Vented cast stone facings for buildings

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Technical Translation (National Research Council of Canada), 1967

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Vented cast stone facings for buildings

Kopatsch, H.

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With the recent trend towards lighter exterior walls thermal

considerations in design and construction are ｾ｡ｩｮｩｮｾ increasing

importance. Condensation on interior surfaces as well as inside the

wall itself can significantly reduce the satisfactory performance of such walls.

Although Canada has, because of its climate, already achieved a

considerable degree of maturity in dealing with these thermal ｰｲｯ｢ｬ･ｭｾ

it is interesting to study the approach used in other countries in

dealing with thermal and moisture problems in walls. It is for this

reason that the Division of Building Research arranged to have this article

by

H.

Kopatsch translated. The article is about the use of vented case

stone facings for buildings and describes German practices, refers to pertinent German DIN specifications and presents certain recommendations for such claddings.

The Division wishes to record its thanks to

W.R.

Schriever, Head

of its Building Structures Section,for ｴｲ｡ｮｳｬ｡ｴｩｮｾ this paper, and to

the Translations Section of the National Research Council with whose co-operation this translation is being produced.

OTTAWA

September,

1967

N.B. Hutcheon Assistant Director

NATIONAL RESEARCH COUNCIL OF CANADA

Technical Translation 1301

Title: Vented cast stone facings for buildings

(Beluftete Fassadenkonstruktionen mit Betonwerkstein)

Author: H. Kopatsch

Reference: ｂ･ｴｯｮｳｴ･ｩｮＭｚ･ｩｴｵｮｾＬ 30 (3): 109-116, 1964

Translator: W.R. Schriever, Division of Building Research, National

Introduction

The development in the field of ｢ｵｩｬ､ｩｮｾ ｴ･｣ｨｮｯｬｯｾｹ and structural

･ｮｾｩｮ･･ｲｩｮｧ in modern buildings has led to a much ｨｩｾｨ･ｲ exploitation of the

strengths of the various materials and consequently to thinner members in

load ｢･｡ｲｩｮｾ walls and exterior walls. Load ｢･｡ｲｩｮｾ exterior walls have

become rather thin. This is even more the case with non-load bearing exterior

walls which, as infill walls and curtain walls in framed construction are now made as thin as possible in order to reduce weight and thus to derive the

greatest economic ｡､ｶ｡ｮｴ｡ｾ･Ｎ The structural requirements of a ｢ｵｩｬ､ｩｮｾ or a

building element are, however, not the only ones to be considered. There are

a number of other important requirements to fulfill which relate predominantly

to climatic effects and the use of the building. Thicknesses of exterior walls

in building constructions of 50 cm (20 in.) or more were common until a few

decades ｡ｾｯＮ These walls were structurally greatly ｯｶ･ｲＭ､･ｳｩｾｮ･､［ from the

point of view of a healthy indoor climate such walls,especially when built of

soild masonry, were very satisfactory. The present trend towards reduction

of the wall thickness to the bare minimum means that many of the walls do not

always satisfactorily fulfill all physical requirements. The obvious solution

to the problem is the use of a multi-layer wall structure in which each layer fulfills a separate function.

So far it has been common in building practice to consider the thermal resistance of elements in the steady state condition as a measure for their

thermal behaviour. The behaviour of building materials and ｢ｵｩｬ､ｩｮｾ elements

from a thermal and moisture point of view have such an influence on each other, however, that the separate treatment of one of these factors alone

leads to an unsatisfactory result. This is true particularly in multi-layer

wall construction as will be shown.

Performance Requirements for Exterior Walls

Exterior walls in addition to structural loading are subjected in the main to the following forces:

1. Thermal forces due to solar radiation and temperature ｣ｨ｡ｮｾ･ｳ from warm

to cold.

2. Moisture effects due to ､ｲｩｶｩｮｾ rain.

3.

Moisture effects from the inside due to water vapour diffusion and

ＭｾＭ

Thermal effects

The exterior faces of ｢ｵｩｬ､ｩｮｾｳ are subjected to daily and yearly

temperature cycles and· the ｲ･ｳｵｬｴｩｮｾ ｬ･ｮｾｴｨ changes or stresses.

