How to paint treated Pine timber boards bleeding resin?

awin1

Hello

I have some bench seating in my back garden. Rendered brick base with painted timber boards for the seating, which had weathered after many years.

In August last year I had someone replace and repaint the timber.

They purchased H3 Treated Pine decking from Bunnings, and used an oil based primer then exterior paint.

After one week, a sticky liquid started oozing out of patches in the timber. See pic1.

The oozing continued into early November then appeared to dry up. See pic2.

In mid November they came back and scraped the timber, sanded it back to bare wood, then reapplied two coats of oil based primer + exterior paint. Within one day bubbles appeared in the paint and continued to leak. See pic3.

I have left it several months to dry, and now the residue is more like the texture of old BluTak or chewing gum. See pic4.

It has been approx 10 months since the timber was initially purchased.

I have spoken to several people at Bunnings including timber and paint departments.

Some of the feedback was "I don't know", but the more credible feedback seems to be that the tannins/resin in the treated pine have been leaking out and causing these issues.

What is less clear to me is what I should do next. The suggestions include: Replace the timber; Scrape and sand back to bare timber; Use Cabots New Timber Prep.

No-one at Bunnings expressed any kind of responsibility for the performance of the timber, and apparently H3 treated pine is the right material for this work, so I don't understand was this a bad batch, did it need time to acclimatise, should my painter have done something different, or is it not fit for purpose?

At this point I don't want to keep throwing money at it and hoping for the best, and frankly I also don't understand why I should have to.

Appreciate if anyone has any experience, knowledge or advice they can share.

Thank you

MitchellMc

Hi @awin1,

Thank you for providing such a detailed explanation of the issue and timeline. I can certainly understand your frustration, particularly after having the seating stripped back and repainted only to have the problem reappear almost immediately.

Based on your photos and description, it does appear that resin bleeding from the treated pine is the most likely cause. One of the key indicators is that the issue seems to be concentrated around knot locations in the timber. Knots are where branches were attached to the tree, and these areas tend to contain significantly higher levels of resin than the surrounding timber.

What is unusual in your case is the extent and persistence of the resin bleed. While some resin movement is not uncommon in treated pine, particularly when exposed to sunlight and heat, it would typically be far less widespread than what you've experienced.

When using treated pine for painted applications, we generally like to see the timber left uncoated for several weeks so it can weather naturally and expel any excess moisture and resin before paint is applied. If the timber is primed and painted too soon, it can effectively trap the resin beneath the coating. As temperatures rise, the resin softens and seeks a path out, causing bubbling, staining and the sticky deposits you're seeing. Unfortunately, once this process starts beneath a coating, it can continue for a very long time.

The painter appears to have followed what would normally be considered the correct remediation process by sanding back to bare timber and applying an oil-based primer before repainting. Oil-based primers are generally the go-to solution for sealing resinous timbers, and in many cases they are successful. The fact that the issue returned within a day suggests there may have been a significant amount of resin still present within the timber.

Given the extent of the issue and the length of time you've been dealing with it, I think it would be worthwhile speaking with the Store Manager at the store where the timber was purchased. They can review the circumstances and discuss the situation with you and ways that we could assist.

If replacement timber is ultimately considered, my recommendation would be to allow the new boards to weather naturally for several weeks before coating them. This gives the timber an opportunity to stabilise and release any excess resin before paint is applied, reducing the likelihood of the issue recurring.

Please let me know if you have any questions.

Mitchell