Replace window trim with PVC or wood and other questions

[atgcpaul]

This is one of our first floor windows which needs exterior trim replacement.
The wood is the pre-primed fingerjointed stock you can find at HD. It's
gotten wet and is rotting out. You can see the chunk I removed with just
my fingers. The siding is Hardiboard so I don't worry about those boards. I
noticed there was no rubber flashing behind these trim boards, though.



I was going to use PVC but that's about 3x more than wood. This trim is
original to the house and made it at least 12 years. It's been on the decline
since we bought the house. Hard to say if we'll be here another 10 years.

The install of new boards seems pretty straightforward except for the metal
drip edge flashing at the top. It should be Z-shaped and slip underneath the
siding above, right? Is that supposed to be replaced along with the trim?
Wasn't that installed before the siding, though?

Thanks,
Paul

[gsmittle]

I'll take a stab at this…

WARNING: Free advice (especially from me) is worth what you pay for it!

Since you figure you won't be there much more than 10 more years, I'd say go with wood. You'll need to keep a close eye on all the exterior wood and repaint as necessary.

I don't know about the rubber flashing, though. Perhaps some silicone caulking under the new trim?

AFAIK, the flashing above the window can stay where it is, unless it's so rusted it needs replacing. It was indeed installed before the siding.

g.

[twistsol]

I'm in the process of doing that now in addition to replacing the siding. We went with PVC because we have a woodpecker issue here. They come by occasionally and drill some holes in the siding or the trim and then head to a nearby tree. We have a single window that is an antique cut glass window and I spent a full day cutting out rotted parts, filling with epoxy, sanding and priming. There's a lot of maintenance with wood, and if it's going to be painted rather than stained, wood offers few benefits.

I would think about the fact that if it lasted 12 years the first time around, and you mentioned it was in decline the whole time you owned the house, what will it look like when you're trying to sell?

[jabe]

I would use PT lumber for the trim. We have mositure & termite problems so it is common practice to use all PT lumber for our homes. My house is 20 yrs. old except for the paint, all my trim boards are still solid.

[chopnhack]

Seriously, that's why they say vinyl is final. The pvc may be 3x today's prices, but factor in your time and having to redo it again with wood at tomorrows prices, or at the very least having to sand, patch, prime and paint just before selling, when in all likelihood you won't have the time or focus to deal with it. Of course its easy to spend other people's money, but if I were in your shoes and I could swing it, I would go the pvc route and never have to look at it again.

[woodturner]

I was going to use PVC but that's about 3x more than wood.

It also doesn't hold up as well or as long as one might expect.

I'd consider Miratec - a water resistant composite trim board material. Works very well, very durable, costs less than PVC.

Another alternative would be fiber cement board, like your siding. It's available in trim board sizes.

[Norm in Fujino]

The wood is the pre-primed fingerjointed stock you can find at HD. It's gotten wet and is rotting out. . . . I
noticed there was no rubber flashing behind these trim boards, though.

The real issue as I see it is, why were the boards rotting out? and can you stop the moisture merely by replacing the boards? There's apparently been a path for moisture to enter behind the boards, letting it settle there and start the rotting process. If you can't stop that point of ingress, more wood will fare no better. That's one argument for PVC or other impervious product, although the water may migrate elsewhere and destroy other parts of the window or sheathing, etc.
On the other hand, if you're able to see all the areas where moisture can penetrate, and fix them with proper flashing (butyl rubber flashing, proper metal cap flashing inserted behind the housewrap, and proper caulking), then replacing with a good wood product (WRC, etc.) primed on all six sides, should be adequate.[/quote]

The install of new boards seems pretty straightforward except for the metal drip edge flashing at the top. It should be Z-shaped and slip underneath the siding above, right? Is that supposed to be replaced along with the trim? Wasn't that installed before the siding, though?

As I noted above, the cap z-flashing should be inserted not just behind the siding, but behind the housewrap as well, and the cuts in the housewrap then treated with proper taping/flashing as well. If the z flashing is merely inserted behind the siding, moisture getting behind the siding can and will run down the housewrap and get behind the trim that way.

[atgcpaul]

I would use PT lumber for the trim. We have mositure & termite problems so it is common practice to use all PT lumber for our homes. My house is 20 yrs. old except for the paint, all my trim boards are still solid.