The surface temperature of a body subjected to solar radiation depends

in the first instance on the ｰ･ｲ｣･ｮｴ｡ｾ･ of the total received radiation

energy which is transformed into heat at the surface. Other factors involved

in the resulting surface temperature are the influence of the conductivity of the surface, the temperature and movement of the surrounding air, the temperature and surface of any other bodies in contact with the considered

surface and the thermal properties of the body itself and any back-up materials. A highly insulated wall material of small conductivity produces a thermal

barrier for the exterior cladding.

Tests on the temperatures of typical surfaces under the influence of

solar radiation and the loss by radiation ､ｵｲｩｮｾ the night are described by

K.

SChropp(l), which indicate marked dependence of the temperature on the

colour of the surfaces.

The greatest over temperatures compared to the ambient air temperature were obtained for black surfaces, the smallest for white surfaces and for

shiny aluminum foil. In contrast to the temperature increases under solar

radiation, it was found that the temperature difference at night, ｲ･ｳｵｬｴｩｮｾ

from long wave radjation to the sky, was almost the same for the white surface

as for the black. The behaviour of white surfaces under the influence of

solar radiation is explained by Schropp by the dependence of the absorption conditions on the type of received radiation energy, that is, on the

wave-ｬ･ｮｾｴｨ of the radiation, or in the fact that it is much smaller for short

wave radiation than for long wave radiation.

Reiher(2) also emphasizes the influence of the colour on the temperature

variations and therefore on the ｬ･ｮｾｴｨ variations of wall materials which are

subjected to solar radiation.

According to SchUle(3), walls facing east-south-east and west-south-west receive the greatest radiation in the months May, June and July, whereas the walls facing south receive the maximum for the other months.

In the construction of exterior stone facings the effects of thermal loads must be considered in the construction requirements such as to reduce

the resulting stresses to a minimum. The specification DIN 18,333, Cast

Stone Construction, does not contain any requirements in this regard. On the

type of attachments, clause ＳＮｾＲ specifies the ｦｯｬｬｯｷｩｮｾＺ Each niece of the

cladding must be anchored to the backup material in such a way that it will

be completely secure. Unless otherwise specified in the contract, each piece

In this requirement for a mortar joint we find contained a general desire

to create a vented zone behind the cladding. It is, however, not explicitly

said that the mortar strip should be interrupted and should not run

con-tinuously over the full height and width of the building. Furthermore there

is no indication in DIN 18,333 of the desirability of making the ｣ｬ｡､､ｩｮｾ

envelope flexible in order to reduce the stresses. As an ･ｸ｡ｭｰｬｾ a

calcula-tion of the stresses will now be made for a given set of boundary condicalcula-tions.

a) Monolithic installation. As a basis of the calculation we shall

use the temperature gradient indicated in Figure 5. It will be assumed that

°

the ｣ｬ｡､､ｩｮｾ was installed at a temperature of 25 C and that the cladding and

the back-up wall had the same temperature. The thermal expansion coefficient

of concrete according to Graf(4) depends largely on the type of aggregate. In DIN 1045, paragraph 16, it is indicated for use in building purposes as follows:

-6

°

at = 10 x 10 / C.

The increase of temperature over the mean value of the back-up wall is

64 - 41 = 24°c. The resulting strain is

-6

4

4

-4

E

t

=

10 x 10 x 2

=

2. x 10

if we assume furthermore as a favourable condition that the back-up wall has

already come to a stable condition so that no stresses result from ｳｨｲｩｮｫ｡ｾ･

and creep which would be transmitted to the cladding. Then the stresses

from the above difference in strain between the cladding and the wall is calculated according to Hook's law with a modulus of elasticity for concrete according to Graf(5)

E

= 1.7

+

(360 (for w b 28 = 300 kg/cm 2) a = 2.4 x 10-4 x 2.6 X 105 = 62.4 ｫｾＯ｣ｭＲＮ

b) Elastic or open joints. This compressive stress in the cladding is

even higher when the shrinkage and creep of the wall is not complete at the time of the installation of the cladding.

