How to inspect a house build, stage by stage

A house is built in layers, and each layer hides the one before it. Steel disappears into concrete, pipes into walls, waterproofing under screed and tiles. Once hidden, a fault can only be found by breaking things open, and by then it is usually too late or too expensive to fix properly.

The whole of inspection comes down to one rule: nothing gets covered until it has been checked. Each point where work is about to be hidden is a hold point. The contractor must tell you before reaching one, and must not go past it until you or your engineer have approved.

What to bring to every visit

Mistakes made here carry through the whole building. A house set out half a foot over the setback line, or wrong by a few degrees, cannot be corrected later without demolition.

1. 1

   Check you are working from the approved drawings

   There should be one set on site, signed and stamped as approved, with the latest revision marked. If the contractor is working from an earlier sketch or from memory, stop and fix that first.

2. 2

   Walk the plot against the site plan

   Confirm the plot boundary pillars or markers are in place, and that the plot dimensions on the ground match the dimensions on the plan.

   • Measure the plot’s sides yourself, with a tape, and compare with the plan.
   • If neighbours’ walls or buildings are close to the boundary, photograph their condition now. These photos protect you from later claims for damage.
   • Note existing levels: the road, neighbouring plinths and drains. These decide your plinth level.
3. 3

   Check the setting out

   The contractor marks the position of the walls and columns on the ground with string and pegs, or lines of lime. Check it before excavation starts.

   • Measure the distance from each boundary to the building line and compare with the setbacks on the approved plan.
   • Measure the two diagonals of every rectangle. If the corners are square, the two diagonals are equal. A difference of more than a few centimetres means the layout is not square.
   • Check the overall length and width against the drawing, and a few key internal dimensions such as room widths.
4. 4

   Agree a datum and a plinth level

   Everything is measured up and down from a fixed reference. The contractor should mark a datum on something that will not move (a boundary wall, a fixed pillar) and write down the plinth level relative to the road and the neighbours.

5. 5

   Look at the ground

   Soil that is soft, filled, black and organic, or standing in water needs the engineer’s attention. If there is no soil investigation and the structural design assumed a bearing capacity, ask the engineer to confirm the soil you are actually standing on is what they assumed.

The foundation is the part of the house you can least afford to get wrong and cannot see once the walls are up. Three inspections cover it: the excavation, the steel, and the pour.

Hold point 1: the excavation

Lean concrete (PCC) under the footings

A layer of plain, unreinforced concrete is usually placed on the trench bottom to give a clean, flat surface to build on. Check that it is the thickness on the drawing, level, and that the surface is clean before steel goes down. It is a working surface, not a substitute for the footing.

Hold point 2: the footing steel

This is the most important check in the whole build. Steel is what gives concrete the strength to bend without breaking, and it is much more expensive than concrete, so it is where savings are most tempting. Check it against the structural drawing, bar for bar.

1. 1

   Check the size of the bars

   Bar sizes in Pakistan are normally given by number: a #3 bar is 3/8 inch (about 10 mm), #4 is 1/2 inch (12 mm), #5 is 5/8 inch (16 mm), and so on, in eighths of an inch. Measure the diameter of a few bars with a caliper or tape and compare with the drawing.

   • Ask for the steel’s supplier and the delivery slip, and check the brand mark is rolled into the bars.
   • The spot check below, weighing a metre of bar, catches under-weight steel that looks the right size.
2. 2

   Count the bars and check the spacing

   Count the bars in each direction in a footing and compare with the drawing. Measure the spacing with a tape and photograph it. Wrong spacing, or fewer bars, is the most common shortcut.

3. 3

   Check cover

   The steel must sit clear of the ground and of the sides. The standard on which Pakistan’s building code is based asks for about 75 mm of concrete cover on steel that is poured against the earth. The drawings state the cover for each member; check that spacers or concrete blocks hold the bars up, and that the steel is not lying on the lean concrete or on soil.

4. 4

   Check the laps and the starter bars

   Where one bar is joined to another by overlapping, the overlap (lap length) must be what the structural drawing says, commonly in the range of about 40 to 50 bar diameters. The starter bars that will become the column steel must be in the right place, the right number, and tied firmly so they do not move during the pour.

