Door Bars and Thresholds: Joining Two Floors
What a door bar does where two floors meet: the movement joint, a step in height, the edge underfoot. The profiles, and the 15 mm accessible threshold.
A door bar is the strip that finishes a floor in a doorway. It does up to three jobs, and which one matters depends on the floors on either side. It gives a floating floor the movement joint it needs at the narrowest point of the room. It bridges a difference in height between two floors. And it protects an edge that would otherwise catch a foot and wear first. This guide takes the three in turn, then the profiles that do them.
On this page
The movement joint
A floating floor needs room to move, and a doorway is where it is squeezed. The EPLF, the European association of laminate producers, lists doorways between rooms among the places expansion joint profiles should be installed. The MMFA says the same for rigid vinyl and other multilayer modular floors, and adds that suitable expansion mouldings with sufficient clearance belong wherever different floor coverings meet. For a floating wood floor, the US National Wood Flooring Association builds transition pieces allowing for expansion space into narrow doorways.
In our range the 36 rigid vinyl floors and the 5 laminates click together and float, so for them the door bar is part of the floor. The expansion gap guide explains why the gap is there and how big it is.
A step in height
Two floors rarely finish at the same level. The Contract Flooring Association says a junction between floor coverings of different height may need a slightly ramped transition. The height to bridge is the whole build-up on each side, board plus underlay or adhesive, not the board alone. Across our range the boards alone run from 5.2 mm and 6.5 mm for rigid vinyl, with the underlay attached, through 9 mm and 10 mm for porcelain tiles and 12 mm for laminate, to 12 mm to 20 mm for engineered wood and 18 mm for solid wood.
The profiles
The NWFA describes the three common shapes. Reducers are used to provide a smooth transition between floors of uneven heights, often between a wood floor and a thinner covering such as vinyl or low pile carpet. T-mouldings are commonly used to join two areas of flooring that are the same thickness, or to join floating wood floors between two rooms, in doorways. Thresholds are designed for the transition between floors of different heights, and are commonly used at doorways, between interior rooms and to the outside.
How it is fixed matters as much as its shape. The NWFA says a T-moulding should never be fastened to the wood flooring; it must only be attached to the subfloor, in order to maintain adequate expansion space. The same applies to trim generally: trim pieces should never be fastened to or through the flooring system. A door bar screwed down through a floating floor pins it, and the floor can then lift elsewhere.
The edge underfoot
A doorway is crossed more than almost any other part of a floor, and an exposed board edge there is where wear and trips start. Approved Document M, the guidance on access to dwellings, gives a useful yardstick in its definition of an accessible threshold: one that is level or, if raised, has a total height of not more than 15 mm, a minimum number of upstands and slopes, and any upstands higher than 5 mm chamfered. A doorway that a wheelchair, a walking frame or a pushchair crosses is better for meeting it.
Choosing the bar
Match the finish to the lighter or the more visible of the two floors; a bar that matches neither reads as a repair.
Common questions
Do I need a door bar between rooms?
For a floating floor, usually yes: the EPLF and the MMFA both put expansion profiles in doorways between rooms. A floor glued throughout follows its own fitting instructions.
Can the same floor run through a doorway without a bar?
Sometimes, if the floor's instructions allow the run. The EPLF notes that manufacturers' recommendations on maximum uninterrupted floor sizes vary greatly, and that the installation instructions for the product should be carefully heeded.
Should a door bar be screwed through the floor?
No. The NWFA says a T-moulding should never be fastened to the wood flooring but only attached to the subfloor, so the floor keeps its expansion space.
What is an accessible threshold?
Approved Document M defines it as a threshold that is level or, if raised, has a total height of not more than 15 mm, a minimum number of upstands and slopes and any upstands higher than 5 mm chamfered.
What joins two floors of different heights?
A reducer or a ramped profile. The Contract Flooring Association says a junction between floor coverings of different height may need a slightly ramped transition, and the NWFA describes reducers as a smooth transition between floors of uneven heights.
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What the published standards say
Who publishes this guide
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