hi there,
We have a gap between our sub floor and the ground, and when it rains water runs down the side of our house. This gap sit beneath some yellow tongue flooring. What do you suggest to water proof?
Hi @Calum_Young,
Welcome to the Bunnings Workshop community, it is fantastic to have you with us.
How wide is the gap at its widest point?
Assuming the gap is reasonably consistent, I would look at filling the majority of the depth with a foam filler rod or abelflex to act as a backing, then apply Sika Sikaflex 11FC Purform over the filler rod, tooling it off to create a neat, continuous seal between the two surfaces. I'd make sure the surfaces are clean, dry and free from any loose material before applying it.
If you can let us know the approximate width and depth of the gap, particularly at its widest point, I can certainly offer some more specific advice on the size of filler rod and how best to approach filling it.
The scenario is different, but the materials and process in How to fill a joint in a concrete slab is much the same as what you would be doing here.
Have a look and let me know if you have further questions.
Jacob
@JacobZ thank you. The gap is 55mm
Unfortunately, that is going to be too wide to simply fill with gap filler foam then overcoat with Sikaflex.
Is there anything you could attach some timber to inside the gap? Is it possible to get some photos showing what is inside the gap?
I am thinking you might be able to attach a piece of https://www.bunnings.com.au/42-x-11mm-5-4m-h3-treated-pine-fj-dar-primed-losp_p0020736 inside the gap, so that it sits above the ground, then seal up the bottom edge with the Sikaflex I mentioned above.
Or alternatively, attach something to the face of the weatherboard, again so it sits just above the concrete, then seal it with Sikaflex.
Allow me to tag some helpful members to see what they think - @Nailbag, @Dave-1, @Noyade.
maybe aluminium flashing @JacobZ ?
Yes, aluminium flashing like this https://www.bunnings.com.au/cagroup-150mm-x-20m-x-0-3mm-weatherflash_p1100454 would certainly work.
You could run it over the gap, attach it to the bottom of the weatherboards with some https://www.bunnings.com.au/zenith-8g-x-15mm-galvanised-button-head-stitching-timber-screws-100-pack_p2420703 and then attach it to the concrete using some masonry plugs and the same screws, then seal the bottom seam with the Sikaflex mentioned above.
This would give you a nice seal that covers the gap well.
Let me know what you think.
Good Evening @Calum_Young
From your photos it looks like the path slopes towards the house? Where would the water that comes from falling down the side of the house go is the first question that comes to mind? The aluminum angle is a good idea and especially if it sealed against the ground as well. 55mm tho is a fair height.
If the water will still pool even with the additions due to the slope I would suggest to install a grill drain next to the wall to stop the buildup of water in the first place. It means cutting the concrete but it would be a long term fix so possibly worth it. The drain will have to go somewhere or be connected to your stormwater which will need a plumber to do so.
Dave
