Author Topic: Exterior Window Trimming  (Read 692 times)

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Offline Mike Goetzke

  • Posts: 894
Exterior Window Trimming
« on: May 26, 2022, 08:53 AM »
I plan to trim the outside of my new windows with brick mold. I watched several videos and they all show applying it flush to the window frame and this is how my old 40 year old windows are. I just found in the fine print of the window directions that they say to leave a 1/4" gap all the way around for siding and 1/2" for brick (for expansion).

So me trying to get ahead of things precut the molding for a pretty tight fit. Not the worse thing if I need to buy more brick mold but wondering is this 1/4" gap necessary?

(I'm having the house re-sided next so maybe have the contractor provide the 1/4" clearance?)

Thanks
« Last Edit: May 26, 2022, 08:59 AM by Mike Goetzke »

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Offline twistsol1

  • Posts: 19
    • Sawdustzone
Re: Exterior Window Trimming
« Reply #1 on: May 26, 2022, 09:05 AM »
The short answer is yes.

I did exactly this with vinyl clad Andersen Casement windows and the trim was up close to the windows and when they tried to expand they had nowhere to go. It made the windows stick  and not fully close in the summer.
A shop full of tools and no talent

Offline Packard

  • Posts: 1394
Re: Exterior Window Trimming
« Reply #2 on: May 26, 2022, 09:09 AM »
If you have ever installed vinyl siding you will see that the holes for the nails or screws are elongated.  Amateurs sometimes don't leave the fastenings a bit loose and the siding buckles.  I am pretty sure you have to  accommodate the expansion and contraction for vinyl siding.  Aluminum siding is less of a problem.

If you are installing in the heat of summer, then I would guess that you would not leave a gap.  In the winter you would have to.  But I think everyone does.

You could cut a recess in the back of the molding and allow the expansion to be hidden.  A commercial installer would never go to that  effort.

https://uooz.com/how-much-does-vinyl-siding-expand-and-contract/

A standard piece of vinyl siding and trim may expand and contract up to 1/2 an inch in extreme temperatures, between the coldest winter day and the hottest summer day.

Offline Packard

  • Posts: 1394
Re: Exterior Window Trimming
« Reply #3 on: May 26, 2022, 09:11 AM »
And make sure you do not block any weep holes in the window.

Offline Mike Goetzke

  • Posts: 894
Re: Exterior Window Trimming
« Reply #4 on: May 26, 2022, 09:20 AM »
And make sure you do not block any weep holes in the window.

Thanks - might have missed this.

My siding will be LP SmartSide engineered lumber but guess I knew the answer before I asked the question  [smile]. $40 error.

Mike

Offline Packard

  • Posts: 1394
Re: Exterior Window Trimming
« Reply #5 on: May 26, 2022, 10:09 AM »
Back in the late 1950s, when aluminum storm windows were brand new to the market, our neighbor had them installed.  The installer was brand new to the installation of these brand new to the market storm windows. 

He did a very tidy job of caulking all around. 

Four years later all the primary windows had to be replaced because of water rot and all the framing directly under the windows had to be replaced too. 

There was probably mold too, but no one knew about mold back then. 

In any case, I remember as a young child "Never caulk the weep holes".

After college I bought an Alfa Romeo Duetto Spyder (the car from the Graduate).  It was really pretty, but they had the reputation for rusting out the rocker panels.  I asked my mechanic to drill out 1/4" diameter holes at the bottoms of the rockers panels.  They did have weep holes but they were already blocked and water drained out when he drilled them. 

But my car never rusted. 

My father had a Jeep Wagoneer.  He got a flat in the dead of winter.  When he went to remove the spare he found that the rocker panel that housed the spare was filled with water and frozen solid.  So he had the same mechanic drill weep holes in his car too. 

My brother-in-laws Acura Legend had a sunroof that leaked.  We snaked out the weep holes and the leak was fixed. 

You can never make anything 100% waterproof.  But you can usually arrange for drainage.   


Offline Mike Goetzke

  • Posts: 894
Re: Exterior Window Trimming
« Reply #6 on: May 26, 2022, 10:58 AM »
Thanks for the replies. Just looked and my vent holes will not be covered by the brick mold. I found out there is an Andersen dealer close by. I went there and they were very helpful. They said they don't leave much of a gap if any between the molding and window and the 1/4" in the instructions is for siding to frame so when applying the siding will need gap/caulk. (I looked and I have a good 1/8" gap between the molding and window.)

Offline Packard

  • Posts: 1394
Re: Exterior Window Trimming
« Reply #7 on: May 26, 2022, 11:05 AM »
Are you using wood brick mold or resin brick mold?

When I use the resin material I like to use the bonding agent they sell on the miters.  It keeps the miters tight.  White caulking for all the nail holes. 

The resin never splits so 15 gage nails, even near the edges are not a problem.

Lately the resin molding is cheaper than wood (in some shapes and sizes).

Offline Mike Goetzke

  • Posts: 894
Re: Exterior Window Trimming
« Reply #8 on: May 26, 2022, 11:14 AM »
Are you using wood brick mold or resin brick mold?

When I use the resin material I like to use the bonding agent they sell on the miters.  It keeps the miters tight.  White caulking for all the nail holes. 

The resin never splits so 15 gage nails, even near the edges are not a problem.

Lately the resin molding is cheaper than wood (in some shapes and sizes).

@Packard  Thanks. Yes I bought vinyl brickmold and yes plan to glue the miters. I saw on the plane looking vinyl clad molding Andersen sells they fasten it to the window from the outside with nails instead of face nailing to the house. Maybe this is better?

Offline Packard

  • Posts: 1394
Re: Exterior Window Trimming
« Reply #9 on: May 26, 2022, 11:31 AM »
I'm not a window installer, but I like that idea.  It will always be snug to the window.  Never sloppy. 

I think the adhesive is like the old Testor's model glue which actually dissolved the plastic a bit and then "welded" the plastic pieces together. 

I think it is basically the same but they have added some white pigments.  Of course you don't have to paint this stuff.  But if you do, you need to use 100% acrylic for the paint (or the primer, or both) for good adhesion. 

White caulk matches the molding nearly perfectly.  When I needed white paint for the surrounding area, I matched the paint to the caulk so there is no obvious seam where the paint and caulk meet.

Offline Peter Halle

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Re: Exterior Window Trimming
« Reply #10 on: May 26, 2022, 05:36 PM »
As someone who has installed miles of the pvc trim - yes caulking can be used to fill nail holes, seams, etc.  But if left unpainted it will attract air borne pollutants and dirt and show up differently than the trim.  I always paint afterwards.

Peter