It should Ъе noted that conunor. Ret-г mixed and placed

at teurpcrutttreQ belovi freeains; Bill not set» And th« str*sr.srtti f"sln wllX be much lewe; t-Mnrerutures nearing

frr-eEini?, v>o special isroc'iist !:■':•'-.- !fia;;i; Ъ* fctifcen. under such conditione.

'i/чвгв is another oonci^ete matorlnl which was developed not long ago and which is of p-ree'- vilue ia. the bxiilding in-dustry - reinforced concrete. The waLn thing about thio material la the combination of coaipressive strength cf concrete with tantdle strength of steel.

Rflnf oroftd oonornto ie a Јi ;re™reo1.sfctrig mp.terinl, Ьэв the 'senrinf; prorert.lon O.f stons and ecte as a heat insulator. Due feo P'J--Ai qualities It is «.t'.iely used in the bulliiinij 1н-

BRICKS jBLOCES

There exiet many kinds of manufactured bricks and blocks used in construction. They иву be used for different pur­poses: common clay bricks are used for general purposes} for facing walls special facing bricks are used, their surfaces sometiaea coloured being either smooth or texturedj engineering bricks should be strong, impemeable to water or highly resistant to changing temperature,their eurfacea being hard and smooth; there are hollow bricks and blocks, which are used when it is required, to decrease the weight of construction, etc, The eises of brides aay vary but usually their length is a little more than twice their width, ia order that they can bo laid to bond.

Bricks and blocks may be made solid or hollow, but of varioufl strength, and the surfaces of вот* are made keyed to assist plastering. ; .

As bricks and blocks are porous, water шду penetrate into the voids in the surface layers. But the moisture evaporates quickly,and therefore it la quite possible.to use bricks and blocks as walling and facing materials. In some places where the atmosphere contains great amount of salts they get with rainy water into the bricks, and whan the ipoisture evaporates, it leaves these salts in the voids. The formation of these sal^s in the pores and on the surfaces of bricks and blocks is called effloi-es-cence» Soaafci-ces salts deposited in deeper layera of bricks may cause the decay and crumbling of the surface layers. Freezing water in voids may also cause cracking and crutibling of surface layers oi' bricks or blocks, Thue ■the weathering of such building siaterijla aa bricks, blockH, stones depends upon their being porous,

Voidis in tha?.E materials may contain nob only water but air as well. Аз air ie. Knosu to Ъв a poor conductor of heat, porous materlalw containing jany voids are rather good heat: insulators,

Aparu frora lsar.ufuctured building вш1".-м"1а1в such as ЬНски, arid blocka uatuxel atones are widely used in construction.

The density of natural .stones varies greatly - from 180-IV ou.ft. for granifce to 135 lb/cu.ft. for some limeotones, end eo does their porosity. Stone builings being "built of, heavy material aro certain to have high heat conductivity, That is why they heat up and cool down slowly,

PLASTICS. . ■

The plastics industry is known to be developing con- , siderably nowadays, and can supply a wide range 6X products. As most of plaetics products have good insulating propei"fciee, are reaiatant to the action of corrosion and of chemicals, and зове have great mechanical strength, they are used in construction and building on a r-idening scale. Builders иве veneers, films, rosins, adhesives, rode, panels, tilea, moulded products for engineering services, facing end deco­rative products and many othei-s. From the builder's point of view it is very interesting the application of such details for engineering services as tubes for cold water services, baths., sinks, t'ubos for-да fit о water where, water ia discharged under low pressure, various fittings and even rainwater pipes and guttering. These details are light, tough, durable, resistant,to corrosion and chemicals, are easily worked and painted.'In positions where materials я with.high absorbtion of sound are required, special plaaticn acoustic tiles and panels may Ъе very useful. They have homogeneous cellular structure, are very lightweight asd may be available of different oolours.

