Sand Blinding Layer

[willbish]

47 minutes ago, SuperJohnG said:

Thanks - seems easier, were these compacted? 

Nope, compacting wouldn't do anything. The type 1 below is fully compacted. As others have said there is no where for this layer to go.

[dnoble]

MBC sorted the sand IIRC but told me what to put down beneath it. Some kind of compacted crushed stone I think (it was 3 years ago now!!)

Are you laying the EPS yourself? If not wouldn’t the EPS laying people be the ones to ask?

[SuperJohnG]

21 minutes ago, dnoble said:

MBC sorted the sand IIRC but told me what to put down beneath it. Some kind of compacted crushed stone I think (it was 3 years ago now!!)

Are you laying the EPS yourself? If not wouldn’t the EPS laying people be the ones to ask?

Below it is fine, its just type 1 then concrete sand which from above seems to be the best option.

 

I'm doing it all (with the help from my groundworks guys).

 

As an update - I'm just trying to boy some thin walled tube we will use. Seems not to expensive to buy 6m lengths sit this down then screed over them.  

[Dan F]

If using DPM on sand, then no issue AFAIK.

 

If EPS is directly on sand (with DPM between concrete and EPS), then in theory you are supposed to use type2 + grit (rather than type1 and sand) so that the EPS doesn't absorb moisture.  It's not there is an strucutral issue, rather the thermal characteristics of the EPS are reduced when water is absorbed. (EPS, unlike XPS, does take up some moisture).

 

 

 

[dangti6]

On 10/01/2020 at 20:06, JFDIY said:

I've always used Sharp sand, then Wacker it smooth. Building sand will just clump up when compacted.

Excuse the thread revival. Worry wart has had a Google and found this thread.

 

I have some building sand left over which I was hoping I could use as blinding to use it up and save buying in sharp sand specifically. 
 

Have others found out the hard way that building sand is no good, or is it a case of not ideal, but useable if it’s what you have at hand?

 

The building sand I have won’t do the whole area, so I’m happy to buy sharp to do the remnants unless it’s best to stick with the one type throughout.

[markc]

Blinding is nothing more than a layer that is a free draining surface that wont damage the DPM etc. resting on it. nothing wrong with using up sand, sharp is better/easier to use/compact

[Onoff]

I got rid of old half bags of play pit, building, block paving sand then some off cement, plaster etc when I blinded my sub base. If really worried mix some cement with it. Only place I deffo wouldn't use building sand personally is under a patio externally. 

 

I'd use the building sand but mix with the sharp. Rake together a bit then level it off.

[Declan52]

It well be fine if it's dry. Building sand holds water that's why you cant use it under paving flags etc as it will turn to mush and the flags will sink.

[dangti6]

Thanks gents, I will mix with sharp.

 

The sand has only be exposed to one downpour in about 2 months so it’s quite dry in there 

[tonyshouse]

I always worry about the sand percolating into the hardcore, “egg timer” effect so never used blinding when I was a builder, mechanically compact, mostly recovered hardcore or 40mm reject stones.