<p>Under stor del av 1900-talet var det enligt nordiska byggnormer förbjudet att använda trästommar i byggnader med fler än två våningar. 1994 upphörde förbudet och istället infördes brandtekniska funktionskrav, vilket innebär att konstruktionen enbart måste uppfylla vissa krav och att material därefter kan väljas fritt. I detta examensarbete har jag undersökt hur flerfamiljshus skall utformas med hänseende till brand och yttre påverkan, samt hur trä som byggnadsmaterial kan begränsa den arkitektoniska utformningen. I Gävle finns för tillfället inga större flervåningshus utformade helt och hållet i trä, därför har studierna utförts i samarbete med Gävle kommun. Examensarbetet består av en teoretisk del och en tillämpningsfas i vilken förslag på byggnadsutformning arbetats fram, tänkt lokalisering för byggnaderna är Gävle Strand.</p><p>Dokumentationer från liknande projekt visar att det varit relativt enkelt att få byggnader i trä att uppfylla de brandtekniska krav som ställs. Vanligaste metoden är att klä in bärande stommar med dubbla gipsskivor, genom att sedan putsa ytterfasaden skyddas även byggnaden mot utvändig brandspridning. Det visar sig dock fortfarande finnas en viss ovilja att bygga stort i trä, detta trots att trä ur brandskyddssynpunkt är likvärdigt om inte i vissa fall till och med bättre än andra byggnadsmaterial. Studier visar även att arkitekten för det mesta inte känner sig begränsad av att arbeta med trä, i de fall där vissa begränsningar uppstått har det berott på valet av byggmetod och inte materialet i sig.</p><p>Examensarbetets tillämpningsfas har resulterat i skisser på hur en av de tänkta byggnaderna på Gävle Strand skulle kunna komma att se ut. Arbetet har avgränsats till att enbart titta på den yttre utformningen och störst vikt lades då på att använda trä som fasadmaterial. Byggnaden är ett fyravåningshus och fasaden har delvis utformats i trä, horisontella band av putsad fasad har varvats med trä och förhindra på så sätt att flamspridning sker via fasaden. Vissa delar av gavlarna är täckta helt och hållet med trä, här fungerar balkongerna som flamskärmar vilket medför att horisontella band av obrännbart material ej är nödvändigt. Träfasaden är tänkt att utformas i ek, träslaget har valts dels för sin färg men även på grund av dess goda motståndskraft i den fria luften. Önskas en heltäckande träfasad runt hela byggnaden krävs en installation av sprinklersystem.</p> / <p>During the most of the 20th century it was forbidden to use wood structures when constructing buildings greater than two floors according to Nordic building standards. In 1994 it became allowed to build with wood but with technical fire demands, which means it is only the construction that have specific demands but material can freely be chosen. With this final thesis I have examined how buildings with several apartments should be build according to fire risks and external risks that can occur from several weather types. I also examined how wood can restrict the architectural design. No greater buildings constructed with several apartments are built in Gävle which only has wood as material. That is why I do this final thesis in cooperation with the Gävle municipality. The thesis has two parts; one theoretical part and one part that consider proposals with building designs. The buildings are meant to be located at Gävle strand.</p><p>Documentations from similar projects have showed that it has been relatively easy to fulfill the technical fire demands. The most ordinary method that is used is to use gypsum boards with double layers around the wood frames. By plaster the external façade the building is also protected against external fire dissemination. With the point of view of fire when building with wood it has been clear that it is similarly and in some cases even better to build with wood compared to other materials. Most of the time the architect is not restricted to use wood according to studies. When a restriction have occurred the cause have been which kind of building methods that is used, not by using wood.</p><p>The thesis application phrase has result in sketches of how one building could look like at the location Gävle strand. The limitation has been to only produce an external design; the idea is to use wood as façade material. The building that is created has four floors and the façade is mostly in wood. Horizontal bounds with plaster mixed with wood are used to prevent the fire to spread along the façade. Parts of the gables are completely covered by wood. This can be done because the balconies can protect against fire flames. This also means that in this part of the building has not any plaster been used. The idea is to use oak at the wood façade. This kind of wood is used for its color but even because oak has a good strength in open air. In case of completely façade built with wood, a sprinkler system must be installed.</p>

