SBI 189

SINGLE FAMILY HOUSES SBI 189 Insulation – moisture protection, acoustics, fire resistance, ventilation and strength.

2nd EDITION SBI-DIRECTION 189 STATENS BVGGEFORSKNINGSINSTITUT 1999

Translation from Danish to English: Karsten Lundager and Roger Taylor

Contents Preface .......................................

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Crawl space external walls ........ 30 Crawl space internal walls ........ 31 Crawl space deck ........................ 32 Timber joists ............................. 32 Concrete and clinker concrete deck ................................................ 33

Introduction ............................ 10 Basements .................................. 36 Thermal prevention ................. 36 Load and load acceptance ....... 12 Basement floor ......................... 36 Terrain classes for wind.............. 12 Basement external walls ............. 36 Stabilising system ...................... 13 Dimensioning ......................... 38 Dimensioning and design............ 14 Heat insulation ......................... 39 Moisture insulation ................ 40 Foundations .............................. 15 Internal basement walls ................ 40 Foundation classes ................... 16 Deck over basement .................... 40 Low foundation class ................ 16 Timber joists................................. 40 Dimensions ............................. 17 Concrete and clinker concrete deck 42 Workmanship ............................. 18 External basement stairway ......... 42 Inserts or recesses . . . . . . . . ...... 19 External walls ........................... 44 Concrete .................................. 19 Thermal insulation ................... 44 Hollow foundation blocks and Moisture conditions .............. 44 solid Fire precautions ....................... 46 light clinker concrete blocks.... 19 Passage of sound...................... 46 Heavy external walls .................... 46 Drainage .................................... 20 Examples of heavy external walls Workmanship ............................. 20 ... 47 Branch drains ......................... 21 Light external walls .................. 48 External basement walls ......... 21 Other external walls .................. . 49 Cleaning ................................ 21 Fitting windows and external doors Drainage ............................... 22 . . . 50 Protection against rats............... 23 Window and door lintels ....... 50 Fascines .................................. 23 Joints ....................................... 50 Ground supported floors .............. 24 Internal walls ............................. Ground conditions ................ 24 Thermal insulation ................... Capillary breaking layers ...... 24 Fire conditions ....................... Heat insulating layers .............. 24 Passage of sound...................... Concrete slab........................... 24 Strength properties ................... Floor finishes ........................... 24 Radon proofing ...................... 25 Walls between joined houses *) Examples of ground supported floors 25 Passage of sound ......................... Crawl space ............................... 29 Ventilation.................................. 30 Crawl space floor ........................ 30

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Water and drain installations . 82 56 57 Floors ......................................... 82 59 Heavy floor constructions......... 82 59 Light floor constructions........... 83 Walls .......................................... 84 Roofs ........................................ 60 Tunge walls ............................. 84 Thermal insulation.................... 60 Light walls............................... 84 Moisture conditions .............. 60 Ceilings...................................... 85 Fire protection ........................ 60 Joints.......................................... 85 Roof coverings, underlay and battens .................................................... 61 Glass ....................................... 86 Underlay roofs ......................61 Glass types ................................. 86 Battens ..................................... 61 Permissible glass area................. 86 Concrete and clay roof tiles . 61 Thermal stress............................. 87 Slates ....................................... 61 Impact........................................ 87 Profiled roofing sheets............. 61 Preventing cutting injuries ..... 87 Roofing felt .............................. 62 Glass as a safeguard . . . . . . . . . 87 Rafter and ceiling construction .. 62 Conservatories ......................... 88 Collar beam rafters ................ 63 Glass roofs ................................. 88 Trussed rafters ....................... 63 Common rafters/joists ............. 63 Indoor climate ........................... 89 Roofing elements ..................... 65 Ventilation .................................. 89 Gable triangles............................ 66 Ventilation principles ............ 89 Roofs with trussed rafters......... 67 Natural ventilation ............. 89 Roofs with collar beam rafters.. 67 Mechanical ventilation ....... 90 Functional requirements Thermal insulation .................... 70 general.................................. 90 Three possibilities.................... 70 Habitable rooms....................... 90 U-value requirements ................... 70 Kitchen, bath room and toilet .. 92 Heated floor area and heated Other rooms, crawl footprint area ........................ 71 space/basements . 92 Heat loss frame............................ 72 Fresh air vents and ventilation Temperatures ........................... 72 ducts . . . 92 Transmission areas ................ 73 Fresh air vents ...................... 92 Possibilities - using Heat Loss Ventilation ducts ................... 93 Frame. 73 Pollution from building materials 94 Examples Heat Loss Frame used Danish Indoor Climate Labelling 95 on single family house.................. 74 Heat producing appliances and Energy Frame ............................. 75 chimneys ................................ 96 Possible window and door area . . . Heat producing appliances.......... 96 76 Setting up ................................ 96 Temperature conditions (in Connection to chimney ............ 97 summer). . 78 Chimneys.................................... 97 Cross-sectional area ................. 97 Wet rooms .............................. 79 Height ..................................... 98 Requirements to wet rooms........ 79 Construction ............................ 99 Zoning .................................. 79 Thatched roofs ........................ 99 Floor slope .............................. 79 Waterproofing........................... 80

