How to stop cracks appearing on outdoor timber rails fixed with builders bog?

[Anil51]

Hi, I have used Turbo Builders bog on my outside timer deck railings few times but within a year or two it starts cracking. I followed the steps correctly like removing the rotten timer, drying out and applying wood hardener. Can anyone help me with my problem.

I even used oil based undercoat before painting.

[MitchellMc]

Welcome to the Bunnings Workshop community @Anil51. It's terrific to have you join us, and many thanks for your question about using Builder's Bog.

Can you post some images of the areas so our members have a better idea of what you're working with? That will allow them to provide informed advice. Let me know if you need a hand uploading images.

It sounds like there might be a bit of movement going on there. It could potentially be the Builder's Bog shrinking over time or the timber moving. Builder's bog works well if it's entirely enclosed by solid material, though it doesn't have much sticking force. If patching with the bog doesn't appear to be working, the next step would be to look at replacing the handrails. The steps you've followed would be correct, so I'd be looking for a more permanent solution, like a replacement.

Please let me know if you have any questions.

Mitchell
 

[Anil51]

Thanks Mitchell for your help. I have attached few photos showing the cracks. White in color are done recently with oil-based undercoat over it. 

Posts should have minimum or no movements. Don't know if I am doing something wrong or Builders Bog is not the right product for this job.

[MitchellMc]

I'd sand those areas back and re-fill the cracks with more builder's Bog @Anil51. It could just be that the amount of bog applied has caused the cracks. I'm relatively confident that these cracks have only formed due to the curing process and that now that it's fully dry, it's sound. By filling the cracks, I don't think you'll continue to have this issue.

To clarify, by movement of the posts, I wasn't referring to them moving around and being wobbly, more so the minute swelling and contracting due to moisture content. This is on a very small scale and could cause fine cracks. I don't think that's the case here, it is more likely the bog has just shrunk slightly during the curing process, forming cracks.

Mitchell

[Anil51]

Thanks Mitchell for quick response. Can Builders bog be applied over dried Builders bog? Do i have to widen the cracks and drill holes before reapplying builders bog. Any special surface preparation is required. 

[MitchellMc]

Yes, Builder's Bog can be applied over the existing bog @Anil51. It would be an idea to try to scrape out the cracks to widen them, allowing you to push the new bog further in. Just enlarge them to 1-2mm so you can push the bog in. I wouldn't do a layer over the top, just push the bog inside the crack and leave it flush with the existing surface, then sand.

Mitchell

[Anil51]

Thanks once again Mitchell. I will do as suggested and let you know. I really appreciate your help.