A GUIDE TO PEBBLE DASHING
[/u][/b] I see I'm coming to this thread a little late, better late than never…. In the late 1960's & early 1970's my Dad's company used to do loads of Pebble Dashing here in Seattle we call it Marblecrete, your description is spot on, hadn't heard about adding a waterproofer to the scratch coat, great idea! One thing I might be able to improve on though is the tool for throwing the rock, - here we use a coal shovel that can be bought from a hardware store, take a mallet and flatten down the sides of the scoop part of the shovel leave a bit of a curve in the scoop part, then widen the top part of the handle, I usually duct tape a couple pieces of wood moulding to the metal, for comfort and to give you more control. If you've never thrown rock before the plasterers that I apprenticed under had you take a couple pieces of plywood and spend a couple of hours practicing different 'strokes & flings' throwing at just the plywood. #1 & #2 size stones the best size to throw, preferably sharps, just about all the jobs I gotten have been to match what was already on the house, and usually it seems like it always comes up what we call a pea gravel (small round stones).
this is the way i do it, there are more ways and this is just one of them.
i have not included mix ratios as it is best if you decide for your self Grin (i think most people use a 4-1 or something like that, i prefer something else Grin)
right first things first, it is best to have a good scaffold as you need to get to all of the wall easily (and quite quick if the sun comes out). i prefer not to use a tower if you are doing a full wall and not just a panel or a bay.
next thing is to remove all of the down spouts and waste pipes, some plasterers like to leave the down spouts on if it is a big wall as you can hide a joint behind them but i would recommend that if the wall is to big then just get more men in to do the work.
with all that done you can now bead up, put all the bell-cast beads on and the corner beads (IF YOU ARE GOING TO USE THEM) most plasterers will never use corner beads as they do not offer enough depth for the stones to sit in the sand and cement and this will cause bald spots down the corners, but you can use the plastic external corner beads as they have plenty of room for the stones Wink
now the next stage is the scratch coat, this should be mixed with waterproofer to the maximum amount stated on the tub (trust me if there is only you doing the plastering and throwing the stones this will help allot). when scratch coating try to fill out your bellcast bead so that when you top coat you get an even amount all over the wall and the bellcast is not built out in the top coat, as when you throw the stones this will stop the sagging. also if you are using the plastic beads make sure you only cover the wings of the bead.
let this scratch coat dry out.
now for the top coat, you can go around and cover all the windows if you are not that conferdent at throwing the stones. you should start on the opposite wall to where the sun is shining and try to complete each wall before the sun comes round. soak the wall with a hose pipe first then when you look at the wall you will notice a glisten on the surface from the water, once the glisten has gone you can start to put the top coat on, some plasterers like to use lime in the top coat to give a lighter background to the finished job, when the top coat is on you should rule the wall with the feather edge and fill out all the hollows until the surface is full and flat. once done you should put down sheets at the bottom of the wall to catch all the stones that dont stick, all your stones should be in buckets on the scaffold and the ground where you are working (they should have been washed and dried out in the sun a day before).
now start throwing the stones, you use the flick of the wrist, its all in the flick of you wrist when dashing load the scoop up and then sort of shake it to level the stone of then throw straight at the wall I've seen guys throwing with the scoop at an angle and it looks awful, if you throw them too hard then you will cause the topcoat to move and sag, you only want to throw them so they stick to the wall as you can press them in with a clean float to make sure they stay on. to throw the stones you should use a hurling trowel but i have used my bucket trowel when i have been caught short, i have even seen guys using the tow of there trowel. be sure to throw plenty of stones at the wall (i throw about three trowelfuls at each spot) as bald spots will ruin the job.
now go and pick all of the stones up from the sheets, these should all be washed and dried out fore the next wall.
if there is no other way and you have to put a joint in the wall and there is no down spout, you should try and make it as short as possible like between windows also if you do the joint in a zig zag it will be less noticeable. but i would avoid this at all costs, just get more hands on the job.
oh and i almost forgot if you are not using corner beads then you will need to hold a straight edge to the corner of the wall and hold it so that it comes out just past your topcoat, this way when throwing the stones you wont knock the corner out of shape.
also this might be a good time to mention that there are all different types and grades of stones and also different types of colours for the sand and cement (colours work best with white cement) so dont be afraid to experiment, gold stones took nice on gold/buff coloured cement or black and white on white cement etc etc....
hope this helps
oh and i will say it again, there are lots of ways to pebble dash, this is just the way i do it Wink
