# Forum Home Renovation Bathrooms  Reinforcing mesh for concrete screed

## dclayw

My shower renovation is upstairs with particle board flooring. I'm probably going to use a screed mix called Eco Screed available from Bayset, they didn't stock ACS Screed. What do people use as the reinforcing mesh, chicken wire? I can get lightweight reo from bunnies, 3mm wire thickness and 75mm spacing between the wires, do you think that would be alright?

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## anangia

I don't think there is a need for reo when screeding.
Then again I am no expert.  
The tiler I used didn't use any reo bars when putting the sceeding. Our screeding was about 35mm deep. Only difference is that we had a concrete slab.

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## dclayw

Well I'm just not sure myself, but this is an upstairs bathroom on particle board flooring. The general recommendation says to use reinforcement in this situation. The product sheet for ACS screed says to use mesh and have min 40mm thick bed, when on wooden flooring. The Eco Screed data sheet just says don't use on particle board at all. When I pulled the old bed out there was no mesh in it. 
I also read somewhere that the use of mesh in screed beds can affect the integrity of the screed, especially when the the bed is not all that thick, like in showers. Recommendation these days seems to be to use polypropylene fibres, anyone heard of that method?

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## johnc

I'd contact Eco Screeds technical department and ask the question, they should be able to provide the answer. I'd prefer use galvanised chook wire myself in that enviroment, the larger squares don't appeal to me in a screed mix, however that is relying on that over used tool "common sense" which sadly seems to have a high failure rate when relied on to much.

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## dclayw

I contacted the makers of Eco Screed and they said the 3mm reo from bunnies would do the job, heavy gauge chicken wire would be OK too. 
Then I came across this other product called Screed Premix 35 made by Demtech: Demtech Australia | Screed Premix 35 Doesn't need reinforcing. Anybody used it as a shower screed?

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## Oldsaltoz

I would stay away from a product that calls for reinforcing, in all my years and thousands of showers I have never once seen a screed used, even in overkill Government contracts. 
Good luck.   :Smilie:

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## dclayw

> I would stay away from a product that calls for reinforcing, in all my years and thousands of showers I have never once seen a screed used, even in overkill Government contracts. 
> Good luck.

  Did you mean to say that you have never once seen reinforcement used in a (shower) screed? 
Other then the Eco Screed I mentioned (which requires reinforcement) I'm having a hard time finding anywhere that sells pre mixed screed. I know I can do my own but I'd rather a ready made mix so I know that it's right and will do the job. I can't find anyone that sells the Screed Premix 35 or the ACS Screed. Does anyone know where I can get either of these products in Brisbane, south-west suburbs preferably?

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## Oldsaltoz

> Did you mean to say that you have never once seen reinforcement used in a (shower) screed?   Other then the Eco Screed I mentioned (which requires reinforcement) I'm having a hard time finding anywhere that sells pre mixed screed. I know I can do my own but I'd rather a ready made mix so I know that it's right and will do the job. I can't find anyone that sells the Screed Premix 35 or the ACS Screed. Does anyone know where I can get either of these products in Brisbane, south-west suburbs preferably?

    Try Beaumont tiles.

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## Footscrazy

4 to 1 washed sand and cement will do the job, polythene on the particleboard and expanded metal reinforcing which most good tile shops sell, 75mm spacings in the reo is too wide in my opinion.

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## dclayw

Ok, I've been researching this a bit more and to be honest it's doing my head in. I know it's easy for you guys who lay screed beds for shower bases day in and day out, but this is first time for me and I want to get it right. 
I'm in QLD and I believe the way it's mostly done up here is to have the membrane on the substrate and then lay the screed over that. Well, I am going to do that too but I'm also going to put a membrane on top of the screed. I know it's overkill but I have all the time in world to get it done so I will do it that way. 
If I were to use a re-enforcing mesh in the screed bed (and some people seem to think that's overkill, even on particle board substrate), where do I put the mesh?? Some people seem to place it down first then screed on top, so the mesh is at the very bottom of the screed bed. Fair enough, but that means the mesh will be sitting directly on top of the membrane and might puncture it. Even if I raise the mesh off the floor a bit (by putting pieces of tile under it for example), there's still the chance it might damage the membrane. 
Some people lay a layer of screed directly on the substrate, then place the mesh, then lay more screed. In this case the mesh is in the middle of the screed and some people say this is a bad idea because it can lead to shearing at that interface and the screed bed is actually weaker because it has mesh in the middle of it. 
So what's the preferred method? I'd prefer no mesh, but on particle board substrate I don't know if that will lead to the screed bed cracking with subsequent cracked/lifting tiles. Placing the mesh at the bottom of the screed bed seems to have problems, and so does placing it in the middle of the screed bed. I want to get it right, so which is the best way, I don't care how long it takes or if it costs a bit extra. 
I can't find the diamond mesh (lath I think it's called) anywhere either. I've tried several h/w stores and tile shops. Tile shops look at me as though I'm from outer space. Actually, mention the word screed and they run for cover.