Solid walls................................ Double walls .......................... Noise from installations ........ Fire precautions ..........................

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Enclosure A. Loads *) ............. Gravity based load .................. Wind load.................................. Design load ........................... Example.................................

101 101 102 103 103

Enclosure B. Fire ................... 105 Fire resistance - building components .. 105 Fastening of mineral wool ....... 105 The fire-technical qualities of claddings (coverings) Class 1 covering .................. 106 Class 2 covering .................. 106 Enclosure C. Acoustics ............ General ..................................... Luftlydisolation ......................... Trinlydniveau ............................ Installationsst0j ....................... Trafikst0j...................................

108 108 108 109 109 109

Enclosure D. The stabilising system ................................................ I ll Bracing the roof plane ............... I ll Vertical anchoring of roof ......... I l l Type classification and dimensioning of anchors.............................. 112 Embedding anchors................ 114 Design of ceiling diaphragm .... 115 Panel cladding ...................... 115 Design of bracing walls ........... 118 Vertical anchoring ................ 119 Solid walls.............................. 119 Stud walls............................... 123 Dimensioning bracing walls and ceiling diaphragm ................... 123 Windload on ceiling diaphragm .............................................. 123 Choosing bracing walls .. 123 Distribution of horizontal loadt ..............................................124 Dimensioning bracing walls ................................... 125 Non-bracing walls .................. 125 Dimensioning ceiling diaphragm .............................................. 126

Data of the building ............... 127 Ventilation ............................. 129 Heat loss ............................... 129 Time constant......................... 129 Internal heat contribution ....... 129 Heat demand........................... 130 Energy Frame ....................... 131 Calculation form 1. External walls, Roofs and floors ........................ 132 Calcualtion form 2. Windows and external doors……………………………… …… . 132 Calcualtion form 3. Insolation.... 132 Shadow factor ...................... 135 Area factor ............................. 136 Glass factor ......................... 137 Example: Heat demand in single family house 137 Summary ............................... 141

Note: Chapters marked with *) are not yet available in this English version

Enclosure E. Heat requirements ................................................127 Heat requirement for a building, main table……………………………… ….. 127

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Preface This SBI Direction is complementary to Building Regulations for Small Dwelling, 1998 and replaces SBI Direction 147: Constructions in small house, which was complementary to Building Regulations for Small Dwelling, 1985. The Direction also replaces SBI Direction 111: Thermal insulation of buildings, 2nd edition. The Direction covers such issues as thermal insulation, moisture insulation, sound insulation, fire, wet rooms, indoor climate as well as strength and stability. As the Direction covers a wide range of subject matters is has been necessary to call upon a wide range of specialist SBI writers. Apart from the project manager, civil engineer Jørgen Munch-Andersen, the following have also participated: Academy engineer Søren Aggerholm, academy engineer Niels Christian Bergsøe, civil engineer Erik Brandt, academy engineer Mogens Buhelt, civil engineer Henry H. Knutsson, academy engineer Peter A. Nielsen and architect m.a.a. Hans Zacharias-sen. The extensive editing work has been carried out by civil engineer Jens Christian Ellum. Several technicians within the Danish building industry have contributed with valuable information. We are very grateful for these contributions. The elaboration of the Direction has received support from By- og Boligministeriel og Energistyrelsen. (Ministry of Housing)

