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How to give a slope to horizontal window trims?

How to give a slope to horizontal window trims?


  #1  
Old 03-23-24, 01:40 PM
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How to give a slope to horizontal window trims?

I would like to add a slope to window sills so that rain water runs off naturally. Any advice would be appreciated. Thank you.
 
  #2  
Old 03-23-24, 02:21 PM
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Add a slope to existing window sills ?
A picture would be helpful there....... How to insert pictures.
 
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Old 03-23-24, 04:04 PM
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Window sills are usually made with the slope built in. If yours are not shedding water then something is wrong.
 
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Old 03-23-24, 11:17 PM
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It may have some slope but looks horizontal to me.
 
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Old 03-24-24, 05:35 AM
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You might need to put a level on the sill to see if it's sloped. Usually it's not much and can sometimes be hard to see.

You can remove the sill that's there and replace with one you make. I don't know if you'll be able to get the original one out in one piece. You can also try carving, cutting & sanding a slope to the existing sill in place. It will be a lot of fussy work but you could put more slope on the middle 90% of the sill.
 
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Old 03-24-24, 05:55 AM
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I second using a level to determine if it has a slight slope. Do you get standing water on it?
 
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Old 03-24-24, 01:55 PM
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I would expect to see damage or water residue here..... and I don't.

 
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  #8  
Old 03-29-24, 04:34 PM
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My apology for not replying earlier. A level showed the window sill had a negative slope. Not much but definitely negative. Rain water puddling on the sill was also noted. Now the remedy. I plan to cut a thin board with a slope and tack nail it with adhesive. A bad idea?
 
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Old 03-29-24, 06:47 PM
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The "correct" thing to do would be to carefully remove the entire top layer of 3/4" board that is on top of the sill in your first picture.

Then you would add a 1/4" or 3/8" shim across the back edge of the sill (just in front of the "step sill", where it now bumps up 3/4") but add no shim in front... so that when you put a new 3/4" board down, it will have more slope than it does now. And you would need to use a good sealant to seal up the back edge of that new board where it meets the step sill, and the front where the two layers of sill overlap.
 
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Old 04-04-24, 06:46 AM
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Would there be a second, inferior option? The right method is too much for me to handle. The horizontal piece cannot be removed without removing other connecting pieces.
 
  #11  
Old 04-04-24, 07:13 AM
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I suppose you could add 3/8" plywood to cover the sill, shimmed in the back. If I did that I'd want to seal all 6 sides/edges of the plywood with primer and then caulk it well. Caulking will be the weak link.
 
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Old 04-04-24, 10:21 PM
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Thank you. I think I can handle the "addition" method.
 
  #13  
Old 04-16-24, 11:47 AM
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Marksr
Thank you. I used a thin luan, hoping it's warping force is small and can be contained by the polyurethane caulk. I need to keep an eye on this. Thank you for encouraging me on this repair because I found a minor rot at the corner. I was able to repair the affected trim.
 
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Old 04-16-24, 12:28 PM
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Luan isn't really weather resistant. You'll want to keep it well painting.
 
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Old 04-16-24, 01:01 PM
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Luan will curl up first time it gets wet.
 
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Old 04-17-24, 09:11 AM
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I wasn't sure of luan, either, and didn't use any nails, only caulked, just in case it needs to be replaced. Also primed and double painted. My hope is more in the polyurethane caulk Vulkem 116 to seal the cut edges of the luan. It has fibers for strength and sticks to everything. Thank you.
 
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Old 04-17-24, 10:29 AM
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As long as the luan stays dry it will be ok but if water finds any voids the luan is apt to start coming apart.
 
 

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