The expensive mistakes are rarely about taste. They are about sequence, scope, and decisions made later than they should have been.
By Alderic Tan · 3dots · Updated 16 August 2026
Quick answer
The costliest renovation mistakes are procedural: deciding too late, comparing quotes that describe different scopes, and spending on visible finishes while under-specifying what sits behind them.
Late decisions are the single biggest cause of both delays and cost overruns.
Lump-sum quotes leave you nothing to compare and nothing to adjust.
Skipping permits or hiring outside HDB’s directory can mean reinstatement at your own cost.
Every renovation has a point where changes stop being cheap. Once carpentry is cut, tiles are laid or a wall is closed up, a change means undoing finished work. Most overruns we see are not bad pricing; they are decisions arriving after the moment they were needed.
The fix is unglamorous: settle the big things early — layout, flooring, whether wet areas move — and treat the schedule of decisions as seriously as the schedule of works.
Three quotes for three different scopes tell you nothing. Give every firm the same brief, insist on itemisation, and compare line by line. The cheapest quote is often the one that has quietly left something out, and you will pay for it later as a variation.
Carpentry is the largest line item in most Singapore renovations, and the easiest to over-commit to before you know how you use the home. Full-height storage in every room looks thorough on a drawing and often ends up half empty.
Build what you know you need, and leave the rest for a second phase once you have lived there. Adding a wardrobe later is straightforward. Removing one is waste.
Wiring, plumbing, waterproofing and levelling are invisible once finishes go on. They are also the only things that require demolishing finished work to fix. In older flats especially, this is the wrong place to economise.
Imported tiles, stone, sanitary ware and some appliances have lead times measured in weeks. A material chosen late can hold up the trades that follow it, and no amount of site pressure moves a shipping schedule.
Appliances, light fittings, fans, curtains and blinds.
Loose furniture, which often costs more than expected once the space is finished.
Post-renovation cleaning, and HDB deposits and fees.
A contingency of around 10%, which is a plan rather than a pessimism.
Permits are not a formality. Work that needs approval and does not have it is unauthorised, and the cost of reinstatement plus fines lands on the homeowner, not the contractor. In HDB flats, only firms on HDB’s Directory of Renovation Contractors may do the work or apply for permits — see our permit guide.
A feature wall photographs well. A kitchen laid out around how you actually cook does not photograph at all, and you will notice it every day. Where budget is tight, spend on what you touch and use, not on what looks best from the doorway.
We front-load decisions, quote itemised so you can see what each choice costs, and say plainly when a plan will cause a problem later. That last part occasionally loses us work, which we would rather do than manage a project everyone regrets.
Deciding too late. Layout, flooring and wet-area changes settled after work begins mean undoing finished work, which drives both delays and cost overruns more than any pricing decision.
Because the cheapest quote is often describing less work. Quotes are only comparable when every firm has the same scope and each line is itemised; otherwise omissions surface later as variations you have to pay for.
Around 10% of the renovation budget is a reasonable planning figure, and older resale flats warrant more, since conditions behind tiles and walls are unknown until work starts.