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Miratec Failure

60693 Views 41 Replies 17 Participants Last post by  Tom M
Sided my own house in 2007-2008 with Hardi and Miatec trim. My house is a modern cape, so I went with a very traditional 5/4 x 4 trim detail with window sills and a kicker at the top. The sills were made from laminated azek and the kicker is azek as well, mounted at a 15 degree angle at the top. There are kerf cuts in the kicker and under the sill as well to drop water. Instead of cutting the frame at a 15 degree angle, I left it square and make a 15 deg dado into the kicker so it actual sat over the 5/4. I then placed aluminum flashing over the kicker and wrapped the tips down the side, and caulked it in. Also should mention that the frames were pre made in the shop, painted on all sides, and glued and pocket screwed together. I figured that using azek on the surfaces that are more horizontal would be better than going all Miratec.

Anyhow, I was washing the siding over the weekend, and that's holding up great, but while if was working, I saw a strange shadow and took a second look. The top corners of the frame are swelling up, somewhere between and 1/8 and 3/16 of an inch. They are swelling starting at the outside corners and traveled in about 8-10 inches from each side. I had to investigate, so out came the moisture meter first. Stab it into the trim at the outside corner, boom 46%. move in a few inches, mid 20's, move in a little more, 8-9%. So obviously the water is getting in at the ends and traveling inward. I'm reasonably confident that everything is flashed and the water isn't coming from above, but at the same time its really bugging me to thing that the small joint between the kicker and the head trim allowed enough water in for it to have this affect, especially considering the fact that the kicker was actually glued/adhered to the head with dynaflex. Had the aluminum flange been just a little bit larger it would have covered this completely.

So out comes the scraper and putty knife. Once I got a corner up on the paint, it basically peeled back in one large piece, taking the factory primer with it, and some material. The surface was noticeable wet and was very soft. Gentle scraping was just peeling layers of miratec off, and sanding it just made the surface fuzz like crazy. So I'm basically looking at an area about 2" x 8" on each side of the window casing that is basically significantly damaged and I'm sure as it dries will form a noticeable rut.

I guess the lesson and most concerning part is that without a rain screen and air behind the miratec, any small gap could eventually result in the trim just dissolving. I think the issue is that the water gets in, and because their is paint on the face, the material can't dry, and it can't dry in due to the tyvek, tar paper, etc behind it. The swelling starts small and just turns the material more and more into a sponge.

So now I'm faced with repair or replace. To remedy the joint, its pretty easy to slip an additional piece of trim coil under the existing flashing to cover the seam, but not sure how to treat the damaged area. First thing is I'm gonna leave it to dry out in the sun and keep it covered in the rain. Thinking about treating it like rotted wood and just using abatron epoxy, first drill it a bunch with a small bit and inject the liquid hardner to make it more solid, and then top it with the epoxy. Its either than or take it off and replace it with PVC. Part of me just wants to replace it because I feel like repair could mean just revisiting it in another few years. The good news is I used screws to hold it on and it should come out without too much of a fight.

Not very happy with Miratec right now, not sure I would use it in situations where air can't get behind it now. I certainly took a lot of care in manufacturing and painting these very carefully to give the product the best chance it could have. Of 22 windows on the house, its only the south side of the house that shows signs of this, probably due to no overhangs, and almost all day sun.

I'll get some pics posted as well.
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I've never been a fan of Miratec.

Always seemed like a glorified MDF to me.

The Abatron consolidant is not a bad idea, but I think your right about it being just a temporary repair.

I personally would replace the south side of the house if you plan on being there for any length of time.

