How to fasten shingles on flat roof???

[DrDan]

I have a flat roof with a pitch on a chicken coop I just finished. Want to put shingles on it since I have some left over from another project but really wonder how you fasten the top row of shingles without putting nails right out in the open where leaks will start.

Also what is the reason for roofing felt? I have some and can put it on, but just wonder why you can't put shingles right over OSB board.

Thanks

Dr Dan

 

[JATO_RaT]

A flat roof with a pitch? A shed roof perhaps is what you meant where you have a slope from front to back. A gable roof where you have a center peak, at any rate, shingle roofs really need to be on a 3/12 pitch to be effective. A 3/12 is a 3" drop for every 12" run or horizontal distance. Typically there is not a problem with exposed nails for the cap shingles. If you felt the need, there are now elastomeric roofing sealants/adhesives available that could possibly do the job without nails, but personally, I would still opt for nails since the expansion/contraction of asphalt products on the roof is significant. Felt is used for both a vapor barrier and additional waterproofing particularly during application. Rat

 

[GlueGuy]

The felt is the primary water proofing member of a roof system. The shingles primary function is to protect the felt.

The GlueGuy

 

[StoneHeartFarm]

Dr Dan,

Put on the felt, it only takes a short time. You'll appreciate it when you have to strip those shingles back off. Most shingles are designed to melt somewhat in the hot sun and stick together, forming a solid mass. Seems to me the felt is there to make it easier to remove the shingles later, since they'll be stuck together and not stuck to the OSB. The felt also provides a second layer of defense against leakage, and a slight cusion to the shingles when you're up there walking around on them. I assume the top row you are talking about is a "cap row", I don't know if you have a shed type roof (one slant only) or a standard roof (inverted "v"). The cap row is usually smaller than the other shingles. You have to cut full sized shingles down (in 1/3rds. Just follow the slots already cut in the shingles). If you look at the back of standard shingles, there is a seal strip (covered with clear plastic tape). You want to save that part as part of your cap shingle when you cut them down. Start at one end of your peak (lets say the left hand side). Pull the strip off the back of your cap shingle, lay it in place and put 2 nails in it at the end opposite the seal strip. Peel another cap piece and lay it over the first, with the seal end covering the nails on the first piece, nail it just like the first one. By repeating this until you reach the far end, you cover all the nail heads on the cap shingles except for those on the end. On the last one, I've always tarred the heck out of it and just stuck it down without nails. Seems to work just fine. The first good hot day, the shingles should start sticking together.

Hope this helps /w3tcompact/icons/smile.gif

SHF

 

[DrDan]

Yup that's what I've got a shed roof. Thank God it's only 4' X 8'! In this heat we'd probably be stuck to the dang shingles too. Man what a guy will go through for a few fresh eggs everyday!

Thanks Guys,

Dr Dan

 

[skent]

Roofing shingles expand and contract at different rates than the wood under them. They try to stick (self-sealing). If you put then directly to the wood (w/o felt) they will try ti stick to the wood and end up not making a good seal (always being pulled and pushed with heating and cooling). Felt is not that expensive and will increase the life of the roof. Small roofs (like a dog house) generally do not have the need for felt though.

Steve

 

[JATO_RaT]

Glue Guy, I would disagree with that statement about the felt being the primary water sealer. At best it is secondary, at worst it becomes the primary. Reroofs over existing typically leaking rotting composition roof types don't necessarily have to have a layer of felt under them. Its advisable, but not required. Actually, I not only won't do reroofs, but time after time it is shown that reroofs will not last as long as roofing over a smooth surface like plywood, OSB, or like they used to use, 1x8. This is proven many tmes over when a previously remodeled home needs a new roof. The reroof is in far worse shape then the roof layed over the remodel. Wood shingles do not allow for felt paper period and its use would surely rot the cedar shingle quickly from the bottom side (thus the skip sheating used as the base for shingles). Shake roofs are about the only roof that heavily rely on 30lb felt to maintain roof integrity from decaying shingles.
Some tips: use 30lb felt. Why? Because the 15lb won't stay put without a thousand nails even in a light wind. Its about twice the price, but still minimal for the whole job. For really troubling areas like low slope valleys, low pitched roofs or areas prone to ice dams, use a product like ***** (bituthane) sp? or Grace water seal. It can be nailed through a thousand times and still not leak. Nails hold better then staples but staples require less frequent (and faster) loading. I always use nails, an air nailer, 1 1/4" nails are good for new roof. Rat...

