BUILDING ELEMENTS  FOR LIGHTWEIGHT TIMBER STUD STRUCTURAL FRAMES

 

Murat Aygün, Ph.D,  Hülya Kuş, Ph.D.

Division of Building Construction, Department of Architecture

Istanbul Technical University

 

 

 

The earthquake of Kocaeli 1999 has brought about an increase in the employment of  timber frames in some upmarket residential projects for high-income property buyers in Turkey.

These frames provide a lightweight structure with elastic behavour for earthquake safety. The structure comprising prefabricated timber panels enable short erection times to be achieved with simple assembly methods in comparison to in-situ reinforced concrete frames by obviating the need for formwork, curing and multiple work trades. Absence of cold bridges and low risk of condensation due to the inherent properties of timber contribute to the overall performance of these frames.

Adversely, fireproofing measures as supplementary layers or treatments are required for providing fire safety to the timber frame. Further restrictions are the limited openings and floor spans as well as the number of storeys that can be obtained, imposing constraints on architectural design and building function. Precautions are also required against woodpests and woodrot, mostly applied as chemical treatments.

The lightweight timber frame consists of various distinct components. Studs and braces with slender sections are coupled with sheathing boards such as OSB, plywood, fibre cement, on the outside as vertical structural members for walls. Studs are connected to rails at the top and bottom. Joists with the same sections provide support to floors in the horizontal plane. The bottom rail rests on the sole plate acting as the interface between the timber structure and the reinforced concrete foundations.

There are three main types of junctions between structural components of the frame: Single-rail, double-rail and baloon frame. The components are connected to each other by mechanical means, i.e. nails, screws, bolts, gang nails and gusset plates.

Thermal insulation is located at one or more of the three positions relative to the stud in the wall section, i.e. outside, inbetween or inside the studs. In the case of the insulation inbetween the studs, the space should be filled tightly with no gaps remaining, hence flexible or semi-rigid materials are selected, e.g. rockwool, glasswool, as opposed to the external and internal locations where rigid materials are preferred, e.g. polymers, glass foam,  to resist compression by the subsequent layers. A breather membrane is laid outside the sheathing boards, for allowing vapour to escape outside while preventing penetration of moisture to inside.

 

1          External walls

1.1        External walls at ground floor

 


1.1.1       Single rail external wall on sole plate on reinforced concrete strip foundation with external waterproofing membrane

 

 

1.1.2       Double rail external wall on sole plate on strip foundation with external thermal insulation and waterproof membrane

 

 

1.1.3       Baloon frame external wall on sole plate on strip foundation

 

 

1.2        External walls at intermediate floor

 

 

1.2.1       Single rail external wall with external and central thermal insulation and external render finish

 

 

1.2.2       Double rail external wall with central thermal insulation and horizontal lapped cladding strips

 

 

1.2.3       Balloon frame external wall with internal and central thermal insulation and external slip bricks

 

2          Floors

2.1        Raised ground floors

 

 

2.1.1       Single rail raised ground floor joists with thermal insulation inbetween and floor boards

 

 

2.1.2       Double rail raised ground floor joists with thermal insulation inbetween and floor boards

 

 

2.1.3       Baloon frame raised ground floor joists with thermal insulation inbetween and floor boards

 

2.2        Intermediate floors

 

 

2.2.1       Single rail intermediate floor  joists with thermal insulation inbetween and floor boards

 

 

2.2.2       Double rail intermediate floor joists with thermal insulation inbetween and floor boards

 

 

2.2.3       Balloon frame intermediate floor joists with thermal insulation inbetween and floor boards

 

2.3        Cantilevered floors

 

 

2.3.1       Cantilevered upper floor joists supported by top rail of external wall with cladding layers extended along the soffit

 

 

2.3.2       Cantilevered upper floor joists supported by top rail of external wall with cladding layers extended along the soffit

 

 

2.3.3       Cantilevered upper floor joists supported by top rail of external wall with cladding layers extended along the soffit

 

2.4        Balconies

 

 

2.4.1       Balcony with floor joists projecting beyond the external wall and with strips of floor boards

 

 

2.4.2       Balcony with floor joists projecting beyond the external wall and with strips of floor boards

 

 

2.4.3       Balcony with floor joists projecting beyond the external wall and with strips of floor boards

 

3          Roofs

3.1        Sloping roofs

 

 

3.1.1       Sloping roof with cladding on battens on thermal insulation on waterproof membrane on roof deck on rafters supported by eaves purlin on ceiling joists

 

 

3.1.2       Sloping roof with cladding on battens on thermal insulation on waterproof membrane on roof deck on rafters supported by eaves purlin on ceiling joists

 

 

3.1.3       Sloping roof with cladding on battens on thermal insulation on waterproof membrane on roof deck on rafters supported by eaves purlin on ceiling joists

 

3.2        Flat roofs

3.2.1       Flat roofs with eaves

 

 

3.2.1.1     Flat warm roof with waterproof membrane on tapered thermal insulation on vapour barrier on roof deck on joists with eaves projection

 

 

3.2.1.2                        Flat cold roof with waterproof membrane on tapered thermal insulation on vapour barrier on roof deck on joists with eaves projection

 

 

3.2.1.3                        Flat roof with waterproof membrane on tapered thermal insulation on vapour barrier on roof deck on joists with eaves projection

 

 

3.2.2       Fat roofs with parapets

 

 

3.2.2.1                        Flat roof with coping board and parapet walls formed by short studs on top rail of external wall

 

 

3.2.2.2     Flat roof with coping board and parapet walls formed by short studs on top rail of external wall

 

 

3.2.2.3                        Flat roof with coping board and parapet walls as an extention of the external wall studs