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Milgard Ultra Wood Clad Leaking at corners

BHosch's picture

We have Milgard Ultra Wood Clad windows throughout the house. These are the hollow extruded fiberglass frames. The problem is that one side of our house takes the brunt of the wind in a storm so there is a lot of wind-driven rain that hits these windows.
The windows leak at the corners as evidenced by the wood laminate getting wet at the bottom corners. I don't believe the frames are sealed in any way at the corners but are mitered extrusions butted together.
Does anyone have any ideas about sealing these corners?

those are a replacement (post #182511, reply #1 of 14)

those are a replacement window , right ?
so the original frame is still there
so...what is leaking ?

Mike Smith Rhode Island : Design / Build / Repair / Restore


Silicone caulk comes to (post #182511, reply #2 of 14)

Silicone caulk comes to mind.

Worst case is remove, celan and re-install them, properly this time.

Thanks for the comments. My (post #182511, reply #3 of 14)

Thanks for the comments.

My thinking is that it is the design of the windows which is at fault. Vinyl windows are welded at the corners and wood windows are solid. These fiberglass frames are hollow and while they are obviously mechanically joined together the corners don't seem to be sealed.

I guess I should silicone the corners and see how that works out. I have been a little hesitant because there is nothing really for the silicone to stick to on the vertical surfaces of the external corners. The gaps, such as they are are hair thin. I have been thinking of taping these areas. Also thinking of plugging the weep holes these frames have on the outside bottom member as water might be driven in to then migrate out through the corners on the inside.

The window units are, I believe, properly installed. The installation features a sloped sill, bituminous flashing tape, flanges caulked and nailed and then trim applied and caulked some more.

For what it's worth most of them are picture windows although there is one casement window which is leaking the worst. That one is a salvage window so I assume it has been racked quite a bit and the corners are obviously loosened.


Any window that has gaps at (post #182511, reply #4 of 14)

Any window that has gaps at the mitered corners and is leaking has not been properly installed - by definition.

I would not "tape" the exterior nor plug the weep holes. Tape falls off and leaves an ugly residue. The weep holes are there for a reason.

Have you ciontacted the manufacturer?

It's hard to suggest a repair method without seeing the item or, at least, photographs.

I guess I cannot disagree and (post #182511, reply #5 of 14)

I guess I cannot disagree and I appreciate you taking time to reply. I have sent an email to Milgard about this problem.

I am uploading pictures taken tonight.

The first two are of a brand new picture window. Very mild water spotting on the peal-and-stick wood "cladding". Still, shouldn't be there. I now see that the weep holes don't even apply to this part.

The second two pictures are of an older, much abused salvaged casement window which is leaking enough to actually leave a tiny puddle inside on the flashing tape. I am holding off doing the trim until I can get this straightened out. This window is six feet tall so it hangs down almost to the floor and gets much more weather exposure for that reason.


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The weep holes are not a (post #182511, reply #6 of 14)

The weep holes are not a problem. They are there to let water out -- a critical function.

You should go outside and stare at these windows for as long as it takes to determine where the water is getting in. And note that water can be very sneaky -- it might be entering right near those corners, or it might be entering at the top of the sash where you'll need a ladder to see the problem.

And once you find where the water is getting in, fix that entry point, probably with some caulk, but maybe with flashing or vycor.

. . . I can't live proud enough to die when I'm gone, So I guess I'll have to do it while I'm here. (Phil Ochs)

I'm having the same problem (post #182511, reply #7 of 14)

I'm having the same problem with a set of the milgard fiberglass picture windows. I have seen reference to this problem elsewhere on the web.

The problem is much worse on the windward side. Only one leak after one storm on the nominally leeward end of the building. But practically every corner on the windward side is leaking after a big storm.

The vinyl widows and the eagle casements on the same side don't seem to have a problem.

Being on the coast I was very careful with the installation.

I need to get out the water hose and air compressor and see if I can re-create the problem. I'm still in the building process and haven't determined if it only happens when the wind blows, but based on the windward/leeward results, I would say that is the case.
I don't know whether it's the amount of water (more wind driving water onto wall/window) or the air pressure that's the key factor.

