Thin coat render problem.

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solway

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Hi all.Did a job lately,there are hollows not humps where the joints are on the boards and can be clearly seen when the sun is on the wall.Filled joints,weber render lac,mesh,primed and top coated with weber tf150.Any ideas why this happened.Scaffold is down now and wall looks poor because of this.Hollows are in horizontal and vertical joints.Oh ya calcium silicate panels is the background.
 
We didn't board the panels,but there was a 3mm gap left.Weber applications man called to site and gave us a talk through on how to complete the job(rendering wise).He said to caulk the joints with the basecoat and mesh with 100mm on all joints prior to fully basecoating.He said to do this 1st thing in the morning before fully basecoating the whole wall.He said "im a brim and braces man myself and I would caulk and mesh all joints to give more strength"."For the sake of an hour in the morning do this,go have yere tea,return and then fully basecoat the wall.He also stated in his "chat" not to apply basecoat over dry basecoat.When we started filling joints the basecoat filler was dry within 30minutes(no messing or exaggeration,30 minutes).He said that by filling the joints that the gear should remain moist for an hour at least.I rang the weber man and put across to him that the joints had dried rapidly within 30 minutes and what to do now.His reply was that to go up now and "key up" the joints with a scratcher and before fully basecoating the whole wall sprinkle the already filled joints with water to kill the suction.He also said that if I found that the boards were "pulling" quickly that to hose down the boards with water prior to basecoating??????Does all this sound right.At our site meeing with builder and meself never once did he mention to dampen any part of any wall or say anything about if this or that starts to dry/pull fast.He said that this gear is lovely to use bladeebladeebla...!He also said that after rulling off your panels to leave to set/take up for about 2 hours before sponging down.I was sponging the 1st section after 40 minutes straight after we finished rulling off.We kept an eye on the panel every 5 to 10 minutes or so as we were putting on the second pass and each time we checked it we could feel it pulling/going off more and more.Now remember these are only handy panels consisting of 7 boards.
 
Hi Rigsby,can u explain the igloo effect.During normal daylight we can slightly see the lines of the board joints but when the sun hits it at a certain angle we can clearly see the straight line hollows.Horizontal and vertical
Rigsby said:
Is this when the sun is at a certain angle? Could be the igloo effect.
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It is what was brought to my attention recently by a ewi rep. Something to do with boards swelling when the sun gets on them and when the sun is at a certain angle it looks like the walls of an igloo.

There is a big gable near me done in Phenolic and it looks a good job until a certain time of day then it looks a bit of a pigs ear. But saying that you can have what looks like a perfectly flat render then when the catches it at a certain time of day it shows all the bumps and hollows.

I now if I can mention it when doing a survey so as to cover myself.
 
madmonk said:
what I said mate I've just had the wetherby rep out to my job that's what he spec so that it is then
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Jesus Monk..... Don't fill the joints with Silicone!!

The only thing that sticks to Silicone is Silicone.... the basecoats will not stick to it!!

If the render system suppliers says that - get it in writing!!

As Solway laid out is the best method - although having the material drying when jointing is not actually an issue.... Not all render system suppliers advise taping and jointing the boards, but if there are gaps between the boards push basecoat into the joints before applying the basecoat.

As Rigsby says, in some lights it will be possible to see all sorts of things in all rendered walls.....but a full chequer board effect is usually more as a result of the basecoat being applied too thinly - best get the system supplier rep out and advise further.......
 
Also - as rigsby pointed out.... Not all render carrier boards or insulation slabs are the same..... some will absorb moisture and swell slightly, then shrink as the render drys.... not great....

It would be best to contact the board supplier and or the render system supplier for confirmation and if possible a written specification to cover yourself!

Anyone wanting specific assistance with boarded render systems, feel free to get in touch with me....

07918766577
[email protected]
 
Don't forget chaps the sun is our worst enermy! .
doest matter what rendering system you use or how much you rule it . As soon as the sun shines down it it looks awful . Then 30 minutes later when it's moved on it looks great again . Never going to get away from that
 
i have seen walls rendered really well by good plasterers that look great when they are finished but when the sun hits at certain times of the day and at certain angles dont look so good, but what can you do when you are rendering in one light then the light changes
 
Runswithscissors said:
Jesus Monk..... Don't fill the joints with Silicone!!

The only thing that sticks to Silicone is Silicone.... the basecoats will not stick to it!!

If the render system suppliers says that - get it in writing!!

As Solway laid out is the best method - although having the material drying when jointing is not actually an issue.... Not all render system suppliers advise taping and jointing the boards, but if there are gaps between the boards push basecoat into the joints before applying the basecoat.

