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I have a bit of a two-pronged question 
Photo of my house attached for reference.
We have a retaining wall out the front of our house, which ends in a bit of an awkward spot and makes it awkward to mow the grass etc. I’d like to extend this retaining wall as shown marked in red on my photo - how would you recommend I go about doing this?
Secondly, I would like to attach blue board to the concrete retaining wall and then render/paint over it in a colour used on the facade of the house to make it look a bit nicer.
1. How would I go about attaching blue board to the retaining wall?
2. Should I dig out a little behind the retaining wall and place some blue board part way down to make for a seamless finish?
Thanks in advance!
Welcome to the Bunnings Workshop community @ashlea16. It's fabulous to have you join us, and many thanks for your question about extending a retaining wall.
Are those concrete sleepers, and if so, how thick are they? I'd suggest you'd need to install an end post on both sides of the area you'd like to fill. This will allow you to slip the final sleeper down into position. An issue you'll have is that the last end post for the existing wall would have been concreted into the ground, preventing you from installing your needed end post for the new section. You could potentially get around this by, instead of concreting in the new end post, you could bolt it into the end of the current run of sleepers and post. If you drill through the current end post and into the end of the concrete sleeper, you could use Dynabolts to fix the new end post in place.
When adding blueboard to a retaining wall, it typically needs to be fixed onto a timber frame that is mounted to the wall. This prevents water from seeping through the wall and blowing the paint off the board. At a minimum, you'd see staining in the paint if the board was fixed directly to the wall. This could potentially be offset by painting the back of the boards with a waterproofing agent like Bastion 4L Exterior Waterproof Membrane. Here's the installation guide for Hume Prima.
Please let me know if you have any questions.
Mitchell
Hi Mitch,
Thank you so much for your response!
A couple more questions for you
1) Could I use timber to construct the last part of the retaining wall and slide into the end post? I’m imagining it would be easier to cut down to the correct size. And given that I want to cover it in blueboard and render it anyway, it shouldn’t matter looks-wise.
2) What would you suggest using for the frame? And how far away from the retaining wall should the blueboard sit ideally? Like what size should the timber frame be?
Hi @ashlea16
It should be ok to use timber sleepers on that last part of your retaining wall. In regards to the framing, I suggest having a look at 70x35 treated framing timber. The gap provided by the timber should be enough space between your retaining wall and the blueboard.
I recommend taking some measurements and drawing up a plan to give you a better idea of how you'll be covering your retaining wall.
If you need further assistance, please let us know.
Eric
