Plasterwork: Tools, Materials, and Methods of Plastering
Plasterwork is essentially the construction or beautification done with plaster. Common examples are the layers of plaster on an interior or exterior wall structure or plaster decorative moldings on ceilings or walls that are found in buildings all around us. This is also referred to as pargeting. The course of creating plasterwork, called plastering or rendering, has been used in building construction for centuries.
Plaster Tools and Materials
When it comes to plastering and plasterwork the key tools and materials include but are not restricted to:
- scratching tools
- utility knives
- lath nails
- plaster of Paris
- A variety of cement, and various ingredients to form color washes.
For the most part, most of these tools have lasted for a long time but innovations have changed some of them.
- Trowels used to be made from steel, but are now made from a polycarbonate material which allows for the application of some new, acrylic-based materials without streaking the finish.
- Floats were made of timber (preferably straight-grained, knot-free, yellow pine), but are now usually finished with a coating of sponge or stretched out polystyrene.
- Laths were the traditional surfaces plaster was laid on, rather than plasterboard as is more commonplace nowadays.
Wooden laths are narrow strips of straight-grained wood depending on the available species in intervals of from two to four or five feet to accommodate the gaps at which the timbers of a floor or partition are set. Laths are usually an inch wide, and are made in three thicknesses; single (1⁄8 to 3⁄16 inch thick), lath and a half (1⁄4 inch thick), and double (3⁄8–1⁄2 inch thick).
Lathing in metal, either in wire or in the form of perforated galvanized sheets, is now greatly used on account of its fireproof and lasting quality. There are many kinds of this material in varying designs, the best known in England being the Jhilmil, the Bostwick, Lathing, and Expanded Metal lathing. The two last-named are also widely used in America. Walls liable to damp are sometimes battened and lathed to form an air cavity between the damp wall and the plastering.
Lathing nails are traditionally made of iron, cut, wrought or cast, and in the better class of work, they are galvanized to counteract rust. Zinc nails are often used but are more expensive.
Lime plastering is composed of lime, sand, hair, and water in amounts varying according to the nature of the work to be done.
The lime mortar typically used for interior plastering is that calcined from chalk, oyster shells or another almost pure limestone, and is known as fat, pure, chalk or rich lime. Hydraulic limes are also used by for plastering, but mainly for external work.
Total slaking of the calcined lime before use is very important as, if used in a somewhat slaked form, it will “blow” when in position and ruin the work. Lime should be run as soon as the building is begun, and at least three weeks should pass between the operation of running the lime and its use.
Hair is used in plaster as a uniting agent and gives grit to the material.
Horsehair was the most commonly used as a binding agent, as it was readily accessible before the development of automobiles. Hair operates in much the same way as the strands in fiberglass resin, by controlling and inhibiting any small cracks within the mortar while it dries or when it is subject to flexing.
Ox-hair, which is sold in three qualities, is now the kind usually recommended; but horsehair, which is shorter, is occasionally mixed with the ox-hair in the lower qualities. Good hair should be long and oiled with lanolin grease which protects against some spoilage when introduced into the very high alkaline plaster. To separate the lumps before use, it must be well beaten or teased. Many types of hair and other organic fibers can be found in historic plasters which shows that hair reinforcement in lime plaster was and is a common practice. It is important to note that damp environments degrade organic material in lime. This problem is what gave rise to the utilization of cellulose wood fibers and polypropylene fibers in the new lime render.
Manila hemp fiber has been generally used as a substitute for hair. The mortar containing the Manila hemp shows greater cohesion and requires some effort to pull apart with the hemp fiber being undamaged than the mortar containing hair. A test was carried out with two barrels of mortar, one of which was made with goat hair and the other with Manila hemp fiber. After several months, the barrels were examined and it was discovered that the mortar made with Manila hemp fiber had more cohesion.
For refined plasterer’s sand-work, special sands are used, such as silver sand, which is used when a light color and fine texture are entailed. In England this fine white sand is procured chiefly from Leighton Buzzard; also in England, many conventional plasters had crushed chalk as the aggregate, this made a very compliant plaster suitable for timber frame buildings.
On account of its strength, durability, and weather resisting external properties, Portland cement is undoubtedly the best material for external work. However, it is not suitable for historic structures that are expected to flex and breathe; this is mostly when lime without cement is used.
Sawdust has been used as an alternative for hair in the place of sand as an aggregate. Sawdust will enable mortar to endure the effects of frost and rough weather. It is particularly effective sometimes for heavy cornices and similar work, as it makes the material light and strong. The sawdust is best used dry. The sawdust is used to unite the mix and to sometimes, make it go further.
Methods of Plastering
Skimming is part of plastering work which is carried out by applying a thin two-coat method for smoothing walls. Finishing process of plastering will further be executed on walls or ceilings to create a smooth finish for painting or wallpapering.
A wet dash finish is achieved by applying 5-13 mm coarse aggregate in the final coat. The simplicity of the activity takes place when the mortar is being flung onto the wall and left untrowelled.
Plasterboard is also known as drywall, wallboard, gypsum board, are used for interior walls and ceilings. Plasterboard is sold and distributed under the trademarks Sheetrock and Gyproc across Cleveland and the United Kingdom. We can also insulate your walls and home for better heat efficiency through the use of insulated plasterboard. This is particularly useful when refurbishing Victorian properties in Cleveland and North Yorkshire.
Roughcasting or pebble-dash is a coarse plaster surface normally used on external walls that consist of a lime compound and usually is a mixture of sand with cement, or can be small gravel, pebbles or shells.
Artex can be plastered over. Firstly we absolutely make sure that there is no flaking or lose sections of the Artex, or indeed ceiling/wall. Then we remove all obviously visible high spots of Artex.
Suspended ceiling, office partitioning, installation of a new ceiling, repair of the damaged ceiling, maintenance of existing ceiling, and design advice
K-rend/weber in different colors (exterior plastering with beautiful finishing-no paint required after finishing). Interior or Exterior Rendering. As well as Float and Set.