Tips on filling in 2-5mm recessed mortar lines (not quite repointing)

[campbeln]

Hello all, and thanks in advance with any tips you can provide to a nubie!
We are painting a besa-block (sump-stones in American) home with Dulux's Medium Texture (see: http://dulux.com.au/html/planning/product_range_exterior_effects.aspx) but it's not quite filling in the mortar lines as we would like. I took a small section and applied CSR Cornice Cement 45 (troweling it over the blocks and into the joints) and it gives us the desired effect after painting.
Now... I'm guessing that Cornace Cement under the Dulux isn't the best route to take (it won't last in the exterior conditions, even under the paint/texture... right?). But mortar is too crumbly in my experience to affix to the 2-5mm depths. So, is there anything like mortar that has the consistency of cornice cement?
Any suggestions are greatly appreciated!

[campbeln]

I've been doing some digging in (seemingly) unrelated topics and found something that may be of use(?):
In http://www.woodworkforums.com/showthread.php?t=42675 JohnC's post:

Do a mix of 2.5 sand to one of cement or buy premix render. To improve the bond you can mix cement and water together into a paint and brush that on first, a bit of bondcrete in the paint mix helps. 1/4" is a reasonable thickness, perhaps put up boards, or lift the form work if it is still there to form an edge to screed to and finish off with float and trowel. A barrow load should give you around 8' square, it goes a long way at that thickness.


I like the sound of the thin coating working (course they speak of 1/4 inch, which is more then my 2-5mm) and the paint-like texture. But is this a possible solution?

[schwerdty]

yep, buy pre-mixed render in a bag-either 20kg or 25kg. It will do about four square metres of wall per bag and cost will be 10-16 dollars. Forget mixing your own. Forget adding bondcrete or any other things; the pre mix is perfect and will fill 1mm if you like. Now, filling the gaps is very very time consuming. If you have the time, remove out whatever you filled them with using a little dragger tool you can buy cheaply from bunnings. Mix up the render to a consistency of tooth paste (no thicker) Press then Scrape into gaps with edge of trowel. When it starts to go off (the shine will disappear) use a damp (not wet) sponge and gently wipe it back flat. Time consuming - but you will get a perfectly flat join and perfect to paint over.

[ozwinner]

Use pre mix if it makes it easier for you, but a sand cement mix of 3 sand 1 cement will do the same.

Wet the wall prior to troweling on the mix.
Trowel it on to the wall, Bondcrete isnt needed.

Let the mix go off a little after you have troweled it on, maybe 1/2 an hour to an hour.
Get a straight edge to use as a screed with a sharp edge, not rounded.
Work the straight edge over the wall in different directions with a zig zag motion.
Fill the hollows with the mortar mix, hollows will appear.
Repeat until no more hollows appear.

Hope this helps.

Al :)

[campbeln]

Firstly, thanks to everyone who tossed their hat in the ring to help out (including JohnC)! I would have continued to wander down the wrong path if it wasn't for you guys!

I ended up getting a bag of pre-mixed acrylic-based render and its worked a treat (got it in Bunnings in the cement aisle). It's not quite as easy to work as the cornice cement, but it'll last in the elements (and I only need to do a single application). It trowels (using a steel gyprock knife) in quite well and sticks a hell of a lot better then mortar. Plus being render itself the texture it leaves on the blocks is what we're looking for anyway.

Had I run into this stuff before, I'd have troweled it into the joints (as I'm doing now) then I would have used a little goodie (http://www.homaxproducts.com/products/texture/19/index.html) I picked up in the states to blow the rest of it up onto the walls. i understand that some renderers have the Homax gear down here, but I couldn't source one in-country a year-ish ago. Anyway... anyone interested in going the Dulux Texture route for DIY rendering this is a valid alternative...

Trowel over the joints to level the wall out (as described above), then get a Homax blower and spray a second coat over the entire wall. Even after getting the Homax blower ($50 USD or so in the US plus shipping) and a cheap air compressor ($99 AUD on sale) you still probably get away cheaper then going the full Dulux route. Course with the Dulux, it's 2 coats and you're done (or 1.5 if you paint it on thick like we have).

All well... least we only need 1.5 coats of the Dulux stuff to get full coverage now!

Thanks again, one and all!