Hope i havent f*cked it up

[Laurent1985]

hi all

me and a mate built a large wall in my garden as a DIY project.
it's built out of concrete blocks, cement etc.

we're both fairly experienced so we decided to give it a try rendering, as it was our own project so didnt really matter.

we tried to mix the render yesterday using;

4 buckets plasterers sand, 1 bucket of cement, 1 bucket of water

however the mix was far too watery, so i topped it up with more sand and cement (totals are now 4 x 25kg bags of sand, 1.5 x 25kg bag of cement, water (no more added!)

it mixed to a much better consistency and we applied it. this morning it has dried nicely with no cracks and looks/feels solid.

i'm concerned now because;

1) i have no idea what my scratch coat mix is (ratios of buckets went out of the window)
2) will this mix last the long term? top coat hasnt yet been applied but its scratched and ready to go.

any thoughts?

 

[vinn]

OP,
If you dont know what the final mix was then how can we know?
I'd suggest take the suction out, & then do a 4:1 sand & cement mix and leave it at that.

 

[roy c]

You got the mix right, but a 4-1-1 mix doesn't mean and one water!! Depending on when you did it, could you scrape the stuff off the wall?

 

[Doggit]

Come on Laurent, switch you're brain on. Your initial mix ended up as 4x25 of sand, and 1.5x25 of cement, so you're mix was 2.7:1. Next time, use 4 bags of sand, and one of cement, and then add the water slowly to get the mix right. and as long as your top coat isn't too thick, then you should have enough for the job. And if you need any more, then work by the bucketful afterwards.

 

[Laurent1985]

thanks all for the replies

good news is the scratch coat is completed and the area is nicely covered

i can't for the life of me get the finish properly on the top coat (wickes plastering sand is utter dross) mainly due to the large stones and grit in it.

i'll be calling in a pro to do the top coat for me!!!

 

[vinn]

OP,
I think that you've picked up bags of the wrong sand - what you describe could be a coarse sand used for paving and landscaping but not for render.
It has a correct name but I cant think of it - maybe someone else can?

 

[Laurent1985]

it's strange as on the bag it specifically says "for external rendering" but the quality of it is atrocious

so gritty and full of small stones