The exposed cells on the surfaces are claimed to diffuse light. All these properties and flexible arrangement of such panels end tiles enables them to be used also for decoration of large areas of walls.

Special self-adhesive plastics caterings may be used eo a permanent finish for walls and ceilingu instead oЈ usual wallpaper. They ere tough waterproof, Bteampxoof₍ gx»aae-proof, hygienic, easy to apply. The teohnioal propettiee of ещ)ел.й&3. plastics sheets швке them particularly suit for insulation. These are a plastics foeffl with eloeed eella filled with air. These sheets consissting 95-98 per cent of $ir, are extremely lightweight and highly heat insulat­ing. Due to the closed cells plastics foam material is va­por 'resistant and can be useful ав insulation not only in houses hut in industrial buildings as well. These sheets are easy to cut and work with ordinary instruments and сел Ъе bonded to any surfaces with special adbeslves with "a very strong binding power. Аз cellular plastics can be moulded into any shape, are inert, resistant to rot and highly insulating they are finding wide use in floor and panel heating.

GLASS.

Many new types of glass have been introduced re­cently into building practice, g^³⁸ being used for иапу purposes', for lighting, for decoration, for insulation. Glass иау Ъе transparent, translucent or opal /in varying degree/. Besides ordinary window glass there exist' special types or glass: wired glass which is reinforced With mesh wirej toughened glass having very high mechanical strength and high resistance to sudden changing of teiap era tare; moulded glass blocks and lenses used in walls, rooflights ^J and pavement lights; decorative glass; fibre glass used .for insulationy priEmatic glass which changes the angle of light falling on it; double;glass sealed sheets uced for heat insulating aM others. Ordinary sheet window glass transmits about 90 per cent of the light falling on it. But in the town the passing oЈ the daylight may be re­duced to the value considerably less than 90 per cent, this depending upon the atmospheric conditions, cleanliness of the glasB itself,,and upon fchd angle at which the light falls on the pane.

Ultra violet rays which are benefit tonealth do not pass through ordinary window glass. Now there is available a special type of glass which does not prevent ultin violet raye to pass through. Strength of glass for windows and doors is the щ»in eon of builders. The isl-rengtb depends upon the thickness, _of the glass and. upon the conditions of exposure and use.

narrow sheets are stronger than those of squared"

In places wjjere breakage is moat likely to occur, for instance in swing doors or in roofligbts, wired or toughened glass is recoinmended to usq. S6und tranemiaaion of glass is rather good, Considerable improvement in sound insulation of glnsa cna bft obtained by double glaz­ing especially if two panes are spaced well apart. Heat transmission of glass 1ms to be also considered by builders, especially in severe ,or hot climates* Ordinary glass trans-Hiits the high proportion of the sun¹ з heat into the build­ing, but that.heat cannot paaa back through the glass from the гооки The reason is that the radiant heat changes its wavelength when ii; strives the'objects and the walla of the гооы aitd thg glass does not transmit back this -changed wavelength. That is why in countries with hot climate the v;indows are often protected from the dix-eet Јuxilight by shield.3 and blind:!-, In places with severa olimato the heat irisulnticn of glees is increased by Tlouble glazing, because the air between two glasses is a ?;ood insulator. It should be remembered that the wider is the space between the two leaves, tbe better is the heat insulation.

PAINTS A IT 1) , PAIH.IHt.

Different kinds of paints are ueed either for deco­ration or for preservation of surfaces, and Boiaetinea to provide a hygienic surface which raay ba cleaned easily. To avoid, painting, delecte great attention has to be paid to the Collowifiij pobstsj correct choici-i of p,iljit for the particular fainted mirfacej wet surfaces should not bo polctcO , a& well na tif.toriala to which moisture

h.nu«> ?coeae ia fulmre; ргосояз of troatiae.at nhould correct. In. consi;ii'..,tdon thore jany bi> opplifid oil Lntf?! vaxnishta-, (ViBt.ompera or iwsfcs'r pulnte, cement paintB etc. Oil paints are paints where pigments are dis- . pereed in such medium as oil or oil vamiehea.

