Installing stone cladding on a painted block wall

Rainwaterman

Folks I have a painted garden wall that I want to installl z-clad natural stone veneer on.Wall built with standard 4 inch concrete blocks and is painted with 1 coat of Dulux Weathershield.Whats the best way to prep the painted wall so that the adhesive will adhere to the wall and take the stone veneer.
I looked into soda blasting the wall but at 850 euro for a cleaning company to do it that a bit more than I wanted to pay out.
Do I just go and attack the wall with an angle grinder and disc and cut slashes into the surface of the block wall to key it?
Do I use the caustic soda and baking flour trick to strip the paint off the wall?
Basicly whats the best way for me to jet a key surface of the wall for the adhesive to stick to.I dont want the stone cladding to fall off.
Wall is 20 meters long and 2 meters high.

dhog4n

You could fix expanded metal mesh to the wall. Much cheaper and less hardship than most of the chemical solutions to your problem.

It can be secured with masonry washer nails or by drilling and screwing or using hammer in fixings. Use enough fixings so that the expanded metal doesn't flap about. Then proceed as if you had a raw concrete block surface.

Rainwaterman

dhog4n wrote: »

You could fix expanded metal mesh to the wall. Much cheaper and less hardship than most of the chemical solutions to your problem.

It can be secured with masonry washer nails or by drilling and screwing or using hammer in fixings. Use enough fixings so that the expanded metal doesn't flap about. Then proceed as if you had a raw concrete block surface.

Thanks for the reply.I have over 1000 5mm red rawl plugs but not a single screw.Typical of me to buy the plugs and not the screws.
What sort of screws would you recommend?
Am I right in thinking that they would have to be galvanized screws like the expanded mesh?
The outdoor panel adhesive comes in a 25kg bag and you just mix 3 litres of water on and apply it to the wall with a tilers trowel.
Do you rekon the adhesive and stone veneer panel will work with the expanded mesh ok then?
Will the expanded mesh work on the wall piers too?

dhog4n

Any type of finished screw should do (passivated/galvanised/etc) along with washers to grab the expanded metal.

Top tip: go to a builders providers or agricultural providers for the materials. Much cheaper than a big name hardware place.

As far as the adhesive is concerned, follow the manufacturers instructions as written on the pack.

Rainwaterman

dhog4n wrote: »

Any type of finished screw should do (passivated/galvanised/etc) along with washers to grab the expanded metal.

Top tip: go to a builders providers or agricultural providers for the materials. Much cheaper than a big name hardware place.

As far as the adhesive is concerned, follow the manufacturers instructions as written on the pack.

Thanks for your help and advice.Think I might they the mesh route.
I even tried powerwashing the walls this morning with a 200 bar high pressure power washer.I did remove some paint and got some of the wall back to bare block finish,but I notied that quite a bit of mortar got blasted away in several places too.So maybe the mesh lath is the way to go now.

albert kidd

the mesh wont work..the cladding wont be wide enough.

Rainwaterman

albert kidd wrote: »

the mesh wont work..the cladding wont be wide enough.

I dont understand you what do you mean when you say the stone cladding wont be wide anough?

Rainwaterman

I also tried a sample tub of Peelaway 1 and 7 and it did nothing to the wall.
I applied a good 3-4mm layer of the paste,covered it over and left it for a day and it didnt even strip 1 single bit of Dulux.So I wont be paying out 150 euro for a tub of it.

650gs

A bucket of Thistle bond stir well and paint the wall just cover up before you paint as it sticks like you know what and should do the job its made for plaster but tilers use it all the time. http://www.gyproc.ie/index.php/products/plasters/thistle-bond-it/94

Rainwaterman

Will thistlebond work on an external garden wall though?
Is it suitable for external application?

650gs

No prob

WUFF

Just give the wall surface a good scud coat use sbr instead of water will stick like s... well you get the idea

prospect

albert kidd wrote: »

the mesh wont work..the cladding wont be wide enough.

Rainwaterman wrote: »

I dont understand you what do you mean when you say the stone cladding wont be wide anough?

I assume he means that the depth of the veneer will not take the mesh if you are using it as a tie into the blockwork, as per a traditional stone Facade.

Albert, the mesh will be fixed flat to the wall to provide a good high-grip vertical surface for the veneer to adhere to.

monseiur

Step 1 Power wash off as much as possible of the paint, use an industrial power washer, the bog standard domestic washers lack the pressure required to strip the paint, they're designed to wash only.

Step 2 Get a wide bolster and lump hammer or small hatchet and hack at every sq. foot of the wall leaving it rough and uneven.

Step 3 Get polybond, unibond or similar, mix 2:1 with water, paint on the wall liberally, mix sharp sand and cement in a bucket 1:1 soft, almost runny, using a small scoop throw this at the wall while the polybond is still wet (it's called scudding) It's a bit messy, wear disposable overalls and safety specs.
The polybond will help the scud adhere to the wall and this rough finish will be the key for your desired finish

You may get away with steps 1 & 2 only depending on how good the ''key'' is and by using polybond when applying the finish.

M.