Defects In Construction.pptx

CONSTRUCTION DEFECTS:DEFINITION Construction defects usually include any deficiency in the performing or furnishing of the design, planning, supervision,inspection, construction or observation of construction to any new home or building.

REASONSFORDEFECTSIN CONSTRUCTION Design Deficiencies • Problems are typically encountered with roof systems, which due to their design complexity, pitched or flat, are prone to leaks. • A majority of roofing problems area direct result of the improper specification of building materials, which can result in water penetration, intrusion or other problems, • The inadequacy of structural members, which can result in cracks and deterioration of roofing components and materials.

ROOFING PROBLEMS

Material Deficiencies

Construction Deficiencies

Subsurface Deficiencies

Common manufacturer • A typical example is • A lack of a solid foundation may problems with building materials water infiltration result in cracked foundations or can include through some portion of floor slabs and other damage to the building structure, the building. • deteriorating flashing, which may create an • If subsurface conditions are not • waterproofing membranes, environment for the properly compacted and • asphalt roofing shingles, growth of mold. prepared for adequate drainage, • particle board, • Other problems include it is likely the property will • inferior drywall • other wall products used in cracks in foundations or experience problems such as wet and/or damp areas,such walls, dry rotting of improperly settling to the as bathrooms and laundry wood, electrical and ground (subsidence), the rooms. mechanical problems, structure moving or shifting, plumbing leaks, or pest flooding and in many cases infestation. more severe problems such as landslides.

PROBLEM-1 DIAGONAL CRACKSIN BRICK WALLS

PROBLEM-2 HORIZONTAL CRACKSIN BRICKMORTARJOINTS

WIDE ATBOTTOM & NARROWATTHETOP

CAUSES

CAUSES 

1. Differential settlement of foundation due to expansion of clayey soil by absorption of moisture.

This may happen when the rain water finds entry in soil or if a tree is cut suddenly in the vicinity of structure so that the soil which was earlier dehydrated by the tree again absorbs moisture andswells.

REMEDIES/PRECAUTIONS 1. In clayey soil, foundation should be taken as much as deep so as to minimize the effect of moisture Entry as much as possible. 1. Adequate plinth protection and drainage arrangement should be made around the building to minimize water entry in the foundation. 2. If from any site intended for new construction, some vegetation is removed, don’t commence construction activity immediately specially if soil is clay. allow the soil to absorb moisture , swells & stabilize

Weakening of mortar due to sulphate attack. these cracks normally occur after 2-3yrs of construction as the reaction is slow.

REMEDIES/PRECAUTIONS 1. Sulphate contents of the bricks should bechecked before allowing their use. 2. Brick walls should not be allowed to be damp because 3. Sulphate attack happens only in presence of moisture. 4. The correct remedy is to reconstruct the affectedareas

C R A C K S W I T H I N T H E S T R U C T U R E

SHEETNO. 2

PROBLEM-3 RANDOM CRACKIN FLOORING CAUSES •

Flooring has been cast continuously without making panels. • Cracks occur due to development of tensile stresses on account of shrinkage and thermal contraction of concrete & occur mostly in the first dryspell.

PRECAUTIONS

•

Cast flooring in panels do adequate curing in the intialperiod of hardening of concrete.

C PROBLEM-4 R CRACKSIN LOADBEARING MASONRY WALLBELOWR.C.C . A SLAB C CAUSES K • Due to absence of slip joint betweenRCC S

slab and wall which doesn’t allow RCC slab to move freely over wall leads to cracking in the wall. • Sometimes the movements of the slab may also causecracking in the wall. • Sometimes the movement of the slab may also causecracking in masonry at lintel and window sill level because here the masonry is weak. • These cracks are observed mainly on top most storey of the bldg, because roof is more exposed to temperaturevariation.