For a slab length of 50 cm the strain is calculated as

-6

4

4

-2

1 = 10 x 10 x 2 x 500 = 2. x 5 x 10 = 0.12 mm.

The joint between slabs is reduced as a result of this by 0.12 mm. If we now

consider shrinkage and creep effects of the wall behind of 0.4 mm/m then the

joint between the cladding slabs is reduced by 0.12 x 0.2 = 0.32 mm. An

-6-obviously in leaving the joints open and to prevent the ingress of driving

rain by means of stepped joints. Under the condition that the cladding stones

are mortared in strips, whereby the mortar strips must also be interrupted, it is possible in this solution to ensure that the strain is reduced to the value of the strain of a single stone and that therefore an addition of the

strain increase and the resulting ｰｲｯｾｲ･ｳｳｩｶ･ stress in the cladding is

avoided.

The maximum strains which can be tolerated by strips of mortar have been

investigated for a number of cases. In order to make the test more simple,

the wall to which the cladding had been fastened was shortened in a loading

test (see Figure 7).

Figures 7a-c show the shortening up to the destruction of the bond. Driving Rain

The DIN standards do not contain any definite instructions regarding the effects of driving rain on buildings and oreventative measures against it.

Brocker(6) proposes the following definition of dri vim; rain : "Driving rain

is precipitation (rain) combined with wind of at least speed

5

in the Beaufort

scale. Heavy driving rain is precipitation (rain) combined with wind of

speed

8."

For wind speeds of

5

and up, the angle of rain impingement exceeds

45°.

Pohl(7) has stated that it is not the kinetic energy of the rain drops but the absorption properties of the wall that are most important.

Even under very high wind speeds the ｲ･ｳｵｬｴｩｮｾ water pressure on the

wall surfaces exposed to driving rain is very small as shown by the following values: Wind Speed km/h m/sec Stagnation Pressure mm (H₂₀₎ kg/cm2 50 65 102 140 13.9 18.0 28.3 39.0 12 20 50 95 0.012 0.020 0.050 0.095

The importance of the wind in driving rain lies in the fact that it

produces a "water film" on the outer surface of the wall. Free-standing and

especially high buildings which are not sheltered by other buildings - a frequent occurrence in our modern type of wellspaced high rise buildings -are especially subject to the effects of driVing rain.

In order to satisfy the requirements of comfort and health in living quarters it is necessary to try to keep the exterior wall materials as dry

reduced considerably.

In ｾ･ｮ･ｲ｡ｬ the capacitv to insulate is denendent on the norosity and

nature of the pores of the wall material. Since the water tends to fill these

pores and since water conducts heat 25 times as much as air, the adverse

effect of higher wall moisture contents is obvious. It is therefore important

to provide a sufficient exterior protection against ､ｲｩｶｩｮｾ rain in order to

prevent an increase of the moisture content of the wall material. Moist walls

in living quarters are frequently the source of illness and very often lead to damage to the building itself as well as to household effects, and not

least there are economic disadvantages since with ｩｮ｣ｲ･｡ｳｩｮｾ moisture content

of building materials conductivity ｾｯ･ｳ un and therefore the fuel consumntion

for heating purposes.

The requirements of DIN 4108 (Thermal Requirements for Buildings) are

limited in the main to minimum requirements of insulation for three climate

zones. The basis for this division into zones was found in local exnerience

in the individual areas with their traditional ｢ｵｩｬ､ｩｮｾ types, as well as

climate data. Using the minimum values of insulation calculated from these

requirements, condensation is usually not a narticular nroblem under normal

boundary conditions, provided the ｩｮｳｵｬ｡ｴｩｮｾ capacity of the wall material

used in the calculation is actually available and has not been reduced by

increased wall moisture The change of the thermal resistance with increasing

In section 7.11 it is merely stated, among

moisture content and the resulting ｣ｨ｡ｮｾ･ in conductivity is illustrated in

the ｦｯｬｬｯｷｩｮｾ table (measurements of Schmidt and Grossmann).