Under stor del av 1900-talet var det enligt nordiska byggnormer förbjudet att använda trästommar i byggnader med fler än två våningar. 1994 upphörde förbudet och istället infördes brandtekniska funktionskrav, vilket innebär att konstruktionen enbart måste uppfylla vissa krav och att material därefter kan väljas fritt. I detta examensarbete har jag undersökt hur flerfamiljshus skall utformas med hänseende till brand och yttre påverkan, samt hur trä som byggnadsmaterial kan begränsa den arkitektoniska utformningen. I Gävle finns för tillfället inga större flervåningshus utformade helt och hållet i trä, därför har studierna utförts i samarbete med Gävle kommun. Examensarbetet består av en teoretisk del och en tillämpningsfas i vilken förslag på byggnadsutformning arbetats fram, tänkt lokalisering för byggnaderna är Gävle Strand. Dokumentationer från liknande projekt visar att det varit relativt enkelt att få byggnader i trä att uppfylla de brandtekniska krav som ställs. Vanligaste metoden är att klä in bärande stommar med dubbla gipsskivor, genom att sedan putsa ytterfasaden skyddas även byggnaden mot utvändig brandspridning. Det visar sig dock fortfarande finnas en viss ovilja att bygga stort i trä, detta trots att trä ur brandskyddssynpunkt är likvärdigt om inte i vissa fall till och med bättre än andra byggnadsmaterial. Studier visar även att arkitekten för det mesta inte känner sig begränsad av att arbeta med trä, i de fall där vissa begränsningar uppstått har det berott på valet av byggmetod och inte materialet i sig. Examensarbetets tillämpningsfas har resulterat i skisser på hur en av de tänkta byggnaderna på Gävle Strand skulle kunna komma att se ut. Arbetet har avgränsats till att enbart titta på den yttre utformningen och störst vikt lades då på att använda trä som fasadmaterial. Byggnaden är ett fyravåningshus och fasaden har delvis utformats i trä, horisontella band av putsad fasad har varvats med trä och förhindra på så sätt att flamspridning sker via fasaden. Vissa delar av gavlarna är täckta helt och hållet med trä, här fungerar balkongerna som flamskärmar vilket medför att horisontella band av obrännbart material ej är nödvändigt. Träfasaden är tänkt att utformas i ek, träslaget har valts dels för sin färg men även på grund av dess goda motståndskraft i den fria luften. Önskas en heltäckande träfasad runt hela byggnaden krävs en installation av sprinklersystem. / During the most of the 20th century it was forbidden to use wood structures when constructing buildings greater than two floors according to Nordic building standards. In 1994 it became allowed to build with wood but with technical fire demands, which means it is only the construction that have specific demands but material can freely be chosen. With this final thesis I have examined how buildings with several apartments should be build according to fire risks and external risks that can occur from several weather types. I also examined how wood can restrict the architectural design. No greater buildings constructed with several apartments are built in Gävle which only has wood as material. That is why I do this final thesis in cooperation with the Gävle municipality. The thesis has two parts; one theoretical part and one part that consider proposals with building designs. The buildings are meant to be located at Gävle strand. Documentations from similar projects have showed that it has been relatively easy to fulfill the technical fire demands. The most ordinary method that is used is to use gypsum boards with double layers around the wood frames. By plaster the external façade the building is also protected against external fire dissemination. With the point of view of fire when building with wood it has been clear that it is similarly and in some cases even better to build with wood compared to other materials. Most of the time the architect is not restricted to use wood according to studies. When a restriction have occurred the cause have been which kind of building methods that is used, not by using wood. The thesis application phrase has result in sketches of how one building could look like at the location Gävle strand. The limitation has been to only produce an external design; the idea is to use wood as façade material. The building that is created has four floors and the façade is mostly in wood. Horizontal bounds with plaster mixed with wood are used to prevent the fire to spread along the façade. Parts of the gables are completely covered by wood. This can be done because the balconies can protect against fire flames. This also means that in this part of the building has not any plaster been used. The idea is to use oak at the wood façade. This kind of wood is used for its color but even because oak has a good strength in open air. In case of completely façade built with wood, a sprinkler system must be installed.