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The target group of this Direction is engineers, architects, contractors and other designers and executors within construction. Also public administration is a target group. Supplements to the SBI Direction will be published at the SBF homepage http://www.sbi.dk. SBI STATENS BYGGEFORSKNINGSINST ITUT Department of Building technique and Productivity, June 1998 Georg Christensen, Research manager Preface to the 2nd edition This is the 2nd edition of SBI Direction 189 concerning »Single family houses«. Compared to the 1st edition a few changes and additions have been made. These are to large degree based on a dialogue with practice which has taken place during a number of seminars where the Direction has been presented. In relation to that SBI would like to express its gratitude for all received suggestions and comments for improvement. SBI STATENS BYGGEFORSKNINGSINST ITUT Department of Building technique and Productivity, November 1998 Georg Christensen, Research manager

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Introduction This SBI Direction contains guidance on and examples of constructions in one family houses. The examples all comply with the requirements laid down in “Building Regulations for Small Dwellings, 1998 (BRS 98) The Direction covers detached as well as semidetached one family houses up to 2 storeys and a basement, as shown in figure 1. The maximum height above ground level is 8.5 m, measured from the ridge. It must be stressed that the examples shown in this Direction should be considered as examples, and alternative solutions fulfilling the requirements in BRS 98 are acceptable. An example: The dimensions stated for load bearing and bracing constructions may in many cases be reduced considering the actual conditions under which they are carried out. This, however, requires dimensioning by an engineer. Reference to other existing literature is either done by full reference in the text (written in italics) or simply by referring to the list of literature at the back of the Direction (only in the Danish Version). The Direction starts with a short introduction to the load-bearing and bracing system with special emphasis on load acceptance. In enclosure D, The Bracing System, it is shown how the bracing necessary to secure the stability of the house can be designed and dimensioned,. Different parts of the house are accounted for. Examples of building components are shown; their design and how they are connected to other building components. In the connection details special emphasis has been put on demonstrating how heat and moisture insulation can be carried SBI Direction 189 Translation KLJ

out in a satisfactory way and at the same time fulfilling the requirements concerning fire resistance and sound insulation. In the shown examples it will in many cases be possible to substitute mineral wool with other insulation materials but care must be taken that the fire resistance requirements are met. Dimensions are stated for usual constructions. Alternative constructions may be dimensioned using the loads stated in enclosure A, Loads. The U-values in the shown examples fulfil the requirements of U-values stated in BRS 98, which are also the basis for determining the Heat Loss Frame for the house. In the chapter Heat Insulation it is discussed how the Heat Loss Frame and the Energy Frame could be used as a tool for choosing constructions with other Uvalues. In the chapters Wet Rooms and Glass examples of fulfilment of BRS 98 requirements in the said areas are shown. The chapter Indoor Climate primarily describes the establishment of satisfactory natural ventilation in one family houses. Issues related to stoking are treated in the chapter Fire Places and Chimneys.

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Ground floor

Ground floor

1 storey with ground supported floor Basement 1 storey with basement

Attic

Attic

Ground floor

Ground floor

1½ storey with ground supported floor

Basement

1½ storey with basement

1st floor

1st floor

Ground floor

Ground floor

2 storeys with ground supported floor

Basement

2 storeys with basement

Figure 1. The Building Regulations for Small Dwellings encompasses one family houses up to 2 storeys and a basement. The houses may be detached or semidetached. The Regulations do not apply to houses with separate dwellings divided by a storey partition (horizontal division).

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Loads, load acceptance and load transmission Houses shall be built in such a way that they can accept and transmit occurring loads. The loads can be divided into: • Gravity based loads, i.e. the dead load of building components, the imposed load (furniture and people) and snow load. • Wind action Wind acts primarily perpendicularly on the surfaces of the house. The external walls and the roof surfaces at the windward side are exposed to pressure. The other surfaces are exposed to suction. Usually, the acceptance and transmission of gravity-based load do not present major problems. However, one must be aware that load-bearing walls are affected by horizontal wind action and vertical load simultaneously. The acceptance and transmission of wind

a)

action require a stabilising system, which is described briefly in the following. Figure 2 shows the most important types of collapse, which must be prevented by the use of a stabilising system. Terrain classes for wind The force of the wind action depends among other things on the type of the terrain surrounding the building. In The Code of practice for Loads for the design of structures (DS 410) three terrain classes are defined. In the Code these classes are referred to as Smooth, Agricultural and Built- up, see table 1. Most new constructions shall be dimensioned for wind action according to the terrain class Agricultural . In an area with low buildings surrounded by farmland the wind action will only be reduced to a level corresponding to terrain class Smooth some 500-600 m inside the built-up area.

