Due to the decorative nature of architrave and the moulding family in general, there are countless specific methods of installation and assembly. In a very literal sense, trained operatives and DIYers alike can very much “make it up as they go along”. This is especially true due to the fact that a large variety of different trims and mouldings are available from most DIY merchants, making it very accessible to homeowners that are looking to renovate their own homes. As such, we as operatives can sometimes come across interesting and unique styles of architraves. Whilst there exist many different styles, for the most part they are all installed following the same general principles. Here we will look at the general premise of architrave and casings, and some of the variations and specific terminology that we may encounter.

Mitred architrave

In the UK, this type of architrave is by far the most common and generally accepted style of lining finish in residential and commercial properties alike. This method sees moulding installed around the lining, with corners being mitred to allow the moulding to seamlessly transition as a change in direction occurs. To install this style is as follows. Start by marking the margin around the door to use a reference for the installation of the pieces. This quirk should be at least wide enough so that the knuckle of the hinge does not interrupt the moulding. A suitable margin of 10mm, or  ⅜” all round is applicable in most scenarios. This quirk can be marked easily with a combi square set to the desired distance, or through the use of a custom jig. The quirk should be marked in the two top corners, and at intervals down the lining to provide a registration mark for keeping the moulding straight during installation. With the margins marked we can begin to cut the legs and the header.

For most common types of MDF moulding, lengths at 5.4m can be readily purchased from suppliers. These lengths are long enough to provide 2 standard sized legs and 1 regular head for a standard internal door lining, making it easy to calculate how many lengths must be purchased. Some merchants provide lengths at 2.1m, which are easier to transport, and each length will provide 1 leg or 2 heads. We begin by cutting the legs to an approximate length, a few inches longer than desired. If many linings are being faced with architrave then cutting all of the lengths to an approximate size and leaning them in place against the wall can aid in efficiency. Once the lengths are cut, we can mark each length accurately by placing against the lining, in relation to the quirk marks made previously. The intersection of the header and leg quirk marks represents the shortest point of the lengths, and it is at this point that the internal corner of the mitre meets. With the lengths in the correct orientation and butted hard onto the floor, make a fine mark where on the inside of the moulding where this intersection occurs. A line can ticked on the face of the moulding to indicate the direction of the mitre - just as a visual precaution.

A chop saw station with enough room to freely manoeuvre the long lengths is optimal for cutting the mitres, though a hand saw can be used if precision is maintained. If the linings are installed correctly, then all of the cuts should be a true mitre at 45 degrees. set up at this point is very useful and effective. Each leg can then be cut with the mitre facing in the correct direction. It’s optimal to cut the legs a millimetre or so short, so that the short side of the mitre can be ever so slightly lifted off the ground to meet the intersecting quirk lines during installation. A mitre can also be cut on the end of the header. This head piece can be taken to the lining, and the mitre can be lined up with the intersecting quirk lines, so that the other end can be marked. Once marked, the other mitre can be cut, and all of the pieces can be taken back to the lining. A check should be made to ensure that all of the lengths are correct, and do not protrude past the intersecting quirk lines.

To install the set of architraves, a few approaches are available. Traditionally, before the introduction of modern adhesives, the lengths were fitted to the wall one by one, with lost head nails being used to attach the lengths to the timber lining. Wood glue was placed on the surface of the mitres, and additional nails were inserted through the corner of the joint to prevent movement over time. Whilst this method has produced countless sets of suitable architraves over the years, there are a couple of drawbacks that can be overcome with modern products.