Abstract This paper is based on interviews, a literature study and seminars. It describes the situation in Halland when it comes to multi-story housing built in timber. From 1874 to 1994, Sweden had a regulation that prohibited construction of timber houses with more than two stories as a result of big city fires. After the regulation was revoked, people started to build multi-story houses in timber again. Compared to the rest of the country there was not that many built in Halland. Construction entrepreneurs here possess the right competence and it is close to the raw material. Even though that, there are only five multi-story houses built in the county. Result from this study shows that the main problem of implementing multi-story housing built in timber is biases and lack of knowledge. Many of the players in the construction industry do not base their decisions on fact when it comes to choose timber or not. This in combination with a lack of information regarding financial issues and unfavorable regulations has resulted in a slow development of the implementation of multi-story houses. The reasons behind this are discussed in the paper and some possibilities of change are presented.

The construction of wooden multi-storey buildings creates issues with the acoustic environment. To meet Boverkets soundproofing requirements the solutions of today results in thick partition building components taking up potential floor space. Crosslaminatedtimber is a solid timber slab that can be manufactured in varying sizes and thicknesses. These boards can then be used as supporting elements in walls, ceilings and floors. This study investigates whether cross-laminated timber can be used to streamline the construction of multi-storey wooden buildings. In this comparative survey a reference building constructed by A-hus was used and current loads, sound insulation, use of floorspace and economy were analyzed. Four different alternative walls and one floor constructed with cross-laminated timber have been studied according to the above named criteria, and then compared with the reference building. The result indicates that a wall with 80 mm cross-laminated timber board has the load capacity required, improves sound insulation and saving 16 m2 of floorspace in the reference building valued to approximately 695,000 SEK in increased sales revenue. Using cross-laminated timber in the floor does not sufficient improve A-hus current construction system and should therefore not be interesting.

Wood is a renewable material, it is strong in relation to its weight, climate smart but also combustible. Owing to its many advantages and the easy access in Sweden, wood is motivated as a topical building material. However, the aspects related to the combustible nature need to be considered in the design of buildings with a wooden frame. Whether and in such cases how to take into account the increased permanent fire load is a problem of which there are shared opinions. Today's regulatory framework is unclear in some aspects in its formulation and thus leaves room for interpretation. The purpose of this work is to investigate the reasonableness of tabulated data for permanent fire load and the sharp boundary between a BR1 building and a BR0 building but also by surveying how the industry handles the issue. In order to assess the reasonableness for the tabulated data, the method has been calculations with two different methods; one that follows BBR's guidelines (method 1) and another where calculations of the charring depth (method 2) have been performed, as well as a survey and a literature study. The result from the calculations in method 1 shows that in order for the level of the total fire load not to exceed the standard value for a residence of 800 MJ/m2, a low coefficient is required, and thus in principle all wood is assumed to be protected. According to the calculations in method two, it is possible to read out how the permanent fire load is affected by different protective linings and carbonation rates. The survey shows that the most common way to dimension fire protection is through simplified sizing, which entails that one does not have to consider whether the permanent fire load increases due to a combustible frame. There are divided opinions about whether Boverket's rules are enough to achieve adequate protection and how to handle it. The literature study shows that for the timber frame to be counted as fully protected it needs to be three layers of fire gypsum board in the ceiling and that two layers on the walls. Several conclusions can be drawn; the calculations indicate that a permanent fire load of 200 MJ/m2 (2013:11) is unreasonable in a wooden frame building also that if the permanent fire load is considered it becomes costly both economically and in terms of space. Even that Boverket's rules need to be clarified and adapted further against tall wood buildings and that fire projectors work differently and the experience of working with tall wood buildings differs greatly.