Table I

Conduction coefficients as function of the moisture content of the wall

Solid brick wall, immediately after construction 1.20 kcal/m hOC

Solid brick wall, three months old 1.00 kcal/m hOC

Solid brick wall, dry, twelve months old 0.75 kcal/m hOC

DIN 4108 does not contain any concrete suggestions or measures to safe-guard the thermal insulation.

other things:

"Exterior walls which are made of non-frost resistant or from rather

porous absorptive materials, have to be protected on the outside ｡ｾ｡ｩｮｳｴ

penetration by water, by a water repellent stucco, or by other adequate weather

-8-or equivalent buildintS materials."

Exterior claddings commonly used in the old days, eSDecially on timber frame houses with masonry infills and on gable ends, with wood shingles, slate and metal plates, stem from the same desire to improve the resistance atSainst drivintS rain and was technically correct since this construction did not

block vapour diffusion ｴｨｲｯｵｾｨ the wall and since thermal stresses and to

some extent also movements of the building could be accommodated by this layer, althoutSh certain disadvantages with regard to durability, health and aesthetics had to be accepted.

In drivintS rain, intensity and frequency as well as predominant wind

direction vary from place to place. ｆｩｾｵｲ･

9

tSives some indication on the

driving rain intensity and frequency for three representative cities. It will

be seen from this that driving rain effects on exterior walls are not limited to the north German lowlands.

Wind LoadintS. Wind loading is an essential factor when considerintS

the structural frame In addition to this, however, elements of the wall

must also be built to resist the wind loads without ､｡ｭ｡ｾ･Ｎ The wind loads

are given in DIN 1055, Load Assumptions for Buildings, sheet 4. The wind

direction can, in tSeneral, be assumed to be horizontal. The wind load which

is composed of a pressure and suction effect, is,

The coefficient c depends on the shape of the building and can be assumed to

be 1.2 for a closed ｢ｵｩｬ､ｩｮｾ with plane surfaces at right angles to the wind.

Taale II

Stagnation pressure of wind loads with shape

coefficient of c = 1.2

Height of BuildintS Stagnation Pressure Wind Load for

m kg/m2 _c

=

1.2 kg/m2_ From 0 to 8 50 60 From 8 to 20 80 96 From 20 to 100 110 132 Over 100 130 156

For closed buildings with a rectangular plane the wind load can be assumed to be composed of a pressure of +0.8 q and a suction of -0.4 q for the

main frame. Walls, roofs and other building elements have to be safeguarded

depend on the type of ｢ｵｩｬ､ｩｮｾＮ

Table III

Coefficients c and suction w per unit of area

w

=

c xq

Type of Structure Coeff. q =

50

q

=

80

q

=

110

q

=

130

c kg/m 2 kg/m 2 ｫｾＯｭＲ kg/m 2

Closed buildings, walls and roofs

in general

0.4

20

32

44

52

The same for

tower-like structures

0.8

40

64

88

104

DIN

1055

also states that along the intersections of wall and roof

sur-faces the suction can be much higher than the above calculations indicate. All building elements therefore have to be fastened very carefully in such areas.

Moisture effects from the interior caused by vapour diffusion and

condensation. The vapour diffusion as a further criterion of building physics

will be treated here only in a general way and only to the extent to which this is necessary for the evaluation of the advantage of a ventilated exterior

cladding. Ordinary household activities produce water vapour (cooking,

washing, breathing). Like all other gases water vanour in the air, as a

result of molecular movement, has a desire to even out density differences.

This phenomenon is called diffusion. Since furthermore water vapour density

and water vapour pressure are proportional, the diffusion can also be regarded

as an equalization of pressure, the vapour movement ､･ｰ･ｮ､ｩｮｾ on the pressure

differences. A pressure difference also exists when, in spite of the same

vapour density, different temperatures are present, since the vapour pressure

increases with the temperature. As a result,vapour movement will take place.