Is there PT just for trim? I thought about this route but the PT I have used (decking) is so wet that it shrinks a ton after install. The stock I need is 1 1/4" thick.

[atgcpaul]

The real issue as I see it is, why were the boards rotting out? and can you stop the moisture merely by replacing the boards?

All the affected windows have rot occurring where the vertical trim meets the
sill. I don't think the end grain was properly sealed. This particular window is
also a western exposure so it gets beat by sun for hours at a time. Maybe
this one gets PVC or Miratec. This thick stock is going to cost me an arm and
leg.

As I noted above, the cap z-flashing should be inserted not just behind the siding, but behind the housewrap as well, and the cuts in the housewrap then treated with proper taping/flashing as well. If the z flashing is merely inserted behind the siding, moisture getting behind the siding can and will run down the housewrap and get behind the trim that way.

Sounds like this requires taking the siding off first or not destroying the cap
flashing during the trim removal, right? This just got a lot more complicated.
I'll take the vertical pieces off first and if the the cap trim is OK, maybe it will
just get painted and stay put.

[JimD]

Moisture is a problem with PT. I like to use it for an application like this in the winter so the boards have been sitting in the rack for awhile. It could be hard to find a dry one now. This could be a reason to get a moisture meter, however. You can tell the supper wet ones just by weight but that may not be good enough. You could find something useful in a pile at the local home center.

Southern Yellow pine is also fairly rot resistant even without the chemicals. Finger jointed stock usually has a mixture of softwoods and some are much more prone to rot than others. The trim around my front door is finger jointed and on one side it rotted, on the other it is sound. They get the same exposure and were treated the same way. So I replaced the rotted piece with PT.

You could also look for cyprus or teak but that would be more than the plastics, I think.

I would look for a dry piece of PT and if I couldn't find that, a piece of southern yellow pine.

Jim

[woodturner]

The real issue as I see it is, why were the boards rotting out?

Very important question to answer. A lot of good information on the historic homeworks site.

Basic principle is that you want to stop water from getting in from above, but provide a way for it to drain at the bottom, if it does get wet. This type of rotting is common because there is usually no exit path provided for the water. Often the bottom of the trim is caulked, further aggravating the issue.

I would flash it well at the top, but stop the trim a little short of the sill to leave a 1/16" or so gap. If you don't like the gap, you can fill it with thin but water permeable foam.

[docrowan]

I think finger-joint is one of the worst inventions in wood working. I've never bought any finger joint that was worth a dern. The pre-prime on finger joint is about as thin as it can get and still be opaque. The glue used to hold the finger joints is usually not up to par either. I've pulled some finger joints apart with my bare hands accidently. I think you're lucky to have gotten 12 years out of that window trim.

I've found that if you paint two thick coats on solid wood or even good exterior plywood on all six sides (faces and edges) before installing it will last as long as pressure treated does without paint or stain. PT does eventually degrade.

I imagine if you doublecoat PT on all six sides (faces and edges), and keep the exposed sides painted every 10 years it will last as long as PVC.

I have to replace a little ramp going into my lawnmower shed and I'm triple coating a 4'X4' sheet of exterior plywood. I'm actually hitting the edges each time I paint a face, so they'll be coated 6 times. I'm betting it will last 10 to 12 years even though it will have complete exposure and direct soil contact on the end.

It takes more time to paint before installation, but the material cost winds up quite a bit cheaper. Most of the time is wait time in drying and you'll have to paint it anyway if it's going up on your house.

[pecker]

I recently bought some synthetic trim called TUF Board at Home Depot.
16ft 1 x 8's were about $35 each. For the amount of trim around your window I doubt it would cost more than $50.

http://www.tufboard.net/products/trimboard

[pelligrini]

Hardie also makes trim boards to match your fiber cement siding. I believe they are cheaper than any PVC or other composites. Around here a 3/4x4x12' goes for less than $10

http://www.jameshardie.com/homeowner..._hardietrim.py

[capncarl]

The cheaper boards and typically finger splice boards create their own leaking problems. They rot away quickly and provide a pathway for water to enter the building and amplify their rotting problem. A pvc or other synthetic board used for trim will not have this probem when installed and caulked properly.
If you install the cheap stuff now it may not make it until you sell the house and you will have to do it again.

capncarl