Dormers on my Roof

[Mike OMelia]

I have two Dormers. It is clear that the casing and siding was done wrong. The casing on the corners is rotted after 7 years. The siding, Hardiboard, is dissolving near the roof. It looks like it was "butted" too close to the shingles. After I drove arround looking at other dormers, I noticed that many had this trim piece running down the dormer, between the roof shingles and the siding. These are not vinyl sided dormers. What is that? Am I missing something? I'm getting ready to pull the bad siding tomorrow. I have the new siding, and bought poplar casing boards. Any advice would be appreciated. Roof is 10/10 and difficult to work, but I have built and placed safety barriers and work platforms.

Mike

[Steve Schoene]

Poplar isn't your best choice for exterior trim. Go with cedar or expanded PVC such as AZAK. Also consider the flashing between the siding and shingles so you can leave the proper spacing between roof and siding without opening avenues for water

[Larry Edgerton]

I'll second Azek.

[Steve Ryan]

Azek all the way, and it is available in 3/4 and 1". Poplar will not make it very long at all. Trim piece at roof line is prob a piece of J channel to cap the end of the Hardi board. Hardi Board is square in section so there are plenty of gaps at the ends for little critters to nest in. Is it really disolving? Cement based product. Could be that it was cut with a Hardi shear and the edges are just a bit crumbly. In any event, you want your siding at least 3/4 form the shingles, maybe even a bit more. This will allow re roof over the old shingles without a complete tear off.

[Mike OMelia]

What is Azek, does Lowes carry it? And, not sure what J channel is.

Thanks!

Mike

[Mike OMelia]

Does not look like Azek is available around here. Gone check a "real" building supply center... any other product? The J Channel is vinyl... lowes has 1/2" which seems about right.

Mike

[David Thompson 27577]

Trim boards should never be installed so that they touch the shingles. Same with Hardie -- leave a 1/2" gap, and don't caulk that gap. In addition, be absolutely certain that the step flashing is done right. It goes up behind the lowest row of siding, and bends out above the top half of a roof shingle (under the tab/lower half of the next shingle).

[Duane Bledsoe]

J channel is a strip of vinyl or aluminum that is literally shaped like a J when viewed from the profile side. It has a high back with a nail strip at the top that is slotted where nails go into it to hold it on the house. It comes down and spans across the bottom and then up the front. It is available in various widths such as 1/2, 5/8, and 3/4 inch. Beware, it will act like a small gutter and channel water that gets into it, but it should escape at the bottom as it runs down the slope of the roof. It's a necessary evil to use it to hide rough edges of materials used to side a house. It doesn't hurt vinyl so water in it doesn't matter, and the high back keeps it from getting up and out on the back side of it so it doesn't get wood behind it wet either. But if you use it to cover some type of wood or other material's rough edges, then you will get water on them.

I'd say the trim you saw on other houses could be a piece of wood or other material, and them it would be wrapped in aluminum trim to protect it. This would be something used to cover the exposed step flashing that is under each layer of shingles. Step flashing is used wherever a roof surface buts to a wall surface. They are L shaped so that water cannot rise up and get onto the back side of them, similar to the J channel high back, only taller even. They are between each layer of shingles so that any water that gets off the shingle and onto the step flashing will just run off the edge of it onto the top of the next shingle down below in the line. When they turn up the wall though, they are ugly if not covered so on houses where they don't use vinyl siding to come down and cover these the trim piece is used instead. If you use some other material for siding other than vinyl then it must be waterproof, even at the edges. If it's not then you'll want to let the step flashing rise up over it to keep water off it's edges, and then cover them with a trim piece such as you saw. I'd suggest using the PVC boards that Lowe's sells. They are available in the mill work department where they sell regular trim for interior rooms, but made from PVC. They come in all sorts of profiles, crown molding, quarter round, base, casing, and more. You can get the basic plank as well, and all these are waterproof, and white so they don't need painted. They are similar to wood in fasteners used also, nails and screws work fine, as well as PVC glue to bond two together if needed. Email me at dcaudeo@yahoo.com if you need further information. I am a home improvements contractor by trade, but I don't check this site often since time is short so I may not notice further questions here. Hope I explained everything well enough to be understood.