Apart from the pressure difference between the two sides of a building element, the specific vapour permeability of the building material is of importance

in considering vapour movement. This property of the material is called

diffusion resistance factor and is a measure of how much the diffusion resist-ance of the building material considered exceeds that of a layer of air of

the same thickness. The amount of water vapour migrating through the material

-10-composition as well as its moisture content. The amount of water vapour

ｾｯｩｮｧ through can be expressed as the product of the vapour pressure ｾｲ｡､ｩ･ｮｴ

and the diffusion coefficient. For a ｾｩｶ･ｮ material the diffusion coefficient

is clearly dependent on its ､･ｾｲ･･ of saturation present in the inside of

the material. The ｨｩｾｨ･ｳｴ values of vapour pressure which can be present at

the various points without condensation depend on the temperature distribution inside the wall.

For mUlti-layer walls the ｡ｲｲ｡ｮｾ･ｭ･ｮｴ of the various layers (with their

various diffusion resistances) take on an important role. The ､｡ｮｾ･ｲ of

condensation is increased when the exterior of mUlti-layer walls have a

greater diffusion resistance. DIN 4108 states in section 4.12 the ｦｯｬｬｯｷｩｮｾＺ

"In multi-layered wall and roof elements inappropriate ｡ｲｲ｡ｮｾ･ｭ･ｮｴ of

the layers can lead to the formation of condensation which may decrease

the thermal insulation considerably. Materials which are permeable to

water vapour, located on the warm side of the wall, favour the

oenetra-tion of water vapour from the ｢ｵｩｬ､ｩｮｾ into the core of the walls.

Possible ways of ｡ｶｯｩ､ｩｮｾ formation of condensation in the ｢ｵｩｬ､ｩｮｾ

materials are:

4.121 - ｒ･､ｵ｣ｩｮｾ the relative humidity inside the ｢ｵｩｬ､ｩｮｾＬ ･ＮｾＮ by

improved ventilation.

4.122 - ｉｮ｣ｲ･｡ｳｩｮｾ the vapour resistance of the warm side of walls and

｣･ｩｬｩｮｾｳＬ ･ＮｾＮ by installation of vapour barriers.

4.123 - Reduction of the vapour resistance on the cold side of the walls, e.g. by the use of materials with low vapour resistance so that

the cold side is capable of ･ｶ｡ｰｯｲ｡ｴｩｮｾ properly."

Water vapour diffusion is not ､｡ｮｾ･ｲｯｵｳ as ｬｯｮｾ as temperature at all

points exceeds the dew-point of the vapour-air mixture. We then have an

equalization process in which an increase of the mdisture content over the

･ｸｩｳｴｩｮｾ equilibrium moisture content does not take place. If, however, parts

of the wall are below the dew-point temperature then condensation will take

place there. This moisture, now in its liquid form will lead to a ｷ･ｴｴｩｮｾ

of the wall and consequently to a reduction of its thermal insulation. The

formation of condensation can be avoided by appropriate ｡ｲｲ｡ｮｾ･ｭ･ｮｴ of the

layers in mUlti-layered walls. The ｡ｲｲ｡ｮｾ･ｭ･ｮｴ of layers must ensure that

the temperature decrease inside to the outside is small at first and then greater, but however the decrease of vapour concentration is first great and

then small. Figures 12-14 illustrate the behaviour of various cross-sections

made from ｬｾｹ･ｲｳ with different properties.

A ventilated cast concrete ｣ｬ｡､､ｩｮｾ provides the desired reduction of

slabs to the back-up material ｡｣｣ｯｲ､ｩｮｾ to DIN

18,333,

Cast Stone Construction,

section

3.42,

provides an effective ventilation of the wall construction.

Open joints between the cast stone elements furthermore permit an equaliza-tion of vapour pressure on the shortest possible way.

