Render advice.

[Onoff]

Just buy any SBR and have a read of these instructions:

 

https://www.sovchem.co.uk/media/media/PDF/Tech_Datasheets/SBR_Bonding_Agent_TDS_29_V2.pdf&ved=2ahUKEwij0qyw-qnhAhUWUBUIHcuIAw4QFjABegQIDhAE&usg=AOvVaw0BYWwdyUnH-WtrJj2kMEQF

[newhome]

3 hours ago, zoothorn said:

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?

 

It's just the terminology. So render is a type of mortar. Mortar for bricklaying will likely be a different mix to that used for rendering. 

 

"Rendering, when applied to the construction or renovation of buildings, refers to the application of cement to external and/or internal brick or concrete walls in order to achieve a smooth or deliberately textured surface."

 

and 

 

"Render is a mortar consisting basically of cement and fine aggregate, usually together with lime or a plasticizer, applied to a wall surface, generally in two or more coats. When correctly matched with the background, the hardened render provides a durable, weather resistant finish enhancing the surface of a building."

 

@nod's suggestion about using the PVA mix is part of the preparation before you put the actual render mix on the walls. Bit like using a primer before you paint walls with the final finish paint. It's a preparation step that will help in the long run. In your case it will most likely ensure that the stuff stays up there better. @nod is a professional in this field so definitely take his advice.

 

 

[Onoff]

16 minutes ago, newhome said:

 

It's just the terminology. So render is a type of mortar. Mortar for bricklaying will likely be a different mix to that used for rendering. 

 

"Rendering, when applied to the construction or renovation of buildings, refers to the application of cement to external and/or internal brick or concrete walls in order to achieve a smooth or deliberately textured surface."

 

and 

 

"Render is a mortar consisting basically of cement and fine aggregate, usually together with lime or a plasticizer, applied to a wall surface, generally in two or more coats. When correctly matched with the background, the hardened render provides a durable, weather resistant finish enhancing the surface of a building."

 

@nod's suggestion about using the PVA mix is part of the preparation before you put the actual render mix on the walls. Bit like using a primer before you paint walls with the final finish paint. It's a preparation step that will help in the long run. In your case it will most likely ensure that the stuff stays up there better. @nod is a professional in this field so definitely take his advice.

 

 

 

 @nod says SBR or Unibond (pva)

[newhome]

Just now, Onoff said:

 

 @nod says SBR or Unibond (pva)

 

I wasn't really highlighting the use of SBR or Unibond TBH (I wouldn't know anyway lol), I was emphasising the need to complete the step, ie don't miss it out even if the render instructions only say to use 2 coats of the standard mix. 

[Onoff]

4 minutes ago, newhome said:

 

I wasn't really highlighting the use of SBR or Unibond TBH (I wouldn't know anyway lol), I was emphasising the need to complete the step, ie don't miss it out even if the render instructions only say to use 2 coats of the standard mix. 

 

Zoot needs it spelling out!

Edited March 30, 2019 by Onoff

[zoothorn]

Damn right.. I do. Still do.

 

My builder says the thing to add, to my mortar.. is lime. But this hasn't been mentioned yet on here. And I don't know what the lime is for (I forgot to ask) plasticity, waterproofing agent? I dont see how a powder addition can have waterproofing properties.

 

So are you suggesting this SBR stuff is the waterproofing addition to the mortar (or solely to do with the primer coat film). Is the mortar mix I have, waterproof already?

 

If SBR or pva.. then that's regarding the primer coat/ film, rather than the suggestion for adding to the mortar.. yes?

 

I'm in a complete fog here going round all these places in town for well i don't exactly know, asking whoever I can for clarity, & I still can't tell what I need!

 

Can we go back a step. I have 2 jobs to do. A primer coat (which I'll use wood pva for 5:1 with water).. then a render. I have the mortar mix tub.

 

A) do I need to add anything to my tub?

B) if so, specifically what?

[Declan52]

First job is clean the patch.  Rake out any loose material then hit it with a hose to rinse any dust off.  Let it dry slightly then apply your prime coat. Do as was mentioned above using pva and some cement.  Let it dry. 

Mix your batch up.  Lightly wet the wall.  This will help with suction plus stops it drying out quick. Lime is just used as a plasterciser to help you work with it.  If you have it fine if not a tiny squirt of fairy liquid will work.  I mean a tiny squirt or it will have to much air in it and go to fluff. 

Don't try to do it in one pass.  If it needs 2 coats then scratch the first coat before it goes of.  A series of grooves cut into the motar using a nail. Let it harden. 

Then damp it down again mix another batch and do the top coat.  Don't try to overwork it.  Put it on and smooth it using a long piece of timber long enough to stretch across the hole.  Let it sit 20 mins then use your float to finish it. 

[zoothorn]

Hi Declan, that's super clear with regard to the steps to take cheers (altho not understanding the 'few handfuls of dry cement' onto the pva:water film suggested by nod.. dry? how do I apply dry cement to this?). So the steps I have info on.

