Wooden constructions for living and recreation

architect: ADR Ltd.,
project processor: AED project, a.s.
client: RAS-REKONSTRUKCE A STAVBY, s.r.o.
implementation project, supply and installation of wooden structure: TAROS NOVA Ltd.
materials: glued laminated timber GL24h - Si, stainless steel ČSN 17 240 (WNr. 1.4301).
implementation time: 2012

SHORT DESCRIPTION OF THE HOUSE
It is a brick building with a reinforced concrete basement and ceilings, with a rectangular floor plan of 15x7 m extended by two additional rectangular floors making up the garage and living room. The adjacent parts of the house have a flat roof. The main part has a gable roof with a slope of 35°.
The wooden facade structure consists of frames made of profiles 100/200 mm with a clear gap of 100 mm, which follow the outline of the house at a distance of 185 mm. The frames are supported by stainless steel joinery elements, which rest on the roof and are anchored using chemical anchors into the reinforced concrete crowns of the load-bearing structure or concrete blocks additionally created in the masonry.

WOODEN STRUCTURE

The load-bearing structure can be divided into: a) main load-bearing structure – straight pipes made of stainless steel resting on joinery elements (which are firmly connected to them) supported on the ridge, at the level of the eaves and anchored to reinforced concrete crowns, or concrete blocks in the masonry,
b) secondary structure – glued straight beams (rafters and columns) forming frames supported and fastened to the straight pipes of the main load-bearing structure,

Main load-bearing structure: straight beams at 5 height levels made of TR-76,1/3 pipes - stainless steel, which are part of the fittings, statically act as continuous beams. They are divided into dilation units of a maximum of 6 m. The steel beams are supported at the gables overhang on the last structural rafter of the roof structure, which is the last support. Between the outer supports, they are supported every 0.6 - 2.3 m, depending on the position of the rafters, most commonly at distances of 2.4 and 2.6 m.
On the main load-bearing structure, there are glued straight beams 100/200, GL24h with a 100 mm gap. The facade is exposed to all weather effects, the wood used for the individual frames is Siberian larch, glued for use class 3, only colorless impregnated. Due to non-typical use, it is recommended that the wood be constantly ventilated - this is fundamental for the structural protection of the wood, as it is essential to maintain the space between the wooden elements passable (risk of increased swelling of the wood and subsequently defects due to rapid drying of the surface layers of the wood - the consequence is the formation of drying cracks and deformation). Due to chemical reactions, no objects should be secured to wooden elements using anything other than stainless steel. Considering the material used (stainless), the steel elements are maintenance-free.

INSTALLATION
Due to the thermal insulation of the house, the joinery elements had to be divided into a part that was embedded before the thermal insulation, and into which a second visible part supporting the wooden frames was then inserted and secured.
The ease of disassembly of the structure was the main requirement during the design of the structure, along with the simplicity of details due to weather influences. However, these requirements complicated the installation, especially the demands on the precision of the manufactured wooden elements. Stainless steel has worse mechanical properties for design than classic steel. For this reason, it was necessary to "add reinforcement" to the protruding parts with inserted steel pipes. The connection of the wooden frames to the stainless steel structure is realized with a dowel joint with internal metal plates. And finally, it is a unique facade in the world.

Architect: atelier dwg, s.r.o.
Statica: Brno University of Technology, Faculty of Civil Engineering, Institute of Metal and Timber Structures
Client of the wooden structure: VCES a.s.
Implementation project, supply and installation of wooden structure: TAROS NOVA Ltd.
Materials: glued laminated timber GL24h, timber – quality class S10 (strength class C24), steel S235, S355
Implementation time: 2011-2012

INTRODUCTORY FACTS AND A BIT OF HISTORY

Friesovy Boudy are located at an altitude of 1200 m in the central part of the Krkonoš between the resorts of Špindlerův Mlýn and Pec pod Sněžkou. The mountain lodges are situated outside the main tourist centers, providing a peaceful environment for vacations.
The first mention of Friesovy Boudy is in the Vrchlabí land registry from 1676, when Jiří Fries received permission to build a lodge. The lodge keepers were engaged in forestry, livestock farming, dairy production, and haymaking. The original building of the Andula accommodation facility was demolished, including its foundations, and immediately afterward, a new wooden structure of the mountain guesthouse began to be built on its site, which this article discusses.

GENERAL DESCRIPTION
The Andula building has a rectangular floor plan measuring 17x37 meters. It is partially basement and consists of two floors and a residential attic covered by a gable roof with a slope of 40° and a ridge height of 12.5 m. The structure primarily has a load-bearing system made of GL24h glued laminated timber.
The load-bearing structure of the building cannot be classified as conventional wooden structures of multi-story buildings. It is notably characterized by high load intensity and thus corresponding dimensions of the load-bearing elements, as well as an unconventional arrangement of load-bearing elements according to the layout requirements and the solutions of structural details.

For illustrative purposes - random climatic loads according to EC:
Wind (V. area)... vb,0 =31m/s
Snow (VIII. area)... sk = 8.41kN/m2
The basic weight of the snow and the normative load from wind were considered based on the binding information from the Czech Hydrometeorological Institute.

Building Layout
On the first above-ground floor (ground floor) there is an entrance area, restaurant, kitchen with operational spaces, sanitary facilities, and a garage for the snow groomer with a workshop.
On the second floor the accommodation rooms are situated.
In the attic there are residential spaces.
The entrance and communication sections of the building (approximately 6.7x11.3m in the space of the 1st and 2nd floors) are considered in a combination of masonry and reinforced concrete structures.
 
