Flat pack punishes impatience more than incompetence. Nearly every ruined build traces back to one of the same dozen mistakes — all avoidable, none requiring skill to avoid, only discipline.
Before you start
1. Not checking the parts first. Lay out and count hardware against the manifest before step one. Discovering a missing cam lock at step 19 is the classic flat pack tragedy — and if something is missing, you want to know while the boxes are still return-friendly. (Here’s what to do about missing parts.)
2. Building in the wrong room. Assembled wardrobes don’t fit through doorways. Build where the furniture will live, with roughly its own footprint again as working space.
3. Working on a hard bare floor. The packaging cardboard is your work surface — it protects both the laminate below and the panel faces above.
4. Starting the two-person item alone. The box says two people because panels crack when one person pivots them wrong. Recruit or postpone.
During the build
5. Fully tightening as you go. The big one — see the FAQ. Loose until square, then tighten evenly.
6. Confusing similar panels. Left and right sides, tops and bottoms — near-identical, except in hole pattern. Check holes against the diagram before every fixing.
7. Ignoring inside/outside faces. Pre-drilled holes face inward; finished faces face out. One inverted panel means visible holes forever.
8. Muscling cam locks. Cam locks close with a firm quarter-to-half turn. If it won’t turn, the dowel isn’t seated — forcing it strips the cam housing out of the chipboard.
9. Full-torque drilling. Drill-drivers are fine with the clutch set low; screws driven at full torque burst through the panel or strip the thread. Last half-turn by hand.
10. Fitting the back panel late or crooked. The flimsy hardboard back is what makes the unit square and rigid. Square the carcass, then nail or screw the back on straight — a crooked back locks the skew in permanently.
After the build
11. Skipping the wall anchor. Every tall unit’s instructions include one. Furniture tip-over is a real, documented danger to children, and “it seems stable” is exactly what an unanchored wardrobe seems until a drawer is climbed. Fit the anchor. Rent or borrow the drill if you must.
12. Binning the spares and instructions. Tape the spare fittings and the manual inside the back or under a drawer. Future-you, dismantling this for a house move, will be grateful.
Or skip all twelve
Every mistake above is one a professional stopped making years ago. If your build involves the items where errors cost most — sliding doors, bunks, big modular wardrobes — the honest comparison is in our DIY vs professional guide, and quotes are free if the list tips you that way.
Frequently asked questions
What is the most common flat pack assembly mistake?
Fully tightening fixings as you go. Almost every frame needs to stay loose until it is complete and square, then be tightened evenly — lock each joint solid immediately and the final panels will not line up, and the forced result squeaks and racks forever.
How do I avoid mixing up similar-looking panels?
Keep parts in their boxes until needed, build one item at a time, and check each panel’s edge holes against the diagram before fixing — near-identical panels almost always differ in hole pattern. Pencil-marking the top edge as you confirm each panel helps on big builds.
Can over-tightening really damage flat pack furniture?
Yes — chipboard threads strip easily, and a stripped cam or screw hole in a structural panel can write off the panel. Tighten to firm, not to victory, and if using a drill-driver set the clutch low and finish by hand.
Prices and timings on this page are indicative, based on typical quotes we see across the UK. Your job may cost more or less — the only way to know is to get quotes for your specific items and location. This site earns a fee when we pass enquiries to assembly firms; this never changes what you pay.