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Heppy
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We have an MBC timber frame house with an insulated raft foundation. The house is cladd in larch but we need to finish the polystyrene base. We want to render it but how do we do this. Do we need mesh first or a special render that would stick and be flexible enough. 

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Our AFT foundation L section pieces came already rendered so we didnt have that problem, although to be fair, when I ordered it I was expecting to render it. My plan was to stick the Marley thrutone cememt tiles that the whole house is covered with on the outside as much quicker than render. I have done this with polyurathane glue (5 minute) on the garden room and it works. 

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4 hours ago, Mr Punter said:

I have used Weber LAC.  First thin coat with mesh bedded, then second thin coat floated / sponged to a sanded finish. It sticks to anything.  Paint with masonry paint. 

Thanks for that. So maybe it’s the mesh I need information about. Can you tell which mesh I need and how to fix it to the EPS please 

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Whatever render that you decide to use you must machinacal fix the mesh Or the render will eventually she’ll 

The ones that I have done have been done as follows 

Prine the surface We often use fancy primers that are extortionately price Simply because they are on the job spec

Morevoften than not with render the primer is simply to kill the suction not to stick the render to the surface So I tend to use one of cheaper primers if it’s not on the drawing

apply a 5 mil base coat k Webber Stuca etc 

Don’t schratch or key 

The following day Drill and knock in render fixing Fischer or simalar 

The apply a render finish 

Hope this helps

 

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12 hours ago, Heppy said:

Thanks for that. So maybe it’s the mesh I need information about. Can you tell which mesh I need and how to fix it to the EPS please 

 

We used pink mesh cloth.  You apply a thin coat of LAC and bed the mesh in while it is still wet.  You can get very thin corner beads as well.

 

On one plinth we did the LAC / mesh cloth, then tiled with slate strips fixed with tile adhesive, which looked quite good.

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  • 2 weeks later...
On 14/09/2018 at 22:09, MikeSharp01 said:

My plan was to stick the Marley thrutone cememt tiles that the whole house is covered with on the outside as much quicker than render. I have done this with polyurathane glue (5 minute) on the garden room and it works. 

Any photos of this please @MikeSharp01? Sounds like something that could work on my build

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there are dozens of EWI render system suppliers to choose from which would be suitable for your EPS. K-rend and Weber are often stocked in builder's merchants these days. You should read the manufacturer's guidance on application but most systems adopt the same approach - typically the basecoat is applied in two passes over EPS - first pass around 3 - 4mm, then it's worked over with a toothed float to ensure an even coverage, the mesh cloth is embedded, then another tight coat of base render is applied, then it's flattened off with a sponge float. Following that you have two choices - prime and then use a system supplied thin coat finish render - it's like textured paint which is troweled on to grain thickness, or you could go with a mineral paint direct over the basecoat (I prefer this over standard paint as it will chemically bond with the render basecoat rather than form a film over it). If the EPS has been exposed to UV for any period you should either by an EWI rasp or use an old saw with the blade held at a shallow angle zand drag over the EPS to remove any UV degraded crust and improve key.

 

For my EWI project I used Baumit render over graphite EPS. The basecoat was StarContact White (a lime/cement hybrid) which was finished with Nanpor fine (a silicate thin coat). Silicate mineralic thin coat is the most expensive but I much preferred it over acrylic or silicone.

 

 

 

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