Blown render!! Please Help!

[Freddie]

no pva

 

[jbonding]

lets say your doing one a week thats 52 a year so you cant say the 69 948 are done the same way. pva is used in schools for glue and it does peel off your hands when it dries so does silicone and silk paint, emulsion washes off your hands so what do you do dont trust them products neither. pick up a litre of pva or (unibond), read the side and it will tell you what it can be used for.

 

[Freddie]

no pva

 

[legs-akimbo]

I wish I could do one a week J bonding, but theese new builds are primarily between 2 and 2500 sq ft not matchbox wimpey homes and having lived here for ten years I am 100% on the methods every plasterer employs in this country and every engineer insists on as a matter of course :
Extracts from good working practices, Ireland.

When considering the final rendering coat it must be borne in mind that some suction is not only permissable but adviseable ( re. no waterproofer in scratch, or school glue on concrete block) Waterproofer is the provision of a dense impervious membrane through which water will not readily pass. Such a material must be insoluble and the main mixes are based on combinations of Portland cement, sand and certain waterproofing agents . Because sand is a granular material it will contain a proportion of voids in its volume. Sands having a high void percentage are unsuitable ( namely soft building sand) A well graded sand, mixed with sufficient cement to fill the main voids will still have minute voids through which water can percolate after the material has cured. (As in it is not totally water resistant)
If J bonding you have ever tried to bring down a 100 sq mtr gable without piecings in February then the last thing you need is to have a backing coat with a rich waterproofer content, unless you are prepared to work till midnight. An amount of hydrated lime will prevent crazing of the render but too much will weaken the mix, so a balance needs to be kept. A well napped huge gable end that is open to the elements will not even require painting and will last for forty odd years with a combiation of good workmanship, the right materials and following correct working procedures.
Pva for the most part is nothing but a placebo and gives peace of mind to those who use it in mostly an unnecessary manner, and as has been shown in this thread is clearly in some situations extremely detremental. Granted it has its merits but it is over used and over hyped, you clearly are an exponent of this product as you did not pick up on what the cause of the blown rendering was, and indeed extolled the use of yet more in a situation that would be of no value whatsoever.

 

[legs-akimbo]

The reference to unibond as pva is me showing my age.... way back when it was allways colloquialy known as uni bond as opposed to pva, just as you might term a hoover as such rather than a vacume cleaner or coke as cola!

 

[jbonding]

I wish I could do one a week J bonding, but theese new builds are primarily between 2 and 2500 sq ft not matchbox wimpey homes and having lived here for ten years I am 100% on the methods every plasterer employs in this country and every engineer insists on as a matter of course :
Extracts from good working practices, Ireland.

When considering the final rendering coat it must be borne in mind that some suction is not only permissable but adviseable ( re. no waterproofer in scratch, or school glue on concrete block) Waterproofer is the provision of a dense impervious membrane through which water will not readily pass. Such a material must be insoluble and the main mixes are based on combinations of Portland cement, sand and certain waterproofing agents . Because sand is a granular material it will contain a proportion of voids in its volume. Sands having a high void percentage are unsuitable ( namely soft building sand) A well graded sand, mixed with sufficient cement to fill the main voids will still have minute voids through which water can percolate after the material has cured. (As in it is not totally water resistant)
If J bonding you have ever tried to bring down a 100 sq mtr gable without piecings in February then the last thing you need is to have a backing coat with a rich waterproofer content, unless you are prepared to work till midnight. An amount of hydrated lime will prevent crazing of the render but too much will weaken the mix, so a balance needs to be kept. A well napped huge gable end that is open to the elements will not even require painting and will last for forty odd years with a combiation of good workmanship, the right materials and following correct working procedures.
Pva for the most part is nothing but a placebo and gives peace of mind to those who use it in mostly an unnecessary manner, and as has been shown in this thread is clearly in some situations extremely detremental. Granted it has its merits but it is over used and over hyped, you clearly are an exponent of this product as you did not pick up on what the cause of the blown rendering was, and indeed extolled the use of yet more in a situation that would be of no value whatsoever.

waterproofers can be liquid or powder form and simply fill in the void or gaps between each sand and cement particle. they tend to make a mix water resistant rather than waterproof. rendering shouldnt be painted any way this only come about in the last 30 years or more. this is what causes a lot of the problems with rendered walls. the reason the render blew like i said on the previos post "Posted: Thu Oct 13, 2005 10:25 am Post Subject:

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mix up the unibond with some cement and a handfull of sand and apply with a roller and let it dry, make sure you rake the joints this is the key.
or fix eml .

 

[jbonding]

lets say your doing one a week thats 52 a year so you cant say the 69 948 are done the same way. pva is used in schools for glue and it does peel off your hands when it dries so does silicone and silk paint, emulsion washes off your hands so what do you do dont trust them products neither. pick up a litre of pva or (unibond), read the side and it will tell you what it can be used for.

iam not doubting its use indoors in a dry situation but outdoors especially as you are against putting waterproofer in the render so it is continually damp--useless.

