Timber frame house on a slope in Międzybrodzie Bialskie

Implementation Details:

Project Model:

Ekodom50

Construction Type:

Timber Frame House

Purpose:

Single-family House

Roof Covering:

Standing Seam Metal

Facade Finish:

Plaster Finish

Window Joinery:

VEKA Windows

Finish Standard:

Developer Standard

Additional Features:

Gas Heating

Additional Features:

Ogrzewanie podłogowe

Additional Features:

Grzejniki

Country:

Poland

Voivodeship:

Silesian

City:

Międzybrodzie Bialskie

Usable Area (m²):

50

Number of Floors:

3

Number of Rooms:

5

Number of Bathrooms:

3

Site adaptation and hybrid building foundation

The start of work in Międzybrodzie Bialskie involved an unusual starting situation, where instead of a "clean slate" in the form of a building plot, we found an existing object intended for partial demolition. The decision to preserve the basement level was dictated by both economy and ground conditions, but it brought with it a number of technical complications. Preserving the old foundation and the ceiling above the basement forced us to conduct a rigorous assessment of the load-bearing capacity of these elements. In construction, unlike in academic theory, we rarely deal with perfectly preserved archival documentation, so we had to rely on exploratory excavations and sclerometric tests of the concrete. It was shown that the stone-concrete base, although old, has sufficient stability to bear the loads of a light timber frame structure, provided that a new reinforced concrete ring beam was made to tie the old structure to the new one.

The key element of this stage was the precise demolition of the old above-ground story to the "zero" level, i.e., the upper surface of the basement ceiling. This is a process that requires precision so as not to disturb the statics of the basement retaining walls, which in this area also serve to stabilize the slope. The use of timber frame technology in this particular case proved to be a godsend due to its much lower dead weight compared to masonry technology. The reduction of permanent loads allowed us to avoid the costly and complicated process of underpinning the foundations. Instead, we focused on waterproofing the junction of the old and new and on the thermal modernization of the underground part, which is often overlooked in such adaptations.

It is worth paying attention to the logistical aspect. Carrying out demolition and construction work on an existing outline requires perfect coordination of deliveries and storage of materials. In the case of this project, every structural beam and every package of mineral wool had to arrive at the construction site in a strictly defined time window. The lack of storage space forced us to work in a Just-in-Time system, which with the variable mountain weather required great flexibility in the schedule.

Ultimately, the foundation stage was completed successfully, creating a solid, hybrid base for the modern body of Ekodom 50. The combination of a massive, heat-accumulating basement with a highly insulated, light superstructure created an interesting thermal arrangement. In winter, the basement stabilizes the temperature from the ground, and in summer, the light upper part does not overheat thanks to proper insulation, which I will discuss in more detail in the following sections.

The table below presents a comparison of loads for the analyzed building assuming reconstruction in traditional technology and the implemented timber frame technology:

Timber frame structure

Moving on to the above-ground structure itself, we built the building based on certified C24 structural timber, which is the absolute standard in professional timber frame construction, although there are still investors trying to save on sawmill lumber. In the case of the project in Międzybrodzie, where we are dealing with the third wind load zone and increased snow load, there was no room for compromise. We made the main frame in cross-sections adapted to static calculations taking into account the specific geometry of the gable roof with a significant pitch. This geometry, visible in the photos, is not just an aesthetic treatment referring to the "modern barn", but a pragmatic solution that facilitates snow sliding.

The assembly of the frame on the finished ring beam was lightning-fast, which is one of the biggest advantages of prefabrication, even if it is partial (so-called on-site prefabrication or assembly from pre-cut elements). A key execution detail was the anchoring of the sill plate. We used chemical anchors instead of mechanical expansion dowels to avoid introducing additional stress into the old, adapted ceiling. Between the sill plate and the concrete, we used double damp-proof insulation and a foam gasket, which levels out micro-unevenness in the concrete, preventing the formation of air bridges at the ground level.

The external walls in this project are a layered system that must meet the strict WT 2021 standards. The frame filled with mineral wool was just the beginning of the fight for the heat transfer coefficient U. On the outside, we used an additional layer of facade insulation, which functions as an eliminator of thermal bridges on the structural posts. Wood, although an insulator, has worse thermal parameters than wool or styrofoam, which is why "covering" the structure with a continuous layer of insulation is necessary to achieve an energy-efficient standard.

