Costly Mistakes When Building a House

Some house-building mistakes are very expensive or nearly impossible to fix later: foundations, waterproofing, roofing, insulation and service penetrations.

In a flat renovation, the wrong paint colour can simply be repainted. In house building, some decisions end up inside concrete, soil and walls, and changing them can mean taking part of the house apart. So the main rule on site is simple: give the most attention to the work that is hardest to fix later.

Building foundations without knowing the ground

Assuming the foundation that works for the neighbour’s house will suit your plot can be risky. Soil type, groundwater level, slope and old fill material can vary even over short distances.

The consequences – cracked walls, sticking doors and windows, settling floors – may show up years later. A geotechnical survey and a structural engineer’s calculation are a small part of the budget, while fixing a foundation problem afterwards is a complex engineering task.

Treating waterproofing and drainage as secondary

Waterproofing of foundations and basement walls, directing rainwater away from the house and a drainage system all disappear from view once the ground is backfilled. Poorly executed waterproofing shows up as damp, mould and failing finishes in the basement.

Redoing it after backfilling means excavating again. That is why waterproofing layers should be inspected and photographed before they are covered.

Not detailing the roof and water run-off properly

Roof problems rarely come from the covering itself; they come from junctions: chimney and wall abutments, valleys, roof windows and parapets. On flat roofs, insufficient falls lead to standing water.

The number and location of gutters and downpipes also need planning. Water running down the facade gradually damages walls, window sills and the foundation.

Gaps and thermal bridges in insulation

Continuity of insulation matters as much as its thickness. Concrete ring beams, balcony slabs, window reveals and the junction between wall and foundation can turn into cold bridges, where condensation and then mould appear on inside surfaces.

Where the windows sit within the wall and how their edges are insulated also affect the result. Once the facade is finished, these details are very hard to correct.

Vapour permeability should not be forgotten either. Wall layers must be chosen so that moisture from inside does not get trapped within the insulation. An incompatible combination of materials can lead to moisture building up in the wall and the insulation losing its properties. This is resolved at the design stage based on the materials’ technical data.

Forgetting service penetrations

Every hole drilled later through a concrete slab or foundation means extra work and a risk to the structure. Drain outlets, water supply, power cables, ventilation ducts, air-conditioning lines and sleeves for a future pool or garden lighting should be shown in the design and placed before concrete is poured.

When the building services design is prepared alongside the architectural design, clashes of this kind drop considerably.

A simple but effective method is to check every sleeve, pipe and duct against the drawings on the formwork before the pour. When both the design engineer and the relevant tradesperson take part, the chance of something being missed drops noticeably, because each recognises their own lines.

Changing the design during construction

If the decision to move walls, add a window or add a storey is made after construction starts, the structural calculations must be reviewed too. That costs time and often part of the work already done.

A similar risk comes with swapping materials for cheaper alternatives. When the blocks, rebar or insulation specified in the design are replaced with something “just the same”, their strength, thermal conductivity or other properties may no longer match the calculations. Every substitution should be agreed with the designer.

A short checklist to avoid costly mistakes:

• Do not start the foundation without a soil survey and structural calculation.
• Inspect waterproofing and drainage before backfilling.
• Detail roof junctions and water run-off separately in the drawings.
• Check insulation continuity at junctions.
• Verify every service penetration on site before pouring concrete.
• Finalise layout decisions before construction begins.

Construction at Zaferoğlu İnşaat begins with topographic and geological maps of the site, because a mistake at that point carries through to everything built afterwards. Get in touch to discuss your house project at an early stage.