4.9 @ 50% reduction=2.45sq. in./button *54 buttons = 132 sq. in. (66 sq. in./side)...1.25 is 2.5 in. diameter of the soffits...

SO NOW WHAT? According to my readings I need that 1:1 ventilation of  input/output vents. The contractors, independent 'consultants' all say that the buttons s/b sufficient...and having the gabel vent will not harm...'more is better'. Also I have not inserted the proper vents/baffle rafter vents, so there may not be proper vent flow....I have inserted 6 together for a test and blocked one of the gables, the other gable has a fan hooked up on a thermostat for 70F or above - summer applications....

There is a lot of bathing goin on recently. I have not insulated the pull down staircase to the attic yet...TBD where the steps is just outside the bath door leading into the staircase...chimney effect.

Dishwasher and laundry and all windows closed up for the seasons add to this moisture. Mold and dampness on the sheathing must be address prior to mitigation.

HELP FRANK

RESPONSE:
Dear Frank,

Remember from my ventilation page that when talking about vents, what you're 00009cin is the Net Free Vent Area of the vent. On your ridge, you have Cobra vent which has 16.9 sq. in. of NFVA per lineal foot which is giving you a total of 591.5 sq. in. of exhaust vent (35' X 16.9 sq. in. = 591.5 sq. in.) Your "button" vents, as you refer to them, will give you 1.6 sq. in. NFVA per vent if they're louvered and about 2.3 sq. in. NFVA per vent if they have only the insect screen in them. With 27 installed, this gives you a maximum intake ventilation of 62.1 sq. in. That's badly off ratio with the 591.5 sq. in. of exhaust vent. I suspect that what's occurring is called a Ventilation Short Circuit. The button vents aren't able to provide enough intake for the proper cross-ventilation so the air is being pulled in through your gable vents to compensate. When this happens, the only part of the attic being ventilated is that area between the gable vents and the ridge vents and a small area down near the button vents. Gable vents usually provide between 40 and 800 sq. in. of NFVA, depending on size and shape.

RECOMMENDED SOLUTION Make sure your ridge vents have been installed correctly and plug the gable vents. Install new vents down under the eaves with a minimum of 22 sq. in. of NFVA each. You'll probably have to use square vents as the largest round vent I know of has only 13 sq. in. of NFVA. A company called Lomanco, Inc. at 800/643-5596 has a model C416 with 28 sq. in. of NFVA that will work. The "More Is Better" rule applies only if you have good ratio. You may prefer to install a continuous soffit vent on either side of your house. These will need a minimum of 8.5 sq. in. of NFVA per lineal foot. Lomanco also makes these. Their model #105 would work fine. (http://www.lomanco.com)

To get rid of any mold or mildew on the underside of your deck, mix up a mild bleach solution (1 cup bleach to one gallon water) and spray apply. Be careful and don't get any in your eyes or on your skin. You may have to do this several times depending on the severity of the problem. If you have any further questions, please don't hesitate to email me. I will forward your problem to others to get additional opinions.

Thank you for visiting RoofHelp.com

E.J. Sandquist

FYI - The 300:1 ratio is a minimum requirement. If the intake/exhaust ratio is okay, exceeding the 300:1 will not adversely affect your energy bills. More Is Better in this case.

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Ventilation Over Steel Decking While Using Adhesives
Contributor Writes:
Sirs;

Thank you for this forum and your spare time. We are building a passive solar home of block and steel.Building is built using commercial materials. Roof slope is 2 in 12. The kitchen roof uses steel web joists supporting steel decking.The insulation is polyisocyanurate with glass reinforced felt backing of thickness to achieve R-35. Then OSB 4x8 sheets will cover this.We are using a product called Inst-stik (a polyurethane foam adhesive) to secure each layer to itself as well as the steel decking.The OSB will then be covered with a product called Peal and Seal,which is a reflective foil covered rubberized asphalt that will be used for waterproofing/weatherproofing.

My questions are:
Will this system work?
Should I ventilate and how ?

Thank you again for your time.

Don L.