b) c)

d)

e)

f)

Figure 2. The stability of the house is ensured by anchoring the various structural elements to each other. The roof trusses must be braced to prevent them from cascading (a) and anchored against horizontal forces (b) and upward-acting forces (c). The walls must be supported at the top by the ceiling diaphragm (d), and this must be able to transmit horizontal forces to the windbracing walls. In ome cases, the walls must also be anchored at the bottom to prevent sliding (e) and collapse or lifting (f)

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SBI-Direction 186: “Stability of small houses” gives a more detailed description of terrain classes and of the possibilities to utilise the wind action’s dependency on the actual shelter conditions in connection to wind from various directions. Table 1 Definition of terrain classes according to “Loads for the design of structures”. The description applies to the surrounding terrain. Terrain class Smooth

Stabilising system The central parts of the stabilising system are the bracing walls and the so-called ceiling diaphragm . Some important terms are indicated on figures 3 and 4. The ceiling diaphragm supports the external walls at the top and furthermore transmits horizontal forces from the roof including the gable triangles. The ceiling diaphragm must be able to transmit these forces to the bracing walls, which may be internal walls as well as external walls. Consequently, the ceiling diaphragm must be fixed to all external walls and to the internal bracing walls. Further, the ceiling diaphragm must be sufficiently stiff in order to secure that forces can be distributed to the braced walls without causing fatal deformations, see figure 5. The stabilising system must be able to transmit the forces to the foundation or floor slab. This will often require a protection against sliding and /or anchoring against upward-acting forces on the walls In addition, the roof construction itself must be braced and anchored to prevent failure as shown in figures 2a-2c. Failure as shown in figure 2c is caused by the considerable lifting force occurring as a result of the longitudinal wind (along the roof). Translation KLJ

Facade

Gable

Transverse wind action

Description of terrain

Smooth terrain e.g. aquatic areas and moors without shelter. Agricultural Farm land with wind breaks, farms with gardens etc. Built-up Built-up areas or woodland.

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Transverse wall

Figure 3. Wind acting transversely: The gables and internal transverse wall may act as bracing walls. Longitudinal wall

Longitudinal wind action

Facade

Figure 4. Wind acting along the house: The facades and the internal longitudinal walls may act as bracing walls.

Wind

Figure 5. The ceiling diaphragm shall be adequately strong and rigid in order to distribute the wind action to the bracing walls.

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Dimensioning and design The dimensioning of load bearing and stabilising structures usually requires the assistance of an engineer. Enclosures A and D can be used to assist when dimensioning. Enclosure A, Loads, gives loads used in dimensioning structural elements affected by vertical action perpendicularly to their plane.

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The chapters concerning the specific construction elements give examples of designs with sufficient strength to transmit the forces. Enclosure D, Stabilising system describes how the stabilising system in 1-and 1½ storey single length houses with pitched roof can be designed and dimensioned.

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Foundations Foundation includes dimensioning and construction of foundations i.e. the structural elements that transmit load from the house to firm bearing stratum. Examples of foundations for various types of buildings are shown in figures 6,7 and 8.

Level of topsoil excavation

This chapter only applies to the construction elements accentuated in these figures. The remaining elements are discussed in subsequent chapters.

Level of topsoil Level of topsoil excavation excavation

Excavation trench profile

Figure 6 Foundation at ground supported floor. Normally in situ cast concrete as a deep strip foundation is used (cross-hatched in the figure). The upper part is often built using clinker concrete blocks. Hollow concrete blocks may also be used especially where the topsoil excavation level is below the topside of the deep strip foundation, thus avoiding the use of formwork for casting the upper part of the foundation. The foundation shall have at least the same width as the wall above and should be symmetrically placed below this. The figure also shows the placement of a perimeter drain and a branch drain, which connect the capillary breaking layer beneath the floor with the perimeter drain. It is not necessary to connect the branch drain directly to the perimeter drain. SBI Direction 189 Translation KLJ

Figure 7 Foundation at crawl space. Often a concrete pad is cast in situ (cross-hatched in the figure) and the crawl space wall is then constructed using clinker concrete blocks or hollow concrete blocks cast with concrete. The wall can also be cast fully or partly in situ, i.e. to the topsoil excavation level. The foundation shall have at least the same width as the wall above, and it should be symmetrically placed below this.

