Trim an internal door.

Professional carpenters use specialised track saws and planes to ensure a perfectly straight edge without splintering the veneer. This guide outlines what to expect when hiring a professional to adjust your doors, the costs involved, and the critical safety considerations regarding fire-rated doors.

What Does the Work Involve?

• Assessment: The carpenter checks the door type (hollow core, solid wood, or fire-rated) and measures the required clearance over the new flooring.
• Removal: The door is carefully unscrewed from its hinges and placed on stable trestles to prevent damage to the faces.
• Marking and Scribing: A cut line is marked, often accounting for uneven floors by "scribing" the specific shape of the floor onto the door.
• Trimming: Excess material is removed using a power plane for minor adjustments or a circular saw with a fine-tooth blade for larger cuts.
• Finishing: The cut edge is sanded smooth and treated with a wood sealant or primer to prevent moisture ingress and warping.
• Re-hanging: The door is refitted, hinges are adjusted for a flush fit, and the leading edge is checked for "binding" against the frame.

Typical Costs

Most carpenters charge a minimum call-out fee to cover travel and setup, which usually covers the first hour of work. For multiple doors, you will likely be quoted a day rate or a fixed price per door.

Prices vary based on your location (London and the South East are typically 20% higher) and the material of the door. Solid oak doors take longer to trim than lightweight hollow-core doors and require sharper, more expensive blades.

How Long Does It Take?

• Single standard door: 45 to 90 minutes, including setup and cleanup.
• Solid hardwood door: 1.5 to 2 hours due to the density of the wood and finishing requirements.
• Full house (6-8 doors): 1 full working day for a single carpenter.
• Adjusting hinges/frames: Add 30 minutes if the frame has settled and is no longer "true."

DIY or Professional?

Trimming a door is a high-stakes DIY task. Modern hollow-core doors have a very thin internal timber frame (the "rail"); if you cut more than 10-20mm off the bottom, you may remove the structural support entirely, causing the door to fall apart. Professionals have the tools to "re-rail" a door if a deep cut is necessary. Furthermore, fire doors should never be trimmed by an amateur, as removing too much material voids the fire certification and compromises your home's safety and insurance.

Choosing the Right Tradesperson

• Look for a carpenter with a City & Guilds or NVQ Level 2/3 in Site Carpentry.
• Check if they have a "dustless" setup, using HEPA-filtered extractors connected to their saws.
• Red Flag: Any tradesperson who offers to trim a fire door without checking the manufacturer’s "trimming allowance" first.

Ask your carpenter: "Do you use a track saw to ensure the cut is perfectly straight, and will you seal the bottom edge to prevent the door from absorbing moisture and swelling?"

UK Regulations

• Fire Safety (BS 8214): Fire doors have strict limits on how much can be trimmed (usually 3mm to 10mm). Exceeding this voids the FD30/FD60 rating.
• Building Regs Part M: If you are raising the floor level, ensure the remaining clear opening height still meets accessibility standards.
• Waste Disposal: If the carpenter removes old doors, they must have a valid waste carrier licence to dispose of them legally.

Common Problems

• Break-out: Using the wrong saw blade can cause the veneer to "chip" or "splinter," ruining the look of the door.
• Moisture Swelling: If the bottom raw edge isn't sealed, it will absorb moisture from mopped floors or humidity, causing the door to stick within months.
• Hollow Core Exposure: Cutting too deep into a cheap door exposes the cardboard honeycomb interior, requiring a new timber block to be glued inside.
• Hinge Bind: Trimming the bottom doesn't always solve the problem if the hinges have sagged; a professional will check the "swing" before cutting.

Frequently Asked Questions