K-Rend Thin Coat Application

[MBurton]

Hello all,

I’m having a debate about the correct way to apply K-Rend thin coat up to base coat stage. I’m not a plasterer, I’m a builder but I have a good knowledge of plastering methods.

The way I see it, is providing you have a level substrate (eg cement board or nicely levelled EPS) you only need to do one coat of basecoat with embedded mesh. So 3mm, mesh, 3mm then rule off and rub up ready to receive primer and TC15 when dry.

If you don’t have a level substrate, e.g. going onto old brickwork then you should apply a levelling basecoat (no mesh required) to dub out, scratch it up and apply the mesh coat as above once you have obtained a level surface.

My mate and several other plasterers are saying this is impossible and you must do a ‘mesh scratch coat’. So rather than rub up as above you just scratch it. Then you come back later and top off with a layer of basecoat (no mesh) and rub that up.

I understand this takes some pressure off as you haven’t got the hassle of embedding your mesh then trying to rub up in one day.

I think that this creates for a much weaker build up though as your final layer of basecoat is unreinforced. Maybe not so much of an issue on solid masonry substrates, but on large areas or those prone to movement such as straight onto EPS, when the render build up flexes for example with an impact from a football, the reinforced layer is going to absorb the impact as designed but the upper unreinforced layer is just going to potentially crack as it will not withstand the same bending and impact force as the reinforced layer.

What do you lot think and more to the point, how do you apply it and what works for you?

Cheers.

 

[Dansouthcoast84]

if its a large area i will apply a slurry coat next day.
but generally we are lay on.. notch...... embedd. then a 2nd coat wet in wet with a spat trowel finish.
giving the 6mm thickness i cant say the depth of the mesh will dictate too much about impact.

 

[Danny]

Hello all,

I’m having a debate about the correct way to apply K-Rend thin coat up to base coat stage. I’m not a plasterer, I’m a builder but I have a good knowledge of plastering methods.

The way I see it, is providing you have a level substrate (eg cement board or nicely levelled EPS) you only need to do one coat of basecoat with embedded mesh. So 3mm, mesh, 3mm then rule off and rub up ready to receive primer and TC15 when dry.

If you don’t have a level substrate, e.g. going onto old brickwork then you should apply a levelling basecoat (no mesh required) to dub out, scratch it up and apply the mesh coat as above once you have obtained a level surface.

My mate and several other plasterers are saying this is impossible and you must do a ‘mesh scratch coat’. So rather than rub up as above you just scratch it. Then you come back later and top off with a layer of basecoat (no mesh) and rub that up.

I understand this takes some pressure off as you haven’t got the hassle of embedding your mesh then trying to rub up in one day.

I think that this creates for a much weaker build up though as your final layer of basecoat is unreinforced. Maybe not so much of an issue on solid masonry substrates, but on large areas or those prone to movement such as straight onto EPS, when the render build up flexes for example with an impact from a football, the reinforced layer is going to absorb the impact as designed but the upper unreinforced layer is just going to potentially crack as it will not withstand the same bending and impact force as the reinforced layer.

What do you lot think and more to the point, how do you apply it and what works for you?

Cheers.

Can't see it making much difference where the mesh is as long as it is in there.

What does the spec say of the render you are using?

 

[zombie]

Can't see it making much difference where the mesh is as long as it is in there.

What does the spec say of the render you are using?

Disagree mesh should be as close to final surface as possible on a thin coat system.

 

[Gibbo]

Hello all,

I’m having a debate about the correct way to apply K-Rend thin coat up to base coat stage. I’m not a plasterer, I’m a builder but I have a good knowledge of plastering methods.

The way I see it, is providing you have a level substrate (eg cement board or nicely levelled EPS) you only need to do one coat of basecoat with embedded mesh. So 3mm, mesh, 3mm then rule off and rub up ready to receive primer and TC15 when dry.

If you don’t have a level substrate, e.g. going onto old brickwork then you should apply a levelling basecoat (no mesh required) to dub out, scratch it up and apply the mesh coat as above once you have obtained a level surface.

My mate and several other plasterers are saying this is impossible and you must do a ‘mesh scratch coat’. So rather than rub up as above you just scratch it. Then you come back later and top off with a layer of basecoat (no mesh) and rub that up.

I understand this takes some pressure off as you haven’t got the hassle of embedding your mesh then trying to rub up in one day.

I think that this creates for a much weaker build up though as your final layer of basecoat is unreinforced. Maybe not so much of an issue on solid masonry substrates, but on large areas or those prone to movement such as straight onto EPS, when the render build up flexes for example with an impact from a football, the reinforced layer is going to absorb the impact as designed but the upper unreinforced layer is just going to potentially crack as it will not withstand the same bending and impact force as the reinforced layer.

What do you lot think and more to the point, how do you apply it and what works for you?

Cheers.

You are right your plasterers are wrong

 

[MBurton]

Can't see it making much difference where the mesh is as long as it is in there.