 

[DrDan]

The dang chicken coop is done!!!! I only had a 4' X 8' roof to shingle (Thank God) and was trying to keep costs down so we had two packages of shingles - one gray and one black. LOL I'll never do that again! Used some 15# felt we found up in the storage building (was used by some contractors for awhile and they vacated and left stuff laying). Anyhow, we alternated every other shingle gray then black then gray, etc. Staggered shingles 6" and ran into trouble at the ends with one row that would have taken about a 2" wide strip. Oh well it came out with some really neat geometric patterns and it should keep the biddies warm and dry. I'll post a picture later. It is a really neat coop. I got the plan off the net - it was a coop used in the Netherlands. Will house 3 full sized birds or 6 banties. Kinda prefer the Buff Orphingtons. With em eating all the grubs and other bugs the eggs are wonderful! Well next it's a small hog shed to raise two or three a year.

Dr Dan

PS Is there a reason to use 1 1/4" nails when the OSB (2 layers) is only 1" thick? I used 1" nails cuz I didn't want to hit my head on nails sticking through.

<P ID="edit"><FONT SIZE=-1>Edited by DrDan on 07/01/01 02:53 AM (server time).</FONT></P>

 

[Rch]

Rat et al, I've got a gamble roof on a barn and the asphalt shingles on the north side keep getting blown half way off, i.e. the edge doesn't seal, the wind lifts the shingle up despite a extra dollop of DAP asphalt sealer(in a tube like caulk) and lifted the 3/4" roofing nail almost out. Undeneath is OSB sheeting, I think 1/2". Is there something about OSB (oriented strand board) not holding on to nails ? Admittedly,It was a hell of a wind and that potion of the roof gets the brunt of a wind out of the northwest. These were common galvinized roofing nail that looked like they were dipped in zinc. The north side of the roof doesn't get that punishing sun and you can see dark fungal staining and even a few colonys of moss. It's an unheated building.

RCH

 

[GlueGuy]

Rat,

I was going to argue with you, except that you mentioned shake roofs as needing the felt (30#). There are still a lot of shake roofs out here. They are getting more rare, but it is still predominant. They absolutely need the felt. On our last home (before we re-roofed with composition), I was doing an inspection, and found one old shake that had worn completely through (could see the felt). That's when I decided we needed a new roof ASAP! Never got a leak though; because the felt was still intact.

But, I agree, the equation is a bit different with compostion roofs. I still believe in the heavy felt (30#), regardless of roof type.

Were you meaning bitumen, or is this some other stuff?

The GlueGuy

 

[DocHeb]

When I worked in a lumberyard we always recommended nails 1/4" longer than the total thickness of shingles and sheathing. The old guys there said you needed to go through the wood so the "peaked" wood around the exit site (inside the house) wedged against the nail and helped hold it in. This is anecdotal - don't know if it is based on fact.

 

[patrickg]

What about the nails with the litle ripples (circular ridges)? I've seen those in either zink plate or galvanized. They hold like the devil compared to regular nails. Why wouldn't you want those in a situation like high wind resistance?

Patrick

 

[JATO_RaT]

Dan, 1" nails are fine but will not hold as well as 1 1/4" nails. Even though the 1 1/4" nail penetrates and comes through, thats part of the reason it holds better. It will have a full thickness shaft, not the point embedded in the OSB. I too use 1" nails wherever its exposed.

OSB does not hold a nail as well as plywood, especially 5 ply. OSB's biggest draw back is once it absorbs moisture it will expand losing some of its density as well as pulling itself through the nails used to hold it down.

GlueGuy, once you see that felt on a shake roof, it really is time to replace. Saturated felt just doesnt hold up well to UV. The product which I was refering to is a 36" wide product much like felt. I believe it comes in 50' lengths. It has a paper backing on its sticky side. You peel off the paper as you lay it down. Once it touches itself (sticky side to sticky side) its a bi-itch. A great product to seal alot of difficult areas especially when nails are needed to be used through it. Rat...