På senare tid har intresset för och viljan att bygga flerbostadshus i trä ökat och medfört en trend att bygga allt högre hus med stomme av trä. En aktör är Lindbäcks Bygg som bygger flerbostadshusi trä med volymelement och lätt regelstomme. Idag begränsas dock möjligt antal våningar med regelstomme till 6 – 8 våningar. Ett relativt nytt material inom träbyggnadstekniken är korslimmat trä (KL-trä) vars användning gjort det möjligt att bygga högre byggnader i trä. Examensarbetets syfte är att studera olika lösningar för hur Lindbäcks regelstomme kan förstärkas med KL-trä, vilket kan göra det möjligt att bygga allt högre flerbostadshus i trä. Samt att jämföra denna lösning med den idag använda regelstommen utan KL-trä. Studien har avgränsats till att enbart behandla ytterväggar. För att uppskatta rimliga laster på ytterväggar i en flervåningsbyggnad togs en principbyggnad (ihopsatt av ett antal volymelement) fram. I beräkningar tillämpades ett antal olika ytterväggstyper, en med den idag användaregelstommen (referensvägg) samt fem med regelstomme i kombination med KL-skivor i olika tjocklekar. För principbyggnaden kontrollerades genom beräkningar hur högt det är möjligt att bygga vid tillämpning av vardera ytterväggstyp. De olika ytterväggstyperna med KL-trä jämfördes även med referensytterväggen utifrån U-värde samt kostnad. Idag används KL-trä ibland av Lindbäcks och då som stabiliserande väggar. I deras fabriker tillämpas en lösning där KL-träskivorna fälls in mellan syll och hammarband tillsammans med reglarna. Beräkningar har visat att det, för principbyggnaden, med denna lösning är möjligt att bygga maximalt 2 våningar högre jämfört med referensytterväggen, detta för den bästa av ytterväggstypernaförstärkta med KL-trä. Det som begränsar ett högre antal våningar är trycket vinkelrätt fiberriktningen på syllen under KL-skivorna. Beräkningar visar att det finns en potential att med regelstomme förstärkt med KL-trä kunna bygga ännu högre om en annan lösning används där KL-träskivorna placeras på utsidan av syll, hammarband och reglar istället för infälld mellan syll och hammarband. Med denna lösning undviks tryck vinkelrätt fiberriktningen på syll under KL-skivor och KL-skivans kapacitet kan utnyttjas effektivare då normalkraftskapaciteten för själva skivan blir den begränsande faktorn för hur högt det går att bygga. Enligt beräkningar är det, för principbyggnaden, med denna lösning möjligt att bygga uppemot 8 våningar högre än med referensytterväggen. När KL-trä används i stommen ökar energiförlusterna genom väggen, dvs. U-värdet ökar, då reglar med mellanliggande isolering ersätts av KL-trä med sämre värmeledningsförmåga. Enligt beräkningar uppskattas U-värdet öka jmf. med för referensyttervägg, detta med ca. 20 – 40 % beroende på ytterväggstyp. Ökningen kan dock begränsas till ca. 0,4 – 14 % genom införande av ett 45 mm installationsskikt med isolering på väggens insida. Även kostnaden för ytterväggstyper med regelstomme förstärkt med KL-trä uppskattas öka jmf. med uppskattad kostnad för referensyttervägg. Detta med uppskattningsvis 40 – 50 %, vilket till huvudsak är en följd av ökad materialkostnad för KL-skivor som delvis ersätter reglar med mellanliggande isolering. / Today there is an increased interest in building taller buildings with timber. Lindbäcks Bygg is one of companies that uses modular construction with light timber stud frames. However, a problem with light timber frames is that the building height is limited to roughly 6 - 8 stories. A relatively new product in timber engineering is cross laminated timber (CLT) and the use of this product have made it possible to build taller timber buildings. The purpose of this study is to investigate different solutions for how Lindbäcks can strengthen their stud frames by using CLT and thereby build taller buildings. The difference with respect to U-value and cost between the walls strengthened width CLT and the typical stud frame wall, that is used today, is also studied. The study has been limited to exterior walls only. A multi-storey building consisting of several modules/volume elements has been used to estimate reasonable loads on the exterior walls. Different wall types, one with the ordinary stud frame (the reference wall) and five types of stud walls strengthened with different thicknesses of CLT, have been investigated. The maximal number of storeys that can be build, the U-value and the cost were determined by calculations for each of the studied wall types and were compared with the results for the reference wall. Today, Lindbäcks Bygg sometimes uses CLT for stabilizing walls. In their factories, they use a solution in which the CLT-plate is placed between the top and bottom plate together with the studs. According to the calculations it is, with this solution, possible to build up to 2 storeys higher then with the reference wall. The limiting factor for how high it is possible to build, is compression