Due to the required height of the attic rooms 2,50 m and from practical experience shows, that hipped roofs with a slope of the roof below 35 ° do not make it practically possible to develop the attic for residential purposes. On the other hand, the use of attics is possible in hipped roofs with knee walls, tj. with thinned outer walls protruding above the attic floor.

The shape of the usable space for attic apartments depending on the type and structure of the roof: a) trusses of rafter or collar beam structure (complete use of the attic), b) trusses of collar beam construction – cold, unventilated part of the attic above the collar beam, c) roof collar with cold, unused eaves space, d) a purlin-tongs structure or a collar without using the ridge and eaves space, e) a roof with a purlin-tongued structure with knee walls, unused ridge space above the ticks, f) mono-pitched roof with full use of the attic; 1 – rafter, 2 – mayfly, 3 – mayfly or ticks, 4 – ticks, 5 – walled, 6 – usable space, 7 – ventilated ridge space, 8 – ventilated space near the eaves (enemy)

For the use of the attic for residential purposes, steep gable roofs and gable roofs with a knee wall are best suited.. Unfortunately, the reconstruction of an existing attic for residential purposes is often difficult or impossible also in the case of a gable roof due to the presence of numerous poles on it., struts, swords, hangers in the structures of complex roof trusses. Any changes to the structure of the truss in order to obtain the usable space in the attic require an engineering solution in each case. The most convenient conditions for use for residential purposes without changing the supporting structure of the roof are provided by the trusses built on the basis of rafter trusses., collar and purlin- on these roofs, in order to get as much space as possible, all the diagonal planes from the eaves to the ridge are usually used as walls or ceilings (for. Lynx. a). Low attic space near the eaves near the external longitudinal walls of the building, also often called a niche or a nook, should be used. The enemy's space can be used for wardrobes, lockers, e.t.c. or use them for heating installations. In the central space of the attic, the height of the residential rooms can be increased by including the entire height of the attic up to the ridge into the cubature of the rooms. (for. rys.a i c).In this case, a ventilated slotted flat roof is made above the living room on the sloping roof slopes from the eaves to the ridge of the roof. Trusses with a rafter structure provide full use of the attic space (for. rys a). The trusses of the collar-beam and purlin-tongued structure enable its partial use (for. Lynx. b, c, d). Trusses with a purlin-tick structure with knee walls provide better possibilities of attic development in the part near the eaves (for. Lynx. e). A single-pitched shed roof with a suitable height of knee walls enables full use of this space for residential purposes (for. Lynx. f).