In such a slender building, exposed to gusty winds in the valley, the sheathing was crucial. The use of wood-based panels with increased moisture resistance ensured the spatial rigidity of the body. At the open shell stage, the building had to withstand sudden weather changes, which is typical for this region. Thanks to the fast assembly technology, the time of exposure of the unprotected wood to atmospheric conditions was limited to an absolute minimum.

Thermal and acoustic insulation (Mineral wool as the heart of the system)

The choice of insulation material in timber frame construction is a strategic decision. In the Międzybrodzie project, we opted for mineral wool as the main filling for the walls and roof. This decision was dictated by three factors:

• thermal insulation,
• fire safety
• acoustics

Mineral wool, unlike PUR foams, allows for a certain "breathability" of the partition (of course, with a correctly made vapor barrier), but above all, it has excellent sound-dampening parameters. In a house with a light structure, located in a natural but also neighboring environment, acoustic comfort is a parameter that users appreciate the most after moving in.

The insulation process required special attention to the roof. We used a two-layer system: the first layer of wool between the rafters, the second under the rafters on a steel grid. This arrangement eliminates linear thermal bridges along the rafters. The total thickness of the insulation in the roof slope was selected to obtain a U-value below 0.15 W/(m²K). This is evident at the attic finishing stage, where the radiators, although present, will only serve as a supportive function on the coldest days.

The facade is another piece of the thermal puzzle. We used an ETICS system (composite thermal insulation system for external walls) in a mixed variant. Part of the walls is finished with silicate mineral plaster on a layer of facade wool or grooved styrofoam (depending on the zone), and part with facade board. The key detail here is the ventilation of the space under the larch board. The lack of a ventilation gap is a professional error that would lead to biological degradation of the wood and dampening of the insulation within a few years. In our project, we ensured free air flow under the wooden substructure, which guarantees the longevity of the facade.

The insulation did not only concern the walls and roof. A serious challenge was the insulation of the floor on the ground in the basement part and the ceiling between the basement and the ground floor. In old buildings, these elements are usually "energy holes". We used hard floor styrofoam with an increased lambda parameter there, which, in combination with underfloor heating (which I will discuss later), created an effective heat radiator.

VEKA Ideal 8000 window and door joinery in practice

The choice of window joinery for an energy-efficient house is always a balance between heat gains from solar radiation and losses through transmission. In the project in Międzybrodzie, we decided on the VEKA Ideal 8000 system. This is a 6-chamber profile with a construction depth of 85 mm, equipped with a system of three seals. Why is this choice technically important? The third (middle) seal creates a so-called dry chamber for the fittings, which in a humid mountain climate significantly extends their lifespan and trouble-free operation.

The glazing units are a standard double-chamber (triple-glazed) filled with argon, with a Ug coefficient of 0.5 W/(m²K). However, the parameters of the glass alone are not everything. The installation is critical. In a timber frame house, the joinery is installed in the insulation layer or at the boundary of the structure and insulation. We used "warm installation" here with the use of vapor-tight tapes on the inside and vapor-permeable tapes on the outside. Without this treatment, even the best window would become a place of heat escape and water vapor condensation, leading to the degradation of the reveals.

The large glazed area at the top of the building (visible in the photos) deserves special attention. This is an element that defines the character of the attic interior, opening it up to the view of the mountains. Structurally, this required the use of reinforced static profiles so that the wind pressure on such a large surface would not cause deformation of the frame and leaks. The entrance doors, also visible in the documentation, are a model with increased thermal insulation, color-consistent with the anthracite roof sheeting, which creates a coherent aesthetic composition.

Roof covering and facade (Standing seam metal and larch board)

The aesthetics of the building in Międzybrodzie Bialskie is a dialogue between modernity and tradition. The roof and the upper part of the facade were covered with standing seam metal. This is a material that is experiencing a renaissance in contemporary architecture. Technically, standing seam metal is an excellent solution for roofs with a steep pitch – it provides absolute tightness and is great at draining water and snow. However, its installation requires a high technical culture of the roofers. Every joint, every flashing of the chimney or roof window must be made with precision, because the metal "does not forgive" mistakes as easily as ceramic tiles.

