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For wood siding, which is installed horizontally on a vertical wall, and the wall intersects a sloping roof :
what is the recommended clearance between the angle cut ends of the siding boards, and the roof shingles?
putting then close to the shingles would help keep water from washing up on the shingles step flashing, but close to the roof would also let water running down the roof work up under the angle cut siding board ends.
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ed.... we kep them 3/4 off the surface.. and we use colored aluminum coil stock as our step flashing unless it's a cedar roof.. which will probably have copper step flashing..
we alo backprime and end prime the siding so it won't wick any moisture up..
most carpenters like to bring their siding right to the roof because it looks "neater"..
but if you drive by the day after a rain storm.. all the siding will be dry except where theirs meets the roof.. that will still be wet for 18" up the side...
*EdThere are many ways of doing this detail. I like Mikes, being sure to seal all rake cuts. This is a problem area and is always one of the first siding details to fail. If your dormers have very little overhang it increases this problem. You might want to think about adding a seperate flashing over the sidewall flashing if this is the case. This flashing would be hemmed and bent in an "L" shape and would be installed over your base flashing and held up to the cut line of your siding. After installing the siding against this flashing, the joint between siding and flashing can be caulked to prevent water penetration. There is no fool proof method that I've seen for this detail, it's a weak link having water next to wood.Terry
*yeah when I bought the house the siding was real close to the shingles, like the 3/4 inch which I think is not good, since the leaves can gather in it and back up water flow. In fact I had a few leaks and in fixing the leaks I put in step flaching and to install that more easily I cut the siding back to an inch or so.Some sort of extra flashing is probably needed - but I don't want caulk as that will not hold. I have 2 20ft runs like this on my house and I wonder as the volume of water increases as it flows down the sloping roof, what keeps it from running into the "slot" formed when a siding board sits up on the board under it? The angle end is open to water running down the roof.the cypress info.com site said maintain 2 inches. In a hard summer storm I wonder if that will keep water out.Odd that this "problem" has never been solved in the wood business.Wonder what the vinyl people do? Its much thinner and the back slot is much smaller.
*Anyone use Ice & Water Shield from the roof up the side of the dormer?
*Ed, I agree with the sum of the above, though I usually give 1-1/2" off the step flashing. I also hold back the ends of my roofing (except metal sheet roofing) 1-1/2" from the sidewall. This creates a nice channel for water to flow . Even with snow loads, I find the metal flashing stays open enough to prevent ice damming. These dimensions require a larger than standard step-flashing however to insure adequate protection.walk gooddavid
*EdFor metal or vinyl siding a "J" channel would be used at all terminations. The flashing I recommended is similiar in design. Take a look at it and see what I mean.
*terry... the problem i see with that flashing is the siding sits on it.. so the water can't drip and will wick up.. the reason i keep siding off the roof surface is so the water can drip... the air can dry.... and the water can run
*Mike My mistake. The one inch I show is above the roof material, allowing a gap for water to flow as you described. My drawing doesn't show this. Essentially what this flashing does is protect the board ends. If you want any water that penetrates the siding to wick out, don't caulk the bottom joint, or better yet drill a weep hole. I just feel the board ends with their endgrain need added protection.Terry
*Depending on the potential longevity of the siding material, I usually like to leave enough gap to allow a reroof in the future. This saves having to cut the siding in the. I think that this is a good idea, especially when the existing shingles are due soon. Of course a tearoff is usually better, but most people just cover the first layer with new shingles. I always use ice and water shield and end grain priming at this junction. Does any one have any good details for the spot where the step flashings terminate at the roof edge? It seem as I this is a serious weak link in the whole system. What is a good way to direct the water away from the sidewall at this point?
*I do what Mike Smith says, 3/4" gap with colored flashing, copper for wood roofs. At the bottom corner of the dormer I wrap a piece of flashing around the corner, overlapping the base flashing. There is one small vulnerable corner that a back up with a dab of butyl caulk. Sometimes solder it if it's copper, but not usually. I also run ice and water shield across the roof and up the dormer sidewall about a foot, in case of snow buildup or wind-driven rain. This is a problem area on a lot of new and old houses; I feel like it's worth a little extra attention up front.
*JeffreyIf the bottom of the dormer continues in a sidewall as I believe you're describing, then you need to move your sidewall flashing out to get the water outside of your siding. Here's a drawing of how I do it.
*Traditionally, we were taught, and required to maintain a 3/4" clearance above the roof shingles. In practice, we give 7/8" above the roof ply. Often, I use a 1 1/2" above the roof frame, resulting in about 1" above sheathing.We also don't put nails near the end, so flashing can be installed later.But! Read the directions on all manufactured sidings. If you care to maintain the warranty, you'll need more. I think 2" is required for LP Siding, and quite possible Hardie Plank too!Does anyone clip the point off the siding, like you do on the shingles on open valleys? I do occasionally, but not as often as I should. And...does the roofer leave a small valley too by keeping the shingles away from the sidewall? I like to keep at least 1/2". I also make sure all flashings have an outlet, for the small amounts that find their way in.Leave those spaces. It allows air drying.blue
*thanks I had trouble opening the document 3 posts above.whats also done at the front edge of the dormer - that is the edge fartherest away from the roof - when there is a vertical corner board that the siding butts up against - does the flashing run on the top of the corner board (hard to do this) , or is it correct to install the siding, and the final step flashing and have the corner board on top of the flashing?Boy I wish there was a web site with pictures!!!!
*you need a corner flash... and the corner board stays up the same as the siding... another reason you don't want to use mill finish aluminum for your flashings... it looks like crap.
*Terry, I am talking about the spot where the steps end at the roof drip edge and the adjacent sidewall above continues forward, above , and below. I do not know how to draw a nifty picture like you did, hope this is better