Sofa Frame Construction: Its Importance in Upholstery

Sofa frame and general furniture construction is a very important factor in upholstery and upholstered furniture. Most people look at a beautifully upholstered sofa or armchair and do not see what lies beneath it. The same is true of a human being. The external appearance of a person is determined by the muscles that lie beneath the skin. These muscles are no stronger than the skeletal bone structure upon which everything else is built.

The skeleton of a sofa or a chair is its wooden frame. We are discussing traditional furniture here, not items fashioned from tubular steel and synthetic foam cushions. A sofa frame must be solid in order to bear the stresses and strains involved when it is put to use. For a sofa to be comfortable, it must be able to tolerate these stresses without sagging.Furniture Construction: The Sofa FrameWhat applies to a sofa frame also applies to a chair. The sofa frame must be constructed from solid wood. The wood should not be so hard that it cannot accept blue upholstery tacks. Frames which are joined with nails or glue tend to be weak and have only a limited life. The strongest wooden sofa frames are constructed using traditional jointing techniques.

The main rectangular frame should be formed using thick solid wooden beams, joined at each corner with mortise and tenon joints. Dowel-reinforced butt joints will eventually come apart, and dovetails joints are unsuitable for this type of thick framework. The wood has to be thick for two reasons: a) it must hold the weight of those sitting on the sofa, and b) it must offer a strong base for tacking on the webbing holding the springs and the covers.The sofa frame will act as the skeleton for the entire sofa, supporting the seat, the back and the arms. It is often crafted from oak or occasionally a dense form of softwood such as certain species of pine. This framework is the most important aspect of furniture construction.

The Sofa Seat

The seat of the sofa will traditionally be supported on a layer of woven webbing. Upholstery webbing strips of 2″ or 5 mm width are tacked to the side, front and back frames and woven across and lengthwise. The lengths are fixed to the frame using ¾ inch upholstery tacks. A web stretching tool is needed to get the webbing to the correct tension.Steel coil springs are then tied to the webbing using upholstery twine. The tops of the springs are connected using lengths of upholstery spring twine tied to the top of each spring. Each spring is tied to its neighbor using the same length of twine. They are tied eight ways, connecting all the springs together and the lengths of twine are tacked to the side, back and front rails of the sofa.

A canvas cover is then placed over the springs, stretched out and tacked to the side rails. The layers of stuffing and padding are then added followed by a second layer of canvas to hold everything together. Finally, the top upholstery cover is stretched over and tacked onto the side rails.You can now see the importance of furniture construction, and why the rails of the sofa frame have to be so strong and well jointed. They are holding every layer of the seat including the springs, and have a large number of upholstery tacks hammered into them. The rails then have to bear the weight of at least two people, or even more for a larger sofa.

The Sofa Back

At one time, the back of the sofa was constructed and upholstered in exactly the same way as the seat, but using shorter springs. However, to save time, a box spring construction is now used. The springs are held in a metal framework which is nailed to the back frame. This method can be used because the back has less weight to bear than the seat.The upholstery layers are then added and tacked to the back frame as normal. The back frame need not be as strong as the seat, and the wood used is generally of lower dimensions all round. However, the joints of the back to the seat and arms must be strong to prevent the back frame from collapsing back.


A sofa frame must be made from strong, thick wooden beams and crossbars. They must be correctly jointed together using mortise and tenon joints, because they have a lot of weight to bear and also a large number of upholstery tacks to accommodate. The wood cannot be too soft or the tacks will not hold, nor too hard or the tacks will fail to penetrate. Oak, cherry and certain species of pine are fine.Furniture construction is very important in upholstered furniture. Unless it is sufficiently strong it will not have the required strength. The sofa frame must last over 100 years and tolerate multiple reupholstery episodes. The springing, if correctly carried out, should itself last over 100 years. Only the padding and top covers should need replacing in a well constructed sofa or chair.