A counterpoint to the cool, industrial metal is the natural larch board used on the lower parts of the facade and on the terrace. Siberian larch, and even domestic larch, is a wood with high natural resistance to weather conditions thanks to its high resin content. In this project, the board was additionally protected (charred using the shou sugi ban technique or with a coloring impregnant – depending on the batch visible in the photos, the final effect aims for natural aging or maintaining a light color). Wood on the facade is not just about looks – it is an additional protective layer for the building's structure.

The combination of silicate mineral plaster, metal, and wood required the design of precise details at the junction of these materials. The places where the plaster meets the board or metal are critical. We used system drip and expansion profiles there, which prevent water from seeping under the cladding. The lack of such solutions is a common execution error, resulting in cracking of the plaster and stains after the first winter. In our project, the priority was the durability of the detail, even at the cost of longer installation time.

List of key features of the facade and roof:

1. Standing seam metal: High tightness, wind resistance, modern design, easy snow sliding.
2. Larch board: Natural biological resistance, aesthetic warming of the building's image, ventilated facade.
3. Silicate plaster: High vapor permeability (cooperation with wool), resistance to dirt and algae (important in proximity to the forest).
4. No eaves: Modern "barn" type body, requiring a precise hidden or system gutter system (in this case, visible gutters, color-matched).

Hybrid heating and utilities

The heating system in the described house is an example of a pragmatic approach to modernization. The building is powered by gas, which, with the availability of a connection in the road, is an economically justified solution (low investment costs compared to a heat pump, with relatively low operating costs in such a small and well-insulated house). The heart of the system is a gas boiler located in the boiler room.

We used a mixed heat distribution system. In the basement (which serves utility/storage functions) and on the ground floor, underfloor heating was installed. Anhydrite or cement screed on underfloor heating acts as a heat accumulator, which in a timber frame house (which by nature has low thermal inertia) is very desirable. It stabilizes the interior temperature. In the attic, in the bedrooms, we decided on low-temperature radiators. The reason is prosaic but technically important: a floor on wooden joists (the ceiling between the ground floor and the attic) is more difficult and expensive to adapt for "underfloor heating" (requires dry systems or screeds on a reinforced ceiling), and radiators allow for a faster reaction of the control system – which is an advantage in bedrooms (quick temperature reduction at night).

Water and sewage issues in mountainous terrain are often complicated. In this case, it was necessary to build our own well and install a septic tank, which is due to the lack of full network infrastructure in the investment area. Building a well in rocky terrain is a challenge, but it provides independence. The sealed septic tank required solid anchoring or weighting so that groundwater (flowing from the slope) would not push the tank out when it is empty. These are details that are not visible at first glance but are decisive for trouble-free operation.

Finishing standard from developer to detail

The building was brought to a developer-ready standard, which in our nomenclature means it is fully ready for finishing work (painting, tiling, installation of final floors and interior doors). The walls finished with plasterboard were plastered and prepared for painting. The electrical and plumbing installations are distributed and terminated in boxes/plugs. It is worth emphasizing that in timber frame houses, installations are run in the walls before they are closed with boards, which requires very careful planning of the interior design at the raw state stage. Moving a socket in a finished timber frame wall is more difficult than in a masonry wall (damage to the vapor barrier).

Outside, the standard included the full finishing of the facade, flashings, and terrace. The terrace made of charred larch wood is an element that connects the interior with the garden. Charring wood is an old Japanese technique (Shou Sugi Ban) that preserves the wood and gives it a unique character. In this case, a lighter variant was used to match the aesthetics of the light wood on the facade (the visible differences in the photos may suggest different stages of work or specific investor decisions regarding the final coloring).

Project summary

The project in Międzybrodzie Bialskie is proof that the Ekodom 50 timber frame technology (in its adapted variant) works perfectly not only for "greenfield" construction but also as a method for extending and revitalizing existing foundations. Thanks to the lightness of the structure, complicated earthworks were avoided, and thanks to prefabrication and the dry construction system, the implementation time was reduced to a minimum, which in the unpredictable mountain climate is a paramount value. We obtained a building with high energy-efficient parameters, modern aesthetics, and a functional layout (5 rooms, 3 bathrooms with a relatively small building area, thanks to the use of the basement), which fits into the landscape of the Beskids, not dominating it, but cooperating with it.