Blown render!! Please Help!

[Freddie]

pva is glue

 

[dougalhouse]

WOW!

I think i've started something here!

No wonder i'm confused if you guys cannot agree, then what hope have i got?

Thanks all the same. This argument about PVA will continue i guess, but the second time i applied the scratch i didn't use any PVA at all, just plasticising waterproofer and it blew again. (having previously wire brushed the wall washed it down and soaked it)

I remember using the scud coat mix method back in my days as a labourer so that is probably the method i will use if it blows again. (i've already scratched it with a 4 to 1 mix with splash of plasticiser.

I'm putting the finish coat on Monday 5:1 mix with waterproofing plasticiser (rendamix).

I'm a bit confused about the use of lime though. All the additive products say that they replace the need for adding lime.

Does the lime delay the setting process and make the coats more flexible?? And can it be used with Rendamix (waterproofing plasticiser)??

 

[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?

Her we go waffle waffle muddle it all up and try and confuse to hide your errors, i havent quoted you word for word because your errors are so blatently obvious.

Nobodies disputing the cleanliness and sound prep job done to the wall just your ridiculas reasoning for using unibond/pva in an outside application where it will do nothing but be depremental to the job.

Your reasoning for no waterproofer in the finish coat may have some standing as regards frost damage if it wasnt for the same thing being able to hapen if the water got behind the scratch coat and frost damage blew that off the wall in the same manner you describe, infact your argument on this is self defeating as it is obvious that waterproofer should be applied to all coats as the more ways of keeping water out the better and the same applies to paint as paint is also a protective covering against the elements and letting the surface underneath the paint breath at the same time.

Your arguments dont stand up and you cant even answer basic questions as regards the use of unibond/pva in exterior situations

i left my pva in work today so i cant get it out of the van and tell you what it says but i found this on the net, hope it helps.

The PVA FAQ
Anyone know the what are the whys and wherefores of when and when not to use PVA ?
It seems to be used in all building applications with a certain amount of gay abandon. What does it do, when should you use it ?
PVA ( polyvinyl acetate ) has many DIY uses;

As an adhesive, It will bond wood, paper, leather, expanded polystyrene, mortar, brick and most other porous materials to themselves and to each other. It makes a reasonable border and edge adhesive for wallpaper.

As a priming agent, Diluted 3 or 4 to 1, it prepares plaster, brickwork and concrete for tiling, rendering, painting or papering.

As a mortar additive. It improves water retention to ensure good curing of the mortar, even in thin layers, and makes the mortar "stickier" so that if you are rendering, the render tends to stay put until it sets. Use 3 or 4 to one diluted PVA as the gauging water. That is the water you use for mixing with the dry components.

As a dust proofer for concrete floors, Sweep the floor and brush over with 3 or 4 to one PVA. An old floorbrush is useful for large areas. PVA is not fully waterproof as the dried resin, but will resist temporary wetting well. In a set mortar it is unaffected by water to any gross degree.

There are also EVA (ethylene vinyl acetate) and PVP (polyvinyl propionate) bonding agents. Neither of these is very much better in the water resistance stakes, and seem to be more common in mainland Europe. For the best water resistance, acrylic or SBR (styrene butadiene rubber) bonding agents are the choice.

Some years ago, about 1985, PVA bonding agents moved from 55% TSC (total solids content) to 44% TSC. TSC is a misnomer, as bonding agents contained 10% of the resin weight as plasticiser. The purpose of the plasticiser was twofold, firstly it acted as a coalescing solvent (lowering the minimum film formation temperature), and to make the dried film flexible. Back then the plasticiser was dibutyl phthalate, but this has been found to be an oestrogen emulator. Nowadays di-isooctyl phthalate is used which is less fugitive. Of course when the solids content went down the water content went up. The viscosity was therefore made higher in one of three ways, By adding a thickener, by upping the molecular weight of the polyvinyl alcohol in the aqueous phase, or by changing the particle sizing of the emulsion.

PVA can be detected by the use of Iodine, either as an alcoholic tincture, or better, as a solution in aqueous Potassium Iodide. The PVA will turn brick red on contact with these reagents. Either that, or the builder who swore blind that he had primed the wall will. PVA is essentially non-toxic (In that it is not really possible to swallow about 10kg of it by accident!) , although it can be irritating in the eyes. The hazchem notification used to read "Caution - may be very sticky". Imagine 20 tons of PVA spilt on a motorway. Should you spill PVA on clothes you value (why were you doing DIY in your best suit/frock?) immerse them in water immediately. As soon as practicable, put them through the cycle you would normally employ. For dry-clean only clothing you have little choice, dry-cleaning fluid will not attack dried PVA. Carpets and the like require scrubbing with water and blotting repeatedly.