And now adhesive manufacturers wont warranty their product because of it in a damp situ--just about answers the question i think.

im not against waterproofer i would add it to the scratch coat, non of these adhesive/waterproofer manufacturers will warranty any of these products unless one of there technicians is there to measure it and watch the application.

 

[Freddie]

no pva glue

 

[jbonding]

raking out the joints would of helped to key the scratch coat, the mix should be different your scratch coat should be stronger than your top coat, a waterproofer in your scratch coat will even out the suction on your top coat. Concrete blocks are high suction so the problem lies in your first coat, control the suction with unibond but provide a key ie raking out the joints.

this is what i originaly said, i dont advise anyone to use pva i just told you what it does. are you saying using the waterproofer in the scratch coat is wrong?

 

[Freddie]

 

[jbonding]

raking out the joints would of helped to key the scratch coat, the mix should be different your scratch coat should be stronger than your top coat, a waterproofer in your scratch coat will even out the suction on your top coat. Concrete blocks are high suction so the problem lies in your first coat, control the suction with unibond but provide a key ie raking out the joints.

this is what i originaly said, i dont advise anyone to use pva i just told you what it does. are you saying using the waterproofer in the scratch coat is wrong?

What i would say is never use pva outside even in a mix as you are just sticking things to the pvs instead of allowing the normal chemical cementing to take place.

Aways use waterproofer in the scratch and the finish coat, there is no point to waterproofing the scratch and not the finish, because if you had waterproofed the finish the scratch coat couldnt get damp could it?

I actually think you are talking pure b ollox and backed yourself into a corner by not admitting you are wrong and it's obvious to all who have read this thread.

freddie youve not got a clue, what you would say is dont use pva outside, like i said read the side of the tub it has its uses. one being in rendering. dont talk about chemical cementing taking place unless you back it up with something. its used to control the suction, raking the joints provides the key ie mechanical. freddie you forget a building needs to breath. what am i wrong about? the use of unibond as a key on rendering, read the side.

 

[legs-akimbo]

They would have you believe unibond could be substituted for weaopons grade plutonium if it sold a few mor litres of it. Freddie is correct there is absolutely no need whatsoever for the use of pva externally ....if a method works, it works...why complicate matters and start adding items that are not needed, pva has clearly been shown not to help in this instance that there is clearly no doubt about, do you agree or not that the use of pva is to blame in this case J bonding?
A liitle test you can do at home : when plastering skim a bit of old board and when dry paint on some pva to half of it, the next day emulsion the lot and see the difference between the two. The emulsion will soak into the plaster and cover nicely the pva'd section will have only stuck to the pva and you will see a dark patch behind the emulsion, this is because the pva is a barrier between the plaster and the paint. I am not saying it is gonna come off of course because it wont be getting damp, but I would not stand by that assertion if the pva was exposed in any manner externally.

 

[Freddie]

pva is glue

 

[jbonding]

Does it say for use externally?

Why when your wall has been prepared to accept cement render as has been done for years do you cover or mix a sticky elastic goo all over it ? what possible benefit could it be?

Wht oh why wouldnt you put waterproofer in the finish coat of render?

Why not paint? i understand that a building has to breath but as Oilman will tell you that paints are designed to let that happen.

You are trying to back track now and muddle around.

You said --NO WATERPROOFER IN THE FINISH COAT OF RENDER.

You said --APPLY UNIBOND/PVA TO THE WALL OF THE HOUSE WITH SAND AND CEMENT

so youve not read it, cant you get someone else to read it for you,lol read it the benefits are it controls suction. the reason for not putting the waterproofer in the top coat appart from ashlar work is if any water gets behind, which it will, it wont get out as easily and when the frost comes you know your phones gonna be busy. if you were ever taught about plastering and rendering and i dont mean of your mate or forums you would of been told render is a finish, the colour and texture can be done without paint. applying pva mixed with water cement and a couple of handfulls of sand mixed too a slurry and applied with a roller similar to a spatterdash coat is a problem?

 

[jbonding]

They would have you believe unibond could be substituted for weaopons grade plutonium if it sold a few mor litres of it. Freddie is correct there is absolutely no need whatsoever for the use of pva externally ....if a method works, it works...why complicate matters and start adding items that are not needed, pva has clearly been shown not to help in this instance that there is clearly no doubt about, do you agree or not that the use of pva is to blame in this case J bonding?
A liitle test you can do at home : when plastering skim a bit of old board and when dry paint on some pva to half of it, the next day emulsion the lot and see the difference between the two. The emulsion will soak into the plaster and cover nicely the pva'd section will have only stuck to the pva and you will see a dark patch behind the emulsion, this is because the pva is a barrier between the plaster and the paint. I am not saying it is gonna come off of course because it wont be getting damp, but I would not stand by that assertion if the pva was exposed in any manner externally.

the test wont prove much about rendering, mix the pva 5-1 or more and see if that has the same effect. is the pva the blame or the lack off key, like i said and keep saying if you applied a key ie racking out the joints, eml or scrabble it, it wouldnt of failed. legs if you come to float a wall that was scratch coated some time ago and you applied pva 6-1 to control the suction do you think the pva would stop it sticking or would the scratch coat do its job?