Correct sand cement ratio for roofing

[1]

I was wondering if anyone could let me know what the correct sand cement ratio should be for setting hip capping tiles. If you want to know the background to this see the 'roofing nightmare' thread.

I have a photograph of two sacks of similar size, one almost empty containing sand and another almost full containing cement left by the roofers who recently did some work on my property. These sacks suggest that the roofers used a mixture of *at least* ten parts sand to one part cement.

Does anyone have any ideas of what the implications of this might be? How good could this information be in negotiating a discount from the quote?

Thanks,

1

[PaulB]

Well dangerous ground since IMNAExpert but years ago when on a carpentry course at the Brick Development Association in Edgeware and next door were the brickies, they were using 9 to 1 because their walls could be easily knocked down and rebuilt whereas 3 to 1 was what you used if you wanted them to stay up.

Take it from there.

Paul

[Andrew Gabriel]

They would have been using Training Mix, which is lime instead of cement. After setting (which is mostly just drying), it is ground up and rehydrated for reuse. Occasionally a little extra lime is added to compensate for the lime actually setting into chalk, but it can be reused very many times over again before being discarded (where it still has many uses, such as mixed in with new compost to make nice soil).

[Chris.Cheney]

[e-mail] (Andrew Gabriel) wrote in news:46de52e9$0$640$ [e-mail]:

Google on e.g. "mortar mix" "roof"

[Mark Ayliffe]

On or about 2007-09-04, [e-mail] illuminated us with:

I've very rarely mixed my own plain mortar but as a sanity check: I've always mixed concrete at around 4:2:1 Gravel:sand:cement by volume, so I'd guess that you need something "richer" than 6:1. Richer because for an equal volume of sand and gravel there will be a lot more surface area to the sand. Also because you'd want such mortar to set stronger than concrete.

And

seems to agree. At a guess for that job you'd bee looking for 1:3 or 1:4. Could be complicated by using lime of course.

[Phil]

3:1 sharp sand to cement. Don't use soft sand as the yellow colour (a) looks awful and (b) is mainly iron compounds and leeches out with rain, staining things in its path.

Phil.

[<me9]

I used 3:1 for bedding tiles about 5 years ago. I used about 6:1 for the ridge tile, so it would be removable without too much trouble the next year, when I did the other side of the roof. That was about 5 years ago, and the

3:1 is perfect. the 6:1 has eroded to a depth of about 30mm. I must get round to doing the other side next year before SWMBO gets too irate.

[Aidan Karley]

DE-hydrated, surely? In which case it could be done with plaster to necessary strength but have low-T recyclability.

[1]

Thanks for the replies, folks.

But does anyone have any suggestions about why our roofer used a cement mix of no stronger than one part cement to six (or quite possibly even nine) parts sand (I will have a more accurate estimate when I go out and weigh the remnants in the sacks in a minute) for setting the capping tiles on the hips after replacing our soffits and barge boards?

Is there a plausible explanation for why they used such a weak mixture? From his advertising he states that he gets work from a very important local institution. One assumes he would be keen to keep his reputation...

Thanks

[August West]

The bags weren't full to begin with?

[Andrew Gabriel]

They already chucked out an empty cement bag?

[1]

I was there when the bags were delivered. It was a twenty five kilo bag of 'Mastercrete Original Cement' and a bag simply labelled 'Building Sand' of a similar size. There are 22 Kilos left in the bag of cement and 3 kilos left in the bag of sand.