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Figure 8 Foundation at basement. Usually a concrete pad is cast in situ (cross-hatched in the figure) and the basement wall is then built using clinker concrete blocks or using hollow concrete blocks cast with concrete. Alternatively, the entire wall can be cast in situ. The foundation pad shall have at least the same width as the basement wall and it should be symmetrically placed below it. The figure also shows the placement of a perimeter drain and a branch drain which connect the capillary breaking layer under the floor with the perimeter drain.

Excavation trench profile

Foundation control classes Foundation work must comply with the directions given in Foundation Engineering DS 415 in which 3 foundation control classes are defined: Low, normal and high control class. In the present SBI direction, it is assumed that the control class is low. This class only comprises small and simple foundations on virgin and stable stratum above the water table. Such foundations can under certain conditions (as mentioned in the following) - be constructed based on empiric knowledge and without prior geo-technical surveys. If these conditions are not fulfilled the foundation shall be constructed according to normal or high foundation control class. In such cases geo-technical surveys of the sub soil shall be undertaken. Likewise, design as well as implementation control shall be carried out by experts. In such cases, we refer to the more extensive treatment of foundation problems in SBI-Direction 181: “Foundation of smaller buildings”.

Low foundation control class Foundations shall be constructed to a dept where they will rest directly on firm bearing stratum. That is usually a packed mixture of clay, sand and stone (called moraine clay by geologists) formed before or during the last Glacial Period. However, a bearing stratum SBI Direction 189 Translation KLJ

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can also consist of packed sand, gravel or coarse silt (called non-cohesive soil). If the bearing stratum is deeper than app. 2 m, it will usually be expedient to let an expert carry out the actual design work. When inspecting finished excavations, it must always be verified that foundation is carried out on firm and stable sediments. This inspection must be carried out by a person who possesses adequate geological and geotechnical knowledge. The local building authorities will in many cases demand to inspect the excavation before casting the first foundation. Likewise, the authorities may demand inspection of other parts of the construction. Usually the following soil layers are not considered stable: Fill, soil which has been excavated before or frozen soil, sediments with content of organic material e.g. turf, mud and certain special fat clays. The latter is characterised by not containing sand or stones and by having a high water content (25-40%), and by the fact that they sometimes crack. Such very fat clays are found in the western part of Funen and in the eastern part of Jutland .e.g. by the Little Belt, by the fjords in eastern Jutland and in the area around Skive.

Apart from resting on a bearing stratum, foundations shall be constructed at least to frost-free depth. Regarding external wall foundations, frost-free depth is usually 0.9 m below the surface. However, with special soil conditions such as silty soil the depth may have to be high. Silt is a soil type with grains rougher than clay but finer than sand. In low foundation control class there must be no digging below the level of the water table. It is therefore important to ensure that the water table is deeper than the planned level of foundation before starting the excavation. The excavation must not constitute any risk of damages to neighbouring buildings, sewer and supply lines, public traffic areas or similar. Thus, conditions in the neighbouring areas can in some cases exclude foundation work according to conditions in low foundation control class.

Dimensions Based on the above presumptions deep strip foundation can be carried out without further investigations - using the values found in table 2.