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## METRIX

> Ok, I've been researching this a bit more and to be honest it's doing my head in. I know it's easy for you guys who lay screed beds for shower bases day in and day out, but this is first time for me and I want to get it right. 
> I'm in QLD and I believe the way it's mostly done up here is to have the membrane on the substrate and then lay the screed over that. Well, I am going to do that too but I'm also going to put a membrane on top of the screed. I know it's overkill but I have all the time in world to get it done so I will do it that way. 
> If I were to use a re-enforcing mesh in the screed bed (and some people seem to think that's overkill, even on particle board substrate), where do I put the mesh?? Some people seem to place it down first then screed on top, so the mesh is at the very bottom of the screed bed. Fair enough, but that means the mesh will be sitting directly on top of the membrane and might puncture it. Even if I raise the mesh off the floor a bit (by putting pieces of tile under it for example), there's still the chance it might damage the membrane. 
> Some people lay a layer of screed directly on the substrate, then place the mesh, then lay more screed. In this case the mesh is in the middle of the screed and some people say this is a bad idea because it can lead to shearing at that interface and the screed bed is actually weaker because it has mesh in the middle of it. 
> So what's the preferred method? I'd prefer no mesh, but on particle board substrate I don't know if that will lead to the screed bed cracking with subsequent cracked/lifting tiles. Placing the mesh at the bottom of the screed bed seems to have problems, and so does placing it in the middle of the screed bed. I want to get it right, so which is the best way, I don't care how long it takes or if it costs a bit extra. 
> I can't find the diamond mesh (lath I think it's called) anywhere either. I've tried several h/w stores and tile shops. Tile shops look at me as though I'm from outer space. Actually, mention the word screed and they run for cover.

  Your really overthinking a simple task. 
For starters I would never put a screed or bathroom directly on timber floor you are just asking for trouble and trust me you will get it, particleboard and water simply don't mix.
You either use tile underlay over the particle board, or preferably rip the particle board out and replace with FC sheeting or Scyon if you want to do it properly. 
Our waterproofers waterproof first then lay the screed, and never use wire in the screed this is really un necesary, if you really want to use wire don't worry about it damaging the membrane, if the membrane your udsing is that susceptible to damage from laying a piece of chicken wire on it, then the membrane is rubbish. 
Particle board will NOT offer you a good substrate for anything to stick to, be it membrane, screed or other. 
Your comment about I don't care if it costs a bit extra, do yourself a favour get rid of the particle board and do the job properly from the start, that way you can sleep easy knowing you have done the right thing.

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## dclayw

Overthinking it, I think you're right. I'll take your advice and use a tile underlay on the particle board and no mesh. Thanks for the tips.

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## METRIX

Make sure to install the underlay exactly as the manufacturer recommends, because it is particle board you will need to use a notched trowel, and cover the entire surface with stud adhesive (refer to below link). 
Make sure to use the corect nails (and not gyprock nails as I have seen done many times), if you don't follow the installation correctly you will chance having a problem in the future.
Finally don't substitute tile underlay for villaboard or similar, these are not the same for this situation.  http://www.jameshardie.com.au/produc...lay+Jan+12.pdf

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## intertd6

> Ok, I've been researching this a bit more and to be honest it's doing my head in. I know it's easy for you guys who lay screed beds for shower bases day in and day out, but this is first time for me and I want to get it right. 
> I'm in QLD and I believe the way it's mostly done up here is to have the membrane on the substrate and then lay the screed over that. Well, I am going to do that too but I'm also going to put a membrane on top of the screed. I know it's overkill but I have all the time in world to get it done so I will do it that way. 
> If I were to use a re-enforcing mesh in the screed bed (and some people seem to think that's overkill, even on particle board substrate), where do I put the mesh?? Some people seem to place it down first then screed on top, so the mesh is at the very bottom of the screed bed. Fair enough, but that means the mesh will be sitting directly on top of the membrane and might puncture it. Even if I raise the mesh off the floor a bit (by putting pieces of tile under it for example), there's still the chance it might damage the membrane. 
> Some people lay a layer of screed directly on the substrate, then place the mesh, then lay more screed. In this case the mesh is in the middle of the screed and some people say this is a bad idea because it can lead to shearing at that interface and the screed bed is actually weaker because it has mesh in the middle of it. 
> So what's the preferred method? I'd prefer no mesh, but on particle board substrate I don't know if that will lead to the screed bed cracking with subsequent cracked/lifting tiles. Placing the mesh at the bottom of the screed bed seems to have problems, and so does placing it in the middle of the screed bed. I want to get it right, so which is the best way, I don't care how long it takes or if it costs a bit extra. 
> I can't find the diamond mesh (lath I think it's called) anywhere either. I've tried several h/w stores and tile shops. Tile shops look at me as though I'm from outer space. Actually, mention the word screed and they run for cover.

