Underlay Essentials

Upgrading a carpet installation

It used to be said that a good carpet underlay doubled the life of a carpet. In these days of contractual obligation, it would be extremely unwise for anyone to make such a sweeping claim, however, it is certain that a poor underlay detracts measurably from the life of a carpet. Investing in a higher quality underlay is the most cost-effective way of upgrading a carpet installation. It is usually better to spend an additional £2 per meter on underlay, than to upgrade the carpet by the same amount. The improved underlay will provide greater support for the carpet, and thus greater wearability. It will also give a feeling underfoot of greater quality. An inexpensive carpet with high quality underlay may well feel better than a high quality carpet with cheap underlay.

We basically classify underlays into three different types:

  • wool felt
  • rubber
  • a combination of the two.

Wool Felt

This is the classic underlay that provided protection for generations of carpets. It is still available, and in the best qualities is still quite satisfactory. The main disadvantages are that it compacts down with use, and becomes a reservoir for dust. Seldom the best option, and therefore not carried in stock. Available within a few days, to special order.


The vast majority of modern underlays are made from rubber (natural, synthetic, or a combination of the two). The quality and performance of rubber underlay varies enormously. The best are excellent, and suitable for most carpet installations: the worst are underlays in name only, providing almost no support for the carpet, and the prospect of disintegration within months. We advise that the most reliable indictor of quality is weight. In the carpet trade (still wonderfully free from complete metrication) it is common to rate ‘blown rubber’ underlays by weight per 18 sq.mt. roll. It is possible that some underlays of lesser weight might prove satisfactory in certain circumstances, but we do not stock blown rubber underlays with a rated weight of less than 100 lbs. (grade ‘A’). We are aware that some carpet retailers might consider a grade ‘C’ 50 lb. underlay to be standard, and grade ‘B’ 75 lbs. to be extravagant. This is a short-sighted view, and the cost of such short-sightedness is eventually born by the customer, who’s carpet deteriorates prematurely. Thick, squashy underlays should be avoided. Although they feel spectacularly luxurious underfoot, they ‘bottom out’ easily, and can cause terrible carpet stretching and delamination problems. The best blown rubber underlays are heavy, quite thin, and highly resistant to permanent crushing. Highly compacted crumb rubber (‘AA’) is absolutely excellent, and good for years of very heavy use. Ours carries a Royal warrant.


In our opinion, combination felt top/rubber base underlay is by far the best. It is what discerning carpet people buy for themselves. It provides a wonderfully luxurious yet controlled tread which cannot be imitated by any other underlay. It is usual to fit such underlay in heavy wear areas (living areas, hall stairs and landings) but its use may also be rationalised in bedrooms where its ability to hide uneven floors can be an advantage. It has two disadvantages. It is quite expensive, although many feel that the difference in price is easily justified by its undoubted virtues. It is also rather thick (about ½”) which occasionally requires additional door easing. Because the top felt layer moulds to some extent into the corrugated back surface of the carpet, this is the most suitable underlay for woven Axminster and Wilton carpets. The majority of felt-rubber underlay is used in commercial applications (hotels, cinemas, and similar high traffic areas,) however it is increasingly being specified for domestic situations where quality is the first concern. Carpet fitters hate this underlay because they have to carry the very bulky rolls.