[Duane Bledsoe]

J channel is a strip of vinyl or aluminum that is literally shaped like a J when viewed from the profile side. It has a high back with a nail strip at the top that is slotted where nails go into it to hold it on the house. It comes down and spans across the bottom and then up the front. It is available in various widths such as 1/2, 5/8, and 3/4 inch. Beware, it will act like a small gutter and channel water that gets into it, but it should escape at the bottom as it runs down the slope of the roof. It's a necessary evil to use it to hide rough edges of materials used to side a house. It doesn't hurt vinyl so water in it doesn't matter, and the high back keeps it from getting up and out on the back side of it so it doesn't get wood behind it wet either. But if you use it to cover some type of wood or other material's rough edges, then you will get water on them.

I'd say the trim you saw on other houses could be a piece of wood or other material, and them it would be wrapped in aluminum trim to protect it. This would be something used to cover the exposed step flashing that is under each layer of shingles. Step flashing is used wherever a roof surface buts to a wall surface. They are L shaped so that water cannot rise up and get onto the back side of them, similar to the J channel high back, only taller even. They are between each layer of shingles so that any water that gets off the shingle and onto the step flashing will just run off the edge of it onto the top of the next shingle down below in the line. When they turn up the wall though, they are ugly if not covered so on houses where they don't use vinyl siding to come down and cover these the trim piece is used instead. If you use some other material for siding other than vinyl then it must be waterproof, even at the edges. If it's not then you'll want to let the step flashing rise up over it to keep water off it's edges, and then cover them with a trim piece such as you saw. I'd suggest using the PVC boards that Lowe's sells. They are available in the mill work department where they sell regular trim for interior rooms, but made from PVC. They come in all sorts of profiles, crown molding, quarter round, base, casing, and more. You can get the basic plank as well, and all these are waterproof, and white so they don't need painted. They are similar to wood in fasteners used also, nails and screws work fine, as well as PVC glue to bond two together if needed. Email me at dcaudeo@yahoo.com if you need further information. I am a home improvements contractor by trade, but I don't check this site often since time is short so I may not notice further questions here. Hope I explained everything well enough to be understood.

[Mike OMelia]

Thanks all. Heading to Lowes. Building supply center has PVC, but they are a long ways away. So, hope Lowes has it. On that J Channel, would it be unwise to caulk it so water would not flow in it? When I thought about it, that thought occured to me as well.

Mike

[Duane Bledsoe]

Yes it's unwise. If you caulk inside the J channel then you are building a dam where water will back up and come inside anywhere where the caulking does not seal (which you may not see). When J channel is used normally, the high back of the channel is high enough that water cannot rise above it to get out so it would run down and come out at the end instead (make sure the area where it comes out is water proofed well). But if you put caulk in it and are not careful "how" you apply it, then you may nullify it's water channeling capacity. If the purpose of using the J channel is to protect the ends of a material that is not water proof then J channel is probably not the right choice. If you decide to use it, then you probably would want to caulk it completely so water cannot get into it at all. That could be messy and use a lot of caulk though. It's not something that is regularly done and anytime I've ever seen it done (I don't do this at all for my work though) it's never turned out well, aesthetically or in use.

[Mike OMelia]

Agreed. I was thinking "P Channel" or an upside down "P". Thats what those other dormers appear to have.

Mike

[Mike OMelia]

Just wanted to let u know that the residing of the dormers is going very well. Both of them had the siding and casing butted to the roof. Rot everywhere. Finished one today, came out perfect. Used Restoration Mill PVC from Lowes for the casing. Nice stuff. Textured surface. Dam happy with it. Have more projects in mind for it. 25 year warranty too! Pics tomorrow.

Thanks all,

Mike