Render under patio doors

[ivahunch]

The render is falling away under our patio doors and so I need to rake it away and replace it. (The floor is a concrete base with synthapruf and scree on top) DAK what material to use? E.g. should I just use soft sand and cement or would sharp sand and cement last longer?

[Mike4]

The render is falling away under our patio doors and so I need to rake it away and replace it. (The floor is a concrete base with synthapruf and scree on top) DAK what material to use? E.g. should I just use soft sand and cement or would sharp sand and cement last longer?

Are we talking inside or outside here? And presumably you mean from the vertical wall. I ask because I don't understand why you would be mentioning how the floor inside is constructed.

A photo would be good!

[Wizard]

The render is falling away under our patio doors and so I need to rake it away and replace it. (The floor is a concrete base with synthapruf and scree on top) DAK what material to use? E.g. should I just use soft sand and cement or would sharp sand and cement last longer?

Plastering sand.

This may be helpful...

https://m.youtube.com/watch?v=UT_8vpsMuCU

[ivahunch]

Are we talking inside or outside here?

Outside - but I mentioned the floor since the render needs to adhere to its edge (and it is concrete not brick)

[ivahunch]

I fogot to mention that I can't paint the render because it is below the dpc

[AsleepInYorkshire]

The render is falling away under our patio doors and so I need to rake it away and replace it. (The floor is a concrete base with synthapruf and scree on top) DAK what material to use? E.g. should I just use soft sand and cement or would sharp sand and cement last longer?

Generally render does not work well below dpc. One possibility is the render has come off for that reason. Replacing it will likely result in the same outcome. I think the initial build detail wasn't brilliant and you're left with the problem now.

Dependant upon the period the existing materials have taken to degrade you could replace as it will be cost effective. Failing which you need to consider an alternative detail. Of course cost is an issue unless you feel you want a permanent solution that looks good you may prefer to opt for replacement with like.

One possible solution could be to build a step using "plastic" decking materials? There are others.

AiY

[ivahunch]

Would it be better to use a 4 to 1 mix intead of the usual 6 to 1 mix of sand to cement? Or could I even use sharp sand?

[fisher]

You can get additives to add to render in order to waterproof it to some degree. This is often done when a chemical damp course has been injected into older properties. The plaster internally is removed for the bottom metre and then the brick is rendered and finally skimmed.

Also used when rendering basements.

This is the sort of stuff they use. It's expensive but may be worth it in your situation.

https://www.tradebuildingproducts.co.uk ... DSEALw_wcB

[sg31]

Would it be better to use a 4 to 1 mix intead of the usual 6 to 1 mix of sand to cement? Or could I even use sharp sand?

I wouldn't go as strong as 4 -1, 6 - 1 should be ok, Definitely use sharp sand. It's sold under different names in different area, washed sand, sharp sand, rendering sand.

Watch out for the DPC, you don't want to render over it. It may be that the cill for the patio doors is at dpc level in which case you are ok but if it's set higher you might need a bell bead at dpc level to stop bridging. A photo would be good.

[Wizard]

Would it be better to use a 4 to 1 mix intead of the usual 6 to 1 mix of sand to cement? Or could I even use sharp sand?

Did you watch the video I linked to?