5. 5

   Check the condition of the steel

   Loose, flaky rust is removed before concreting; steel covered in oil, mud or mortar is cleaned. Bars must be tied tightly at crossings so they do not shift. Bent and re-straightened bars that have been bent cold more than once are rejected.

Hold point 3: the concrete pour

Good concrete is a matter of the mix, the water, the placing, the compaction and the curing. Mistakes on any one of these make weak concrete, whatever the steel.

1. 1

   Confirm the mix before the pour

   The mix is on the structural drawing or specification: either a grade (such as a strength in psi or MPa) or a proportion of cement, sand and aggregate by volume. For site-mixed concrete, ask how the materials are being measured. Counting shovelfuls is not measuring; gauge boxes of known volume are.

2. 2

   Watch the water

   Extra water makes concrete easy to place and much weaker. The mix should be stiff enough to hold together, and the labourers should not be adding water to the barrow or the truck to make it flow. If ready-mix is used, check the delivery slip for the grade, the time it left the plant, and that no extra water is added on site.

3. 3

   Make sure the concrete is placed and compacted

   Concrete should be placed in layers and compacted with a vibrator or by rodding, so there are no gaps around the steel. Dropping it from a great height makes it separate. Check there is no standing water in the pit and that the steel has not been trodden down.

4. 4

   Take samples

   For any structural pour, ask for sample cubes or cylinders to be cast, labelled and tested at 28 days at a laboratory. They are the only record of how strong the concrete actually is.

5. 5

   Cure it

   Concrete gains strength through chemical reaction that needs moisture, and in Pakistan’s heat it dries out fast. Keep it continuously wet, or covered, for at least 7 days (longer in hot weather or if the engineer specifies it). Concrete that was poured and left is weaker and cracks.

This stage is quick and easy to rush, and the problems it causes appear years later as damp walls, peeling paint and termites. Everything here gets buried, so it is a hold point.

1. 1

   Check the plinth beam and the columns up to plinth

   Steel and shuttering for the beam at plinth level are checked as for any beam (next chapter): bar sizes and number, stirrup spacing, cover, and starter bars for the columns above.

2. 2

   Check the plinth level

   Measure the top of the plinth from the datum. The usual aim is for the finished floor to sit above the road and the surrounding ground, so that rain does not run into the house. Compare with the level you agreed before work started.

3. 3

   Check the damp-proof course (DPC)

   A DPC is a continuous layer at plinth level that stops moisture rising from the ground into the walls. Check that it is in the specified material and thickness, is continuous without gaps at the joints and corners, and sits at the right level. A DPC with gaps does not work.

4. 4

   Check the anti-termite treatment

   In most of Pakistan, ground termite treatment is applied to the soil in the trenches and under the floor before backfilling, by a pest-control firm. Ask for the invoice and the name of the chemical, and watch it done. It cannot be done after the floor is laid.

5. 5

   Watch the backfilling

   Fill under floors should be clean soil or sand, put in layers and compacted, each layer wetted and rammed, not dumped in and levelled. Poorly compacted fill settles, and the floor above it cracks. Fill with rubbish, organic matter or large lumps is rejected.

In a typical Pakistani house, the load is carried by a reinforced concrete frame, and the walls are infill. The frame is the structure, so columns and beams get the same careful steel check as the foundation.

Columns

Beams

The pour

• The same rules apply as for the foundation: the mix as specified, no extra water, concrete placed in layers and compacted, and samples cast.
• Concrete should not be dropped from a great height into a column form. It segregates, with the stones falling to the bottom. A funnel or a chute, or placing in stages, prevents it.
• A column must be poured continuously. A stop partway is a weak plane.

When the forms come off

The surface of the concrete tells you how well the pour went. A smooth, even face is good. Look for honeycombing (stones with gaps between them), exposed steel, and bulging or leaning. Small surface flaws can be repaired by the engineer’s method. Honeycombing deeper than the cover, or exposed bars, is a structural defect and must be reported to the engineer before anything is patched or plastered over.

