The Basic Recipe:
Like I mentioned before a simple 3 parts sand to 1 part plastic cement ratio is adequate for most stucco and stone scratch coats.
You can add water until a pudding like consistence is achieved and/or the mix can stay on a trowel at a 40 degree angle without slipping off. Going by weight is the easiest method to achieve this ratio:
Other Recipes:
This is a basic recipe and is the simplest and fastest way to mix a decent scratch coat up. There is a few more variations of stucco recipes out there that call for lime, fiberglass, acrylic and other elements but a basic recipe will suffice.
Methods To Mixing The Mud:
There are three basic ways you can mix the scratch coat mix and these are with a wheelbarrow, a bucket and drill or a mixer. I have made a page that explains the different methods to mix base coats, like the scratch coat so I won’t go into any more detail about it here.
How Much Should I Mix Up?:
So, you will have to do two basic calculations to see:
- how much material you will need to buy and
- how much mud to mix up
Sand:
You can buy sand by the bag (which is quite expensive) or in bulk from a landscape yard or other material yard. If you do buy it in bulk, try to find a masonry type of sand. A yard of sand can weigh anywhere from 2,200 lbs. – 2,800 lbs depending on how much water is in it so we will take the average of 2,500 lbs. for this example.
A 3 to 1 ratio for a yard of bulk sand would be enough to mix roughly nine bags of Portland cement (94 lbs.). So for every yard of sand you get, you can expect to buy 9 bags of cement. If you plan on using bags of sand, then just calculate about 282 lbs. for every 94 pound bag of cement.
Cement:
Cement comes in either 47lb. bags or 94 lb. bags but for this example we are going to use the 94 lb. bags.
Yield: The scratch coat is typically 3/8″ – 1/2″ in thickness and a three to one ratio of sand to cement will cover approximately 50 – 80 sq. feet. I am going to use 50 sq. feet as a conservative measurement to allow for dropped mud on the ground, application method (hand troweled, sprayed, etc.) and to make sure there is enough material rather than too little.
