Rendering an extension - help needed

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spark2010

New Member
Hi,

Been given the go ahead on a rendering job. The extension is 7m long x 3m wide x 2.4 high. I have been asked to render the outside and inside of the extension. The outside of the extension has to be pebbledashed. After the inside is rendered I have to skim the walls also. Inside the extension where the old exterior wall was (back of the house covered by the extension) has old pebbledash slightly bigger than your normal spar and is painted. They want me to smooth over and skim. Maybe I could float and set it or maybe I need to use sand and cement as it may have moisture in it as it was exposed all its life,

The outside of the extension is common bricks and inside is thermalites. This is the biggest job I have been given on my own. Just a couple of questions as guidance...

1. How will I treat the walls? As the bricks and blocks are both high suction will I just hose down and render? or will I treat the internal blockwork?
2. I was thinking of 4-1 on the external brickwork and 5-1-1 on the top but what about the dashing?
3. As the Therms are internal, can I just do the normal 5-1 then 6-1-1?
4. Somebody said apply the therms with 1 sand/1 cement/1 pva and throw on leave to set then render?
5. Could Hardwall be used on the therms (i know its exterior) but the bricks will be rendered?
6. Im sure as the therms are internal is it the normal 2 coat work?

lastly the interior dashed wall, whats the best way to deal with it?

A lot of questions I know, but any help would be appreciated

Thanks
 

spark2010

New Member
painted pebbledash bigger than normal aggregate? is it not roughcast?

Thanks for reply chris...

I never thought of that...

The old pebble dash does not look like your everyday dashing, not joking it looks like
someone dashed with 20mm shingle?

what is rougcast?
 

Chris W

Well-Known Member
Thanks for reply chris...

I never thought of that...

The old pebble dash does not look like your everyday dashing, not joking it looks like
someone dashed with 20mm shingle?

what is rougcast?

imagine mixing render and adding 20mm shingle, then throwing the resulting lumpy mess at the wall....

roughcast...
 

Chris W

Well-Known Member
search the forum for roughcast, some of the oldschool boys know the right mix and method, something like a 3:2:1 or a 3:3:1 I think, p'ss wet, basically concrete... Ive never had the dubious pleasure of getting covered in it myself...

i'd worry about the paint, if its sound maybe just use a bonding agent, bonding coat, and skim it, prolly some degreaser on it first... if not scabble as much paint off as will come off and hardwall it...
 

spark2010

New Member
nice one, sounds quite difficult, but im going to leave that wall to the very last, priming the wall and bonding over
sounds good, I'll check the paint tomorrow and see what its like.

meanwhile im going to have to dash outside of the extension, i think he wants it blended to the existing
what may be roughcast as you said. im going to have to think hard about this one...
 

Chris W

Well-Known Member
might be an idea to sub a bit of help in on this one, no shame in it... that sounds a tricky job even for an oldschooler, blending dashing? sooner you than me mate....
essex andy, church etc.... them the southern render boys... others too but those two spring to mind...
 

spark2010

New Member
..your right and i admit this job is bit too big for me.

Good job i didnt design a website and go out on my own... i can see my logo on the side of my van now...
"NO JOB TOO SMALL.....SOME JOBS TOO BIG" lol

I have a bit to go before I consider that move

I have a few mates being plastering quite a long time, but they seem short of knowledge on dashing and they are busy, I'll have a chat with the guy tomorrow and may have to contact essex andy and church..
 

lucius

Well-Known Member
Chriss is right mate we call it slopdash in my neck of the woods you need to get someone in who has done it before the rest is all quite straightforward just go for it
 
The trouble with doing slop dash /roughcasting is getting the right mix of render and shingle you need to mix 20mm with some bigger stones to many 20mm or larger stones in the same place and it looks Sh*t
 

henry

Private Member
When you roughcast there is no giving pattern to it . You can do what chris says above I have also seen it done with large pebbles about the size of golf balls he used a coal shovel to flick then on, and flatten with the back of the shovel. It's a random pattern at best.
 

spark2010

New Member
Thanks for replies lads, He got 10mm shingle delivered to the job and said dash with that. Thank God i didnt have to roughcast it as that sounds a nightmare
I have my mate with me now so we went there and scratched it all up today, went well.....
 
E

Essexboy

Guest
Hahaha. Lmao. Please post some before and after pics, letting is know which is the after picture. This is going to be hilarious. :RpS_laugh:
 

essexandy

The Lake Governor
hows the house going mate?

It's going fine thanks mate almost finished this one now then the big extension and refurb starts on my place, which be the first external rendering I've done in over a year. I might need to come on here for some advise if I've lost the touch so perhaps I'd best be nice...............nahh
 

superspread

Well-Known Member
ive done roughcast (wet dash) .bloody nightmare, make sure EVERTHING is protected.
 
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dieselpower

Active Member
ive done roughcast (wet dash) .bloody nightmare, make sure EVERTHING is protected.
That's roughcast, dirty stuff to work with but pretty forgiving stuff.
 

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dieselpower

Active Member
Sorry monk, meant to say that's k-rend roughcast to match house but the pea gravel we have up here is pretty much the same size, varies from 6 to 10mm and leaves a nice finish..
 
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