A slab is poured in one go and you only get one chance to inspect it. The inspection happens when shuttering, steel and electrical and plumbing sleeves are all in place, and before a single barrow of concrete arrives.

1. 1

   Check the shuttering

   It should be level, with props at the agreed spacing, standing on firm ground or on slabs with boards, and braced. Check there are no gaps for the concrete paste to leak out and that the surface is clean, with no rubbish, wire or sawdust.

2. 2

   Check the thickness

   The slab thickness is on the drawing. Mark the depth on the edge shuttering, or push depth pins in, so the contractor can see when it is reached.

3. 3

   Check the bottom steel

   The bars at the bottom of the slab, in both directions, match the drawing in size and spacing. Measure and count. Check the bars are lifted off the shuttering by spacers, so they are in the concrete, not on it.

4. 4

   Check the top steel

   Extra bars go on top of the slab over the beams and walls, where the slab tries to bend the other way. These are often forgotten or sunk to the bottom during the pour. They must be on supports (chairs) that hold them at the right height.

5. 5

   Check the conduits and sleeves

   Electrical conduits and pipes through the slab must be placed before the pour, and fitted without cutting or moving the steel. Boxes, sleeves and pipe holes are marked. Anything left out must be cut into the slab afterwards, which weakens it.

6. 6

   Plan the pour

   Agree the day: not if rain is forecast, and not in the middle of a hot afternoon. Check there are enough people and equipment, and that the concrete supply will not run out halfway. The pour is continuous: a stop is a weak joint, and where a stop is unavoidable the engineer must say where.

7. 7

   Watch the pour

   No water added, concrete compacted with a vibrator around beams and corners, the surface levelled and finished, steel not trodden down. Walk the steel during the pour to check top bars stay at the right height. Take samples.

8. 8

   Cure for at least 7 days

   Keep the surface covered with water, by ponding with small mud or sand bunds, or wet hessian. In summer, wet it several times a day. Concrete cured poorly has a weak, dusty surface and cracks.

Stairs

• Check the steel in the stair slab (the waist), including the top bars where it meets the landing and the beam.
• Every riser in a flight must be the same height and every tread the same depth. A variation of more than about 10 mm between steps in a flight is a trip hazard.
• The landing and head height are as drawn, with enough clear headroom.

After the pour

When props come out, look at the underside of the slab for honeycombing, exposed steel and cracks, and check there is no visible sagging by sighting along the soffit. Hairline cracks from shrinkage are common and harmless; wide or growing cracks, cracks running right through the slab, or cracks at the supports must be shown to the engineer.

Walls carry no structural load in a framed house, but they keep out heat, cold and noise, and they are where the cracking that owners notice first begins. Good masonry is a matter of good material, full mortar joints and straight lines.

1. 1

   Check the units before they are laid

   For bricks, a good one is well and evenly burnt, with sharp edges, rings when knocked and does not crumble or soak up water quickly. Reject piles with many broken, soft or very pale bricks. For blocks, check the stated size and strength, and that they are cured and not cracked. For AAC, check they have been kept dry.

2. 2

   Soak bricks, not blocks

   Clay bricks should be wetted before laying; dry bricks pull the water out of the mortar and the joint is weak. AAC blocks are laid with thin-bed adhesive and trained masons, not ordinary mortar, and should follow the maker’s instructions.

3. 3

   Check the mortar

   The mix is in the specification, commonly a cement and sand proportion such as 1:4 to 1:6 for internal walls. Check the ratio being used, and that sand is clean. Joints must be full: filled with mortar on the bed and in the vertical joint, with no gaps.

4. 4

   Check the bond, line and level

   Courses stagger so that vertical joints do not line up. Hold a spirit level and plumb bob against the wall: it should be plumb and straight, and courses should be level. Walls that lean or bulge are rebuilt, not plastered over.

5. 5

   Limit the height built in a day

   Fresh mortar is soft. A wall built too high in one day squashes the lower joints and bows. Good practice is to stop at around 1.2 metres in a day.