Thermal insulation and surface temperature. Aoart from the protection

of the wall from ｷ･ｴｴｩｮｾ by rain and the imporvement of drying of the wall

from its initial construction moisture, the ventilated cast stone cladding has

the ｡､ｶ｡ｮｴ｡ｾ･ of ｩｭｰｲｯｶｩｮｾ the thermal insulation. Measurements in the

laboratory and in the field have shown that an air SDace of 1 cm provides

a thermal resistance of l/A =

0.16

m2hoC/kcal in spite of ODen joints

(accord-ｩｮｾ to ｆｩｾｵｲ･

6).

If exterior walls are constructed from a thermal point of

view ｡｣｣ｯｲ､ｩｮｾ to the minimum requirements of DIN

4108

only, an improvement

of the thermal resistance is obtained as shown in Figure

16

in percentages.

The surface temperature of space-enclosing elements, consequently also

exterior walls, influences the comfort of the inhabitants. The surface

temperature depends, besides other factors (temperature difference between

both sides, interior surface resistance), on thermal resistance. An increase

of the insulation value brings about an increase of the interior surface

temperature. According to the literaturq an interior surface temperature of

16°c

is desirable to satisfy the comfort requirements of the inhabitants.

ｆｩｾｵｲ･ 17 shows the possible imporvements in inner surface temperature for

a wall with stone ｣ｬ｡､､ｩｮｾ with a 1 cm air snace, in relation to the surface

temperatures achieved according to the DIN values and the assumed average

ｦｲ･･ｺｩｮｾ temperatures in the three climate zones. Figure

18

shows the same

values for a greater ｲ｡ｮｾ･ of exterior temperatures.

Cast stone ｣ｬ｡､､ｩｮｾ standards. In DIN ＱＸｾＵＰＰＬ Cast Stone ｃｬ｡､､ｩｮｾＬ

Quality, Test and Application, this ｣ｬ｡､､ｩｮｾ is defined as an artificial stone

which is manufactured with standard cement with natural or crushed stone

aggregates in a concrete plant according to DIN

4225, 3.

DIN

4225

requires

that a concrete manufacturing plant possesses certain installations for the

ｭｩｸｩｮｾ of concrete, protected indoor space for the manufacture of cast stone

and certain minimum transportation facilities. Concrete cast stone can be

made out of one layer of the same material or out of a core concrete with a

surface concrete (two layers). The treatment of visible surface layers is

made by means of sandblasting, ｷ｡ｳｨｩｮｾＬ grinding or sanding.

Minimum requirements. Concrete cast stone must have a minimum ｳｴｲ･ｮｾｴｨ

of

225

ｫｾＯ｣ｭＲ at age

28

days. Water absorption must not exceed

15

percent

by volume. The quality control must be maintained by at least semi-annual

-12-Size tolerances for wall slabs are ± 1 mm in ｬ･ｮｾｴｨ and width and

± 2 mm for the thickness. The pieces shall be free from any chipped edges

or other faults which ｭｩｾｨｴ impair their appearance or value.

DIN

18,333,

Cast Stone Works, requires that each piece of the cladding, except in the case of small tiles, must be anchored to the base in such a

way as to carry the full load by the anchors. The anchors (or clips) must

be made from steel that can be bent in the cold state and is protected against

rusting. Furthermore, unless otherwise specified, it is stated that in wall

cladding the individual pieces be set on strips of mortar. The composition

of the mortar must be appropriate to the application and type of cast stone cladding.

Summary

Cast stone has a number of specific advantages such as high strength, resistance to ageing, variable surface texture and colouring, the ability to perform structural functions if it is suitably reinforced, and some scope for

mOUlding it into various shapes. In addition, when properly designed and

installed as a facing material for walls, cast stone can fulfill the

require-ments applicable to an external wall from the viewpoint of residential ｨｹｾｩ･ｮ･

and comfort. The present article deals with the conditions affecting external

walls, with special reference to thermal, wind and moisture effects.

Les produits en beton manufacture presentent une serie d'avantages

specifiques p. ex. la resistance elevee, la resistance contre les intemperies,

une structure de surface et une couleur variable, des fonctions de supports avec une armature appropriee et, dans un certain sens, des formes variables.