WOODEN STRUCTURE AND ANCHORING
In addition to GL24h glued laminated spruce timber and grown timber from conifers C24, some elements are made of steel – namely two columns and one beam on the ground floor and canopies hangers.

Basic parts of the spatial load-bearing system
Columns are designed for the height of the floor and are hinged at both ends. The columns have a rectangular or square cross-section of 160 to 240 mm / 200 to 350 mm. At the garage, two columns made of rolled profile HEA 240 are planned.

Beams are placed on the load-bearing columns of the building, both longitudinally and transversely. They act as simple or continuous beams over various spans. The beams have a rectangular cross-section of 160 to 240 mm / 300 to 650 mm. The largest profile 2x200/650 is located above the garage, where there is also a beam made of rolled steel profile IPE550, which is connected to the steel columns in a frame manner. Notably, there are two beams above the restaurant – kitchen area and one beam above the garage for the snow groomer, which are supported by truss beams embedded in the walls of the 2nd floor – the beams form the bands of these trusses, the diagonals of the trusses consist of elements 160/200 mm from C24 wood.

Ceiling beams of the 1st and 2nd floors are designed from rectangular cross-section of grown timber (C24), dimensions 140/300 mm (ceiling above 1st floor), and 120/280 (ceiling above 2nd floor) respectively.
The securing of the beams and ceilings, their transverse and torsional stability, as well as mutual interactions, is secured with cladding (wooden boards placed at a 45° angle).

Rafters consist of a top rafter (rectangular cross-section 240/450 mm), mid rafters (rectangular cross-section 240/450 mm), eaves (or longitudinal beams with a cross-section of 240/400 mm), supporting columns, braces, rafters (at the connection points 160/260 mm glued, otherwise 140/260 mm from grown wood), collar beams, sloping cladding of thickness 35 mm, and supplementary elements. The boards in fields with roof windows are laid parallel. The entire cladding is additionally diagonally braced with diagonal bracing strips.

Flat roof is formed by transverse beams 160/400 mm and rafters 200/400 mm. To ensure their transverse and torsional stability, they are clad with boards placed diagonally at a 45 ° angle.

In front of the restaurant, a canopy is designed along the longitudinal outer wall with an overhang of approximately 2.20 m. The canopy consists of long-oriented elements 120/240 mm (C24), which are supported by beams made of glued timber GL24 with dimensions of 160/400 mm. At the end of the overhang of the beams, hangers made of steel pipes TR ø 76/5 (steel S355) are installed.

After the cladding and vapor barrier, the roof envelope has thermal insulation based on polyurethane PIR (polyisocyanurate) of thickness 160 mm. Above this layer is a ventilated gap of thickness 60 mm formed by counter battens 60/60 anchored with screws into the rafters through the thermal insulation. On these counter battens, a second wooden cladding is made, on which a titanium zinc sheet of slate gray color with angular and standing seams with an embedded seal is placed. The ridge of the roof is ventilated, with a modification against snow entry.

Exterior walls are insulated from the exterior in the base part with extruded polystyrene, and further, with expanded polystyrene anchored and glued to fiber cement boards. Additionally, the exterior envelope has thermal insulation based on mineral wool. On the outer side, the polystyrene is protected by a coating with a reinforcing mesh.

The gable walls of the structure and the wooden cladding of the dormers are made of planed boards. The cladding is treated with a red glaze in several layers.
All elements of the wooden structure are treated with impregnation. The steel connection elements inside the building and exposed to the external environment are hot-dip galvanized.

Connections and Joints
The joints of wooden elements are considered of peg type – steel nails, screws, dowels, precise dowels, and pins – with embedded steel plates, or systemic geometric elements are used.
The anchoring of the columns to the foundations is considered using steel anchoring plates and chemically glued anchors water-tight securely in the area of waterproofing.

BRACING
The load-bearing wooden structure of the building forms a spatial rod system with load-bearing surface wall and ceiling elements.
The wall panels are with wooden reinforcement elements 60/160 and double-sided load-bearing cladding made of 12.5 mm thick fiber cement boards attached with steel staples. On all transverse walls without internal reinforcements, which ensure stability in most cases, the walls are reinforced with diagonally oriented steel elements made of bars ø16 mm (S235).
The cladding of the ceilings and the roof is placed at an angle of 45°, thus creating a rigid unit, which is connected to the load-bearing stairwell core, which is made of POROTHERM 45 P+D and has monolithic reinforced concrete ceilings with a thickness of 180 mm from C30/37. Wooden elements of the ceilings are placed on this core.

INSTALLATION
The complexity of this construction was realized early in the production process, as each of the eleven frames was different. The amount of various details led to the creation of 201 pieces of wood processing and resulted in 141 types of atypical joinery elements. The design of the wooden structure from many different profiles, while ultimately saving on wood costs (which are based on volume), was complicated for implementation, whether in the production documentation projection or during assembly and subsequent cladding of the structure.
The assembly of this construction set, made of wooden elements and internal plates secured with dowel-type means, was assisted by cranes: initially a truck crane with a capacity of 20t, later a tower crane.
Due to the snow accumulation, assembly was interrupted after the first floor of the building; the skeleton was covered with a foil for continuation in the spring. The construction is now completed, and you can see its beautiful view of the Krkonoš as well.

Sources:
http://www.friesovyboudy.cz/cz/aktivity/historie/
http://www.penzionandula.cz/
http://stavba.tzb-info.cz/nosne-systemy-drevostaveb/8928-drevene-nosne-soustavy-budov
http://byznys.ihned.cz/c1-39193330-domy-na-horach

text: Bc. Eva Grochalová, TAROS NOVA Ltd.