Table 2 Dimensions of deep strip foundation under walls in small single length houses. The dimensions given require that the width of the house is less than 9 m. Width of deep strip foundation in m Under load-bearing and Under load-bearing internal walls non-load-bearing external walls 0.20 0.30 1 storey with ground supported floor 0.20 0.30 1½ storeys with ground supported floor 0.25 0.30 2 storeys with ground supported floor 0.25 0.30 1 storey with crawl space 0.35 0.30 1½ storeys with crawl space 0.35 0.35 2 storeys with crawl space 0.25 0.35 1 storey with basement 0.35 0.35 1½ storeys with basement 0.40 0.40 2 storeys with basement The foundation height should be chosen to at least 0.30 m under load-bearing internal walls. However, in houses with ground supported floor, at least 0.20 m. Brickwork chimneys and fireplaces require a foundation of the same height as stated for the deep strip foundations. Type of house

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The dimensions are valid for traditional single length houses that is, houses with loadbearing facades and possible load-bearing longitudinal walls placed close to the centre line of the house. Deep strip foundations shall have at least the same width as the wall above and should be placed symmetrically beneath this. In houses with basement where the foundation is used as abutment for the concrete slab in the basement floor, the foundation shall be at least 0.10m wider than the basement wall. This will usually be fulfilled if the width is chosen to 0.50m. Non load-bearing internal walls can usually be founded directly at the floor deck concrete slab. The maximum linear and point loads, which can be transmitted, depend on the concrete slab and the insulating material. Reference is made to product catalogues from the insulation manufacturers . Alternatively non load-bearing internal walls can be founded on top of the capillary breaking layer, see figures 19 and 21 on pages 27 and 28. If bracing walls are not founded as loadbearing walls one must ensure that the vertical reaction can be absorbed by the bed on which the wall is resting (e.g. concrete slab). Workmanship Foundation work starts by excavating an area similar to the geometry of the building - for example to a level corresponding to the upper side of the deep strip foundations (see figures 6, 7 and 8). However, topsoil must be removed to a depth where the stratum is no longer weak and compressible (removal of layers containing organic material). Hereafter commences the excavation of trenches for the foundation according to dimensions (widths and depths) given in table 2. Dug out material must under no circumstances be filled back into the trenches. Notice that the foundation level (depth) shall at least correspond to the underside of the floor to be constructed later. Concrete 5 or better is used for the casting,

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see paragraph on concrete. Internal wall foundations in houses with ground supported floor shall only be taken down to load bearing subsoil, as they will not be exposed to frost (due to the temperature conditions under the house). If the oversite excavation level is lower than the topside of the deep strip foundation the upper part of the foundation can be cast using formwork. Alternatively hollow blocks of concrete or clinker concrete as well as massive clinker concrete blocks may be used.. The hollow blocks are stacked on the strip foundation with tight joints and bonding. When casting no more than two courses must be cast at one time using 5 or better. The concrete is carefully compressed with immersion vibrator. Horizontal construction joints shall be placed along the centreline of the blocks. Solid clinker concrete blocks are laid with filled joints using mortar KC 20/80/550 or better according to the “Code of practice for the Structural Use of Masonry” (DS 414) . When oversite excavation reaches deep down it might be expedient to build the entire foundation of hollow blocks on top of a concrete blinding. The underside of the foundation shall be horizontal. Stepping shall be carried out as shown in figure 9. Where service lines are taken across the foundation, the foundation must be carried out according to figure 10.

Max. 0.60m

Max. Slope 1:1

Figure 9 The underside of deep strip foundations shall be horizontal and even. Stepping must have a maximum height of 0.6m. The gradient depends on the soil conditions, but cannot slope more than 1:1. 18 14

Normal foundation depth

Figure 10. Where service lines cross the deep strip foundation, the underside of the foundations shall be at least 0.1 m deeper than the crossing line at a distance of minimum 0.6 m on either side of the line. Trenches for sewer and drain pipes which are dug parallel to the foundation must not be dug deeper than the bottom of the foundation. . Inserts or recesses To ensure the stability of the house it is often necessary to anchor the roof construction and/or the walls to the foundation. The placement of anchors must be determined prior to casting the foundation because the fixing of anchors can be done either simultaneously to casting or recesses can be made in the concrete for later fixing. The same applies to the placement of branch drains, which will be further elaborated in the chapters; “Drainage” and “ Domestic Ground supported floor”.