Oil paints can give glossy or matt eurfacea, and are usually impermeable to water. Varnishes are based on dry­ing oil and some quantity of resin. Varnishes aro used also for covering the painted surfaces to give then a tran­sparent glossy film. Distempers or water paints are . mle of pigments suspended in, such .medium as-water or emulsion of oil, resin or bitumen. Cement paints consist of pigments and. Portland ceaent, thus being compatible with ceaent sur-1Жсез and providing a good decoration on cement products, Bitun.in.ous paints are "based on bitunen with, a proportion of dryisg oil. They are,used for covering steel and iron to make them waterproof. These exist also special painte, to make surfaces heat-resisting, fire-proofing etc.

As paints aro to give protective covering it is very important for them to be impervious to penetrating of moisture. If moisture accumulates under the paint coat, it destroys not only the paiivb film cut the backing material аз well. Durability of paints depends very mich upon the nuiaber of coats. A good treatment with paintB required several coats, at least three: primer, undercoat and finish. Surfaces to Ъе painted should, be properly preparedi they should be clean, dry and. free fron. dust. It should he kept in mind also that not only the surface but the v.'hols material be dry as well, ea moieture from the йелр~ ar layers may rise and cause the damage. Paint may bo '• applied with brush or spi-ay ana the method of application affects both cost and quality,. Spraying ia quicker and cheaper, especially when extensive areas ere painted, but brush treatment gives better adhesion. Sufficient tine should be given for each coat of paint to adhere and dry thoroughly. Most types of paints u^ed require the drying time from several hours to one day.'

S Н В Е I¹ Ч ATEH1A.I.S.

Many kinds of sheet materials are already employed in building, and development; goes en all -tribe* time in __ . finding new and better types, They have various properties, and these are certain to be taken lrr;o consideration by builders. As the heat insulating property of a material is roughly inversely proportional to its density, the lighter is the sheet material, the higher ie its neat insulation value. (There arc many good heat insulators among the. eheet materials, and their insulating-value т-чу Ъо increased considerably'by using air space between sheets, or by proper way of fixing sheets to studs or to a frame. Sound insulation value of roost shset natiyrials is rather loi? because of thoir having -small weight. But this value may be increased by enploying steggerc-3 studding. Aa for sound absurbtion, there вге svpocial acoustic typos of fibre boards, or plastic boards, ' whlc.i can' e,ive hifih eouiid absorbtiorij ЪхЬ- moot of. coiEnon зЬсеЬ Si.3 to rials are poor sound absorbents. The Qtrerigtb, er,d riridity oЈ ehe^fc raatbrialo vaj^y greatly, and d-epend coriEicterably upon the way of fixing thorn and upon the position the;/ are used- in. In. posit?; дав where-sheet's шау sag or buckle oloae spacing of nails or studs is of great taporbance. Used i» external position only few, аз, for instance, asbestos cement, plastics boards or supoxhord boards, are durable. Most of -others can be recosr.ended to u?e externally only if protected wibh special coverings, tinder internal conditiono all sheet taateriala are durable. Xet it should be kept in mind that in damp conditieno they reduce their durability - for instance, plasterboards, plywood, fibrebo-irds. "aterials coataijxiBg wood are liable to attack by rot or by beetle* 'Лапу eheet materials are able to form bends._,- either being wetted or steamed, or'being heated. This макез ttiea very ndvnn in special positions and usosv

Light framed construotionn covered with гзЬяе are coming Into wide use nowadays, 5hus thin rigid sheet materials are becoming of great importance especially in stressed, skin constractione, end new types of sheet materi­als are being developed, and will be developed in the future.

ПЙВИ.,

Timber ia widely used for building purposes, the main , use being for joinery and for decorative parts of buildings. Softwoods are Ealnly used for joinery, and hardwoods — for floors,and other parts where resistance to abrasion is de­manded.