REMEDIES • Before casting RCCslab over bricks wall, smooth bearing plaster should be done over brick walls coupled with white wash/bitumen coating over it. • It allows slab to move freely over wall

W I T H I N T H E S T R U C T U R E

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PROBLEM-5 VERTICAL CRACKSATJUNCTION OFR.C.C. COLUMN AND MASONRY

PROBLEM-6 DIAGONAL CRACKSIN WALLOVERR.C.C.LINTELS. CAUSES

CAUSES •Differential movement between R.C.C. column and masonry due to thermal expansion/contraction shrinkage. •Differential settlement of R.C.C.column because of its different foundation.

Due to drying shrinkage of lintelsand sudden deflection of lintels after removal of shuttering.

W I T H I N

REMEDIES •A groove in plaster should be made at the junction of R.C.C. column and brick wall so that crack remains hidden in the groove and doesn’t look unsightly. •Alternatively, chicken wire mesh should be provided in plaster at the junctionof R.C.C. column and brickwalls.

C R A C K S

REMEDIES •Use precast lintels as far as possible for small openings. •Construct brick wall over lintel after it has undergone considerable shrinkage. •Construct brick wall over lintel after shuttering below it is removed sothat it doesn't undergo sudden deflection with the construction of brick wall over it.

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T H E S T R U C T U R E

PROBLEM-7 VERTICAL AND HORIZONTALCRACKIN PANEL WALLIN R.C.CFRAMED STRUCTURE

PROBLEM-8 HORIZONTAL CRACKSBETWEEN BRICKPARAPETWALLAND ROOFSLAB

CAUSES

CAUSES

Panels wall too lightly built to the R.C.C. beams so that the beams are not free to deflect ,load is transmitted the wall and vertical and horizontal cracks are

differential thermal expansion and contraction and differential drying shrinkage of R.C.C. slab &brick wall. Due to thermal expansion and arching of slab ,it is not free to expand .this situation mainly occurs in case of non projecting slab.

produced in the depending upon the direct in which wall is more slender (i.e height and length

REMEDIES

REMEDIES

•Make parapet wall a little inside •Some gap should be left between top of panelwall of the edge of slab so that crack and soffit beam /slab so that beam can deflect wont be visible. freely. •This gap can be fill by weak mortar . •Providing a groove in plaster at the junction ofparapet •If lateral support is required to be given to wall beam then some special wall and slab so that crack forms in the groove and lateral connections can be made in such a way free deflection of beam is doesn’t look unsightly not hindered in vertical direction. •put chicken wire mesh in the plaster at the junction of parapet wall and slab . •Provide adequate insulation cover over roof slab so that its thermal movements are minimized.

SHEETNO. 5

C R A C K S W I T H I N T H E S T R U C T U R E

PROBLEM-9 VERTICAL CRACKBELOWOPENING IN LINE WITH WINDOWJAMBS CAUSES

PROBLEM - 10 VERTICALCRACKSIN THE SIDE WALLSATTHE CORNERSOFALONG BUILDING. CAUSES

These cracks are caused due to vertical shear cause by differential strain in lightly loaded masonry below the opening and heavily loaded portion of wall having noopening

REMEDIES •Too much difference in stress in different walls or parts of a wallshould be avoided. •Portions of wall acting as pillars and having too much concentric loads should be replaced by RCC pillars if possible .

1) The cracks are due to thermal expansion sometimes aggravated by moisture of long brick walland would be noticed in hot weather. 2) There will be more chances of such cracks occurring in building constructed in cold weather.

W I T H I N T H E

PROBLEM -11 CRACKINGDUE TOARCHINGAND UPHEAVING OFAFLOOR. CAUSES 1) Due to sulphate action in base concrete. 2) Due to expansion of clayeysoil below by absorbing moisture.

REMEDIES 1) TAKEALLMEASURESTOPREVENTCONTACTOFSULPHATESWITH CEMENTORUSESULPHATERESISTENTCEMENT.

C R A C K S

REMEDIES 1)As far as possible long stretches of walls should be intercepted by cross walls and expansion joint should be given at suitable intervals. 2)Bricks should be allowed to undergo initial moisture expansion before use.

