Plaster or Drywall, which should you choose?

PLASTER OR DRYWALL

(e.g. For historic accuracy choose plaster instead of drywall when replacing walls in 1930′s vintage home).

Drywall guys will tell you they can match any texture, but drywall is still very different from plaster. Before you dive into hanging drywall in a vintage or high-end home, consider the alternative of plaster.

Plaster vs Drywall

These days you have two general options when it comes to finishing walls: the first is standard drywall, which we’re all pretty familiar with. It’s everywhere, and so is the dust from installing, sanding and finishing it. Drywall consists of gypsum sheets (sheetrock) screwed or nailed to the studs. Drywall compound and tape are applied to the seams between boards, and the compound is also coated over the fasteners to cover up the heads. A high-end level 5 drywall finish includes a final skim coat similar to a plaster job, but most drywall jobs aren’t done at that level. Even when they are, the finish durability is still underwhelming when compared to cement-like plaster.

Modern plaster, on the other hand, is typically applied over a special type of wall board referred to as blue board. 

The old style was usually applied over lath, but that method is exceedingly rare these days. 

Blue board looks like Sheetrock (other than the color), but it’s designed to handle the high degree of moisture in wet plaster, and it’s engineered to create a tight bond with the plaster compound. 

The plaster is applied over the blue board either in multiple coats with a scratch and then finish coat (a more traditional style), or in a single or double veneer coat. 

Either way, the plaster covers the entire wall surface. 

Don’t confuse blue board with green board, (green board is typically for bathroom and not made for plaster).

Many people consider plaster finishes to be more high-end than drywall, and they have seen a surge in popularity.

I think mainly because of the unique expertise required

(There is on average 1000 Drywall installers to every plasterer).

Plaster projects tend to cost a bit more but are worth the investment.

What type of plaster should you use?

What is Plastering?

Plastering is a process used to produce an acceptable final wall or ceiling finish to a building prior to decoration. A substrate is the surface to which the plastering system is to be applied.

Backing coats which cover the substrates are between 9mm and 40mm thick under normal circumstances and the overall thickness can be built up in coats as is necessary.

Ceilings and Partitions

In older building, these areas are covered in a layer of timber laths which are plastered over.

When strength is required, a thin steel sheet mesh called expanded metal lath is fixed in place and then plastered over. In contemporary fast-track work plasterboards are fixed in place, the joints taped with a fibre mesh tape (scrim) to prevent cracking and then skimmed over with a finishing coat of a gypsum plaster.

Plasterboards

Basic plasterboard is a flat sheet of gypsum between 9mm and 12.5mm thick, sandwiched between sheets of durable paper. Boards are also available with various backings of differing thickness to improve insulation, restrict the passage of water vapor and to protect against fire. It has become common practice to bond or fix plasterboards to substrates to serve as the backing plaster coat. This method is known as dot and dab or drywall.

Finishing Coats

Finishing coats are usually between 3mm and 5mm and bring the backing coats to a smooth skim finish. Finishing plasters used to produce these setting coats are available as premixed gypsum plasters. Finishing coats can also be lime putty and fine sand or a mixture of lime, sand and gypsum known as gauged setting stuff.

Solid Plastering

Solid plastering denotes backing coats of a paste or mortar-type consistency comprised of an aggregate and a binding matrix. Binders include lime, gypsum and cement. Aggregates include sand, vermiculite and perlite.

Choosing a Plastering Material

Lime plasters are compatible with old buildings containing slight dampness. They are said to breathe, which means they allow moisture to evaporate from the wall before it shows as damp patches. It is always worth considering why moisture is present in the wall in the first place?

Gypsum plasters set much quicker than lime plasters, so speed up waiting times between coats. In cold conditions gypsum backing plasters can take a long time to dry. Gypsum backing plasters (and this includes standard plasterboards) should never be used on damp walls. Gypsum plasters are compatible with dry brickwork or blockwork, preferably to internal surfaces of cavity wall construction.

Cement-based plasters or renders have their uses, they can be gauged with lime and used externally, and can be useful for waterproofing and tanking. Strong mixes can pull away from weak backgrounds and are brittle – cracking if slight movement of the building occurs, they can also be cold and attract condensation.

Ornamental Plastering

Decorative plasterwork has a long history. Mouldings were originally run in-situ with ornaments cast in carved boxwood, pear-wood  or hard plaster and gelatine moulds using composition materials and gauged setting stuff. At a later date fibrous plastering techniques arrived, first used in France, the technique involves the use of Plaster of Paris with hessian/canvass scrim to reinforce casts and timber laths to assist fixing. With some timber, sheet steel, moulding compounds and a few bags of casting plaster, all manner of ornamental plasterwork can be created.

WHAT IS A PLASTERER?

Plasterer

The Plasterer is a skilled craftsman who can spread plastering materials over a *substrate* producing a finish as required by the client.

Although plaster can be projected onto walls with pumps or sprays and one-coat plasters are available, most high class work still applied by the plasterer using hand tools in 3 coats consisting of  a scratch coat to even out suction, a float coat to give an even surface and a finishing coat to produce a smooth finish.

 
*The word substrate comes from the Latin sub - stratum meaning 'the level below' and refers to any material existing or extracted from beneath the topsoil, including sand, chalk and clay. The term is also used for materials used in building foundations or else incorporated into plaster, brick, ceramic and concrete components, which are sometimes called 'filler' products.