How to fix widening fence cracks in Hardieboard?

5Thumbs

My boundary fence is the old Hardie fence type. It is in good condition, except that I've noticed a crack developing and widening from the top to the bottom. I've chatted to my neighbour to see if there are plants that might be causing the problem, but there is nothing nearby. How can I stop the crack from widening? Is there a material I can paint on that strengthens the fence to keep it going? Would appreciate any advice.

MitchellMc

Welcome to the Bunnings Workshop community @5Thumbs. It's wonderful to have you join us, and many thanks for your question about repairing a cement sheet fence.

A photo of the damage would be beneficial for our members when they are providing advice on repairing the crack. 

How old is the fence? Any old Hardie fence with a wide corrugation profile should be considered asbestos unless otherwise known to be standard compressed cement.

It sounds like replacing the panel would be the most straightforward approach. Alternatively, you could fill the crack with Sika 300ml Grey Sikaflex 11FC Plus Polyurethane Adhesive Sealant. It's not really going to prevent a fence under stress from continuing to crack, but it will fill the gap and hopefully reduce the severity of the issue.

Not that I've seen it done before, but I suspect you could use fibreglass tape to reinforce your repair. Fill the crack and apply a thin layer of 11FC to either side of it on the face of the sheet. Place Builders Edge 50mm x 20m Fibreglass Builders Joint Tape over the still tacky sealant. You'd then come back and apply another layer of the 11FC over the tape. This will bed the fibreglass tape into your repair, hopefully holding the crack together and preventing it from migrating further.

Please let me know if you have any questions.

Mitchell