What mortar to fill a gap that will hold vertically?

[Coolaholigah]

I need to fill/repair the degraded mortar (seems to be sand and cement mortar - I can scrape grains off with my fingers) which is between sandstone at the top and a PVC slot drain at the bottom. The green /blue in the foreground is fibreglass of a chlorine swimming pool and is not part of the repair but that does let you know that the location is exposed to pool water as the pool spills over into the slot drain. Someone in the past has also put a layer of what seems to be waterproofing type ‘paint’ under the mortar at some stage. I am concerned that water will ‘bleed’ back through or under the mortar and under the deck above and behind. 

My thought is to fill the gaps, then maybe waterproof paint vertically over the top of that.

I have researched concrete repair mortars but I’m not sure if that’s appropriate as it is not actually concrete which is being repaired.

I don’t want a quick set type thing as I feel I need longer work time as access is awkward and I am not a professional. Any help or suggestions appreciated.

[MitchellMc · Accepted solution]

Hi @Coolaholigah,

As you've mentioned, it will likely be a two-part repair. I'd suggest using Prep 750g Watercrete Multi-Purpose Patching Cement to fill the void, and once it's dried, run some Sika 300ml Transparent SikaSil Premium Pool Silicone between it and the fibreglass pool shell. If you can then apply water-proof paint over the top of the whole area, all the better. Both Watercrete and the SikaSil silicone are suitable for use around and in swimming pools.

Please let me know if you have any questions.

Mitchell

[Coolaholigah]

Thanks Mitchell. Sounds like I am not too far off track. But that Watercrete is quick set. Are you aware of an equivalent that is not quick set? I like the look of Lanko 731 but I can’t find anywhere to buy it. Could Bunnings get it for me as a special order do you know?

thanks!

[MitchellMc]

@Coolaholigah,

Unfortunately, Lanko 731 has been discontinued by the manufacturer. The closest equivalent would be Lanko 136, but it's a rapid patching mortar allowing around 10 mins work time. Although this sounds like a limited amount of time, you don't need to complete the whole job in one go. Would can pack out the void and do your final coats in separate steps. You'll get much better results if you go along and use several batches to fill the void. After that has begun to set up, you can do a final coat over to smooth everything out.

Mitchell