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nugentoffer 03-22-2010 11:12 PM

Help with replacing exterior window sill molding
Hello all,

I was a little freaked out today to find the wood molding around my kitchen window that faces my yard has heavily rotted away.

All the paint jobs in the past had not covered the surface underneath the molding, and the heavy rains recently did not help. The wood had pretty much broken away in my hand when I pressed on it.

I was planning to remove all the wood surrounding the window and repainting it. I will post some pictures of the damage and the extent of the work desired tomorrow.

My initial questions (please excuse the noob questions, my first time at this):
1. What type of wood should I use to replace this?
2. Should the wood be pressure treated?
3. What type of nails should I purchase?
4. What tools will be necessary?
5. Will I need to cut into any of the interior woodwork?
6. What other preparation should I do before I begin to tackle this job?

Appreciate any help or advice you can give.

Just Bill 03-23-2010 05:59 AM

I assume you are talking about brickmold molding?? It is not uncommon for that to rot, even when kept painted. It is usually nailed to the window framing and to the house framing, just find the nail heads and start pulling. There will also likely be some caulk that needs to cut away with a utility knife.

Replace with solid vinyl or a vinyl composite, available at home stores, lumberyards. Won't rot, often does not even need to be painted, if you like white.

oh'mike 03-23-2010 06:08 AM

I think the molding you are talking about is called-'Brick Mold'

That trim as available in white PVC (plastic) --nice--no rot no paint needed--holds nails well.
Buy it at the Depot. Azek is one brand.

The brick molding is actually all that is holding in the window.--(along with the inside trim)

Removing the rotted stuff is a matter of cutting loose any old caulking--and very carefully prying off the bad molding--a chisel is handy to split the old molding at the nails-(if they don't pull out easily)

Once the old molding is gone--remove or cut off any nails that are left.

Miter the new trim to size and nail it in. Caulk with siding caulk at the siding and painters caulk at the window. Fill any nail holes --done

The trim is easy to cut--If you don't have power tools a saw and miter box will work fine.--Mike--

nugentoffer 03-28-2010 04:52 PM

THanks for all the replies all...

I've removed most of the old wood molding around my window..but I"m having trouble with the paperlike backing that was behind the wood on the sides... please see pictures #1 and #2 below. WHat is this material called? Can I just keep it or should I remove it before I install the PVC type molding?

Should I remove ALL of the old molding? The top and bottom pic#3 and #4 are currently still remaining.

Last question : Read about "drip edges" on some of the DIY sites, do I need to worry about this in my case? Looks like there's already an overhang over my window.

Will head to Home Depot to see what types they have and report back. Thanks.

Tom Struble 03-28-2010 05:10 PM

hmmm i think you may have more than a rotten trim issue
looks like ice dam or maybe your gutter is backing up and getting in from behind
or possible a leaking window

you should definitely check this out before installing any type of trim

oh'mike 03-28-2010 05:10 PM

That soft pressed board is called Celotex--That is the sheathing---You need to replace that,if its missing.

Here is the typical exterior wall--1. 2x4 studs----2. sheathing(1/2 plywood--OSB---celotex--insulated foam board) 3.vapor barrier
4.siding and trims.

To replace the missing sheathing -I suggest OSB or foam board---for a vapor barrier --felt paper(black tar paper)

If you are putting wood back in there to replace the rotted trims--then the top board can stay.( Modern wood rots very quickly-
paint the back before you install it)

I use Azeks (white PVC trim boards) not real wood--no paint-no rot --A bit pricey but that eliminates doing it over in a few years.


nugentoffer 03-28-2010 05:55 PM


Originally Posted by tomstruble (Post 420882)
hmmm i think you may have more than a rotten trim issue
looks like ice dam or maybe your gutter is backing up and getting in from behind
or possible a leaking window

you should definitely check this out before installing any type of trim


Which picture are you looking at that makes you say this? What part of the trim are you looking at?

Mike, can you chime in on this?

THanks again all for helpful info.

oh'mike 03-28-2010 06:06 PM

I'll have to let Tom speak for himself--

I'm guessing that he is concerned with the water staining under the window--
That looks like damage from leaking trims and no proper tape and vapor barrier on that area.

Before installing the new trims---there is a special tape used to seal the window flange to the vapor barrier.

Looks like a 3" roll of foil with a tar backing--if the caulk between the window and the trim ever leaks--

any water that gets behind the trim will not get to the framing--Mike--

Tom Struble 03-28-2010 07:38 PM

the old trim rotted out from water intrusion
if you put new trim on without correcting that your still going to have problems whether the trim is rot proof or not
the stained framing,is a tell tale sign something is wrong,and damage from ice dams or gutter back ups tend to be worse on projecting windows such as bays and bows and box bays which is what you have

or the [what looks like]lack of insulation could be causing condensation on the backside of the trim and framing

nugentoffer 03-28-2010 09:39 PM


Would you suggest that I remove the stained framing studs and investigate the cause of the moisture intrusion? What would I need to look for? I'm not really sure what ice dams are (we don't see a lot of ice here in texas), but my gutters are pretty clean so far.

The removed rotted trim was pretty badly soaked after the last round of heavy rains. I just assumed that this moisture spreaded up the trim and into the framing.

Mike, what brand and model of vapor barrier should I use? What brand and model for the special tape?

Tom Struble 03-28-2010 10:35 PM

sorry about assuming it could be icedams,thats why its important to post your location

oh'mike 03-29-2010 05:58 AM

For a vapor barrier --use 30# felt paper-( tar paper)---That is tried and true---Tyvek will work --more money -no better in this situation.

I can't recall a brand of tape--it all works well --I never paid attention to the brand.

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