  It used to be in the standard to use reinforcing mesh in the screed, but I think it has been made redundant in the more recent standards, some tilers still do it, by rights it should go on a thin bed of screed so as if there are any sharp parts of the cut wire the thin layer of screed will separate the wire from the membrane & prevent the puncturing of it.
The only way you would get shearing at the intersection of the reo & the screed is if there was too greater time lag between the layers where the bottom screed went off & there was a cold joint.
regards inter

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## shauck

> Your really overthinking a simple task. 
> For starters I would never put a screed or bathroom directly on timber floor you are just asking for trouble and trust me you will get it, particleboard and water simply don't mix.
> You either use tile underlay over the particle board, or preferably rip the particle board out and replace with FC sheeting or Scyon if you want to do it properly. 
> Our waterproofers waterproof first then lay the screed, and never use wire in the screed this is really un necesary, if you really want to use wire don't worry about it damaging the membrane, if the membrane your udsing is that susceptible to damage from laying a piece of chicken wire on it, then the membrane is rubbish. 
> Particle board will NOT offer you a good substrate for anything to stick to, be it membrane, screed or other. 
> Your comment about I don't care if it costs a bit extra, do yourself a favour get rid of the particle board and do the job properly from the start, that way you can sleep easy knowing you have done the right thing.

   

> Make sure to install the underlay exactly as the manufacturer recommends, because it is particle board you will need to use a notched trowel, and cover the entire surface with stud adhesive (refer to below link). 
> Make sure to use the corect nails (and not gyprock nails as I have seen done many times), if you don't follow the installation correctly you will chance having a problem in the future.
> Finally don't substitute tile underlay for villaboard or similar, these are not the same for this situation.  http://www.jameshardie.com.au/produc...lay+Jan+12.pdf

   :2thumbsup:  What he said

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## cherub65

Just a note on the mesh side, you can use expanded metal [stainless or gal]

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## intertd6

> Just a note on the mesh side, you can use expanded metal [stainless or gal]

  that is where a separation will occur using that type of reo, screed mix is too dry to get in around & around all the complex angles, & small openings, only good for wet render mixes, a open type of mesh should be used such as bird wire.
regards inter

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## Footscrazy

> Your really overthinking a simple task. 
> For starters I would never put a screed or bathroom directly on timber floor you are just asking for trouble and trust me you will get it, particleboard and water simply don't mix.
> You either use tile underlay over the particle board, or preferably rip the particle board out and replace with FC sheeting or Scyon if you want to do it properly.

  I have laid many floors on a particle board substrate, some of them are getting on to 20 years old and I've never had a call back.
You must lay a sheet of polythene first, the screed does not go directly onto the yellow tongue, then it's a 4 to 1 mix washed sand and cement, not wet but not dry, you get a feel for it after a few, laid to a minimum 20mm depth and reinforced with galvanised expanded metal.
I'm not sure exactly what the metal is called, my supplier sells it in 10m x 1800mm rolls.
Back in the 60's and early 70's the screed was mixed wetter and the tiles laid on the wet screed but that eventually led to drummy tiles, these days it's allowed to stand overnight then an adhesive is used, Conflex or Ultraflex can be used the next day before the screed has fully cured.
If the shower is graded rather than an acrylic base some waterproof is added to the screed mix then a membrane like Dampfix 2 is applied before it's tiled, the wall/floor junctions need to be well sealed before the membrane is applied.

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## intertd6

This is for a bathroom floor, so plastic underlay is definitely out as the particle board should have a membrane over it & prepped with a primer so there is a good bond between the 2.
regards inter

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## dclayw

I was going down the path of using a mesh because that seemed to be the done thing in this situation, i.e. with a substrate like particle board that is prone to a bit of movement. Seems to be a bit of controversy about whether or not to use mesh though, so I might steer away from it. When I ripped the shower apart the screed had no mesh and it was in tact. The particle board had a fibre glass coating over it and this extended up over the (wooden) hob and some way up the shower walls. There were a few hairline cracks in the fibre glass but both the particle board and the wooden hob were in pristine condition, like they were laid yesterday, no water ever got in there. The bathroom is 23 years old and never been touched since it was built. Just shows that some of the old methods worked pretty well. 
The screed on my bathroom floor did have a chicken wire mesh in it, laid on the bottom. There was one crack in this, from the corner of the shower hob and across to the far wall (not far). The bathroom floor tiles sitting on top of this screed bed were cracked in the same place. These tiles were laid directly on top of the screed, there was no tile adhesive as such, shower floor tiles were laid the same way. There would have been no give with the tiles laid like that and I guess that's why I got cracked tiles. They were pretty hard to get off too, I had one of the Ozito hammer drills, great little machine that. 
To throw another spanner in the works does anyone use an additive in their screeds to give it a bit of flex in this type of situation. By additive I mean something like Davelastic or Lanko 753.

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