As Rigsby says, in some lights it will be possible to see all sorts of things in all rendered walls.....but a full chequer board effect is usually more as a result of the basecoat being applied too thinly - best get the system supplier rep out and advise further.......
Click to expand...
We're nowhere near starting it yet if at all weather just shows you that's what he said clearly doesn't know.
I will just fill them with the base coat like you said its wetherby k a bedding adhesive apparantly
 
solway said:
We didn't board the panels,but there was a 3mm gap left.Weber applications man called to site and gave us a talk through on how to complete the job(rendering wise).He said to caulk the joints with the basecoat and mesh with 100mm on all joints prior to fully basecoating.He said to do this 1st thing in the morning before fully basecoating the whole wall.He said "im a brim and braces man myself and I would caulk and mesh all joints to give more strength"."For the sake of an hour in the morning do this,go have yere tea,return and then fully basecoat the wall.He also stated in his "chat" not to apply basecoat over dry basecoat.When we started filling joints the basecoat filler was dry within 30minutes(no messing or exaggeration,30 minutes).He said that by filling the joints that the gear should remain moist for an hour at least.I rang the weber man and put across to him that the joints had dried rapidly within 30 minutes and what to do now.His reply was that to go up now and "key up" the joints with a scratcher and before fully basecoating the whole wall sprinkle the already filled joints with water to kill the suction.He also said that if I found that the boards were "pulling" quickly that to hose down the boards with water prior to basecoating??????Does all this sound right.At our site meeing with builder and meself never once did he mention to dampen any part of any wall or say anything about if this or that starts to dry/pull fast.He said that this gear is lovely to use bladeebladeebla...!He also said that after rulling off your panels to leave to set/take up for about 2 hours before sponging down.I was sponging the 1st section after 40 minutes straight after we finished rulling off.We kept an eye on the panel every 5 to 10 minutes or so as we were putting on the second pass and each time we checked it we could feel it pulling/going off more and more.Now remember these are only handy panels consisting of 7 boards.
Click to expand...

Hi Solway

If you are going to use Knauf Aquapanel Exterior, do not soak the boards before applying the basecoats...... yes the basecoat will pull in fairly quickly to strt off with, but this is good, as the basecoat is soaking into the face of the board..... but a 5mm basecoat will not fully dry in a few hours!

Different boards and conditions will define the drying speed and thus the timings for smoothing / sponging..... in most cases, it is a mater of experience and watching the basecoats drying and changing colour.

Good Luck in the future mate
 
madmonk said:
We're nowhere near starting it yet if at all weather just shows you that's what he said clearly doesn't know.
I will just fill them with the base coat like you said its wetherby k a bedding adhesive apparantly
Click to expand...

Nice one Monk

you can use Knauf Aquapanel exterior with Wetherby BS renders as well....

let me know if you want any assistance.

Good Luck
 
madmonk said:
ok mate do you know the stockists in the mcr area cheers mate
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Encon, Sheffield Insulation, CCF, Travis Perkins (some of them anyway), Keel Supplies

Give our office a call and ask for the Manchester area rep and they will be able to point you in the right direction - 01795424499
 
It is sometimes advisable to take a note when the sun is side on both early and late. More so on the flat finishes. Then should you get a complaint about it looking bumpy etc you know what times not to go back.

We all know no matter how flat we think we have have got a wall and to the very best of our ability the sun will always make a liar of us and the customer will never understand that the sun cast shadows and makes a 1mm dip look more 5mm!
 
In the summer any basecoat you like will be dry as a chip over a render board in an hour. We had major trouble using a grey basecoat over aquapanels this summer and yes rich it was 5mm thick not my usual 3mm lol x
 
Im not saying it was dry before sponging up but it was ready for a sponge after 40-45 minutes compared to weber mans "hold for 2 hours no problem".Also why did the areas where we joint filled pull in and set at a different level to the rest of the wall.We didn't fill the joints on the rest of the gables after seeing what happened on the first gable and there is no sign of this problem on these walls.It seems the joint fill coated areas sucked more moisture from the base coat than it did from the calcium silicate boards and in turn left a hollow due to it drying at different rates.Surely the weber man should have had enough knowledge to tell us that this could potentially effect the appearance of the wall upon completion.
 
solway said:
Im not saying it was dry before sponging up but it was ready for a sponge after 40-45 minutes compared to weber mans "hold for 2 hours no problem".Also why did the areas where we joint filled pull in and set at a different level to the rest of the wall.We didn't fill the joints on the rest of the gables after seeing what happened on the first gable and there is no sign of this problem on these walls.It seems the joint fill coated areas sucked more moisture from the base coat than it did from the calcium silicate boards and in turn left a hollow due to it drying at different rates.Surely the weber man should have had enough knowledge to tell us that this could potentially effect the appearance of the wall upon completion.
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Could you not use an sbir or similar primer just on the joints before you base coat to to help with the suction just a thought
 
I've never had a problem with the joints going off too fast. I've had issues where the sub has been roasting the boards then you try and apply a grey base coat and it dries a bit quick but that's to be expected
 
Some funny shizzle on this thread.

Wetheby lol solicone the joints up hahaha.

This issue on phenolic insulation is a different problem. Uneven insulation and the curling of phenolic once fitted can cause all sorts of problems later but.......

This sounds like a difference in suctions to me having been over the joints first. Calc boards suck like mad and the lac already on should hold off a little otherwise maybe a build up of material






www.jfe-rendersystems.co.uk
 
The weber man told us to only cork the joints with foam , that if you cork them with the base coat it will soak water in the rain and show up the joints later on
 
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