When PVA dries will it redissolve, and why does it turn white?
This is generic for PVA, EVA PVP, and acrylic emulsions. Minus the bit about coalescing solvent, it is true for natural and synthetic rubber latices. The polymer comes in the form of an aqueous emulsion, i.e. polymer globules in water. There are various compounds to keep the emulsion stable, so that creaming and settling tend not to happen. As the water dries off the polymer forms a continuous film, which does not tend to redisperse. Most of these polymers tend to reabsorb water, which makes them whiten and reduces their strength to some degree. Another consideration is the minimum film formation temperature (MFFT) If a polymer emulsion loses water below its MFFT, it will not form a cohesive film. Almost all DIY polymer emulsions contain what is called a coalescing solvent, which is in quantity sufficient to lower the MFFT to about 4 degrees C. Some also contain a plasticiser to make the film less brittle. When possible the manufacturers use a solvent which performs both functions.


I have seen powdered PVA about. How do they do that?
This is a spray-dried version of PVA, known in the trade as redispersible PVA. It is widely used in cementitious compounds to promote adhesion. It's all very clever, but it seems to do the trick. I was recently informed of a novel use for powdered PVA in email. It appears that the groundsmen at a number of top-rank cricket pitches are using it to make the creases more resistant to wear during matches, providing a more consistent surface. PVA is biodegradeable, by the way, so it is no worse than using lawn food on the ground. Yet another use for an amazing material!



Copyright notice: With the growth of the net, copyright law has become very complicated. You may reproduce this FAQ in any form from stone tablets to putting it on your homepage. You may distribute it to absolutely anyone. You may even add your own bits to it. However, if you remove my name from it, or try to pass it off as your own work, I will be very, very angry with you.

To the index

John Schmitt <[email protected]>

Last updated 24/09/05


i dont think he made it up aswell as me and every pva/unibond manufacturer. he forgot to mention school glue but im sure your right

 

[Freddie]

pva is glue

 

[legs-akimbo]

Derrrrr! he said it bonds wood and paper, aint that just what seven years olds do with it.
He also states it acts as a primer for tiling surfaces and when i find it I will post up again mudsters very informative post as to why it doesent. That guy has probably plastered about as much externally as you have J bonding which is about as close to **** all as you can get. Are you not the same Jbonding who stated you have not done ANY wet dash (hurling) in your life, who clearly has done no dry dash judging by your ill informed post a while bak that advised to dash onto a 4to 5mm wet render coat, thats almost a skim You advocate pva while simultaneously dismissing out of hand exterior paints ...the likes of sandtex that have been around for years on end. Where you live do renders without waterproofer not soak in driving rain, then when the temperatures go sub zero does this water not freeze like everyone elses????
Why on earth would you want to ****s around with uni bond to reduce suction before a scratch, when the blindingly obvious alternative is as simple as a b c..........Guess what it is!! its a hose pipe and its water, No great revelation there, though it may be to you.
I have a Bungalow of 2300 sq ft to start in a couple of weeks time and am gonna post up regular photos as we progress, look and learn, I think you need it.

 

[jbonding]

Jbonding

I have used PVA glue ( Evostick and others ) for 15 years manufacturing Pine furniture and now fire surrounds.

As a glue it will only work under extreme pressure of wood clamps etc, otherwise it is just a sticky substance that will dry but turn to poo when it gets wet again, and is easily washed off your hands or clothing.

Once turned to poo it never goes back to the same dried state as before.

I dont doubt it's use's for sealing an interior wall or for dust sticking a floor.

It will not however stick things to a wall which will get damp or wet again.

It will do nothing to aid tons of render to an exterior wall infact it will most likely ruin the natural cementing action once it gets damp again.

STILL YOU HAVE AVOIDED THE POINTS YOU HAVE CLAIMED ABOUT THIS STUFF AND YOUR BOZO CLAIM OF HOW TO RENDER AN OUTSIDE WALL WITH WATERPROOFER.

If you are going to give advice to people on a forum who are going to take it as gospel and follow it which may end up costing them thousands of pounds, please do put your name and address up so at least they can come round your house and shove a gallon of unibond/pva up your backside sideways.