6. 6

   Check the connection to the frame

   Walls need to be tied to the columns, by projecting bars (dowels) set in the column or by the method on the drawing. Without ties, a gap opens at the junction of every wall and column.

7. 7

   Check openings and lintels

   Door and window openings are the size on the drawing, in the right place, and square. Each opening needs a lintel (a beam over the opening) which rests on the wall at each end by at least about 150 mm (6 inches). Check the lintel’s steel before it is concreted.

8. 8

   Cure the masonry

   Keep brickwork wet for several days after it is laid, so the mortar does not dry out before it has gained strength.

This is the stage where the inspection turns from looking to testing. A pipe may look fine and leak when it is under pressure, and a wire may look right and be too thin. Do the tests, and get the results in writing, before any wall is plastered or any floor tiled.

Electrical

Plumbing and drainage

1. 1

   Check the layout against the drawing

   Taps, the geyser, the kitchen sink, floor drains and fixtures are where the plumbing drawing puts them. Decide kitchen and bathroom layouts before the pipes go in: moving them later means breaking the wall.

2. 2

   Check the materials

   Pipe type, size and class match the specification. Fittings are the same quality as the pipe. Hot and cold lines are different pipes, and the hot line is insulated if the spec says so.

3. 3

   Pressure-test the water lines

   Before the walls close, fill the supply lines, pressurise them to the pressure the engineer specifies, and watch the gauge for the time they set (commonly several hours up to a day). A falling pressure means a leak. The result goes in the inspection record.

4. 4

   Check the drains

   Drain pipes must slope continuously toward the outlet with no flat spots or back-falls. Check the slope with a level, and the position and level of manholes and inspection chambers. Run water down every drain to confirm it flows.

5. 5

   Check the traps and vents

   Every fixture needs a trap to stop sewer gas rising. A vent pipe carries air so that traps do not siphon dry, and it must rise above the roof.

6. 6

   Check wet areas

   Bathroom and kitchen floors are sunk or sloped to the drain, and the pipes through them are sleeved and sealed. This links to the waterproofing, covered in the waterproofing guide.

Finishing is where the budget is most flexible and where quality varies most. It is also where most of the cosmetic complaints begin. The checks are simple and mostly visual, but they need to be done at the right moment: before the next layer covers the last.

Plaster

Floors and tiles

Doors, windows and joinery

Paint

Fixtures and final tests

Finding a defect is half the job. The other half is getting it fixed before the next stage, and keeping a record that shows you asked. A spoken complaint is easy to forget. A dated written report is not.

What a good inspection report contains

Three levels of finding

• Critical. A structural problem, or something that cannot be fixed once covered. Work stops at that point until it is corrected and re-inspected. Examples: wrong or missing steel, wrong column size, concrete placed without approval.
• Major. A defect that must be fixed before the next stage, but does not stop the whole site. Examples: poor compaction in one area, a leaking joint in a pressure test.
• Minor. A cosmetic or small defect to be listed and fixed before handover. Examples: uneven paint, a door that catches.

Getting it fixed

1. 1

   Send the report the same day

   Send it to the contractor in writing, by message or email, with photos, and keep a copy. Do not rely on a conversation on site.

2. 2

   Agree the fix and the deadline

   For anything critical or major, the engineer states how it is to be corrected. The contractor confirms in writing.

3. 3

   Re-inspect before the next stage

   Do not accept “it has been fixed”. Visit, check it and photograph it. Only then close the item.

4. 4

   Link payment to closed items

   If your contract ties payments to milestones, a milestone is not complete while critical or major findings are open. See hiring and paying a contractor.

If the contractor disagrees

Disagreements are best settled by testing, not by arguing. If concrete strength is in doubt, the sample cubes or cylinders cast at the pour are tested. If those results are missing or poor, the engineer can order tests on the concrete in place: a rebound hammer gives a quick surface indication, a cover meter finds steel and its depth without breaking the concrete, and cores cut from the structure are tested in a laboratory. Agree beforehand, in the contract, that the contractor pays for tests that show the work is defective and the owner pays for those that show it is sound.