En plus de ces avantages, son faGonnement ingenieux lui permet de remplir

ses fonctions comme revetement des parois du point de vue de l'hygiene

d'habitation. Le present asperqu traite les proprietes d'une paroi exterieure

en prenant specialement en consideration Ie comportement thermiaue, celui au

References

1. Schropp: Die Temperaturen technischer Oberflachen unter dem Einfluss

der ｓｯｮｮ･ｮ｢･ｳｴｲ｡ｨｬｵｮｾ und der nachtlichen Austrahlung (Temperatures

of construction surfaces under the influence of solar radiation and

nocturnal heat loss by radiation). ｇ･ｳｵｮ､ｨ･ｩｴｳＭｉｮｾ･ｮｩ･ｵｲＬ 1931.

2. Reiher: ｖｯｲｴｲ｡ｾ auf internationaler ｂ｡ｵｦ｡｣ｨｴ｡ｾｵｮｾ Hannover-Messe 1963:

Warmeschutz und Feuchtigkeitsverhalten von Aussenwanden (Thermal

insulation and moisture behaviour of exterior walls. Paper presented

to the International ｂｵｩｬ､ｩｮｾ ｍ･･ｴｩｮｾ at Hanover, 1963).

3.

Schule: Kurzberichte aus der Bauforschung: ｕｮｴ･ｲｳｵ｣ｨｵｮｾ･ｮ uber die

thermische Beanspruchung von Aussenputzen (Studies of the thermal

stresses in stucco: Short reports on bUilding research).

4.

Graf: Die Eigenschaften des Betons (Properties of concrete).

2. Auflage 1960. p. 188.

5.

Graf: Die Eigenschaften des Betons (Properties of concrete).

2. Auflage 1960. p. 188.

6.

Brocker: Die Widerstandsfahigkeit von Aussenwanden bei ｂ･｡ｮｳｰｲｵ｣ｨｵｮｾ

durch ｓ｣ｨｬ｡ｧｲ･ｾ･ｮ (The resistance of exterior ｷ｡ｬｬｳＮ｡ｾ｡ｩｮｳｴ driving

rain). Dissertation 1954.

7.

Pohl: Warmedurchgangsmessungen bei Windanfall und ｓ｣ｨｬ｡ｾｲ･ｧ･ｮ (Heat flow

measurements under wind and driving rain conditions). Dissertation 1937.

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Outside temperature and surface temperature of variously coloured facing panels as functions of time.

The measurements were performed at the Holzkirchen establishment of the Institute for Technical Physics, Stuttgart, on 25/26.7.1963

Shear force Facing slab Mortar strips Wall Base Fig. 2

Test arrangement for determining the heavy-load value

kS 4000 3000 2000 1000 ;

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Shear strength in relation to the age of the fixing mortar

- 0 - -ｾ ｏｉｎｾ - - 0 - -ｾＧｏ＼ｉＧｉｓｽｴｬ

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4

Shear force in relation to the pre-treatment of the masonry

Fig.

5

Heat curve (measured). Average excess temperature of facing above averai?;e temperature of wall:

-16-

""J-lJ

Fig.

6

Open joints between slabs to compensate for thermal expansion

J:

Uppe loading platen

Steel plate Wall Mortar strips Facing slab, ｾ vert. ｆ｡｣ｩｮｾ slab, horiz. Lower platen Fig.

7

Test arrangement for determining the maximum difference in

t 70 60 !lO 40 30 20 10 0.5 1.5 t 25..,.----,-- 20-t----t-15 10-f--,l1Y--+---+--+--..., 5 - P " ' - - - t - - + - - - t - - - t - - . . . , Fig. t«

Shortening of solid brick masonry (MZ 100 bricks) until the strength of the bond between panel and masonry is exceeded or until failure load

of the masonry is reached

Fig.

7b

Shortening of masonry constructed of pumice concrete hollow

block

HBL 25

0.5 t5 2.5mm1m I 25ＮＭＭＭＭＭＭＭｲＭＭＮＭＭＭＮＭＭＭＭＭＢＬｾ 20ＫＭＭＭＫＭＭＫＭＭＭＷｉＧｦｾ 16+---1--- 12+---+-8 Fig.

