Underlay, Trims and Accessories

Crumb rubber underlay is dense, heavy and firm underfoot. It is made from recycled tyre rubber bonded under pressure, which gives it a long working life under heavy foot traffic and makes it the usual choice under wool and wool-mix carpets in busy households or hallways. It does not compress permanently the way cheaper foams can, so carpet pile keeps its bounce for longer, but it is a poor sound absorber on its own compared with a bonded felt or a layered acoustic product.

PU foam (polyurethane) is the lightest and softest of the four, and it is what most budget carpet packages default to. It gives an immediately plush feel underfoot but the cheaper grades compress and go flat within a couple of years under regular walking, especially on stairs and in front of sofas, which is when carpet starts to look and feel tired even though the pile itself is fine. Higher density PU foams close that gap but move closer to crumb rubber pricing.

Felt and felt-rubber composites sit between the two: firm, dense and good at sound deadening, traditionally used under natural fibre carpets like wool berbers and sisal-look weaves where a very stable, non-stretch backing matters. Sponge rubber, the ribbed waffle type, is now mostly specified for lower-traffic domestic rooms or as an entry-level option; it is comfortable but the least durable of the four under sustained heavy use.

Most leasehold flats carry a lease condition requiring a minimum Impact Sound Insulation rating, commonly a stated dB reduction figure or reference to Building Regulations Part E performance, and this applies to hard floors far more strictly than carpet. The underlay has to be tested and rated for impact sound, not just sold as acoustic, because footfall noise travels through the floor structure into the flat below as vibration, not airborne sound, and ordinary comfort underlay does very little to stop it.

For LVT, laminate and engineered wood in a flat, that usually means a dedicated acoustic underlay, sometimes combined with a decoupling layer, chosen to meet the specific dB figure the lease or management company asks for. We keep the test certificate for the product used on record for exactly this reason, because a managing agent or a neighbour's complaint can ask for proof after the job is finished, and a verbal assurance is not evidence.

For carpet in a flat the requirement is usually easier to meet because carpet plus a reasonable underlay performs well for impact sound by nature, but it is still worth checking the lease wording rather than assuming, since some blocks specify a minimum underlay thickness or type regardless of floor covering.

Gripper rod is the row of angled pins fixed around a room's perimeter that carpet stretches onto and hooks into, and it needs to sit close enough to the wall that carpet tucks fully into the gap without a visible gap or a lifted edge, but not so close that it catches skirting. Getting gripper positioning wrong is one of the most common reasons carpet lifts at edges within months of fitting, and it is a fitting error rather than a carpet fault, which is why we set gripper ourselves rather than relying on whatever was left from a previous fit.

Door bars and threshold profiles cover the transition between two different floor heights or materials at a doorway, and the right one depends on both the height difference and the materials either side. A single-floor T-bar suits carpet meeting carpet at roughly equal heights; a reducer or ramp profile handles a step down to a thinner LVT or laminate; a cover strip in aluminium, brass or matt-finish nickel handles a bigger height difference or a wet-room threshold where a screwed-down bar is more secure than an adhesive-only strip.

Metal choice is partly aesthetic and partly practical: aluminium is the standard low-cost workhorse, brass suits older or higher-spec properties and takes a polish, and satin or matt nickel finishes are usually chosen to disappear against grey or pale floors rather than stand out. Height and profile matter more than finish for how well a threshold actually performs day to day.

A stair nosing covers the leading edge of each tread, and on carpeted stairs it usually takes the form of a metal or timber edge protector fitted before the carpet, or a soft nosing built into the underlay and carpet fit itself to stop the front edge of each step wearing through before the rest of the tread. On LVT or laminate stairs the nosing is a structural profile, not decorative, because the front edge of a stair tread takes more repeated impact and abrasion than any flat area of floor in the house.

Stair nosing choice also has a safety dimension that flat flooring does not: a worn, loose or mismatched nosing changes the depth a foot expects to find on the way down, which is a genuine trip risk on a staircase used daily. We treat stair nosing as part of the specification, not an accessory added at the end, and check tread depth and existing nosing condition on every staircase survey.

Two identical floors, one finished with mismatched, ill-fitting trims and one finished properly, read completely differently even though the main material cost the same. A gap at a threshold, a wrong-height door bar, or scotia in the wrong colour draws the eye immediately, because trims sit exactly where people look: doorways, stair edges and skirting lines. The floor itself can be first-rate and still look like an afterthought if the finishing details were an afterthought.

This is the reason we specify underlay and trims as part of the same quote as the floor covering, rather than leaving them to be sorted on the day. It also means we can source less common items, like a specific metal finish for a threshold or a matched stair nosing colour, ahead of the fitting date rather than substituting whatever is closest on the fitting van.