I agree with Wild Infusion. You need to find out what the cause of the water penetration is before you cover it up - this will only keep breaking down as the water is coming in through the brick and pushing out behind the render. No matter what product you put on the wall it will keep bubbling off over time. You need to see if the soil is above your slab line. If the wall is retaining soil on the outside there is a fairly good chance the waterproofing membrane has broken down (if it even exists). It it isnt retaining soil then the surround ground may have been increased in height and may now breach the damp course. Another problem that you could look at is the down pipes and storm water system. Check for cracking of fitting and joints you may have a water leak that is causing an excess of moisture in the area. Call your local Master Builders office and ask who the best person is to look at this problem and if they can suggest anyone in particular.

We have been a supplier of OSMO Hardwax Oils for a while now and have found that they have been great in all applications. They have an Oil specifically designed for Kitchen benchtops. OSMO Top Oil which is foodsafe and contains linseed, carnauba wax, candelilla wax, sunflower oil, soybean oil & thistle oil. You can buy it from VCS Products in Perth or Natural Timber Oils in Melbourne.

We had timber tri-folds (also facing north) in our previous home and whilst our landlord sanded and re-finished every couple of years, they didn't stay fresh for very long and it affected the integrity of the timber too (slight warping and 'furring'). I used some Haymes Exterior Solarshield recently and it was brilliant over very poor quality timber and I noticed it's guaranteed for 20 years?! It was acrylic and very easy to use, but has sealed the timber beautifully. It may be better option for the longer term if you're happy with the look of painted. It would look lovely and one less thing to worry about!

Dont rely on google images, they are heavily edited and inaccurate, definately order swatches for accurate comparison. Below is a photo of Dulux Elements powder coating swatches which I have in my office - in the photo you can see (and from my own perspective of this colour) up close Surfmist is definately not 'white' but search the images on the web and yes it looks white (FYI first colour is 'Basalt', second colour 'Surfmist', third colour 'Black' and fourth colour 'Monument') Below also is one of my company's recent projects, chairs in Surfmist and tables in Monument, but looking at the image you'd swear it was 'white and black'. Before you decide Id suggest getting the actual powder coat swatches from Dulux which you can order via their website and then you can compare them and decide. Note: Colorbond Surfmist / Monument and Dulux are the same tone. Good luck!