 

So from this info- I either add a plasticiser, or a waterproofer (assuming SBR's primarily a waterproofing agent here), or PVA as a waterproofer.. was that the suggestion, or have I got that wrong.

 

How then if I had chosen lime... would it be waterproof? I mean a render's prime function surely isn't to look smart n tarty, its to stop water getting to the brick underneath it.

 

 

Edited March 30, 2019 by zoothorn

[Onoff]

Lime I believe is also referred to as "hydraulic lime"? Something to do with the particle sizes being really small and it gets "sucked" into the face of the bricks by hydraulic action. Given the age of your place is it possible the rest of the face is lime rendered and that's why the builder said to you about using lime?

 

Why not jfdi and have a go? Worst it'll do is fall out and you'll have gained some experience.

 

I've generally done this for patching:

 

1 trowel full of cement

1 trowel of sharp sand

3 trowels of building sand

 

Or if no sharp then 4 of building sand.

 

Mix 5:1 pva or sbr. Clean the test patch area with a stiff brush. Prime with the mix. Let it go tacky. 

 

Dry mix the sand and cement. Add the same 5:1 water/pva (or sbr) mix to wet it a little at a time. (I sometimes mix in a bucket with a stick if small quantities). You want it creamy but not to the point it slides off a clean, pointy trowel too easy if you turn the trowel from flat, to 45deg, to vertical. Starting to slide at 45deg then falling off at 90deg. You want it like say a bit thicker than cake mix where as you mix it up and it leaves little troughs and waves, the waves don't "slump" but stay where they are. Apply with a hawk and trowel - pointy trowel not the thing to use. Slightly over fill the area. When gone off but not dry use a straight piece of timber longer than the patch is wide. Don't scrape but hold either end starting from the bottom and jiggle left and right as you work your way up to cut off the excess. 

 

 

[zoothorn]

@Onoff

 great ok now I'm on board with 5:1 water:pva to add to the mortar, as well as, to the pre-film-coat. As a poor man's 2nd to sbr or lime I'd imagine but I have to crack on today (no sbr/ jewson not open & screwfix sbr is £70 a gallon).. as rain's coming in tmrw am/ & a changeable week so I MUST do am today. bugger wish Id understood this y'day.

 

Ok as you say jfdi & if falls out then a learning step. Im just worried about the exposed flunky brick & the rain.

 

I'm sure my builder who rendered big areas, similar blown brick face, around the side.. just did one coat/ no float smoothing even. prolly cos I was easiest to hoodwink / no idea it needed a scratch-coat 1st. Is it imperative I do 2 coats?

[zoothorn]

2 hours ago, Onoff said:

Lime I believe is also referred to as "hydraulic lime"? Something to do with the particle sizes being really small and it gets "sucked" into the face of the bricks by hydraulic action. Given the age of your place is it possible the rest of the face is lime rendered and that's why the builder said to you about using lime?

 

Why not jfdi and have a go? Worst it'll do is fall out and you'll have gained some experience.

 

I've generally done this for patching:

 

1 trowel full of cement

1 trowel of sharp sand

3 trowels of building sand

 

Or if no sharp then 4 of building sand.

 

Mix 5:1 pva or sbr. Clean the test patch area with a stiff brush. Prime with the mix. Let it go tacky. 

 

Dry mix the sand and cement. Add the same 5:1 water/pva (or sbr) mix to wet it a little at a time. (I sometimes mix in a bucket with a stick if small quantities). You want it creamy but not to the point it slides off a clean, pointy trowel too easy if you turn the trowel from flat, to 45deg, to vertical. Starting to slide at 45deg then falling off at 90deg. You want it like say a bit thicker than cake mix where as you mix it up and it leaves little troughs and waves, the waves don't "slump" but stay where they are. Apply with a hawk and trowel - pointy trowel not the thing to use. Slightly over fill the area. When gone off but not dry use a straight piece of timber longer than the patch is wide. Don't scrape but hold either end starting from the bottom and jiggle left and right as you work your way up to cut off the excess. 

 

 

 

Onoff.. Ive whacked on the mix: I found very tricky to

 

A) get right consistancy/ still no idea or confidence here (slightly slid off trowel.. when it stuck only a tad of movement 45*,, it just felt way too dry)

 

B) didn't seem to adhere well, half fell out

 

C) i just cannot do 2 coats (Im WAY up a ladder/ for me its high, & at edge of wall wind coming in).. so just has to be one coat.. for safety if anything.

 

Ok so I can see it going off slightly, but its got trowel marks over, even smoothing off as best I can. Its not appalling, but it aint good..  & marks will be clearly visible once masonry painted. So Id like to get smoother.

 

Can you please just refresh me as tp what I can do now, to smooth it, & when to do so.

[Declan52]

10 minutes ago, zoothorn said:

 

Onoff.. Ive whacked on the mix: I found very tricky to

 

A) get right consistancy/ still no idea or confidence here (slightly slid off trowel.. when it stuck only a tad of movement 45*,, it just felt way too dry)

 

B) didn't seem to adhere well, half fell out

 

C) i just cannot do 2 coats (Im WAY up a ladder/ for me its high, & at edge of wall wind coming in).. so just has to be one coat.. for safety if anything.

