What should I use to fill the gap between my door frame and patio?

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Hello All!

I've noticed a damp on my concrete floor coming from under the front door, so had a look and there is a huge gap between the tiles and the threshold as seen in the pics.

Obviously I would need to fill it out with something that is waterproof to stop the damp. What would be the best material to use? Silicone? Mortar? Or something else?

I'd really appreciate any product or technique recommendations to rectify this.
Thank you!
 
Soldato
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I can't see the pics, but if it's external then low modulus, neutral cure silicone is what you want. I think it's call builders silicone on Screwfix. If its a really big gap then you might need to fill it with some 'foam joint backer rod' first. Cut the nozzle to around the same size as the gap and slowly pump the silicone into the gap, trying to keep it as even as possible. Then spray the silicone joint with some soapy water and use a wetted finger, or piece of smooth wood that has been soaked in soapy water and carefully tool the surface to a smooth finish.
 
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Soldato
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Ahh, I assumed it would be sat on a row of bricks and the gap was between the brick and sill. I think that might be better pointed up with sand and cement. I'm guessing water is pooling up in the gap and finding its way in, so blocking the gap and adding a bit of a slope to the mortar away from the sill should help. Although someone else might have a better solution.
 
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What about the waterproof part? Should I use cement as a base and finish it with a sealant? And if so, which sealant would be best? Thank you.
 
Associate
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To be honest that gap is far too wide to silicone, as mentioned above there must be a gap underneath the cill and between the brickwork the door frame sits on/above. Is there a visible gap between the concrete floor inside and the bottom of the frame inside? A pic would help, (horizontally looking at the bootom of cill inside the house). Digging out the sand cement in the gap between the slabs and cill would probably help if thats filling with water, the water would drain off rather than flowing back under the cill.
 
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From the pic it looks like the outside ground level is higher than the damp proof course as it looks right under the door drip tray (need a wider pic to see for sure) if it is I'd lower the height of the slabs and outside ground, don't fill it with cement as it'll make it worse

^ This ^

As above need more images but those slabs need lifting and the material making contact with the wall removed to expose the damp course. Ground level should be 2 bricks below the damp course.

Having the slabs so close also runs the risk of the rain splashing up the walls which can also cause damp as its above the damp course.
 
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Thank you very much for your help guys! There was a tiny gap between the sill and the door frame which caused all the issues. I filled it up with builder silicone and there is no more damp. Thank you again! All the best!
 
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