We have an outside cupboard (probably was once an outdoor loo), attached to the house but accessed by a door in the garden, that is structurally sound and waterproof with a good tiled roof, but with internally crumbling plaster and brickwork.
We'd like to use it to house a chest freezer and put up some shelving for storing food tins and jars.
What I'd like to know is a simple and effective way of making good the inside walls so that bits are not flaking off every time you brush against them, and that would allow us to put up some simple shelf brackets. It really does not need to look great or be perfectly smooth, it can be a rough and ready finish, I just want it to last and be strong enough to carry a decent weight of shelving.
Any suggestions for products and techniques very welcome! Thanks.