 

Ok so I can see it going off slightly, but its got trowel marks over, even smoothing off as best I can. Its not appalling, but it aint good..  & marks will be clearly visible once masonry painted. So Id like to get smoother.

 

Can you please just refresh me as tp what I can do now, to smooth it, & when to do so.

You have to let it sit.  It won't go smooth with a float until it has dried out a tad. How long you wait will depend on how much water is in your mix plus how warm it is and wind all help in speeding up the drying out. 

[zoothorn]

Thanks all for replies Declan, nod, newhome, PeterW, Onoff et al.. I'm a bit ashamed to show results after the help, apologies! its not great, but best I can do up my ladder one handed. If I can smooth it, it might pass as just acceptable & stay on for a while.

 

A tough lesson this for me, a D+ only. Ive got to figure out this consistancy thing as I don't know what's going on.. scrap tests on a free day.

[newhome]

You’re giving it a go, and next time will be easier. Better to fiddle around and practice at ground level first though ?

[zoothorn]

4 minutes ago, Declan52 said:

You have to let it sit.  It won't go smooth with a float until it has dried out a tad. How long you wait will depend on how much water is in your mix plus how warm it is and wind all help in speeding up the drying out. 

 

I couldn't use a float, just a trowel (one with the rounded tip, not the pointy ones) so had to try & smooth thus far inch by inch. Its contoured/ not a smooth flat surface, this would be nigh on impossible for me to acheive, so it goes in & out where the brick faces had badly dmgd ~3cm in.

 

Its got sun on at the mo, & a dry wind too.. shall I spray water on to stop it drying too fast? seems like its drying quick.

[PeterW]

So keep damping it with a big wide paint brush. If you haven’t got one then an ordinary soft sweeping brush will do, and it will help smooth it off too. 

 

Slow, damp not wet, and very little pressure ..!!!

[zoothorn]

Ok PeterW understood.

[jfb]

a slightly damp sponge can smooth off a lot of the ridges - just have to catch it when there is still some movement in the render but not too soft.

[Declan52]

22 minutes ago, zoothorn said:

 

I couldn't use a float, just a trowel (one with the rounded tip, not the pointy ones) so had to try & smooth thus far inch by inch. Its contoured/ not a smooth flat surface, this would be nigh on impossible for me to acheive, so it goes in & out where the brick faces had badly dmgd ~3cm in.

 

Its got sun on at the mo, & a dry wind too.. shall I spray water on to stop it drying too fast? seems like its drying quick.

The float is easier to use.  Like grand master mister miyagi you do the wax on wax off movement.  Don't apply much pressure.  Your just touching it and Polish it up. 

When you say trowel with a rounded top are you using a gauging trowel?? 

https://www.screwfix.com/p/forge-steel-gauging-trowel-7/1191c

 

[zoothorn]

Yes Onoff guaging trowel.. the only one I have confidence to use tbh. pointy's a pain, huge mofo scares me,  grout float's for wusses/ metal tiling one not right.

 

Ok brush seemed ideal for the smoothing- great recommendation & just in time: got warm sun bang on it alas/ drying fast now with cold dry wind too: not ideal. But I dare not touch it again I'm sticking right here/ done.

 

thanks alot.

[Onoff]

Totally the wrong trowel I'm afraid! This sort, the type you use for plaster is what you what. The action of using it to apply also pushes the render into the bricks and helps it stay there. A cheap 11" long one would do you.

 

 

Fwiw your attempt looks the right colour and that it's staying there at least.

 

You can use a small offcut of timber just big enough that you can hold with outstretched fingers...say square beer mat size to gently rub over the surface of the patch of render once it's gone off. If the wood takes the render off then its not yet dry enough to "buff". I've even used a bit of tile batten on occasion.

 

Another trick as above is to unscrew the head off a cheap plastic broom and sort of brush it all in when slightly gone off.

 

 

[zoothorn]

All understood Onoff.. but really its the only one I could use, up there on the ladder, doing all with one hand: the bigger flat trowel I couldn't get into the tub anyway & 2 hands needed: not safe.

 

Its far from a pro job this ever going to be: its contoured below the brick upper floor, so getting it flat never was the plan- I just need it to stick, get into the cracks & gaps, which my curved point trowel was ideal for. I just couldn't use a corner of that big one to force into my tricky in-outs.

 

Its like my chopsaw for my pine forraged 5" dia logs: on paper wrong tool yes sure, but in practise actually -the- perfect tool for the job.

 

thanks alot.

[Declan52]

Once it goes of and is solid you could always sand down any real bad bits. 

[zoothorn]

Yup understood Declan.. I've got my fingers x'd its not rub-away poor mix I managed before.

 

Btw how long until earliest its rainproof? [christ am I gonna get a job done.. in 2 thread pages? woohoo!].

Edited March 31, 2019 by zoothorn

[Onoff]

That picture with the ladder against the wall...

 

Is it rendered up so far then some sort of textured paint above?

 

What's the plan for the exposed brick areas, just repaint?