(with something other than Miratec)
I have always been very weary of miratec, it seemed to similar to MSG and the old Masonite siding that failed to miserably, I never really wanted to even give it a try. I prefer pvc, or a hardi trim. I would replace with pvc and be done with it.
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Just a exterior grade of pressed cardboard. Using it and any other pressed card board siding is just future replacement work.
We tried it out at the request of a customer a year or so ago and while it looks nice I won't use it again. I took a piece about 12" long and left it sitting in a bucket of water, within a few days the end had noticeable swelling.
I just hate the fact that many of the products now rely so highly on the primers, like lp smart side and miratec. You look at what the substrate is comprised of I just can't trust it.
I have stayed away from mirtec because I don't like the way it's made. Nothing bad to say about it, but like others have said, it looks like hard board or pressed builder board.

I'm also leary about LP siding too, but I've used it.
ive had pieces literally laying in my yard with no noticeable swelling..that being said i would replace the head with Boral
some pics be nice:thumbsup:
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Same here. I bet some scraps are 5 years old.

My only issue with Boral is that it is easy to brake.
ive had pieces literally laying in my yard with no noticeable swelling..that being said i would replace the head with Boral
;) can snap on ya unsuspecting like:rolleyes:,but you can still install the 2 pcs then glue fill and sand
I did a miratec job a few years ago. I was kind of skeptical at first. Then I left a scrap submerged in a bucket of water for 2 weeks. I cut into it with my razor knife and the water hadn't done anything to it.

I do like boral, kinda tough to use when working solo though.
I think either the composition changes over time and it becomes more prone to absorbing water as it ages as I did the bucket test before I installed it as well, or its the vapor seal of painting it that just locks the water in. If the material can breath from one side maybe its probably able to dry. In my case if I tapped the area that was swollen with a hammer it spit water at me.
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So I pulled it off the house today and here's what I found. The top corners are swollen a full 3/16 of an inch. Based on the stains on the back, all the water got in at the joint between the kicker, which is azek, and the top trim board. Looking back, beveling the top of the trim instead of cutting the angled dado in the kicker might have slowed this or prevented it, but the best thing would have been to extend the aluminum to completely cover the joint.


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A few More pics:

BTW, this dewalt knife is killer for cutting through the caulking and doing work like this. Great knife to add to the collection.

So what else did I learn here???

- Stainless fasteners are the way to go, no rust on any of them
- Dap Sidewinder/3.0 caulking has maintained is flex great over the last 7 years, would recommend it over Quad
- Geocel SWD 2300 dries a bit harder, but has good adhesion to FC. Not quite as flexible as the sidewinder.
- Dap Dynaflex 230 has also held of well. I use this for joints that I know there will be squeeze out and will need clean up. I think its one of the best water based caulks out there. Not exposed to sun here, but I find as long as its painted it holds up well to the sun.

And Mainly:


I'm very on top of my upkeep on the house and to have failures like this after 6-7 years seems like product failure. With expansion and contraction your going to have a little water exposure here and there and it doesn't look like Miratec is going to handle that well.


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how much trim has been affected like that?
The North and south faces of the house are the gables and there are no overhangs. So far look like its just 2 windows on the south side, but I have to go and look at the second floor windows on that side as well. Just using a straight edge and placing it on the trim, the swelling becomes apparent quick. Being on LI, most of our weather comes from the southwest, so the south sees more weather than the north, and on the north side I only have 2 windows due to the garage being there.

Everywhere else the tops of the windows have overhangs, so while the same condition exists, its far less likely.

I really did everything possible to prevent this. The frames were built in the shop, all joints glued with Titebond 3, and pocket screwed with SS screws. Coat of additional primer and 2 top coats of Duramax paint. My plan as of now is to replace the 2 that are damaged with PVC trim, and inspect all the rest. At the least, I'm slipping a small pieces of trim coil under the existing flashing to cover this joint completely.

To be fair to miratec, I have it as the skirts around my porch as well, which sees plenty of weather. I think the real key is that it is blocked off the framing so air gets all around it. With the windows, the trim is sitting on top of vycor, once the water got it, it had nowhere to go I guess. But do I think they oversell the durability of the product??? Yes.
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also i am not a believer in caulk to seal siding to trim...never goin to happen imo,i caulk to the wrb,paint the cut edge and but to trim,no surface caulk


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