The normal height for a crawl space ranges from 0,6-0,8 m. The purpose of a crawl space is to obtain a distance from the ground to the ground floor, to prevent contact with ground moisture. See figure 22. A crawl space must be protected from ground moisture and sur-face water.
The external wall must be constructed so that it can withstand the surrounding earth pres-sure.
Fire demands
The floor (deck) over the crawl space, be-cause it can be used for storage, must fulfill the same fire demands for a floor over a basement (BD 60 for 1 '/4 + 2 storey houses).
U-value
The deck over a crawl space must fulfill the heat frame demand of U-value 0,20.
Figure 22
Crawl space deck construction can be of prefabricated light weight slab with 100 mm insulation bonded to the underside. The outside edge of the slabs by the external walls, should be insulated in between the external leca blocks, to prevent thermal loss (cold bridge).
The timber floor construction over the slab must be protected from building component moisture with a 0,15 mm polythylen DPM, laid on the slab. 75 mm extra insulation is laid on the DPM to prevent condensation on the overside of the DPM.
Figure 23
It is recommended that ventilation vents are placed every 6 meters in the external walls. Each vent must have a minimum cross area of 150 m2. The vents must be placed so that still air pockets are' prevented in the crawl space.
Air vents must be placed in internal walls when necessary, to create airflow from external wall to external wall.
It must be possible to inspect the full area of the crawl space by inspection hatches and openings.
With regards to the inner walls stability the inspection openings must not be placed by the external walls. If the crawl space's deck is constructed in concrete or similar non-moisture sensitive mate-rial, the number of vents can be reduced by 50%, but there must be at least one vent at each corner.
Ventilation
Moisture, that enters the crawl space is re-moved by ventilation. For size and position-ing of vents see figure 23 and 24.
Crawl space floor
The floor in the crawl space is normally cast in 80 mm non reinforced concrete 5 or stronger. The concrete slab can rest on the ground if the top soil is removed. It is recom-mended to cast the concrete on a 0,15 mm polythylen sheet.
Crawl space external walls
Crawl space external walls can be constructed of concrete foundation blocks that are cast with concrete or of (leca) light weight con-crete blocks.
The external wall can also be cast on site in form work with concrete 10 or better. The walls must have at least the same thickness of load bearing walls above. The foundation blocks must be bonded together on a strip foundation and cast together highest two courses at a time with concrete 10. Horizontal joints must be placed in the concrete in the middle of the block. Leca blocks must be bricked up with full joints, with mortar KC 20/80/550 or better. The blocks can be reinforced with 2 pieces of BI steel or 2 pieces of 6 mm tentor steel in every 1/3 horizontal joint. The reinforcement must continue along the wall and around corners.
Over lapping must be a minimum of 300 mm.
SBI Direction 189 30
Translation RHT
Figure 24
The vents in the crawl space walls must be placed 80-100 mm over the ground and end under the crawl spaces deck (under side floor). A horizontal vent channel through the external wall can cause the ground floor level to lie too high over the ground. This distance can be reduced, if the vent channel is bent down and inwards. If so the channels cross section should be increased min.
50%.
The casting of the wall should be done at one time, the concrete must be compressed care-fully with vibrator.
Holes and indentations must be repaired with cement mortar 1:3.
To be sure of the walls stability, because of ground pressure, see max. wall size page 38.
The house must also be stabilized against wind suction, with casting of anchors in the crawl space external wall or foundation, if the walls are constructedwith leca blocks. The crawl space's external walls must be moisture resistant. The walls of blocks must be rough rendered in the full height and then fine rendered on the visible part over ground level and 150 mm under ground level.
The rest of the external side of the wall mus' be coated with bitumen. The same for walls cast in concrete 10.
Filling out at the external wall must not be started before the crawl spaces floor is cast and internal cross walls are constructed. If a 4 sided supported wall is implemented then the deck over the crawl space must be con-structed.
Internal walls
Internal walls in crawl spaces are normally constructed in concrete foundation blocks, leca blocks, light weight concrete. The walls must be a minimum thickness of the load bearing walls above.
Minimum 80-100 Minimum
80-100
Crawl space deck
The deck (floor) over the crawl space is normally constructed with timber floor joist or prefabricated elements of leca concrete.
