How to repair rotting garage door jamb?

Hi. I’ve recently moved into a new house and found the bottom of the garage roller door jamb / cladding beginning to rot away. I’m not sure whether I can simply remove the soft rotted sections, apply wood hardener and then use some exterior wood filler, or whether I need to start cutting off trim and attaching new pieces of wood. The area that has me the most confused is that thin white section that appears to have some form of metallic webbing within it. Does anyone know what that is and whether it’s replaceable? I’ve read that the bottom of the cladding shouldn’t go all the way down to the concrete slab, but that would seem to expose the timber frame behind to the elements. I would very much appreciate any guidance. Thank you.

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Nailbag

Hi @Hayman

Obviously that section is subject to water pooling causing the rot. The first thing to establish before the repair is to confirm how the water is getting there, so that any repair is long lasting.

Does it come in under the closed garage door during heavy rain? Or does it enter externally even with the door closed and possibly running internally down the wall? With the door closed, pointing a garden hose around the area will help solve that problem.

The exposed metal is an external angle used with both plasterboard and rendering to provide a straight, strong and durable edge as in the images below.

What you propose to both repair and have read is spot on. Cut the section out higher than the affected area, apply your hardener but instead of filling, I would fit a new piece of "hardwood" thats 5mm shorter than a snug fit. This needs to be primed on all sides other than the joined side. Once fitted, prime the join and apply the colour coat of paint. Then apply silicone to the 5mm gap. to prevent water ingress underneath.

Nailbag

Screenshot 2025-01-26 at 7.30.58 am.png Screenshot 2025-01-26 at 7.31.13 am.png

JacobZ

Hi @Hayman,

A warm welcome to the Bunnings Workshop community, it is wonderful to have you with us.

My thinking is much the same as @Nailbag's in that we should start by identifying why the rot has occurred and taking steps to address this issue. It looks like the land is sloping towards this spot which is obviously going to cause some issues.

Can we get a wider shot of the affected area? This will help us look for ways to address the water issue to prevent issues in the future.

Once the water issue has been managed, you'd simply cut out the rotted section and replace it with new, water-resistant framing, whether it is hardwood or suitably treated pine.

Once the timber has been reinstated, you can replace the cladding material and blend it into the surroundings.

Are you aware of what the cladding material is? Is it plasterboard?

As Nailbag has said, the metal piece is an external angle and the type of angle that has been used is commonly used with plasterboard.

Knowing the type of cladding material will help us plan for the rectification works.

Let me know what you think.

Jacob

Hayman

Thank you so much @Nailbag and @JacobZ for your replies. And within a day…unbelievable! You’re right, I will need to address the ingress of water. There are so many entry points at the moment. The bottom seal of the garage

door doesn’t sit well due to a dent in the bottom panel of the sectional door, the seal itself is about 10cm short of the garage door jam on both sides, and the entire roller door in a tad too short for the frame, leaving a 1cm gap or so at the top when closed. I plan to replace the bottom weather seal when I install weather stripping to the sides and top. Bunnings has the brush weather strips that I was thinking of using. A thin piece of trim along the top of the garage door frame could take care of the roller door shortness. But repairing the subtle dent has me stumped. There are videos on hammering it back into shape, using a hair dryer to heat the steel first, but I’m not sure how successful that will be and I don’t really want to be banging on something attached to those wires and springs. A replacement bottom panel might be the best solution if anyone does that. I need to repaint the whole door anyway. I had the original garage door company out recently but they’re only interested in replacing the whole door for a few thousand dollars. There is also some split wood on the same garage door jamb (higher up) that I plan to remove and patch and paint with Selleys PlastiBond as the wood beneath seems solid and dry. Oh and there’s a crack in the top centre of the roller door where the arm would be pulling in the door from behind. The previous owner has had a metal strut installed along the inside top of the roller door to lessen the pull but not addressed the crack. I’ve bought a fibreglass cloth repair kit to address the crack from the inside of the door and am thinking about trying the PlastiBond on the front (where the crack has an indentation) before painting the while door. Ah, and the external join between the garage door jamb and the brickwork is all cracking. I have some Sikaflex Pro in cream for this after I scrape away all the loose sealant/plaster. I understand now why people are keen to buy new 😅 Thank you for all your suggestions. I really appreciate it!

JacobZ

Hi @Hayman,

With multiple issues, it sounds like the replacement door might be worth considering as it is a much more long-term solution that will address more than one of the issues that is present.

Unfortunately, I can't say I've ever heard of a garage door having individual sections replaced and repairing a dent considering the tension on the door is not something I would recommend. You can certainly patch and repair the door and add seals to help with the water, but if the door is not sitting as it should firmly against the concrete, then I can't see anything being 100% effective.

When the garage door is opening and closing, do you notice any movement from the jamb?

With the cracking all around the jamb, I suspect the jamb is moving when the garage door is operating. Looking at the location of the water damage, this cracked caulking could be a major entry point for water. If water gets in behind the jamb with nowhere to drain, it will sit there rotting the timber out, so fixing any movement in the jamb is essential to stopping water entry in this location.

As the garage door looks to be fixed to the framing behind the jamb, then this connection is likely going to be the cause of movement in the jamb.

You can certainly remove and replace the existing caulking, but if there is movement caused by the garage door, then I imagine it will crack in a similar fashion sooner than you'd expect and water will continue to get into this problem location.

Ultimately, there are things we can do to reduce the water ingress issues in the short term and the actions you've mentioned cover most things, but longer term, a replacement door looks like it could be the way to go.

I'm happy to offer advice on some short-term solutions, but I think the issues you are experiencing will require the assistance of a professional garage door installer.

Let me know what you think.

Jacob

Nailbag

Hi @Hayman

I would agree with all the follow up comments by @JacobZ. But do check around regarding getting just a section replaced for the damaged one on the door. A mate of mine backed in to his with the tow-bar and got his replaced. Albeit it was a newish door.

Nailbag

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