SHEETNO. 6

S T R U C T U R E

PROBLEM- 1 DAMPNESS IN THECEILING BELOWROOFSLAB/TERRACES/BALCONIES. CAUSES 1. Roof slopes not proper. water stagnates at some points. 2. Rain water pipe choked. So water collects around that location and gradually seepsbelow in the roof. 3. Overhead tank not water proofed so water seeps fromit through its pillars tothe roof slab. 4. Area around overhead water tank at roof not properly cleaned. so some vegetation starts growing due to dampness and makes its way through the roofing from where water also seeps. 5. Water proofing of roof not properly carried up to the pillars of overhead water tank because of which water can seep through this junction of pillars to the roof slabs. 6. Water proofing treatment done over roof not carried up to specified height over parapet wall.

REMEDIES

3. Roof area around and below the water tank should beproperly cleaned and no vegetation should be allowed to grow due to dampness. 4. Overflow pipe provided in the O.H.T. at roof should becarried up to the nearest rainwaterpipe.. 5. Roof topping concrete should not be cast continuously but rather laid in panels and the grooves between panels should be filled with a sealant or polymer mixed cement.

D A M P N E S S

D E F E 1.Since the parapet load is low, the roof slab bends C to lift at its corners due to deflection causingcrack.. 2. Since the parapet load is low, slab is also able to T move due to thermal contractions/expansion & S

PROBLEM-2 SEEPAGE IN THECEILING BELOWROOF SLABIN THE CORNERSALONGJUNCTION OFWALL ANDSLAB.

1. Correct the roof slopes shrinkage. wherever required by putting Remedies screed concrete and put adequate number of rain water 1) By making brick or concrete cornice at the bottom of parapet wall and making drip mould in it. pipes. 2. Water proofing should be done 2) By extending roof slab itself by 2” to 3” beyond the loadbearing inside the overhead water tank wall and making a drip mould at the bottom. 3) By taking precautions that minimum water drips through roof on roof. and parapet wall to the outsidewall.

SHEETNO. 7

PROBLEM- 3 PROBLEM- 4 SEEPAGE IN THE WALLS OF TOILETABOVETOILETFLOORLEVEL ROOF/TERRACECONCRETESLABPOROUSIN GENERAL AND LOTOFFINE HAIR LINE CRACKSBECAUSEOF CAUSES WHICH WATER SEEPS Leakage in water supply lines which are concealed in the walls.

REMEDIES

CAUSES Concrete not cast properly and mixing and compacting not done uniformaly and properly.

1) Make a chase in the wall along the route of water lines in the toilet/bathroom and expose these lines at the location+ of dampness . then examine them for REMEDY leakage. Apply water profing coating overthe 2. In extreme cases some pipe piece can also be found cracked rusted concrete slab. (specially when pipes have become quite old) which should be PROBLEM-5 WATER ENTERING THROUGH DOORSAND replaced. WINDOWS OFTHE BUILDING AND CAUSING 2. As a preventive measures, during the time of new construction , all the water lines DAMPNESSINSIDETHE BUILDING must be pressure tested before concealing CAUSES them and before accepting the work. this will save much of future maintenance problem. 1. Chajjas not provided over doors and windows REMEDIES 2. Stilts not provided at the bottom of door 1. Provide chajjas over doors and windows on the outside 2. Gaps between doors/windows frame and jambs should be properly sealed through sealant. 3. Floor not sloping away from external door 3. Rubber gasket/beading should be provided on edge of door/ window 4. There is gap between door /window frames and jambs shutters if you want a perfect leak proof door/window. 5. Glazed windows are opened inside the room instead of 4. Glazed windows should always open outside and not inside the room. outside

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D A M P N E S S D E F E C T S

PROBLEM– 2 DEFECTIVEFLASHINGS

PROBLEM-1 CRACKSTO BRICKWORK

CAUSES

1. Flashings to the base ofthe cavity have been installed.

1. This is the lack of tying in of brickwork. 2. Wall has been constructed and not tied into the adjoining brickwork 3. Case a half brick has been cut and abuts the joining wall 4. There is no form of tying in of the brickwork, nor fixing

REMEDY By construction of the two brick walls atthe same time with the brickwork being interlocked

2. These flashings are designed to collect any water entry to the 3. Building and discharge it to theoutside 4. In this case the end of the flashinghas not been turned up at the 5. Ends and would allow any water trapped within the cavityto 6. Form a water leakage

REMEDY The flashing in this case should have been turned up at the ends to prevent the leaks at the door sill.