Personally i think you are a clown--a fool would have more sense.

so you dont beleive a word of it ,pva must be a con, ive not had this much abuse since i recomended my mate to paint his bike with emulsion,lol.read the tin, render will absorb water and dry out, waterproofer in a top coat will absorb water but will not dry out, probably freeze out. i advise you stick to wood glue , MDF and your trusty router with your quarter inch bit,lol

 

[jbonding]

Derrrrr! he said it bonds wood and paper, aint that just what seven years olds do with it.
He also states it acts as a primer for tiling surfaces and when i find it I will post up again mudsters very informative post as to why it doesent. That guy has probably plastered about as much externally as you have J bonding which is about as close to **** all as you can get. Are you not the same Jbonding who stated you have not done ANY wet dash (hurling) in your life, who clearly has done no dry dash judging by your ill informed post a while bak that advised to dash onto a 4to 5mm wet render coat, thats almost a skim You advocate pva while simultaneously dismissing out of hand exterior paints ...the likes of sandtex that have been around for years on end. Where you live do renders without waterproofer not soak in driving rain, then when the temperatures go sub zero does this water not freeze like everyone elses????
Why on earth would you want to p****d around with uni bond to reduce suction before a scratch, when the blindingly obvious alternative is as simple as a b c..........Guess what it is!! its a hose pipe and its water, No great revelation there, though it may be to you.
I have a Bungalow of 2300 sq ft to start in a couple of weeks time and am gonna post up regular photos as we progress, look and learn, I think you need it.

bonds wood and paper and isnt that what 7 year olds do, i think hes having a dig at you freddie,lol.what mudster said about pva and tiling is a completely different thing like i said pva has more than one use (kids glue).ive not done any wet dash, bring the post up. bring up the other post about 5-6mm and lets see if theres more to the post. ive not advocated pva on its own as a bonding agent for render, bring that post up aswell.you didnt understand the post about the scratch coat, i didnt say the pva was the way to go , iwould soak it aswell. the question was would the top coat still stick with the pva to control the suction. The answer is yes because the scratch coat provides the key not the pva, that controls suction and seals dust. posting pictures of rendered bungalows will look nice so does the room in diy sos,changing rooms,1hour makeover and so on.

 

[Freddie]

pva is glue

 

[legs-akimbo]

Well thanks be to f**k we wont be building another 70,000 houses this year with waterproofer in the floating coat on a predominantly napp finished render.....Do you even know what a napp finish is and just how many have you done if you do?
Because now us thick ole Paddies know that all our renders are gonna fail cus we never followed the J bonding work ethic we will be saved . God bless ya, No more Waterproofer , no more waterproofer Just one point ...how come I am yet to see any blown, failed, perished renders anywhere when every single one bar none of the tens of thousands of houses where I live have all used this obviously incorrect working practice according to you. Dont suppose you would care to show some of your work up on this forum then J bonding would you ...now theres a challenge.
Give it up J bonding you have been well and truly crushed stick to dot and dabbing wimpey houses and lets those who know their stuff do the talking.

 

[Mudster]

The information in the internet sourced PVA advice is misleading, legs mentioned a post I made some time ag o on screwfix, I'll paste that here, it explains why PVA should not be used as a primer to tiling.

As for it's use in Plastering, I've never fully understood this so would prefer to neutral on that point. What I do know about is tiling.....and generally the misinformation provided above is something I come across on a daily basis.

Pasted post as follows:-




I'm a professional tiling contractor, I now mainly specialise in natural products but over the years I've stuck up (or down) every type of tile there is.

I have to give guarantees for my work (many of these projects are commercial such as sports centre showers and changing rooms). For me to be able to give guarantees I need to follow strictly the specification of the adhesive manufacturers.

Ardex, BAL and Nicobond are the three suppliers I use most. Their products are similar in many respects, sometimes one will make products the other don't, and I also find some of there products more useful in different applications. All three of them have one thing in common, they all specifiy that under no circumstances may PVA be used before using any of their adhesives. If you do all guarantees are void.

OK why then? Well I asked this question to Ardex when I once had problem, I'd tiled a bathroom that had been constructed in 25mm Marine ply. Thinking he was doing the right thing, the builder got his guys to seal the ply with unibond PVA...I wasn't aware of this.

I tiled it and 6 months later every single tile fell off the ply, the adhesive solidly stuck to the tile but came clean a whistle off the ply.

We had Ardex Technical down to the site to compile a report, the basis of which was it's the PVA that causes the problem.

When you treat a surface with PVA it partly soaks in and parlty sits on the surface of the substrate much in the same way as wallpaper paste.

