Preventing water damage on Hardi-sided dormer
I have a dormer with fiber cement siding that’s getting more water exposure than any other part of the house, and it’s damaging the siding. The dormer has 16″ eaves, but the problem appears to be caused by run-off from the dormer itself hitting the roof and splashing up onto the siding. It’s not obvious in the photo, but the bottom lap is falling apart and already needs replacing. I suppose the problem would be solved with guttering, but I would prefer not to for aesthetics. Anyone have a suggestion for an alternate solution?
Replies
der
The problem also seems to be gaining ground on the corner board as well (from this vantage point).
When it was sided, did they seal the bottom-cut edge of the siding?
Did they read the instructions on install that says what the recommended gap should be between the hardi and a roof?
Was there a kickout step flashing applied at the bottom of the dormer at the corner board?
Looks to me like the siding was installed improperly. There should be a visible gap (backed by flashing) between the siding and the roof surface. I suspect the install instructions call for 2" or so.
And, of course, the cut edges should be primed before installing.
Take it down and do it right is one suggestion
Here is a link to Hardi's installation instructions:
http://www.jameshardie.com/pdf/install/hardieplank-hz5.pdf
As you'll see-minimum 2" between the bottom of hardi and roof, deck, etc convergent planes.
Kickout flashing instructions also.
Prime paint seal all field cuts.
So, seems no other recourse but to do it the way it should have been done in the first place.
If the siding is not deteriorated beyond this method-cut it back by running a saw on a guide board that will shim your saw up the required 2" up the side of the dormer-being careful to not cut through the step flashing (boy, that's not easy). You could use a board of the proper thickness and fasten it to the siding which will give your depth of cut a consistent plane to gauge it so you MIGHT not cut the flashing.
Hopefully the step flashing is high enough........................
After you remove the crap, counter flash over the steps (so the flashing does go high enough and install a kickout flashing at the bottom at corner board to guide the water out away from the corner so that doesn't rot down the line. (the corner board too should be 2" shy of the roofing surface.
Then SEAL all your cuts.
real good!
Or, since it's such a small area-pull the siding, counterflash the steps, install a kickout and then reside
SEALING ALL CUTS.
Install is bad, but is that the problem?
Thank Dan & Calvin,
I'll probably re-do the dormer siding next spring, following the installation instructions (thanx!).
That said, I still feel like most of the damage is a symptom of the bigger problem, which is the amount of splatter from the dormer run-off, as evidenced by the fading a good 2' up from the roof surface. So I guess guttering is probably the only way to deal with that. I'm thinking just put the downspout at the back, and elbow it out to flow directly onto the roof, minimal fall.
der
When you run that gutter I would refrain from dumping out on the roof at the top of the dormer wall. If anything, run a spout down past the corner.
Introducing a concentrated amount of water up top will not do the siding any favors.
The Hardi is too close ot the roof. I'd cut the siding 3 1/2 inches up and install a piece of 1 X 4 Azek. That would get the Hardi up where it's supposed to be and protect the edge.