Screed Fibres

[sotal]

I'm raising a floor. I posted on here before for advice on what to do and am just about ready to do the screed.

The only problem I have is that it was recommended that I use fibres in the mix to make it stronger etc.

It's 75mm polystyrene with 75mm of screed on top.

I've been to Wickes but they don't sell the Fibres.

I've been to Build Centre but the bloke had never heard of them and suggested putting chicken wire in.

I went to a concrete manufacturing place - they said they'd used them for special projects but couldn't remember where they got them from.

I've found a couple of online sites which seem to sell it but wanted somewhere I could just buy it from really.

Other than searching google I've found that local mini mix places advertise it mixed in to ready mix screed - but I doubt they'd sell it to me.


So, how important are the fibres? Is there anything else like chicken wire that can be used instead?

Should I add anything else to the mix like plasticiser or similar?

Many thanks


Additional info I can think of:

The room will have light foot traffic
The floor covering will be laminate flooring on top of underlay
The room will be cool whilst drying - there is no heating in there at the moment
I'm going to use a 4:1 mix of sharp sand and cement

 

[^woody^]

Fibres are a intended as a modern way of controlling initial shrinkage cracking, nothing else.

You don't need them

Chicken wire does the same and also strengthens the screed, but again you don't need that either unless for some specific design reason

 

[sotal]

Thanks for the info,

I've since managed to source some fibres and as they were expensive got a bag, figured it would be better to use them and not have needed them to have not used them and have needed them!

It was one of the members on here who recommended using them.

The only warning I was given was to make sure I double clean the mixer as the fibres make it harder to clean etc? Should get the screed down by the weekend at the latest.

 

[sotal]

Can I just ask for some advice regarding the mix ready for when I do this.


I've been told a 4:1 mix will be best.

I'm using a Belle Mini 150 Mixer which has a 90 Litre Capacity.

I realise that the 4:1 should be on volume rather than weight, will the following be close enough for each mix:

2 Bags of Sharp Sand
1/2 bag of Cement
Handful of fibres
Water to suit

If not can you recommend an easy way of measuring?

Thanks

 

[^woody^]

I don't know how big this bag is that you have, but its normally 1 bag (100g) per bag (25kg) of cement. Not just "a handful" of fibres

The easiest way to measure is with a bucket or heaped shovel - as long as the heaps are the same

And you don't use too much water - the sand out of the bag may be damp enough

 

[noseall]

And you don't use too much water - the sand out of the bag may be damp enough

Only near the bottom Woodstock.

 

[sotal]

The bag of fibres is 900g which said it should enough for 1 cubic metre of screed. I'm laying less than this but can weigh out 100g to see roughly how much it is.

I've got the sand in 25kg bags and it's been stored dry in the garage so hopefully isn't too wet, and I have the cement in similar size bags - that's why I was hoping for a simple way of measuring them out (I've only ever used loose sand before and used the shovel method) So my idea was to saw the bags of cement in half then add half a bag with 2 bags of sand to get roughly 4:1 - it won't be perfect but neither would shovel sizes - will it be close enough though?

Thanks

 

[Nige F]

Thanks for the info,

I've since managed to source some fibres and as they were expensive got a bag, figured it would be better to use them and not have needed them to have not used them and have needed them!

It was one of the members on here who recommended using them.

The only warning I was given was to make sure I double clean the mixer as the fibres make it harder to clean etc? Should get the screed down by the weekend at the latest.

First - go over to the plasterers forum - they lay screeds Second - don`t mix for too long - it`ll end up as little balls of cement I did that once

 

[sotal]

All laid now - so hopefully I got it all right!

Looks good at the moment - will just have to wait for it to dry now