Also, shakes are still used but fewer and fewer. 2 reasons I think account for this, 1. other products are filling the market, composition has become more attractive, and cement products have become more attractive. 2. The quality of shake is less then what it was. The trees are smaller and the shakes tend to curl and cup as a result. I still love shake. Putting down heavy shake is almost theraputic for me. The smell, color and choice makes it enjoyable.

 

[StoneHeartFarm]

Nails need to be long enough to penetrate through the wood to get a good grip. Nails with rings or ridges are okay to use, however, if you ever have to take the shingles back off, the job will be a bear. I used 30# felt on my roof as opposed to 15#. The primary reason being that the felt is heavier and doesn't move around as much, so the roof could be felted on Saturday and the shingles applied the following several satudays without the felt moving. Felt tends to sag and slide down the roof in hot weather. The 2 most common reasons here that people don't use shake shingles is cost and the hint of fire danger from drifting embers.

We used to run a wide strip of aluminum sheeting along the eave before starting our shingles. Anywhere from 16" to 36". The shingles would start at the top of this strip. The reason is to prevent ice dams. The aluminum is slick and any ice that builds up will slide off on a sunny day. The problem is that half a ton of ice falling from the eave of a house can do significant damage to anything setting underneath it. The latest technology is to use the Bituthene (sp?) product. The brand name at the local lumber yard is "Ice and Water Dam". The stuff is about 3' wide, has self stick strips and gets nailed down first, with shingles right over. Almost all new roofs are being done this way. Surprisingly, the product works and doesn't. While it prevents water from seeping in where it has been applied, ice dams frequently get bigger than the water and ice proofing. The water gets deeper and deeper on the roof and finally flows over the water proofing, under the shingles and into the attic. The aluminum caused the ice dam to fall off. the Water and Ice proofing does not.

RCH
Your bottom edge of shingles isn't sealing? Usually, we run a double bottom course, one shingle upside down and one right side up. The upside down row is a starter row, because the backs of the 2 shingles stick together, it makes this starter row twice as heavy, which helps it to stay down. About the only thing I can suggest is to get a gallon can of roof sealant and smear it under the shingles to help them seal. Doing it on a hot day will help. If the tube stuff isn't working, that's about the only thing I can think of that might help.

SHF

 

[RPM]

Nails will hold better if they fully penetrate the plywood or OSB. Reason is that the nails driving through the wood force the fibers apart - it is the resulting compression of the fibers on the nail that holds it there.

If the nail penetrates then the compression acts along the whole length of the nail ...

The rings that you get on nails are only any good if the nail is loose - the primary anchoring force is the compression of the wood on the nail. Good idea on decks and stuff where the wood may decay around the nail and loosen it up - but probably not shingles.

 

[Rch]

SHF, It's not just the bottom row of shingles that aren't sealed down, it's the bottom edge of many of the shingles all over the roof. I don't know the brand of shingles nor the weight of the underlying felt. The house has the same shingle and that has not been a problem. This is primarily on the lower (steeper) part of the gambrel roof on the north side (less sun).

RCH

 

[StoneHeartFarm]

RCH,

Are the corners on the tabs curling slightly?. When you stand back and look at the roof, does it look "patchy"? (Does it have spots with curling shingles and spots where the shingles look normal, "patches").

The reason I'm asking is that I have noticed the same phenomenon on a number of roofs. All 3-8 years old, and here are patches of curling shingles. The first time I saw it, I guessed the roof at about 15 years old. I was surprised to be told it was 5 years. Since then I have watched carefully and seen several other cases. Frankly, I have no idea what is causing it, but I suspect faulty shingles. Probably out of the same factory during the same period. If you look carefully and think about it, you can see where the roofer opened different bundles. Typically, the roofers lay several rows at a time, so an open bundle will be in a squarish patch rather than just run straight across in a line.

What I'm not sure about is the cause of the faulty shingles. I don't know if it is from the factory, shipping or storage. Shingles sitting in the back of a semi in the hot sun are going to be different when delivered than those dropped at the yard in the middle of winter or cool weather.

Until the roof starts leaking, it doesn't sound like there is much to be done, and when it does start leaking, you face the task of re-roofing. For the moss buildup, you might try some of the copper attachments. These are small formed sheets of copper that slip under the shingles. Apparently there is some chemical action between the copper, weather and roof that kills moss and keeps it from growing. Some of our roofers have told me they are using copper clad nails now to do the same thing.

SHF