PROBLEM- 3 SPALLINGOF CONCRETE(CONCRETECANCER) CAUSES REMEDY

• The problem occurs because the •The new mesh which has been fitted is also bolted steel reinforcing has insufficient and fixed to the affected concrete slab above to “cover” which allows either provide adequate fixing. Spalling of concrete is commonly called moisture or salt laden air to concrete cancer . This occurs when the steel affect the steel reinforcing. •This confirms the mesh is only fitted reinforcing rods within the concrete are to provide some bonding agent for affected by moisture, or a salt environment, the later rendering tothe underside of which causes the steel to rust which then the slab. expands and pushes off the surface

SHEETNO. 9

P O O R

W O R K M A N S H I P

1. CONCRETECREEP

2. CARBONATION

It is the property of concrete by which it continues to deform with time •Carbonation occurs in concrete because the calcium bearing under sustained stress. the total deformation of concreteelement can phases present are attacked by carbon dioxide of the airand converted to calciumcarbonate. be divided into two parts: 1. An initial, instantaneous deformation at an application of load. 2. A time dependent deformation due to creep.

•Carbonation may be recognized in the field by the presence of a dis colour zonein the surface of the concrete. the colour may vary from light gray and difficult to recognize to strong orange and easy to recognize. carbonation can be visualized by using phenolphthalein.

I N

REMEDY REMEDY 1. Design the structure with a mind to the degree of restraint during drying or cooling of theconcrete. 2. Pre stress wherever feasible.

1. Use the minimum water content necessary for workability;do not permit over wet consistencies. 2. Place the concrete uniformly, and take account of early settlement in theforms, around reinforcement , on slopes, and elsewhere.

3. SHRINKAGE The moisture loss results in concrete shortening of length. The shortening of length of a member or contraction of the concrete per unit length due to drying when concrete sets in known as shrinkage. this is an irreversible process.

D E F E C T S

REMEDY 1. Provide competent inspection, and back it up. 2. Use materials known to have a good service record with regard to cracking, irrespective of shrinkage or other tests on single contribution causes. 3. Use the minimum cement content consistent with design requirements.

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C O N C R E T E

4. CORROSION OFTHEREINFORCEMENT

INSUFFICIENT STEELREINFORCEMENT Due to the insufficient amount ofsteel present in the concrete element it will not perform to the design and if overstressed, suffer from carbonation or other damages and will not have sufficient factor of safety.

•Corrosion of steel bars is due to oxygen andmoisture. •Any common steel will corrode slowly when exposed to the air with no protection. •when ordinary steel is used to in concrete, it automatically protected from corrosion by means of:

POOR FIXING OF BETWEENSTRUCTURALELEMENTS •lack of stitch bars between precast units in in-situ joints. •continuity re bars not passing through all connecting hoops.

1. 2. 3. 4.

D E F E C T S I N

cover of concrete and alkalinity of concrete. steel in corroding expands and can double its volume. C layers and lumps can flake off. O as most reinforcement is embedded in concrete, this expansion •connecting hoops and tie-rods bent over where they did not line up N can push off the surrounding concrete. •ties and pre-cast panels not pulled out to make in-situconnections withC in-situ elements. R REMEDY FLOWCHARTSUMMARIZING THEDEFECTSDUE E TO CHANGEINSIZE. •Cure the concrete moist or sealed, beginning very early. T MOISTURE OR THERMAL EXPANSION •Avoid extremes of temperature. E •Protect the concrete in service from moisture and temperature MOVEMENT IN MATERIALS changes wherever feasible, as by backfilling, shading, or coating. CHANGE IN SIZE OF MATERIALS CRACKS REMEDY

EXPANSION JOINTS

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