Under wet rooms the joists are replaced with concrete slabs.
Timber joists
For joists dimensions, see page 41. To obtain a U-value of 0,20, the joist con-struction must be insulated with approx.
200 mm mineral wool. Approx. 1/3 of the insulation shall be placed under the joists to prevent moisture concentration. The insula-tion must be fixed carefully so that air cur-rents do not penetrate the joints. The deck must be wind resistant so that draughts are prevented from the floor. This can be done by placing a DPM under the floor boards and fixing it at the back of the skirting board. This will also prevent radon expo-sure.
The floor joist construction must be insu-lated against moisture at the walls by laying a DPC of bitumen felt between the walls and timber.
The ends of the joist in the external wall and the joist sides by the external wall must be coated 2 times with timber impregnation paint.
Figure 25 shows an example of a timber joist construction, and figure 26 shows an example of a concrete slab under a wet room.
Figures 27 and 28 show examples of con-nections between joists and external walls.
To limit the joists height it is normal to use a height of 150 mm as shown in figure 25.
This will reduce the max span of the joists, therefore extra load bearing walls will be constructed in the crawl space. Foundations dimensions from table 2, page 17 can be reduced to the half of the given sizes though min. 0,15 m.
Mineral wool 39, 150 mm between joists
Stiff, wind resistant mineralwool boards 36, 75 mm Fixed under joists
U = 0,18
Figure 25
1/3 of the insulation placed under the joists.
Reduce the insulation thickness between the joists to 125 mm, increases the U-value to
0,20.
Wet room with concrete slab cast in situ Floor tiles laid in mortar
Concrete slab with/without heated floor
Pressure resistant insulation, 30 mm Concrete slab
Insulation X-kl.36, 150 mm
fixed mechanically U = 0,19
Figure 26
Crawl space deck constructed with timber joists and concrete slab under a wet room.
To keep the timber joists from the wet room, they are load bearing on brick piers.
•Timber joists over crawl space Floor boards
DPM
Joists 75 x 150 mm
SBI Direction 189 32
Translation RHT
Figure 27
Timber joist crawl space deck. A cold bridge is avoided by placing c
vertical pressure resistant insulation in the middle of the wall. Heating pipes fixed under the joists are insulated independently. DPM laid directly under floor boards prevents draughts and radon from the crawl space.
Figure 28
Timber joist construction.
Cold bridge between stud frame and timber joists is prevented by placing insulation vertical over the leca block. The DPM must be bonded to the internal wall cladding to prevent draughts and radon. The bottom frame of the wall must be pressure
impregnated.
For dimension of concrete slab cast in situ, see page 42. Leca concrete deck can be developed in standard size and load bearing capacity.
To obtain a U-value of 0,20 the concrete and leca concrete must be constructed with insulation, 175 - 200 mm depending on the slabs own insulation ability.
With timber floor boards on battens or other sensitive floor coverings a DPM must always be laid on the overside of the concrete deck for protection against building component moisture.
In this case a layer of insulation max. 75 mm can be placed over the DPM to prevent condensation forming on the overside of the DPM.
Figure 29 is an example of a leca concrete with insulation cast on the underside. Figure 30 is an example of a wet room floor
construction on a leca beton slab. An example of the connection between slab and wall is shown in figure 31. The figures 32 and 33 are details of external door and slab construction.
Floor boards Timber joists
Mineral wool between joists Stiff, wind resistant mineral wool Boards under joists
Heating pipes under timber joists
Stud frame with timber cladding
Electricity pipes on the warm side of the insulation
Floor boards, DPM Timber joists
Mineral wool between joists Stiff, wind resistant mineral wool under joists
Ventilated crawl space
Leca concrete component over crawlspace Floor boards on battens. Mineral wool 39, 75 mm, DPM.
Deck component, sandwich construction 160 mm density 600 kg/m3.
Mineral wool 39,100 mm.
Cast on component in the factory U = 0,20
Figure 29
Crawlspace deck of leca concrete
component with insulation. Only a minor part of the insulation must lay over DPM.
Figure 31
Leca concrete component deck as show in
figure 22. The deck construction isplaa as low as possible in connection to the ground level, approx. 150 mm underflow level.
If the level between in and out should be reduced even more, a trench could be established along the external wall.
