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How to fix gap between concrete and external wall?

Samchan30

Hi Folks,

Please advise how can I seal the gaps between the external walls and the concrete floor?

The gap is around 15mm generally and 20mm at some places.

The water ingress is making it worse 🙁

Please suggest something that not only fills the gap but is also waterproof.

Thanks in advance!

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Comments

EricL

Hello @Samchan30

I suggest using the Moroday 15mm x 25m MGF1 Gap Filler Rod in the gap. Try not to push the filler rod too deep as it will serve as the stopper for the gap filler, I propose a depth of 5mm and not much more than that. I suggest using Sika 300ml Concrete Grey Sikaflex 11FC Purform to fill the gap. For larger gaps, I propose twisting on Moroday 6mm x 5m White Gap Filler Rod onto the main body of the 15mm rod. This will stop the filler rod from sinking too far into the gap.

If you have any other questions we can help with, please let us know.

Eric

Samchan30

https://www.workshop.bunnings.com.au/discussion/comment/58990#Comment_58990

Thanks a lot, Eric, for your response.

Can I ask you 2 more questions?

1. The depth of gaps is about 120mm as shown in the image below. Should I fill sand or something to reduce the depth before using filler rod and Sikaflex or is that not necessary?

2. In which scenario is a joint filler foam used?

Cheers,

Sam

JacobZ

https://www.workshop.bunnings.com.au/discussion/comment/91999#Comment_91999

Hi @Samchan30,

The filler rod is just there to act as a backing to stop the sealant from falling through. As it is an expansion gap, which is there to allow the concrete to expand and contract, a foam rod is the best option because it will friction fit in the gap and compress with the expansion of the concrete. Other fillers like sand or mortar will not allow for this expansion.

Filler rod is used because the other option is to just fill the whole gap top to bottom with Sikaflex, which is hugely more expensive and much more time-consuming to do.

In your situation, the 15mm foam rod Eric mentioned should work, but if you find it falling down you may need to use a wider diameter filler rod such as this Sika 20mm x 50m Abelrod Gap Filler.

You just need it to sit in the gap about 5-10mm down from the top so you can apply Sikaflex over the top.

Let me know if you have any further questions.

Jacob

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