External render options

[cwr]

Hi folks

 

I am deliberating over external render choices, would be great to get some opinions on this. Wall construction is concrete block, and we want a durable white finish. The options so far seem to be:

 

1. Sand/cement render, painted. We've ruled this out as don't want to have to keep re-painting every few years

2. Monocouche render such as K-Rend. Have heard a few bad things about K-Rend such as discolouration, green slime growth... Not sure if that is due to lack of maintenance, poor application or just the way it is?

3.Thin coat silicone

4. Thin coat acrylic

 

 

Has any else had good/bad experiences of K-Rend? Or any opinion on how it compares to one of the thin coat systems?

 

Cheers,,

Chris

 

[ProDave]

For sheer durability, I would use what is traditional in this part of Scotland.  A sand / cement render made with snowcrete and a bit of lime. Gives an off white finish all the way through with no painting.

[cwr]

I've heard the of snowcrete but know nothing of it. What mix would you typically use? 

I might get hold of some and do a trial.

[Carrerahill]

22 minutes ago, cwr said:

I've heard the of snowcrete but know nothing of it. What mix would you typically use? 

I might get hold of some and do a trial.

Snowcrete is just white cement, it is also stronger, but I understand that is a function of the manufacturing process of a white cement rather than intended. 

 

If you google render mixes you get literally 10's of options. 

 

I am going to go for 5:1 but may add lime to and go 6:1:1.

 

I just did a scratch coat last night using: https://www.enewall.co.uk/surerend-base-coat/

 

It was ODD stuff to mix, the water literally just ran over the powder and it took some mixing until it started to blend up - it was like the powder was coated in wax! I am therefore assuming there is some sort of silicone waterproofer or something in it.

 

Worked well, oddly although a fine powder it had some 2-3mm bits of grit through it which just made a nucence of itself. Checked it this morning and seem solid and I'll get the final coat on to it this weekend with some luck - not sure what though! I think it will be their magnoila top coat with a white/off-white chip. 

 

For the back of this same garage I am going to do as @ProDave says and use a sand cement (snowcrete) finish as I will never see the back of the garage and I just need a good solid surface with no maintenance. 

Edited August 2, 2019 by Carrerahill

[Jeremy Harris]

Our retaining wall is rendered with a mix of white cement, hydraulic lime and the local (rather orange coloured) sand.  Came out a nice cream colour, that seems to be weathering well (been there 6 years now).  The colour seems to depend primarily on the sand that's used.

[Declan52]

You can use snowcrete with different colours of sand to give you different variations in the final colour.  You can use everything from white sand to silver sand and a mild yellow sand. Each will give you a very different colour. But things like white and silver sand depending on where your building might be hard to come by and thus might be expensive to source.

[Carrerahill]

What are peoples thoughts on the exact sand, I have have 20 odd answers on this.

 

Plastering sand, is it a must?

 

Building sand and sharp sand seem to be used - so just what is the answer here.

 

I have rendered some columns and a brick build coal-bunker in building sand and cement and that was probably 15-19 years ago - it's fine. The column I did is fine too. 

 

I know building sand is fine, and using some mortar as a bit of a render where you maybe make a bit up too much and "fix" something it goes on very smoothly, but it works... 

 

Edited August 2, 2019 by Carrerahill

[Declan52]

For doing a scratch coat then a plaster finish then yes plastering sand all day long. It gives a rougher and tougher surface to which the finish coat will key to.

For an external render like a dash top coat then yes it's the better option.

But for a coloured render it will depend on the type of sand. Silver and white sand is a very fine sand so it's more like motar when you mix it. 

You could put a scratch coat of plastering sand on then a silver sand on top but you run the risk of the grey colour scratch coat affecting the top colour. 

 

[cwr]

Intrigued with the responses above, I got some silver sand, snowcrete and lime and did some experimenting on an old shed. 5:1:1 mix.

 

Reasonably happy with this. With hindsight I should have put some effort into to applying it smoothly rather than rushidly throwing it on, as I think it would look better with a smooth surface finish. 

 

[dpmiller]

that's pretty white!

[Pocster]

My external Renderer is starting Tuesday . K rend ‘off white ‘ . He said it can dis colour with mould etc . But it washes off with no issue . Photos once he’s done some work !

[cwr]

So, would a silver sand/snowcrete/lime  render need any maintenance or re-coating? 

[cwr]

Re-visiting this as still not really clear on which route to go. Each builder that I asked to quote for the silver sand/snowcrete/lime  render ultimately declined and quoted for a trad sand/cement render, and said I could then paint it. They gave a variety of reasoning including 'it would be difficult to get uniform colour' and 'it would only be suitable for old stone built walls'.

One builder suggested the K-rend thin coat TC10, though double the cost of sand/cement render

 

So, is K-rend TC10 a better choice over the standard k red?

 

I didn't want to paint for fear of never ending maintenance, or am I being unreasonably concerned given modern paints? We're talking about 460m2 of exterior surface which rather puts me off even putting one coat on myself...

[bassanclan]

I had a similar problem. 

SWMBO wanted a very smooth finish which you cant get with k rend.

I found someone to do it in sand white cement and lime to give a "stone" colour, but they under quoted and finished off the last 10% sloppily so it looked patchy around the windows so I ended up painting it with Johnsons self cleaning paint.