Figure 30
Wet floor construction on leca
concrete components see page 29. If an extra 50 mm insulation is fixed on the underside of the deck a U-value ofO, 18 can be obtained.
Or to fulfill the heat loss frame the extra 50 mm insulation can be placed on another building component.
SBI Direction 189 34
Translation RHT
Figure 32
Detail of an inward opening door with a construction as shown in figure 31. There must be a landing of steel mesh or ground raised to the same level of internal floor covering. There must be a gap between the raised earth and external wall to prevent moisture penetration. This could be achie-ved by placing a paving stone on its edge to hold the soil away from the external wall.
The air gap should be so wide that it is possible to clean it for leafs, dirt etc. If the entrance is designed with an open porch a smaller open drain channel will be
sufficient.
Figure 33
Detail of outward opening entrance door with a construction as shown in figure 31. To be sure, that the door can open in all conditions, the landing should lay a min. of 20 mm under the doors leafs under side. The difference in levels can be solved with a steel meshed ramp etc. placed between the landing and external wall.
SBI Direction 189
Translation RHT 34
Basements
A basement must be insulated against heat loss, moisture and radon penetration from the ground. The basements external walls must withstand ground pressure. The deck over an unheated basement must have a U-value of 0,40 or better.
Fire prevention
Basements external walls, load bearing in-ternal walls and deck must be constructed with a minimum of a BD-building component 30. In houses of 1½ or 2 floors and basement the load bearing construction must be con-structed as a BD-building component 60, and a stairway from basement to ground floor must be separated from the basement or ground floor with a minimum of a BD-building component 60 with a BD door 30.
The walls and ceilings must be constructed with a minimum of a class 2 cladding.
Basement floor
A basement floor is normally constructed with a concrete slab with contraction
rein-forcement, heat loss, insulation and a capil-lary breaking layer or a combined insulation and capillary breaking layer. The U-value for a basement floor is U-value 0,20. See figures 35 and 36. Radon penetration can be prevented by casting the slab floor and the external walls foundation and internal walls foundation as shown in figure 34. The concrete floor can rest on the ground
Basements external walls
Can be constructed of concrete or concrete foundation blocks or solid light weight con-crete blocks. Or can be cast in situ with shut-tering or form work with concrete 10 or stronger. They must have a minimum thick-ness of the wall it carries from above. See fi-gures 34,38, 39 and 40.
Foundation blocks are laid on a strip founda-tion in a bond and are cast out max two courses at a time with concrete 10 or stronger.
Solid light weight blocks are laid with full joints with mortar KC 20/80/550 or stronger referring to masonry norm. There must be laid Bl-steel or 2 x 6mm tentor steel or similar steel with the same strength in every third horizontal joint. The reinforcement must continue along the wall and around corners.
Overlapping must be a minimum of 300 mm.
The casting of the wall should be done at one time, the concrete must be compressed care-fully with a vibrator. Holes and indentations must be repaired with cement mortar 1:3. If the basement wall is constructed as a cavity wall, it is recommended to fix an extra row of wall ties under the deck.
_A
SBI Direction 189 36
Translation RHT
Figure 34
The section referring to low and high lying terrain. The top part of the external basement wall is constructed as an insulated cavity wall. The insulation in the cavity must overlap the external insu-lation with a minimum of 200 m. In this case the top part can not be counted as (with the basement deck) load bearing for ground pressure. The basement window is constructed on the outer leaf with a brick lintel and inner leaf with a prefabricated concrete beam A cold bridge is prevented with
SBI Direction 189
Translation RHT 36
Concrete basement floor 100 mm concrete
Plastic membrane to prevent radon 100 mm pressure resistant insulation 150 mm capillary breaking layer of gravel Pressure resistant insulation X-kl. 39 U = 0,21 Pressure resistant insulation X-kl. 36 U = 0,20
Figure 35
Concrete slab basement floor with separate insulation and capillary gravel layer
Concrete basement floor 100 mm concrete
Plastic membrane to prevent radon 250 mm Ieca modules Wcl.80 U = 0,20
Figure 36
Concrete basement floor combined insulation and capillary layer of Ieca nodules.
The specified external basement wall in this, chapter fulfills the fire prevention demands and radon prevention recommendations.