7c

Shortening of masonry constructed of

-18-Satur. time up to wetting of a horiz. joint 20 to 25 cm length Uo to first wetting 186 h ii}:i:)'::166 A 1 2 ₃

1 - 24 cm solid brick; 2 - 24 cm solid brick

with facing slab vertical; 3 - 24 cm

solid brick with facing slab horizontal

Fig. 8 hours. structure: 18.0 m/sec 0.8 litre/m2

90°

0.2 - 0.5 rnrn Saturation times in Factors affecting the wind velocity

amount of rain

impingement angle of rain diameter of raindrops min SNOW CUXHAVEN ESSEN-MULHEIM I.'

I

wi ;; 116(1 h ii 0.) Fig.

9

FElOOERG /lS 03 03

I

Ii Annual hours of rainfall associated with wind

velocities exceeding 17.5 m/sec. for the four main wind velocities

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,,:;,,5

Vented cast stone facing. No

condensate is formed within the wall section, as the cold side has low vapour resistance and

can let evaporation take place

svr : .,)o·c, jOio REI.... \10l"lm,T" 15 .,.., .10 :;l: (; £10 0 ｾ Jt, UJ ｾＱＰ Of ｾ 5 ri ｾ _& 'J 0 _ｾｚｏ (). II: ,. 0 Fig. 11 INT:+.zo·C,100'10 REI.... "0""'011''1 I.S c. .. !>1'OLC.()

Cast stone wall facing with fully

mortared and pointed joints. In this case

condensation occurs behind the closed facing, under the same boundary conditions as in Fig. 10

-20-fl.,.: ＭＢＧｯＧｾＬ &0,,/. IIEL.. \.101<\\0\"1',/ IPIlT: +'-'0 0(" bo1o REI..., H<.II"\'O'1'"" 20 .20 15 .10 0"') ｾ E10- 0 f: I I ＮＺＭ［Ｇ＾ｸｾ

-...ｾＭＭＭ Fig. 12

ｈｩｾｨ thermal insulation on the cold

side of the wall and high resistance to diffusion on the warm side prevent condensation within the wall if

thermal insulation is adequate

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High thermal insulation on the warm side of the wall in conjunction with low resistance to diffusion of water vapour gives rise to condensation

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5",.,

ＢＬＬﾥｯｾＢ 1'IlE!»\lQE o .10 ｾＭＱＰ 15 oJ' <II W t!5 III ｾ g a: > 0 Fig. 14

High thermal insulation on the warm side calls for a vapour barrier to prevent

condensation within the wall

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Heat levels (laboratory values) in a slab facing with 1 cm wide air cavity between the fixing mortar

-22-.,.! 80:70 -60 50 1---+-+--1' 40ＱＭＭＭＫＭＫＭｴＭＳｾ 301---+-1---; Fiil;. 16

Increase in the thermal resistance

l/A (m2 h o C / k c a l ) in percent, ｴ｡ｫｩｮｾ

account of the ｩｮｳｵｬ｡ｴｩｮｾ value of

a 1 cm wide air cavity behind the

ｦ｡｣ｩｮｾ panels

-15 -12 -lOoe

OUTDOOQ TEt'\9'.

ｆｩｾＮ

17

1 = international surface

tempera-ture of external walls with minimum thermal insulation values according to DIN 4108 in the insulation ranges

I - III.

2 = increase in surface temperature

due to 1 cm wide air cavity behind facing panels

.

....

--- ---ｾＭＭＭ ---m I I OC19 18 17 16 15 0: 14 s: ｾ 13 w 12 d If11

'"

ｾ ＱｾＲＰ -ts Fig. 18

Internal surface temperatures of external walls with the minimum values of l/A in accordance with DIN

4108 (lines 1,

3, 5)

in relation to

the outside temperature. Increase

in surface temperature due to 1 cm wide air cavity behind facing panels