If PVA gets wet it becomes slightly live again, it doesn't completely return to it's liquid state but it becomes sticky.

When you spread tile adhesive onto the wall, the water in the adhesive makes the PVA live and stops the adhesive from penetrating the substrate and providing a mechanical grip. Basically your tiles, grout and adhesive are being held to the wall by a thin layer of PVA.

Most tile adhesive works by crystalising when it sets (some are slightly different such as epoxy based ones) but generally they all work the same way. Once the adhesive starts to set crystals from and expand into any imperfections in the substrate surface (at a microscopic level) to create a grip. PVA stops this process by creating a barrier between the substrate and the tile adhesive.

Ok so whats the difference between this and Ardex or BAL primer, well basically the tile manufacturers primers soak right in to the substrate and stop the sponge like "draw "effect but they don't coat the surface in any way, they are an impregnator as opposed to a barrier.

I hope this clears up any misunderstandings.

 

[legs-akimbo]

Bravo mudster, and as you would be well aware there are many a tiler still using pva in a detremental manner as you have outlined in your superb post. In the same manner there are plasterers doing exactly the same thing and J bonding is a prime example of a tradesman being over reliant on a product that does a specific job but is simply not a cure for all ills. Your post more or less reiterates Freddies points in full and while it is all well and good being able to relate to certain pdf's or extracts from the internet J B only the wealth of experience will tell you what works and what does not...Forget what the manufacturers tell you ( to a large extent) learn from those who know better and be humble enough to take heed and generate an informed opinion, I may be blowing up my own ar*e, but there is not a man I have met who can do my job better than me!

 

[jbonding]

Jbonding

I have used PVA glue ( Evostick and others ) for 15 years manufacturing Pine furniture and now fire surrounds.

As a glue it will only work under extreme pressure of wood clamps etc, otherwise it is just a sticky substance that will dry but turn to poo when it gets wet again, and is easily washed off your hands or clothing.

Once turned to poo it never goes back to the same dried state as before.

I dont doubt it's use's for sealing an interior wall or for dust sticking a floor.

It will not however stick things to a wall which will get damp or wet again.

It will do nothing to aid tons of render to an exterior wall infact it will most likely ruin the natural cementing action once it gets damp again.

STILL YOU HAVE AVOIDED THE POINTS YOU HAVE CLAIMED ABOUT THIS STUFF AND YOUR BOZO CLAIM OF HOW TO RENDER AN OUTSIDE WALL WITH WATERPROOFER.

If you are going to give advice to people on a forum who are going to take it as gospel and follow it which may end up costing them thousands of pounds, please do put your name and address up so at least they can come round your house and shove a gallon of unibond/pva up your backside sideways.

Personally i think you are a clown--a fool would have more sense.

so you dont beleive a word of it ,pva must be a con, ive not had this much abuse since i recomended my mate to paint his bike with emulsion,lol.read the tin, render will absorb water and dry out, waterproofer in a top coat will absorb water but will not dry out, probably freeze out. i advise you stick to wood glue , MDF and your trusty router with your quarter inch bit,lol

Still not answered any questions i asked and now try to say i dont believe something i havent stated a word about.

I am afraid you have lost any credability you had here and have shown youself to be just full of s h i t --- i suggest you dont try and give people your hocus pocus hair brained advice anymore and stick to bed time stories for the deaf.

what

 

[jbonding]

The information in the internet sourced PVA advice is misleading, legs mentioned a post I made some time ag o on screwfix, I'll paste that here, it explains why PVA should not be used as a primer to tiling.

As for it's use in Plastering, I've never fully understood this so would prefer to neutral on that point. What I do know about is tiling.....and generally the misinformation provided above is something I come across on a daily basis.

Pasted post as follows:-




I'm a professional tiling contractor, I now mainly specialise in natural products but over the years I've stuck up (or down) every type of tile there is.

I have to give guarantees for my work (many of these projects are commercial such as sports centre showers and changing rooms). For me to be able to give guarantees I need to follow strictly the specification of the adhesive manufacturers.

Ardex, BAL and Nicobond are the three suppliers I use most. Their products are similar in many respects, sometimes one will make products the other don't, and I also find some of there products more useful in different applications. All three of them have one thing in common, they all specifiy that under no circumstances may PVA be used before using any of their adhesives. If you do all guarantees are void.

OK why then? Well I asked this question to Ardex when I once had problem, I'd tiled a bathroom that had been constructed in 25mm Marine ply. Thinking he was doing the right thing, the builder got his guys to seal the ply with unibond PVA...I wasn't aware of this.

