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close this bookAttic Completion Work - Course: Timberwork Techniques. Trainees' Handbook of Lessons
close this folder3. Building-in of Roof Superstructures
View the document3.1. Building-in of Roof Superstructures in a Couple Roof
View the document3.2. Partition of Rooms in the Attic
View the document3.3. Covering of Visible Roof Rafters in the Room and of the Roof Superstructure

3.2. Partition of Rooms in the Attic

The rooms to be built into the existing space under the roof (attic) must be limited in their floor space and height. With a purlin roof, the length, width and height of the rooms are not optional but depend on the supporting structure of the roof.

Figure 16 Partition of rooms in the attic

1 king post, 2 trussed purlin, 3 stair landing, 4 staircase, 5 partition walls of rooms, 6 partition wall for attic walkway, 7 door to be built in, 8 opening direction of door

Any king posts and struts in the attic are fixed points for the partition of rooms since supporting structural parts must not be removed or interrupted.

Existing angle braces can be covered or included in the partition of rooms.

Why must supporting structural parts not be removed or interrupted?


Upper limitation of rooms

If purlin roofs have no valley beams, wooden beams must be built in for fixing of the subceiling. The wooden beams are to be placed and fixed on the trussed purlin.

Figure 17 Fixing of wooden beams

1 Trussed purlin, 2 wooden beam, 3 steel square, 4 additional rafters, 5 protection against trickling matter (faced particle boards)

Steel squares with boreholes are recommended for fixing the wooden beams to the trussed purlins by means of hexagon-head wood screws.

Fixing to the trussed purling is necessary to prevent any displacement of the wooden beams or lift-off when the subceiling is nailed from below.

The distance of the wooden beams to be built in must not exceed 1000 mm.

The cross section of the wooden beams depends on the span between the trussed purlins.

With a wooden beam distance of 1000 mm, a span between the trussed purlins of 4000 mm and no top ceiling, a beam cross section of at least 100 cm2 will be required.

If the spans between the trussed purlins are greater or if a top ceiling is to be provided in order to make use of the room above, a top beam can be built in to reduce the span. Otherwise the cross sections of the wooden beams must be statically verified.

Figure 18 Built-in top beam

1 trussed purlin, 2 wooden beam, 3 top beam, 4 machine bolt l span between purlins

The wooden beams and the top beam are to be connected with machine bolts.

For safety reasons, static calculations are also required for the top beam!

In order to make the subceiling as light as possible, it is recommended to use faced particle boards.

Whether the particle boards can be directly fixed to the existing valley beams or built-in wooden beams or whether additional rafters will be required, depends on the working/processing instructions for the particle boards used.

Wood-wool slabs are not recommended because they need to be plastered which would result in additional load on the wooden beams. If sound or heat-insulating measures are required, insulating mats are to be placed on the particle boards or other types of protection against trickling matter used.

At the existing valley beams or built-in wooden beams the insulating mats are to be placed upwards and to be fixed with wooden strips.

Figure 19 Mounting of sound-insulating mats

1 wooden beam or valley beam, 2 protection against trickling matter, 3 additional rafters, 4 sound-insulating mat, 5 lath, 6 nail, 7 longitudinal side of insulating mat

If the mats are not wide enough, they are to be placed so as to overlap at their longitudinal sides by at least 100 mm, thus avoiding sound or thermal bridges.

Lateral limitation of rooms

Laterally the rooms can be limited by partition walls with king posts and struts being fixed points.

The king posts can be used for stabilization of the partition walls by fixing the wall covering (facing) directly to them. Between the king posts a framework will be required to hold the wall covering.

The thickness of the partition wall depends on the dimensions of the king posts.

Door openings are to be provided in the partition walls for access to the living rooms in the partitioned attic.

The partition walls inserted to permit use of the attic for housing purposes must, in any case, have sound insulation.

Why must the living rooms in the attic have sound insulation?


For sound insulation the partition walls are to be provided with sound-insulating material. Textile fibre mats, mineral wool mats or glass wool mats are recommended as sound-insulating material. When mounting the sound-insulating mats it is to be made sure that no sound bridges are produced.

Why must no sound bridges be produced when mounting the sound-insulating mats?


To avoid sound bridges, the sound-insulating mats are to be placed so as to overlap at the heading and framing timbers of the framework for the wall covering and are to be fixed with laths.

When mounting the sound-insulating mats, special care is required at the top connection in the area of the ceiling. Here, too, it is indispensable to fix the insulating mats with laths at the transom of the framework, at the trussed purlin, if used, at the valley beam or built-in wooden beams.

Neglect of fixing to the timberwork would result in a waste of material, money and labour employed in the entire sound-proofing measure.

When mounting the wall covering, it is to be made sure that no openings are left to provide access for animals who prefer to live in textile insulating materials and would destroy the insulating mats, thus making the sound insulation ineffective.