RESPONSE:
The system you are having installed sounds as if it will work. Insta-Stik is fairly new to the market but has had good results. One thing you may want to consider is that some manufacturers of roof insulation are making what's referred to nailable insulation which is polyisocyanurate with 1/2" OSB factory-attached to it. (Visit http://www.atlasroofing.com/insulation/acfoam2.html for an example.) The argument against using this has been that, if attached seperately, the OSB would cover the insulation joints in case of a leak. My response to this is that when you have a leak, the water will have to travel from the joint in the OSB to the joint in the insulation, making the leak that much more difficult to detect which can prolong repair time. Please don't let me deter you with this talk of leaks. Being in the roofing industry, it's obviously my number one concern in all situations.

Peel and Seal is a good product. I don't have any experience with it other than doing repairs to roofs and sealing duct work and the like, but I've had excellent success with it in those situations. A good friend of mine has successfully installed it and really likes it. You can read a bit more about it at http://www.coshocton.com/mfm/peelseal.htm.

As far as ventilation is concerned, you don't need to ventilate. With the configuration you have and the aluminum surface and high R-value you should experience good energy savings in a comfortable environment.

Best of luck to you in your new home. Please let me know if I can be of further assistance.

Thank you for visiting RoofHelp.com.

E.J. Sandquist

RoofHelp.com

RoofHelp's #1 Piece of Advice: It doesn't matter how good a roof system is if it isn't properly installed. Proper installation of a roof is the #1 key to a quality roof system. Be careful when choosing a roofing contractor.

Contributor Writes:
Mr. Sandquist;

Thanks again to you and thanks for the rapid response to our questions.The roof I spoke about goes on tomorrow !!!

Thanks;
Don L. and family

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Horizontal Cracks In Shingles
Contributor Writes:

E.J.,

Thanks in advance for taking the time to read my e-mail. My wife and I are first time home buyers and when we had our roof inspected we found out that we had cracked shingles. Approximately 10 - 15% of the shingles had horizontal cracks in them. The roof has a very nice slope to it - I can't give a technical slope to it. If someone where to get on the roof to do repairs they would have to use boards to keep from sliding. There are 2 layers of shingles on the roof and the most recent layer is approximately 13 years old. The roofers we have talked to are saying that they would be able to rip the top layer of the cracked shingles off and replace them - some they would have to tear down to the board.

The house is located in Sun Prairie, WI, and building code allows you to have 2 layers of shingles on a roof and so long as your not replacing more than 25% of the shingles, you can repair the roof.

My questions are:

- should I have the damaged shingles torn down to the board?

- if I only have the damaged shingles torn down to the board, do I run the risk of having water accumulate in those areas since the rest of the roof?

- will have 2 layers of shingles?

- if I need to replace my roof in 5 years, will I also be replacing the shingles I fix this time?

- what recommendation would you make?

Well those are my questions. Once again let me thank you for taking the time to look at and answer my question.

Thanks!!

Alex A.

 

RESPONSE:

Dear Alex,

Cracks occur in shingles because the shingles are in the process of failing - it's a manufacturing defect. A certain shingle manufacturer had a class-action suit filed against them for this very reason in the southeast.

If 10-15% are cracked now, a larger percentage may crack later on. You may wind up needing to replace even more. Here's my suggestion if the roof isn't leaking. Don't repair the shingles. Let them stay cracked and start putting money into a separate bank account where it will draw interest. That way you'll have a head start on your finances when it comes time to reroof. Your roof could last another 5 years before the problems become severe enough to require replacement, especially with it being as steep as it is. My guess is you probably have at least an 8:12 slope which is excellent for shedding water.

Should you decide you'd prefer to go ahead and replace the shingles, here are my answers to your questions:

1. Don't tear down to the roof deck if it can be avoided. It makes proper tie-in more difficult. The need for a felt underlayment is eliminated if only one layer can be torn off.

2. On a steep roof, water will not accumulate. The difference in thickness will be only about 1/4" or so.

3. If you replace the roof in five years, then yes you will be replacing the shingles you patch right now. It's very difficult and not cost effective for a roofer to try to work his way around and tie into a bunch of shingles in the middle of a roof. The added labor would be much more than the cost to simply remove and replace the shingles.

4. My recommendation is the 2nd paragraph above.

Please let me know if I can be of further assistance.

Thank you for visiting RoofHelp.com.

E.J. Sandquist
RoofHelp.com

 

Contributor Writes:

E.J.,

Thank you so much for you help. I appreciate it and will make sure to spread your site's name around.

Alex

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