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Discussion Starter · #1 ·
Hi-

I'm doing an exterior restoration on an 1860's Gothic revival. I've milled new clear WRC clapboards for the job as well as a lot of new replica millwork. There is a lot invested, and I want to make sure it is done right.

Originally the house had simple sawn bevel siding over the studs. No insulation, no flashings, etc. We want to preserve the original windows, but judging by the copious amounts of caulking removed, the windows have leaked in the past (though no rot thanks to the abundant airflow).

I know how to start at a sill pan and go up for newer windows, but these windows are not conducive to that approach. Other jobs I have been on have simply had a single head flashing and nothing else. That seems a bit iffy. The windows are not coming out, they were all built in place.

What is the best way to flash an old wood window considering the plywood and tar paper choices under the clapboards?

Thanks
 

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i would try to get a 6''aluminum strip under the side casing,extending under the existing drip cap and past the sill,terminating it over the top of the next to last full panel under the sill

this would be over top of whatever paper your using,i would use a metal drip cap with end dams

the sill if it's notched to receive the siding would be tough to get a pan under unless you pull the sheathing under it
 

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Not an easy question to answer.
Those old windows were meant to allow for lots of air flow, lots of energy needed back in the day to keep the house warm as there was no consideration of insulating the walls.
Are the windows the old counter-weight type double hungs?
I have worked on lots of those around here in the Orange Historic District.
Trim of the windows were probably caulked to keep out the wasps and such form building nests in the cavities of the windows by people that just did not know better. The house was not built to be sealed very well.
That being said, I would only use a custom built copper Z-flashing for the sides, custom build sill flashing and head flashing and never use caulking for anything on it.
On a side note, I would not use a vapor barrier of any kind and only use non-faced batt insulation in the walls.
Also if possible, I would not use a latex paint for the exterior, oil only if available. Those houses simply were not set up for vapor barriers.

Just my opinion for whatever that is worth.

Andy.
 

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what do you mean Z flashing Andy?Capping over the casing edge?

and yes copper would be best..or lead..
Ooh, lead might be good. Though I wonder how it would do in a vertical position like that of the legs.

One edge of Z under the siding about 3/4", return toward the exterior to cover ends of siding, then the other edge of Z to return into the trim towards the window.
The edge under the siding can be tacked in place lightly (not too lightly), copper nails would be good.
The edge that returns toward the center of the window would not be attached at all but should be snug to the back of the trim. I find this allows for a good place for the head flashing to rivet or solder onto.

Andy.
 

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It sounded to me like you were replacing siding directly attached to the studs and new replicated millwork. So I assume the windows themselves will stay put.

In this case I like Toms solution.

1. lay vertical flashing on the sides over the bottom cedar plank (notched into sill) The flashing would only go the distance of the siding lap at the bottom and run up 6" or so above.
2. install side trim boards over the side flashing. The side flashing should be as wide as the trim plus 2 inches to conceal the siding butt joint.
3. install new head casing with wood drip cap applied to the top.
4. install copper flashing over the wood drip cap.
5. install siding as normal

But then......you say something about plywood and tar paper so the whole idea is shot now
 

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Discussion Starter · #9 · (Edited)
The original windows are single hung, with no weights.

The original siding was nailed straight to the studs with no further nod to waterproofing.

I have replicated all of the millwork, which was originally the only part of the job.

On this job, the structural engineer has specified plywood to add diaphragm and to allow for a waterproofing layer (tarpaper). There is no flashing schedule specified. So I am trying to figure out how to flash a window that was never really meant to be flashed.

I like Tom and Tom's plan so far.

I'm so used to being able to use a sill pan that I still don't have a good plan for the sill though.

Thanks for all of the help so far.
 

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Why not extend the jamb & sill instead of overlapping it so the option of a window change can happen in the future? I doubt has too much effect either but....shear wall panels aborb wind loads I think I would want a window to act independantly rather connecting them.

The same flashing process can be done.
 

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Personally, I wouldn't flash with metal around those windows - that's a serious moisture barrier.

Around here, these originally were all done with what was then 15 lb tar paper. Since there are 2 standards now, a lot of 30lb corresponds roughly to the old 15 lb. The ends of clapboards were set into lead putty and nailed off - the excess putty was tooled off. The lead putty was similar to the traditional window glazing putty, so it eventually dried out. cracked and degraded away.
 

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Discussion Starter · #14 ·
Why not extend the jamb & sill instead of overlapping it so the option of a window change can happen in the future? I doubt has too much effect either but....shear wall panels aborb wind loads I think I would want a window to act independantly rather connecting them.

The same flashing process can be done.
Normally I would, but the stop runs the full length of the outside edge, so it's a perfect place to make up the difference.

The wall is framed with hewn beams and sash or pitsawn studs. By modern standards it's a mess. The windows are integral to the openings, with no cripples. The siding was originally nailed to the window jamb.

This house is very cool, but it is only a couple steps up from a barn in the actual construction methodology.
 

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Discussion Starter · #15 ·
Personally, I wouldn't flash with metal around those windows - that's a serious moisture barrier.

Around here, these originally were all done with what was then 15 lb tar paper. Since there are 2 standards now, a lot of 30lb corresponds roughly to the old 15 lb. The ends of clapboards were set into lead putty and nailed off - the excess putty was tooled off. The lead putty was similar to the traditional window glazing putty, so it eventually dried out. cracked and degraded away.
I hear you on the moisture barrier, it is a concern of mine too.

I have seen simple strips of tar paper laid out as flashing on some old windows. They seemed to work pretty well, but that house had a lot of roof overhang. I'd need a broader base of comparison.
 

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You may need to use a metal head flashing no matter what.

Regarding the sill, a lot of the old windows around here didn't have a groove to accept the siding - a ~1/2" piece with a drip groove was cut and applied to the bottom of the sill after the siding was installed.

Roof overhangs have an effect on how wet the siding gets, but worse case is always with wind driven rain, which will soak the whole side, cause pressure differentials that can push the water through any cracks, and cause the whole structure to move. If you use tar paper, it gets gooed to the window trim, and pressed in with a board to make a neat edge.
 

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Discussion Starter · #17 ·
You may need to use a metal head flashing no matter what.

Regarding the sill, a lot of the old windows around here didn't have a groove to accept the siding - a ~1/2" piece with a drip groove was cut and applied to the bottom of the sill after the siding was installed.

Roof overhangs have an effect on how wet the siding gets, but worse case is always with wind driven rain, which will soak the whole side, cause pressure differentials that can push the water through any cracks, and cause the whole structure to move. If you use tar paper, it gets gooed to the window trim, and pressed in with a board to make a neat edge.

There will be a copper drip cap for sure.

I'm not 100% sure what you mean about gooing the window trim. Do you mean sealing the inside (window) edge?
 

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There will be a copper drip cap for sure.

I'm not 100% sure what you mean about gooing the window trim. Do you mean sealing the inside (window) edge?
Yes, you just run tar paper ~1/4" long, crease it at right angles so it will sit flat against the side of the window trim. A little goo on the side of the window trim, then press the tar paper into it. The creasing and pressing into the goo is easy if you use a piece of 1X4.
 
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