I tiled it and 6 months later every single tile fell off the ply, the adhesive solidly stuck to the tile but came clean a whistle off the ply.

We had Ardex Technical down to the site to compile a report, the basis of which was it's the PVA that causes the problem.

When you treat a surface with PVA it partly soaks in and parlty sits on the surface of the substrate much in the same way as wallpaper paste.

If PVA gets wet it becomes slightly live again, it doesn't completely return to it's liquid state but it becomes sticky.

When you spread tile adhesive onto the wall, the water in the adhesive makes the PVA live and stops the adhesive from penetrating the substrate and providing a mechanical grip. Basically your tiles, grout and adhesive are being held to the wall by a thin layer of PVA.

Most tile adhesive works by crystalising when it sets (some are slightly different such as epoxy based ones) but generally they all work the same way. Once the adhesive starts to set crystals from and expand into any imperfections in the substrate surface (at a microscopic level) to create a grip. PVA stops this process by creating a barrier between the substrate and the tile adhesive.

Ok so whats the difference between this and Ardex or BAL primer, well basically the tile manufacturers primers soak right in to the substrate and stop the sponge like "draw "effect but they don't coat the surface in any way, they are an impregnator as opposed to a barrier.

I hope this clears up any misunderstandings.

well informed mudster and as a tiler you know your job, nice one in pointing out your neutral in the uses of plastering. theres a few points to take into account and that is what was the mix ratio of pva on the ply, was it tacky when you applied the adhesives.was the ply damp when the pva was applied, who knows but pva has its uses and mixed proper it does its job even if thats sticking paper together,lol.

 

[jbonding]

Bravo mudster, and as you would be well aware there are many a tiler still using pva in a detremental manner as you have outlined in your superb post. In the same manner there are plasterers doing exactly the same thing and J bonding is a prime example of a tradesman being over reliant on a product that does a specific job but is simply not a cure for all ills. Your post more or less reiterates Freddies points in full and while it is all well and good being able to relate to certain pdf's or extracts from the internet J B only the wealth of experience will tell you what works and what does not...Forget what the manufacturers tell you ( to a large extent) learn from those who know better and be humble enough to take heed and generate an informed opinion, I may be blowing up my own ar*e, but there is not a man I have met who can do my job better than me!

im not over reliant on the stuff, i use it when its appropriate not for cures, do a search yourself to back up what your saying about pva and waterproofer in the top coat and you cant use freddies posts,lol. forget what the manufacturers tell you because legs gives his own guarantees,photos, im sure when you come to sell these will look nice if you put them in a frame.

 

[-dj-]

but there is not a man I have met who can do my job better than me!

except for me eh legs

anyway on the point of pva. there is no way i would ever use it in rendering an external wall.
you have legs who has been at the plastering rendering game a lot of years who knows where and when to use pva, mudster who's reputation should preceed him and geo, err freddie who has spent many years making dressers/ fire surrounds etc i have seen excellent photos and advice from all three of them. if i was after advice in certain fields then i would not need to ask a second opinion after asking one of these three.

me, well i have been in the game some 15 years and i have never had a problem with rendering and i have never used pva in the mix as has been said on numerous occasions pva comes back which is why it shouldn't be used outside outside.
you saw mudsters post as to why you shouldn't use pva so i wil post the reply i made on the origional screwfix thread of where it can be used with perfect results, i would only ever use pva on an internal wall when i'm skimming over origional plaster. in short don't use pva in a rendering mix and the origional rendered wall probably failed because of this factor...........




dj.

Posts: 1,669
Registered: May 1, 2004
Re: Tiling On Concrete
Posted: Aug 26, 2004 5:28 AM Reply


handyandy
i have pasted most of your answer from mudster with a few adjustments for treating before plastering.....

When you treat a surface with PVA it partly soaks in and partly sits on the surface of the substrate much in the same way as wallpaper paste.

If PVA gets wet it becomes slightly live again, it doesn't completely return to it's liquid state but it becomes sticky. this is where it is ideal to skim

When you spread plaster onto the wall, the water in the plaster makes the PVA live but stops the plaster from penetrating the substrate and providing a mechanical grip, thus giving a barrier from the existing wall plus an adhesive for your new skim.
there is no need to skim whilst pva is still tacky as, with your new skim, it 'comes back' with moisture conterary to popular belief.
hope this clears a few things up &
thanx to mudster.
dj.