Table 3. Concrete mixing ratio (cement: sand: stone) Concrete type

Mixing ratio according to volume Concrete 5 1:4:7 Concrete 10 1:3:5 Concrete 15 1:2:3

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Mixing ratio according to weight 1/4/6 1/3/4 1/2/2½

Concrete Concrete 5 or better is used, cf. table 3. According to” Code of Practice for the structural use of concrete” (DS 411). the crushing strength of the concrete shall be controlled but factory control is considered adequate when concrete is supplied by a concrete manufacturer being a member of the “The Concrete Manufacturers’ Control Board” (In Danish FBK) or “The Danish Concrete Certification” (In Danish DBC)

Furthermore, concrete can be mixed on site without strength control as stated in table 3. The slump range of the concrete should be between 60 and 100mm and must not exceed 150mm. The requirements for concrete aggregates and the implementation of concrete work are described more thoroughly in the ”Code of Practice for the Structural Use of Concrete” (DS 411) Concrete and light clinker concrete hollow blocks shall fulfil the requirements for strength class 3.0 Mpa and must be delivered from a factory affiliated to an approved control system (i.e. marked with a triangle). Solid clinker concrete blocks shall fulfil the requirements for strength class 2.6 MPa according to “Code of practice for the Structural Use of Masonry” (DS 414) and must be delivered from a factory affiliated to an approved control system (i.e. marked with a triangle or marked “LBK”)

Note: According to new standards concerning concrete strength the values in the table are no longer applicable. When using prefabricated concrete it is recommended to prescribe concrete 4, 12 and 16 respectively

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Drainage Houses shall be built in such a way that surface water, ground water and earth moisture do not cause damage. Hence, surface water shall be drained off by establishing an adequate slope in the ground away from the house, see figure 11. Where the subsoil is not adequately self-drained, that is where infiltration water does not quickly soak away by itself, drains shall be established along the external wall foundations of the house – a socalled perimeter drain. However, a perimeter drain can be left out in houses where the surface of the floor deck is more than 300mm above the external ground level. The purpose of draining is to reduce or completely remove water pressure on construction carried out directly against the soil. In this way seepage in the construction can be minimised and building components below ground can be kept reasonably dry. Draining does not eliminate moisture and, depending on the circumstances, draining must therefore be supplemented with moisture insulation. In this chapter only draining of houses in noncomplicated situations will be described, that is where the ground water level is below the

Flat terrain

Perimeter drain

Slope

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Sloping terrain

Intercepting drain

drainage level. In this case, drainage only includes the draining off of infiltrated surface water. Draining shall be carried out in accordance with the Code of Practice for the groundwater drainage of structures (DS 436) and Code of Practice for Sanitary Drainage - Waste-water installations (DS 432). A more comprehensive discussion on the subject can be found in SBI direction 185: Sanitary Drainage Installations. Workmanship A drain consists of two parts, namely the drainage pipe and the drainage fill. Drainage fill is a filter (for instance gravel) which ensures the collection and transportation of affluent water from the surroundings. At the same time it prevents unwanted pollution and possible blocking of the drainage pipe (in the form of sediments). Thus the filter shall be build of a material with a grain size that fulfils the so-called filter criteria (criteria that regulates the size and the grains in the filter and the grains of the surrounding soil). The drainage pipe, which usually consists of a perforated pipe (with slits and holes in the pipe wall) directs the captured water to e.g. established waste water installations. When building a filter the pore size and the flow Figure 11. Ground levelling must drain surface water away from the house. On flat terrain the slope away from the house must be minimum 20 per mill (1:50) within a distance of 3 m. On sloping terrain the ground must be levelled on the side of the house where the initial level is highest, and an intercepting drain must be installed at the intersection between the initial terrain and the levelled ground

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openings should increase from the surroundings towards the drainage pipe. Drainage pipes shall be laid with a grade of at least 3 per mille. Due to the risk of frost damage the overall bottom level should be at least 0.60m below finished ground level. Moreover, the highest bottom level should be at least 0.3 m below the construction part to be drained. Excavations must not be carried out below the bottom level of the foundations. Pipe dimensions must not be less than 70 mm (as smaller dimensions may cause cleaning problems). Pipe and fittings must fulfil the requirements laid down in the Code of Practice for the groundwater drainage of structures (DS 436). Pipes without socket joints should not be used. Figures 6,7 and 8 show examples of placing a perimeter drain. If the surrounding soil consists of clay (firm cohesive soil), the filter may consist of a layer of small pebbles (2-8 mm) or pea gravel (5-16mm). A coarser material may be used when 80mm perforated PVC pipes or similar are used. In sand and similar (noncohesive soil) a filter of wellgraded sand with d10>0.3mm and 1,5mm