The installation of the pieces one at a time can be time consuming, and trying to keep the components in the correct alignment with one another during installation can be difficult for beginners. Uneven wall surfaces can make this method particularly difficult and laborious, even for seasoned carpenters. To speed up the process, and ensure a perfect result every time, modern mitre adhesives can be implanted instead. These products, which are sold as a bottle of what is essentially super-glue and a can of spray accelerator to speed up the process of the glue drying, can be use to assemble the architrave on the ground. By placing all of the pieces on a flat surface, adhesive can be applied to the mitres, and each joint can be securely fastened together with more precision then attempting the process on the wall. Nails can still be installed through the corner of the joint to offer a failsafe in the event that the glue gives way over time, though these adhesive products are designed specifically for bonding timber materials together. If the mitres are cut at true 45’s, then provided the joints are making full contact during gluing, the set will be perfectly square when assembled. The accelerator provided with the adhesive allows the glue to set within seconds, allowing for rapid assembly.

Once the set is assembled on the ground, standard construction adhesive can be applied to the intersection of the wall covering and the door lining, to provide additional hold to the set once installed. The set can be lifted into place, and adjusted with the quirk lines. Whilst lifting, the set can be a little fragile at the joints, though if fully supported no issues should arise. With the set in place on the lining, the mitres can be pinned off first. This will ensure that any adjustment to the lower portion of the legs will not pull the mitres apart. Second fix brad nails are installed through the moulding into the edge of the timber lining, with the adhesive behind attaching the moulding to the wall surface. With an appropriate amount of nails installed down each length and across the head, the process can be repeated on the other side of the lining. 

Craftsman casings

Craftsman casings are a type of window/door casings that are assembled from multiple components to produce an intricate and detailed header. Whilst this style of architrave/door casing is more commonly found in American homes, this period aesthetic can still be found in stately homes within the UK. It is also beginning to see a re-emergence in larger new builds due to the pioneering trends of US construction. Despite the ornate appearance, the assembly of these types of casings are relatively simple. This being said, the range of components involved can range from few to many. Here we shall look at some examples of craftsman style casings.

Rosettes and corner blocks

Rosettes and corner blocks were utilised for centuries in higher end construction, and are still used today in the assembly of some casings. More often associated with period and stately homes, they can provide an interesting aesthetic to a set of casings. Traditionally carved by hand, rosettes can be purchased from speciality manufacturers in milled timber or formed MDF varieties. The designs within can range from simple geometric patterns to intricate carved designs, with some historical examples displaying carved flowers and even animals/carved figures. In modern carpentry, rosettes and corner blocks are installed in lieu of a standard mitre joint where the leg and header of the casing meet. Rosettes as we understand them within carpentry have evolved over time to mimic the thematic building styles of ancient cultures. Rosettes and entablatures feature prominently in architecture across multiple historical cultures, such as the Greeks, Romans, and Sumerians.

Entablatures

In an all encompassing definition, an entablature is a collection of horizontal mouldings that are assembled in a decorative manner, typically sat above vertical pillars or supports. Whilst this is mostly associated with stone masonry and historical architecture, this term also applies to the horizontal assembly of moulding involved in the creation of intricate craftsman style casings. Here we shall look at the different components of an entablature, and some common examples and how they are implemented.

Fillets and beads

Fillets and beads are thin moulding strips that are installed over or between the transitions between other larger components. These fillets are decorative mouldings, typically rounds or chamfered lengths, that are found specifically between the legs of the architrave at the beginning of the entablature, and between the central frieze and the crown moulding.

Friezes

A frieze is the central wide length of timber that forms the bulk of the entablature. Typically, it is just a regular piece of square planed timber, though it can be shaped or carved to feature more decorative elements. The frieze sits either directly atop the legs of the architrave, or on top of the architrave bead/fillet that sits atop the legs.

Caps and crowns

These terms can be used interchangeably, and both describe the decorative moulding that sits at the top of the entablature, on top of the frieze. To give the correct aesthetic, the crown moulding typically overhangs the frieze, and is the widest part of the total architrave assembly. The transition between the crown moulding and the frize is typically softened by a decorative fillet.

Plinth blocks

Plinth blocks are timber components that are installed at the bottom of door casements to provide an aesthetic transition between the skirting boards and the architrave. These blocks are typically wider than the architrave and taller than the skirting, creating a wide feature piece that receives both of the mouldings. The plinth block itself can be plain or machined in a decorative manner.