To use timber to its full strength, architects and builders should have good knowledge of general structure and of structural properties of different species of wood. Wood пав cellular structure, and belle are in the direction of the length of a tree. Then, as trees grow by adding freeh layers to outside of the tree, the structure of wood is not homogeneous across the section of the trees the wood in the ceatre of a tree called heart, is older and harder the younger wopd situated near the bark and called вар wood is softer. There are knots which greatly decrease the Btrength of wood. All this means that specific properties of timber such as strength and moisture movement are not equal in different directions and in different parts of a tree.

Manufactured products made of wood are more homogeneous and that is the reason of their being widely used nowadays. Wood has a rather low thermal conductivity. As an insulator wood is jsainly used in the form of boardijng without airgape between individual boards.

Wood in thin sections is not fire-resis4ant but heavy bulks of timber are difficult to ignite end burn very slowly. Fire resistance of wood may be improved by chemi­cal impregnation and sometimes by special paints. Tiaber, especially if it is not dry enough, is liable to attack of fungi which may destroy-wood entirely. To proteot timber from fungi's attack it is impregnated wltn creosote or other cheralcals. Eaw timber contains a great' amount of wator. To decrease this entrant of moisture .tim-" ber is dried, and'this process of drying timber Is called eeasoning. There are sijvoral methods of seasoning: a) "natural seasoning", which means that tiaber is dried under exposure of natural atmospheric conditions; t>) "kiln seasoning", when timber is placed in special drying roomo, artificially heated_f where huxduity is controlled by admission of etoaaj c) "chemical seasoning" - by impregnating with special cberaicals

When,dried, timber cnanges it© Bizes tied, sometitses, its _t fora. This process is ©ailed ehrinkego* Bat if dry timber is placed in damp atmosphere it absorbs moisture again end itв strength decreases. It is a very iaportani; point for a builder to гешааЪег. Conversion of trees into timbers of different sizes and forma is made at emr-nills. Proper conversion affects the appearance cЈ timber_f good tano* to wear, extent s.nd таппм of ikd.scuxa a

P L A S T S R I H G and HI !!,B E.HI КО .

' P о r. plastarlng and rer.dering different mate­rials «ay be used t liises (quicklime and elaked or.hyd- • ratiti:-d He*}.,- cenent and. pleafcer of Paris, Jlixes containing eenerrfc or plaster of Paris sot very rapidly,, and therefore care sbouia be taljen to risir.13 them within short period of tiate after mixing. If plaster is applied ia two layers / (rendering and then plastering) tiae ;jliould be allowed for the firet layer to dry end shrink. If this condition. is not observed t.be Ehrin3rag;9 of the first leysr (render-1пк) иву сагше tbe cracJsing ol the 'itdeMns coat. 7ery -ufteft plaeteriJic A*⁵ ajyplled to a large area. It is diffi­cult to obtain "n good joint bfifcwdea the work of cms dny snd that o.f the next. ЧЬятх it is recoE-iRenfiod to arrange some division of the whole area into pintle» war! frbo llv*3 t( this uivitsliT» ehould coin/side vith '.Ьъ 11п«и wher огаоке иду develop. As there ie some difficulty of Baking good damaged plastering end especially readerlag, all holes for pipes should be joade aad all engineering servi-oieo should be fixed before the plastering is applied. For the same reason, eometinea scaffold independent of the wall eupport ia being used. Plastering aad readsring may de­velop craokieg» It e^ould be kept ia mind that rich, cement

mixes are most likely to develop cr&oking, and ealoiua eulphate plaetere give the least oreeking. Rough textured surfaces ae beizig less liiely to ehow oracking than smooth finishing are widely used nowadays. Mechanical damage is most likely to arise on the loner parts of walle or oa exposed external aagles. Ia such position hard materials are used.