Help- needing to correct poor external monocouche job


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I posted a while back asking is my builders renderers had done a good job on my house.... long story short, they haven’t. It’s awful. So after waiting months my Builder has finally lined someone up the week after next. I have a couple of questions though if someone can help?

1) The guy is saying I should have a silicon coat over the whole thing. I have paid for monocouche (monoblanco) scratched back to a fine finish I must have at least 15mm of this on already in waves all over the house... he plans to just go over with silicon coat? Is this the same thing and will it give the same finish (that stone /crator look) ? If you recommend this is there a good brand?

2) he also mentioned putting in an extension bead so he could do the side in 2 parts.... I have never heard of this or seen it but apparently “you won’t even notice” can you confirm this is the case? I don’t want a random stripe down side of house.

3) is this weather (it’ll be starting 28th November) suitable to apply external render??

Thank you, I’m desperate for advice.
if you have waves already then it needs basecoating the silicone topcoat is only 1.5mm.
it creates a small pitted uniform.look.

if unsure ask for a sample
Do you mean a expansion bead? If so then the smallest size I have used is 4mm which the final silicon top coat alone will not bring out flush with finished wall and even if it was flush(and same colour) then you would still see it. Unless he was doing a tape day joint which will be a little less obvious. You can silicon straight onto mono (with a primer 1st) but I would want to basecoat with mesh 1st.
As the Lads have said. If it’s that bad a Silicon Top Coat wont sort your issues. As for the bead you will definitely see it
Does anyone have a picture example of what an extension bead looks like? I can’t find one.

I’m not paying for a silicone coat. I paid a fixed price for monocouche to my Builder and it was the guy he instructed that mucked up. He is now getting someone else in to fix it. Is silicon as good quality as monocouche? (Or is he going for a cheap option?) I dont really understand, the pictures I see look more bumpy as opposed to the crator effect of scratching back.
Expansion Bead, not extension.

Movement Joints: MJ4

Help- needing to correct poor external monocouche job

Help- needing to correct poor external monocouche job
Help- needing to correct poor external monocouche job

Locally manufactured from recycled plastic, Renderplas PVCu movement joint / expansion joint beads are designed for areas of render over 20 square metres and should be specified every 4-6 metres, over structural movement joints and changes of background giving a discreet attractive finish. Also for use as an internal corner with plasterboard

Performance: design data
Federation of Plasterers and Drywall Contractors

Horizontally or vertically on all standard rendering applications, external wall insulation systems, timber frame; as a day joint to divide rendered sections; at changes to background material; with plasterboard as a control joint or internal corner

Zero chemical reaction with water, sand and cement, acrylic render, water based paint; avoid organic solvents, chlorate bleach, strong acids and alkalis

Impact resistant; dissipates shock waves; outlasts metal; cleaned in same way as render

PVCu beads are a fraction of the price of stainless steel; added value over galvanized steel as PVCu beads are guaranteed not to stain or corrode and can reduce installation time. Reduction of impact damage

Locally manufactured; high recycled content; fully recyclable; low Ecopoint score of 0.004/kg delivered

Class 1Y. Combustible within fire source, self extinguishing upon removal of flame, will not contribute to the combustion of the system

Health and Safety
PVCu beads are safe to handle removing the dangers of cut metal; suitable for prisons and schools

Ideal for all habitable climates; eliminates cold bridging

Fit for purpose for the lifetime of the render and at least 25 years

Flexible plastic membrane gives a certified range of +/- 2.5mm which exceeds British Standard for thermal movement (BS EN 13658-2:2005). Protective tear off strip allows quick removal of render from the joint

Ecologically benign; non-hazardous in water; non-hazardous if ingested; does not release substances into the atmosphere

PVCu beads offer sufficient strength for these applications. The chemical bond between flexible and rigid parts prevents separation

Flexible plastic membrane provides a watertight seal. Not affected by weather and should be specified in all regions of high moisture or high salt

Specification: standard data

BBA certified; manufactured to ISO 9001:2000; complies with BS EN 13914-1&2:2005; fire tested to BS 476; fomplies with REACH

Brand Names

4mm PVCu Movement Joint Beads (Expansion Joints)

Exterior grade impact resistant UV stable unplasticised PVCu

Dimensions (mm)
13mm exposed width and 25mm wings each side

Depth (mm)
4-6mm render depth; 2-3mm plaster depth

Weight (kg/100m)

Stock Colours


25 lengths in triwall fibreboard box

Cut lengths

Price (£/100m)

Content %


UV stable; any discoloration is uniform over a single facade and within industry standards

Site works
Standard industry practice and tools can be used. Large irregularities in the substrate should be dubbed out and allowed to set hard prior to application. Cut to length with tin snips or fine tooth saw. Fixing with a continuous line of adhesive mortar is preferred on blockwork, or alternatively a bed of render. Non-corrosive mechanical fixings can be used as well but are not required. With external wall insulation, non-corrosive fixings alone are sufficient

This explains where and when to use them. Sometimes if it is a big or difficult wall then the applicator will use to help break up the wall into smaller panels. So no you may not need them.
Silicon thin coat render is a good product if applicated correctly.
If when you say waves all round building meaning walls are not flat a thin coat system won't help this unless time is spent on it and most renderers would swerve straightening up other people's work,silicone finish is a nice finish in the right hands but not pitted like monocouche,both nice but different
As said above, if you have waves it is going to take a clever bloke to straighten this wall up. But if they can then all well and good.

If they are talking about using an expansion bead then they will be applying a thin coat system base coat first. An expansion bead is a convenient way of splitting the wall up to a manageable size. The silicone finish they are talking about needs more time management than monocouche and if you don’t have the man power then it is a good idea. Also it will disguise the irregularities better. You will hardly notice it.

Weather wise well for application the cold will make it more manageable. If they use Jub they have a thin coat system for both the mineral thin coat and the silicone that can be applied at +1c and will need a dry day for application and dry night following application. But you would need this in summer as well.

So if they can get over the waves problems then go for it. It will be a better finish than monocouche.
I'd give this guy a swerve ,as others have pointed out thin coat is only going to follow the undulations on the walls and doesn't look like mono.
I have gone over a few bad Monocouche jobs in the past with no problems so this could be your answer,getting the result your after.
The expansion will be noticeable and probably isn't required as Rigsby said probably there to break the work up.
Explain to the builder that there is no margin for error this time as there's too many have a goes out there.
That' the silicone finish close up courtesy of the polish lads on my job personally I like to see a nice clean finish on the beads ....
As above silicone over a wobbly monocouche is wasting your time..


  • Help- needing to correct poor external monocouche job
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tell ya what's happening these days every c**t. Is having a go at mono thinki it's easy half of em are not even ruling it or spatting just putting it on then rubbing out the rough high spots with the scratcher and it ends up shitt
tell ya what's happening these days every c**t. Is having a go at mono thinki it's easy half of em are not even ruling it or spatting just putting it on then rubbing out the rough high spots with the scratcher and it ends up shitt
I see terrible jobs all over London ,
Not done by me ,