Filling in around the basement external walls must not start before the basement floor and internal cross walls are con-structed. If a 4-sided supported basement external wall is to be implemented the deck over the basement must be constructed, also before filling in.
Dimension
The soil pressures forces on the basements external walls, as a rule will only be sup-ported along 3 sides, the bottom side and two vertical sides, see figure 34; A basement deck of light weight concrete with correct construction detailing together with the basement walls, for example with
reinforcement to compensate for the weak-ened construction due to the cavity wall, can be classed as a 4-sided supported con-struction. Basement walls or non-reinforced concrete cast in situ (concrete norm 5.55) can be constructed in sizes given in table 4.
Table 4 Maximum sizes h x I for non-reinforced concrete 10 basement walls or foundation blocks cast but with concrete 10.
h and I is given in figure 37.
Supported Wall thickness, t
300 mm 400 mm
3-sided 4-sided
10 m2 15 m2
13,3 m2 20,0 m2
For wall thickness between 300 m and 400 m, the maximum size is calculated with interpolation between the
SBI Direction 189 38
Translation RHT
Concrete external basement wall Expanded polystyrene, X-kl.39, 125 mm, with vertical drain chan-nels and large meshed fibre sheet against the ground. 300 mm concrete.
U = 0,28
Figure 37
For a 3-sided supported basement external walls the max area is decided with hxl where h is the height of the forces from the earth pressure and I is the distance between the cross walls, t is the walls thickness.
Figure 38
External basement wall of concrete and ex-ternal insulation. Insulation with drain chan-nels, if a non-drained insulation is imple-mented. The basement wall must be moisture insulated.
On 4-sided supported walls h is measured to the underside of the floor partition. Sizes of external basement walls constructed in foun-dation blocks are calculated as the same as non-reinforced concrete walls cast in situ with the same thickness. Sizes of external basement walls of leca blocks can be constructed with 60% of the size for non-reinforced concrete walls with the same thickness.
Insulation
The U-value for a external basement wall is U
= 0,30.
Insulation is preferred on the outside of the basement wall underground level as the wall will be warmer and dryer. Insulation material can consist of pressure resistant material e.g.
mineral wool batts or polystyrene boards with drain channels clad in fibre sheeting. See figure 38 and 39.
Over ground level the basement external walls are usually constructed as a cavity wall with 100 mm insulation in the cavity, the insulation
Leca block basement external wall Drain fill
Pressure resistant mineral wool 39. 75 mm Bitumen coating Thin cement coating Leca block 330 mm Render
U = 0,28
Figure 39
Basement external wall
offoundation blocks or leca blocks with external insulation. Moisture insulation can be made with corrugated plastic sheeting with or without thermal insulation with drain channels.
I.,,
SBI Direction 189
Translation RHT 38
Concrete external basement wall Drain fill Thin cement coating Bitumen coating
Render Concrete 300 mm Mineral wool 39,15 mm LWC concrete
Component 75 mm Density 645 kg/m3
U = 0,29
Figure 40
External basement wall with internal thermal
insulation.
overlapping the external insulation, see figure 34.
External basement wall with internal thermal insulation of mineral wool batts fixed
mechanically and clad with light weight concrete components, see figure 40. This solution is the best considering moisture protection and internal insulation.
Moisture insulation
To prevent water pressure against the basement walls a wall drain must be laid either with a drain layer gravel etc., bricking up a wall of blocks (leca) on the external side of the basement wall or insulation material with properties for draining.
Note that pressure resistant insulation has not this ability. There must be a connection from the wall drains to drain by the footings.
A basement external wall must be constructed in such a way to prevent moisture damage by surface water the visible top part of the wall must be rendered to approx. 150 mm under ground level.
Moisture penetration on the rest of the wall is prevented either with two coats of liquid bitumen or fixing thin hard plastic, corrugated sheets.
The bitumen coating must be on a plane base and protected by a thin layer of cement mortar 1:3. See figures 39 and 40 for construction with drain blocks and external thermal
insulation. Moisture insulation is not necessary on concrete walls with external thermal
insulation with drainage properties, see figure 38. Concrete walls of concrete 15 or better rendering is not necessary.
insulation with drainage properties, see figure 38. Concrete walls of concrete 15 or better rendering is not necessary.