My theory is that the wind and/or amount of water raises the water level inside the window (i.e. it doesn't drain out the weep holes fast enough) high enough to flow to the interior side of the frame which is not well sealed.

I will post my results. I am interested to hear from others that have root caused the problem and/or found a good solution.

One trick that is used in woodworking, and may work here, is to use a vacuum cleaner to create a vacuum inside the window (connect vacuum to weep hole?) which will help pull sealant into the small gaps.


This could be a tough fix, (post #182511, reply #8 of 14)

This could be a tough fix, with the windows installed and glazed. I used to build hundreds of direct set units using Anderson's (permashield ?) material. Similar, I think to Milgard's ?

EVERY corner, on assembly, was sealed with a Tremco Architectural sealant. The stuff was a thick liquid, color matched, and the cans had the brush in the lid. Without this, direct water flow, or condensation, can quickly settle in the corners, inside the extrusion.

I can't really see anything adhering to the face of extruded fiberglass for very long.


Epoxy will stick to (post #182511, reply #10 of 14)

Epoxy will stick to fiberglass - forever. Get some color-matched epoxy and fill a syringe-type dispenser. Drill a small hole in the miter joint. Insert the nozzle of the syringe and dispense the epoxy into the joint. Use some of the epoxy to fill/plug the hole you drilled, hiding your intrusion.

A less invasive technique would be to put some color-matched epoxy on the surface and rub it into the crack with your finger tip. Work it in.

The key to both the above is getting the surfaces cleaned. Scrub the outside with a rag dampened in alcohol. Wipe along the gap to remove/clean the miter joint. If you do drill, reach inside with a solvent dampened Q-tips. Use as many as you have to and keep wiping until they come out clean. Then bond.

I have some friends in (post #182511, reply #9 of 14)

I have some friends in Whidbey Island, WA that had Milgard windows installed on their beach home, which receives up to 90 mph winds directly at the windows. They, too, had an issue with the windows leaking. Milgard came out and checked the windows and replaced them all at no charge... twice. Whatever the problem was, they haven't had an issue with leaking now in over 5 years. I don't know if they still do that, but they were great both times.

Thanks everyone for the (post #182511, reply #11 of 14)

Thanks everyone for the replies and ideas.

Milgard is coming out next week and we'll see what happens. The person I spoke to said they usually take out the glass unit and reseal. It looks to me that the window is leaking in a separate section from the glass channel but as someone said, water is sneaky. I will leave it up to Milgard to figure it out.

Unfortunately for me the windows that are leaking the worst are the salvage windows. I will probably try the epoxy route. Another thought I had was to drill a hole and fill the bottom corners with foam but then I run the risk of trapping water in the unit which would be bad.


P.s. I found a cross sectional drawing on Milgards website and then drew all over it.

woodclad_cross_section.pdf32.55 KB

milgard ultra leaking (post #182511, reply #12 of 14)

besides the design flaws pointed out by others, and the possibility of an improper installation approach, it should be pointed out that replacement or retrofit windows are a bad idea from the start...penny wise pound foolish as i like to say.  I live in so cal and even in our climate, i only do retrofits on houses with a minimum of 24" overhang which means I elminate more than half the homes in the city.  And if i do them, i make sure i use every possible trick to seal them during installation.  they work best on wood sided with wood trim around windows. never have found a way to seal them with any real certainty on stucco houses...i just use tons of the best caulking I can buy (hence the 2' OH requirement).  in the mid west, east coast, mountains, northern states other words anywhere other than the south west states at elev. below 5000 ft- i would only do new construction.  These days however i just run away from any retrofit job.   :)

Did you get resolution? (post #182511, reply #13 of 14)

Hi Bob - I am having a similar issue with Milgard windows just installed in new construction, and wondering if you ever got resolution to your issue with Milgard?

This is an 8 year old thread. (post #182511, reply #14 of 14)

This is an 8 year old thread. Sorry to say that none of the guys who posted on that thread have been here for many years.

Florida Licensed Building Contractor, 50 years experience in commercial remodeling, new homes, home remodeling and repairs and all types building maintenance.