zoothorn

Render advice.

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I'm having 'schoolboy' errors using this stuff

 

https://www.screwfix.com/p/cementone-general-purpose-mortar-5kg/36857?tc=AA4&ds_kid=92700034796463876&ds_rl=1241687&ds_rl=1245250&ds_rl=1249407&ds_rl=1245250&ds_rl=1247848&gclid=EAIaIQobChMIm-Ko4Zmo4QIVirftCh3DSQP5EAQYASABEgKhw_D_BwE&gclsrc=aw.ds

 

.. Ive used to patch a few outer wall spots of my house, badly crumbled away. My mix once applied, next day is crumbly itself: I can pick & rub it away like soft wet sand almost. What am I doing wrong? 1/2 the time Ive knocked up say a bowl-full, to do a patch repair, & fine/ sets hard. Ive lost my confidence.

 

On tub it says for general mortar & also -render- jobs. I have an outside 3/4 sq metre area of badly frost damaged brick faces, & repointing I just discoved last thing in the day.. dammit: all nice & prepped tho. But I must do tmrw- last good dry day.

 

So is this stuff sufficient? (if I can figure my mix out ok) or is there, preferably as Ive lost confidence with this stuff now, is there a small bag of ready-mix render available? or if not what do I need for my 1 hr job (~1m area). I have tiling floats to use, should be fine. I don't know actually what the difference is between render, mortar.

 

Thanks, zoot

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If the existing render is sand a cement then there are generally 2 coat.

 

A scratch coat which goes directly on the bricks or blocks 4:1 (plastering sand:cement) with waterproofer 3 in 1 and is then scratched before it goes off.

 

Second coat 5:1 with just normal plasticiser.

 

It sounds like you put too much water in stuff you are using or its old and the cement has gone off.

 

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My builder though did the outside of the house, bigger patches but exactly same deterioration/ I'm just doing a bad bit round the sides they missed 2 yrs ago.. & it was just one thick coat they slapped on. A good job too. This is simply what I want to use, just about a fraction of the area.

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Is it old, damp or did you put too much water in?

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Is the mix old, or the house/ wall old? or is the mix damp? sorry Im not following your Q. appreciate the replies tho.

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Its basically just what do I use for 'render' to do a small area approx 0.5m square. in one go like my builder did. Ive picked all the loose rotten mortar & crumbling brick face bits (frost damaged?). I mean no point me buying a cement bag, 25kg of sand, 1kg lime (or whatever render is made from) & waste almost all of it.

 

And what is render compared to mortar, or is it the same thing?

 

And for the repointing.. is it the same mix as the render?

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I meant is that tub of screwfix render old or damp or did you put too much water in?

 

Mortar is usually made with building/ soft sand.

Render with plastering sand which is a "washed" sand 

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I guess if I was mixing say 0.5 litres of mortar, just for a bit of outside crumble I found as I went along (masonry painting was the main job Ive been doing whole front of my cottage).. & one mix was hard, then another seemed all brittle: then it has to be me & too much water & not the stuff too old?

 

how long can I keep a tub like this for, & keep dipping in for ~2 trowels for, anyway?

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The dry mix certainly wasn't damp, it seemed just as dry as when new.. but.. we do have a phenomally damp climate here out in wildwestwetwales, I mean weirdly so. But then all my 0.5l mixes would be consistantly bad.

 

I was watching a pro brickie t'other day (pissing him off asking a few Q's), on a site.. & his mortar was generally sloppier than mine with this stuff.

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Should last 9 months from new if in orginal container and dry according to the manufacturer.

 

There will be a set amount of water you should use. Borrow some kitchen scales and weigh it out properly

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Don't add water to your dried up mortar to "knock it up" and get it use able and try to get it on the wall again

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But I can't do this each time weighing ~2 trowels of mix & then water.. its just a Q of mixing until its 'right'. I mean I can tell/ feel when its too sloppy, or too dry: you get it ok so it sticks to trowel, maybe moves a wee bit trying to slide off. I mean that sounds about right yes?

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3 minutes ago, bassanclan said:

Don't add water to your dried up mortar to "knock it up" and get it use able and try to get it on the wall again

 

You mean don't re-add water once its been around a short while & stiffens a bit? is that what 'knocking up' means?

