Internal rendering job -

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spark2010

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I did my first proper rendering job yesterday. It was an int/ext wall obviously. My mate was upstairs skimming and he said I could jump on the rendering. Its just a bit of guidance im after.....

It was all hacked off a metre high. It was previously been injected because of a rising damp problem. Whoever done specified the wall be EML lathed, and a 3-1 mix of render with a special additive (which had to ordered by TP) had to go into the mix. I read the tub, it said is used for re-rendering applications and where a wall has been treated for damp.

Anyway I mixed the stuff up with water in a bucket and knocked up my render (3 buckets of sand to 1 bucket cement) and added the premixed water. Starting from the right I splashed the wall wall with water through the EML and then layed on the render. When I got about a metre across the render starting to harden straight away and I did soak the wall. I continued across using water proof PVA but the suction was the same.

I thought a weaker mix would have been better as the suction was similar to Thermalites

few questions

Was a 3-1 mix too strong for this type of job?
Should EML have been used?
As the render dried I kept going back and splashing water on it as it was drying to prevent cracking, is this correct?
Can you apply a top coat to scratch same day or next in internal rendering?

When I top coat it tomorrow will have to use a 3-1 mix as specified or should I do a 4-1 as I know top coat has to be weaker than scratch?
 
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beddy

Well-Known Member
2 coats on internal work? maybe you were putting it on too thin. how thick is the existing plaster?
 

beddy

Well-Known Member
25mm may be too thick for one coat, but still thats two coats of 12.5 mm. shouldnt be drying that quick. either its on too thin or the background hasn't been treated properly.
 

S a plastering

Private Member
an sbr slurry would of helped mate an why use eml on a damp course unless its stainless askin for allsorts of trouble
 

flynnyman

Well-Known Member
Well firstly the guarantee is not worth the paper its written on, cannot see the point of the EML and either there was a problem with the cement or its a suction problem. Who told you the spec and why arent they doing it?
 

church

Well-Known Member
cause they take all the money from the job doing the injection ,then a spread goes in to finish the job on daywork , who also will get the blame if there any come backs .
 

Pug

Well-Known Member
I'd say 3:1 is too strong for just about any background but you don't say what you were going onto. you say you splashed some water on, did you keep splashing it on till it stopped sucking in?
 

bubbles65

Well-Known Member
Sounds like you're going onto old brickwork here spark - so a good soaking with a hose would be best, although not always practical. As for the spec - get a written copy from the specifier, or as church says, you will get the blame when it fails:-0
 

kevmc

New Member
normal speck is 3 to 1 for dampcourse work but never heard of eml speck before .you would normally rake out the joints to form a key
the eml will rust andd stainless would put far to much cost on the job as for the rendering drying out to quick .? seems like it didnt need a damp course in the 1st place if it is that dry .-
 

spark2010

New Member
25mm may be too thick for one coat, but still thats two coats of 12.5 mm. shouldnt be drying that quick. either its on too thin or the background hasn't been treated properly.


I did soak the wall, constantly dipping into the bucket of water and drenching the wall, but i dont think i kept splashing it until the water hung around...

so yes, i probably didnt treat the wall properly..
 

spark2010

New Member
an sbr slurry would of helped mate an why use eml on a damp course unless its stainless askin for allsorts of trouble

SBR for internal rendering? I never thought of it, we didnt have any there but i should have thought about it the day before...

yes, i did question the use of EML?

I thought EML was only for ...
+ on top of wood
+ backgrounds using over 25mm of backing plaster/render
+ Subsidence (crack repair)
 

spark2010

New Member
Well firstly the guarantee is not worth the paper its written on, cannot see the point of the EML and either there was a problem with the cement or its a suction problem. Who told you the spec and why arent they doing it?

Looking at these replies could have been a suction problem, which is my fault for not treating it right. By the way It was very very old looking bricks behind the EML
 

spark2010

New Member
I'd say 3:1 is too strong for just about any background but you don't say what you were going onto. you say you splashed some water on, did you keep splashing it on till it stopped sucking in?

very old bricks behind the EML

And yes i dont think I kept splashing until the water stopped soaking, but i did drench it
 

spark2010

New Member
Sounds like you're going onto old brickwork here spark - so a good soaking with a hose would be best, although not always practical. As for the spec - get a written copy from the specifier, or as church says, you will get the blame when it fails:-0

ya your right, old brickwork...
I will say it to the guy who took on the job for a written copy from the specifier...

Im worried now the render might crack over the suction problem
 

spark2010

New Member
normal speck is 3 to 1 for dampcourse work but never heard of eml speck before .you would normally rake out the joints to form a key
the eml will rust andd stainless would put far to much cost on the job as for the rendering drying out to quick .? seems like it didnt need a damp course in the 1st place if it is that dry .-

I knew it, i said to the guy im working with, why did he EML the wall? He said it was on the specification,
 

beddy

Well-Known Member
if it was on the spec then thats not your problem. if the bloke you were working with did it cause he thought it was right then thats his decision. a splash brush and a water bucket are never enough for soaking a wall. always a hose, even if its on slow, just wack a tarp on the floor if needs protecting
 

broonster

Member
Brush off any dust with a soft sweeping brush then dampen down wall,always give it a scrtch coat first then when it takes up top it off as normal....school stuff..
 
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S a plastering

Private Member
Brush off any dust with a soft sweeping brush then dampen down wall,always give it a scrtch coat first then when it takes up top it off as normal....school stuff..
exactly its just straight forward never heard of eml before on damp work not to think of it rusting through aswell madness
 

spark2010

New Member
Brush off any dust with a soft sweeping brush then dampen down wall,always give it a scrtch coat first then when it takes up top it off as normal....school stuff..

takes up top? what?

Can it be be scratched and topped same day for internal rendering?
 

spark2010

New Member
So rendering internally can be scratched and top same day?, as ext rendering takes upto a week between coats

So would it have to be topped witha weaker mix ...say 4-1?
 

S a plastering

Private Member
yes it can be topped in same day its different to external stuff for one its not exposed to any weather conditions which has a big factor in rendering
 

kevmc

New Member
I THINK YOU WILL FIND THAT IT CANT OR SHOUDNT BE skimmed the same day. as it may craze due to the differant propertys in cement and plaster plaster actually expands when setting and cement shrinks .
 
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