What does the spec say of the render you are using?

We are using K-Rend HP14 base coat and will be applying TC15 finish.

Anything I find from K-Rend (instructions, videos) says to apply levelling coats if necessary then apply your 6mm mesh coat in one wet on wet pass. Rub up to a good finish ready to receive TC. I can’t find any information on doing a scratched mesh coat, allow to dry then topping off with an unreinforced coat later.

It’s a mixture of old brickwork on two elevations and one elevation with new EPS stuck on with HP14 and pinned.

The EPS is flat as f**k, to my mind it’s the perfect surface to stick on 6mm beads directly on, then do your 6mm mesh coat in one pass. This area is 12m long, 2m high at one end and 2.6m at the other.

Old brickwork is not so good but not terrible, I think the tightest coat possible on this to get it to acceptable flatness, scratch and leave to set. Then bead up and apply 6mm mesh coat, wet on wet. These areas are 2m x 6m and 2m x 3m.

Is this asking the impossible by hand?

I’m not a plasterer, and at long as it looks good, doesn’t fall off, and doesn’t crack that’s all that matters. But I’m interested in what’s correct and what others do in the real world, correct or not.

Cheers.

 

[vfr12]

Hello all,

I’m having a debate about the correct way to apply K-Rend thin coat up to base coat stage. I’m not a plasterer, I’m a builder but I have a good knowledge of plastering methods.

The way I see it, is providing you have a level substrate (eg cement board or nicely levelled EPS) you only need to do one coat of basecoat with embedded mesh. So 3mm, mesh, 3mm then rule off and rub up ready to receive primer and TC15 when dry.

If you don’t have a level substrate, e.g. going onto old brickwork then you should apply a levelling basecoat (no mesh required) to dub out, scratch it up and apply the mesh coat as above once you have obtained a level surface.

My mate and several other plasterers are saying this is impossible and you must do a ‘mesh scratch coat’. So rather than rub up as above you just scratch it. Then you come back later and top off with a layer of basecoat (no mesh) and rub that up.

I understand this takes some pressure off as you haven’t got the hassle of embedding your mesh then trying to rub up in one day.

I think that this creates for a much weaker build up though as your final layer of basecoat is unreinforced. Maybe not so much of an issue on solid masonry substrates, but on large areas or those prone to movement such as straight onto EPS, when the render build up flexes for example with an impact from a football, the reinforced layer is going to absorb the impact as designed but the upper unreinforced layer is just going to potentially crack as it will not withstand the same bending and impact force as the reinforced layer.

What do you lot think and more to the point, how do you apply it and what works for you?

Cheers.

You are wrong! Typical builders thinking!

Can't see it making much difference where the mesh is as long as it is in there.

What does the spec say of the render you are using?

and so is you . It does make a difference where the mesh is...... huuuuuge difference, But only if you want it done right , if not is mr Burton all the way.

 

[MBurton]

You are wrong! Typical builders thinking!

and so is you . It does make a difference where the mesh is...... huuuuuge difference, But only if you want it done right , if not is mr Burton all the way.

So, VFR12 we are both wrong? What is the right way then?

 

[vfr12]

So, VFR12 we are both wrong? What is the right way then?

Sorry mate, just saw @Gibbo post and it’s a pain to admit he is right! He is senior and @Danny is the boss! Wtf was I thinking

 

[Vincey]

Just thinking I might build an extension

 

[MBurton]

Just thinking I might build an extension

Go for it mate. Some of the best builders I know are plasterers by trade.

Anyway, do you think @Gibbo is correct or is it acceptable to put an unreinforced layer of basecoat over your already cured mesh layer? Or don’t you know?

 

[Vincey]

Go for it mate. Some of the best builders I know are plasterers by trade.

Anyway, do you think @Gibbo is correct or is it acceptable to put an unreinforced layer of basecoat over your already cured mesh layer? Or don’t you know?

I am good laying bricks tbf I enjoyed it too mate , I only use vimark thincoat but agree with Dan

 

[Danny]

You are wrong! Typical builders thinking!

and so is you . It does make a difference where the mesh is...... huuuuuge difference, But only if you want it done right , if not is mr Burton all the way.

i would be interested in understanding the science behind it as i am a stickler for doing things right

 

[Danny]

Disagree mesh should be as close to final surface as possible on a thin coat system.

would like to understand more as to why... I would have guessed it needs to be near the background rather than the top?

 

[Danny]

Just thinking I might build an extension

the hardest part is knowing what order to do everything in

 

[vfr12]

i would be interested in understanding the science behind it as i am a stickler for doing things right

I would love to educate you but then my next client will read it on here and quoting me on the job , playing the know it all expert . One think I have realised in the past few months- the forum works both ways for us

 

[Gibbo]

just like mono the mesh needs to be as close to surface as possible to provide impact damage and to avoid cracking

 

[Gibbo]

doing mono that needs a basecoat i would put it in the mono not base as the mono is more prone to crack than the correct base