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For eg: I repointed a bit of the old stone (slate) above the window where I found some old rotten mortar: picked it out, brushed bits out (I recall repointng doing labouring 30 yrs ago) repointed & has set hard. I dont recall any major difference to the mix consistancy, to a similar hole I did an hour later, which I can just rub off with my fingers.

 

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Ok that tub stuff is ok if you use it all at once but the cement settles out a bit. First mixes may be a bit strong, the rest may be weak which is why you’re having issues. 

 

Get a new tub, mix it all and use it and see how you go. 

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To make life a bit easer Clean the brick faces off with a wire brush 

add a bonding agent SBR or Unibond to 5 parts water and a few handfuls of dry cement 

and paint it on the area to patch 

Leave it for a couple of hours 

Then apply your first coat 

You will find that it sticks much better and doesn’t dry as Quik 

Second coat can go on after a couple of hours 

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Morning chaps- many thx for replies/ info. The vid looks remarkably like my house/ white bubbly crap stuck onto brick etc.

 

So @PeterW I can use -a new one/ I'll bin this then- this tub mix stuff without having to add anything to make it a "render"?

 

Can I just establish 1st, what render is. Is it just a term for the same stuff but for a different application? IE a render is usually a vertical-spread 'coat' on a wall face, ~2 cm depth. A mortar is to bond bricks together.

 

But they are the same stuff. is this correct.. or not? Or for eg.. I pass a brickie who kindly gives me a bucket of mortar from his barrow/ he's laying bricks. I nip back in 10 mins. Can I then use this, up a ladder, as render? is this the correct stuff?

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9 hours ago, nod said:

To make life a bit easer Clean the brick faces off with a wire brush 

add a bonding agent SBR or Unibond to 5 parts water and a few handfuls of dry cement 

and paint it on the area to patch 

Leave it for a couple of hours 

Then apply your first coat 

You will find that it sticks much better and doesn’t dry as Quik 

Second coat can go on after a couple of hours 

 

Nod hi there,

 

Do you mean a builder's pva? (isn't wood glue the same stuff.. I have this to hand for a small 0.5 area mix).

 

Ive then got to establish what this 'coat' consists of. What render is.

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21 minutes ago, zoothorn said:

 

Nod hi there,

 

Do you mean a builder's pva? (isn't wood glue the same stuff.. I have this to hand for a small 0.5 area mix).

 

Ive then got to establish what this 'coat' consists of. What render is.

Wood glue is the same as PVA 

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With my first house, not knowing otherwise I added PVA to EVERYTHING, render for walls, mortar for bricklaying, concrete, EVEN plaster. Put it this way none of it's come off! I would religiously add 5 of water to 1 of PVA and used that to mix whatever in place of plain water. I'd size walls with the 5:1 mix also. 

 

Not all PVAs are created equal! I used to use Wickes waterproof one. Now it's about £25 for 5L. Sometimes I'd use Unibond's offering.

 

527690441_01_1.jpg.1ab8aaf6f4dc7afb3006b99be0b9ca8a.jpg

 

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So this SBR stuff https://www.jewson.co.uk/building-materials/chemicals/other-building-chemicals/products/CMSKA954/sikabondc2ae-sbr2b-e28093-bonding-agent-and-mortar-admixture/ is used with water 5:1 as a film alone, prior to the render?

 

But it says on it that its an addition, to the render itself though.. nothing related to using 5:1 alone. I'm confused as to what consitutes a mortar, & a render. The main specs of this SBR says its an addition 'for mortar'.. then in the smaller specs its says its an addition 'for render'.

 

Is mortar the same as render then?

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Sorry another Q!

 

Ok say I wire brush, then apply pva 5:1 water on the area in my photo. If the rain hits before I can get render on.. will this 5:1 give some waterproofing?

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I'm totally confused as to the addition to put in with 4:1 sharp sand/ cement. Plasticiser, sbr, waterproofer.. & a myriad of different brands & prices.

 

Coincidentally my builder just popped in, said to render this I need 4:1 sharp sand to cement.. with a bit of "waterproofer". But just make it a bit sloppier so more spreadable. Also said I can use my tub mix of mortar.

 

But what is this "waterproof" stuff? is this "sbr" (which says in its spiel its an additive with waterproof properties) or "plasticer", or is it something alone called waterproofer.. or are all these the same thing?

 

 

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