perpendicular to the grain on the bottom plate underneath the CLT-plate. If a solution where the CLT-plate is placed on the outside of the frame (consisting of studs, top and bottom plate) is used instead of between the top and bottom plate does the calculations show that a higher number of storeys is possible. With this solution, the compression perpendicular to the grain underneath the CLT-plate is avoided and the limiting factor is instead the compression strength of the CLT-plate. This means that the CLT can be used more efficiently. Calculations show that it is possible to build up to 8 storeys higher with this solution compared to what is possible with the reference wall. With CLT increases the energy losses through the wall, i.e. increased U-value, since studs with insulation in between is partially replaced with CLT that has worse thermal conductivity. According to the calculations, the U-value is 20 – 40 % higher (depending on the wall type) compared to the reference wall. The increase in U-value can be limited to 0.4 – 14 % by adding an extra layer with 45 mm insulation on the inside of the CLT-plate. The cost for the wall types strengthened with CLT is also higher compared to the estimated cost for the reference wall. The main reason for this is increased cost of materials since the studs with insulation in between is partially replaced with the more expensive CLT, which is an engineered wood product. The increase in cost is estimated to roughly 40 – 50 % of the cost for the reference wall.

Multi-story wood frame construction is a highly relevant topic today because of the need to continue to develop the relatively new building technique to create a sustainable way to keep constructing new buildings. Because the use of wood as a frame material in multi-story buildings is still new, there are still issues that come with the choice to use it. One of these issues is in the detailed technical solutions that are constructed, they often have faults that may lead to problems with moisture. The purpose of this degree project is to investigate these problems and more importantly the process behind constructing them. This work is also examining what can be done to counteract or minimize the issues in the planning phases of the construction as well as look at why it is important to continue developing wood construction. There are two parts of the method used in this degree project. The first part is a literature study which brings up the attributes of wood, factors for using and not using wood, the techniques used to build multi-story buildings in wood, as well as a look into the detailed technical solutions that are used and the planning process behind them. The second part is the interview study where experts in the field are interviewed to get answers about the issues that this work brings up. The interviews provided a lot of information that is relevant for this work and the result consists of the most important answers from them. The biggest factor for continuing to develop the use of wood as a frame material, from the interviews, was about the eco-friendliness of the material. The attitude to use wood in multi-story buildings varies quite a bit depending on which part of the construction sector is asked. The developers are curious but still a bit worried, because of this they have not yet taken the next step in using it more. The entrepreneurs are still sceptical about the use in multi-story constructions and there is not enough knowledge about it for them to earn the same amounts of money as if they were to use concrete or steel. Because of that they are also worried about taking the next step towards using wood more. The consultants, like the architects and construction engineers, are more positive to the use of wood and are inclined to use it more and more. The issues that come up the most are different types of attachments of balconies and exterior corridors, parts that are installed too close to the ground and solutions where the end grain of the wood is in water. There were three main problems that came up repeatedly. The biggest one was the lack of knowledge in the planning and the production phases. The second one was about how there is often no one who looks at the bigger picture in the projects which entails mistakes that could be caught. The last issue was in the installation where the construction workers might not do it according to the construction drawings or a lack of drawings which leads to improvisation at the construction site. Recommended improvements could be a standardisation of the solutions that are proven to work for everyone to use. There is also a need for better communication which provides feedback to the designers of the solutions, that way they will know what to do better in the future. More relevant education within the topic and better coordination will also prove vital in the continued development of multistory wooden constructions.