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Seeking advice for the repair of two identical (mirror image) trim pieces from the base of Pella casement windows. Each piece is cracked through its thinnest portion, which is only about 1/4" thick or less. I'm concerned that gluing and clamping will not be sufficient for a lasting, durable fix.

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These are specialized pieces that are nearly 30 years old and not made anymore, with intricate cutouts and machined sections and so are effectively irreplaceable.

In the past I've fixed stuff like this by drilling a small hole and gluing in a dowel to join the two pieces (as well as gluing the broken seam). In this case that would require extremely precise drilling through thin, irregular sections and the dowel could barely be more than toothpick-sized.

Is there some kind of fiberglass tape I can glue or epoxy to the non-visible underside of the seam? Open to other ideas.

Complicating matters is that the inner workings of the casement window mechanism tend to push out on the inside of these wooden pieces in such a way that almost certainly led to their failure over time. Also one of the pieces looks to be water damaged, and could be more brittle as a result.

These trim pieces were breaking or broken when we bought the house about a year ago (along with the crank mechanisms, which have been fixed) -- we're not going to replace the windows and we can't find new trim pieces, so we're going to have to do our best to patch them up.

Any advice from the community would be most welcome! Also happy to provide more info as will be helpful in suggesting an approach.

Eli
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  • Welcome to WSE. IF there is good contact between pieces, a good wood glue such as titebond should do the trick on its own (the glue is stronger than the wood). You are not going to get much extra strength from epoxy alone. If you have access to a woodshop, woodworking tools (saw, planes, & chisels) and have some experience you can reproduce these pieces. Otherwise find an experienced woodworker to make them for you. – Ashlar Jun 26 '22 at 00:32
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    If done well (and this is the critical thing) glued joints in wood are literally stronger than the wood around them. This means that in the right circumstances repaired pieces are stronger than the part was new, as paradoxical as that seems. You can really only guarantee ahead of time that one of three critical conditions are met to ensure the strongest glue joints possible. The other two requirements may be impossible to meet and that is for the surfaces to be absolutely clean (like fresh wood) and that the surfaces come together perfectly (so no splinters or anything hold the joint apart). – Graphus Jun 26 '22 at 17:25
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    "and the dowel could barely be more than toothpick-sized" This isn't a dealbreaker as both bamboo and the right hardwoods can make extremely strong small-diameter dowels. If felt necessary you could always use brass or stainless steel. But not sure if you can be confident the parts will be strong enough for service; if you want some assurance of a long life I think new parts may be the only really good option. Presume you're not in a position where you can make something this complex or you'd have already done so? So you'll have to find someone who does have the requisite experience/skills. – Graphus Jun 26 '22 at 17:35
  • Thanks for the guidance -- I believe it as regards glue being stronger than wood. I tried gluing and clamping today but the issue I'm having is with all the beveled edges. To apply clamping force normal to the glue face(?), I need to clamp beveled edges that are not ultimately parallel. This creates a moment and the whole thing keeps flying apart. I have some ideas as to how to create a jig or similar to hold it properly.Unfortunately I don't have access to a proper shop but I'm reasonably resourceful and can buy an inexpensive tool or two that will come in handy down the line. Suggestions? – Eli Jun 27 '22 at 02:47
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    Big chance you ruin the pieces during repair attempts. I think you must start looking for woodworker to manufacture new ones! – Volfram K Jun 27 '22 at 05:37
  • Just to make sure it's clear, it isn't glue that is stronger than wood it is the glue joint. Sorry if this seems unnecessarily pedantic but it's vital to see the distinction being made where strength is of utmost importance. And it's especially important in relation to both PVA and foaming polyurethane, which are very poor gap-filling adhesives. – Graphus Jun 27 '22 at 16:24
  • "I tried gluing and clamping today" FYI this attempt may already have undermined the possibility of getting the strongest joint you can get, sorry. Without going into detail, on long-grain wood surfaces you get basically one shot at glueing which is why it's so important to do dry runs to make sure things go as planned before proceeding. If you have no alternative but to keep going you're going to have to do your best to clean the glue contamination from the mating surfaces without otherwise harming them (bending over fibres, losing splinters) which will further interfere with a good result. – Graphus Jun 27 '22 at 16:31

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If gluing is your only reasonable choice (which is to say, you can't make replacement pieces yourself, and you don't care to spend the many dollars having them custom made would cost), then I would suggest that you build a jig to immobilize the pieces in their proper configuration. Hardboard, double-sided tape, and masking tape should be sufficient to create such a jig. Once you can immobilize them in a configuration that satisfies you, I'd tack them together with small areas glued using CA glue (superglue). Finally, once they are secure, I'd remove enough of the fixture to have clear access to the joints from both sides, and finish the repair with a good epoxy that is thin enough to infiltrate the joint thoroughly. You can dam one side of the joint using hot melt glue, or a putty, to make getting the epoxy to stay in the joint easier. Note that you can clean the epoxy you will inevitably get all over the piece doing this once the epoxy is semi-set using alcohol or acetone (edited to change this from warm water).

We commonly use techniques like this in restoring old furniture pieces. The key is in getting adequate strength in the initial immobilization, to be able to work the repair safely.

Walnut Close
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  • Warm water? Other than the potential for warping or raised grain, what epoxies are you working with that water has any effect on them once mixed? Alcohol or acetone are universally given as the go-to cleaners for excess epoxy, with acetone strongly in the lead in effectiveness. – Graphus Jun 27 '22 at 16:41
  • @Graphus. - indeed, epoxy can be dissolved by either alcohol or acetone, but not by water. Nonetheless, when working semi-hardened epoxy off damaged wood, I typically use warm water on a rag. It doesn't dissolve into the epoxy, but does lubricate it, and make it easier to wipe off, and it swells the wood fibers under the epoxy, making the epoxy come away. For large amounts of squeeze out, I do use acetone. – Walnut Close Jun 27 '22 at 20:03
  • Thank you for the thorough response! I will set up a jig. – Eli Jul 01 '22 at 16:58