It's certainly tempting to consider installing new carpeting over the old carpet, skipping the removal process. It saves on the cost and labor of tearing up and disposing of the old carpet, and it keeps carpet waste materials out of the landfill. And if the existing carpet was glued down, not tacked, it can be a huge time-saver to lay the new carpet over the old. Leaving the existing carpet provides one extra layer of insulation for cold floors. Plus, installing a pad is not necessary, as the existing carpet acts as padding.
But despite the apparent advantages of laying new carpet over old, most carpeting industry professionals respond to this approach with a single phrase: Don't do it. There are several reasons to avoid this method:
- Tack strips are difficult to install. By leaving a layer of carpet, you make it that much harder to nail down the tack strips. The anchoring nails on tack strips are only about 3/4 inch long— far too short to penetrate the old carpet and pad and reach into the subfloor. In fact, the difficulty of placing tack strips may be the single factor that prevents you from laying new carpet over the old.
- Carpet is an inadequate base. Carpeting needs a solid base for proper installation and performance. Carpet installed with an improper base will wear out quickly. There are many aspects to this, but consider just this one: Traffic patterns already worn into the existing carpet will quickly be telegraphed up to the new carpet.
- Old carpeting harbors dust and mold. Studies show that mold and mildew in carpeting are exacerbated by the presence of dust. Dust and moisture, with high temperatures added, equals mold and mildew. It is virtually impossible to clean an old carpet enough to remove all of the dust. But if you choose to have the old carpet professionally cleaned first, you're already spending money that could have been spent on removing the carpet.
- Dual carpet creates additional floor layers. By adding an extra layer to your flooring, you are effectively lowering your ceiling. In a basement or any other height-challenged room, every inch counts. And Don't forget that adding height to your carpet will mean that doors will scrape and thus will need to be cut off at the bottom. Also, wood trim will have to be removed and reinstalled.
- You lose the chance to check and repair the subfloor. Ripping up carpet, on the other hand, lets you assess the status of your subfloor and identify and repair any damage to it.
Other Advantages to Carpet Removal
Old carpeting can sometimes be recycled. Concerned about dumping carpet in landfills? There is a non-profit consortium called Carpet America Recovery Effort that helps connect homeowners to companies that recycle carpeting. If your reason for leaving the old carpet in place is an environmental concern, a variety of re-use stores may gladly accept carpeting that is in relatively good shape. Even a very old carpet may have good sections that can be cut out to serve small rooms or to make area rugs.
Removing glued-down carpet is often easier than you think. Glued-down carpet is notoriously hard to remove, but when it becomes old, the adhesives may have cracked and broken up. Before you assume that a glued-down carpet will be impossible to remove, test a corner of the carpet—you might get lucky and find that it comes up rather easily. If the labor required to remove glued-down carpet is too oppressive to think about, consider using a power tool, such as a multi-tool with a scraper attachment. It's also helpful to have a heat gun to loosen up the stubborn glue. Be very careful when using a heat gun near textiles and carpeting, though.
Tips for Installing New Carpet Over Old Carpet
After reviewing these considerations and cautions, if you still feel that installing carpet over the existing carpet is the best route for you, here are some tips for pursuing that strategy:
- Choose a low pile. The best choice for a carpet-over-carpet installation is a carpet with an extremely low pile. The lower the pile, the better, since will minimize the degree to which the floor will be raised.
- View it as a temporary solution. At best, carpet-on-carpet should be a short-term solution. So, if you are house-flipping or intending to stay in your home for only a short while, this may be a viable option. Placing an area rug on the existing carpeting is also perfectly acceptable.
- Apply a thin underlayment. Laying down a thin plywood underlayment atop the old low-pile carpet is better than just putting the new carpet straight onto the existing carpeting. The underlayment will provide a rigid base for the new carpet and a place to attach tack strips. Make sure to securely nail the underlayment down to the subfloor through the old carpeting.
Haines, Sarah R et al. Modeling microbial growth in carpet dust exposed to diurnal variations in relative humidity using the "Time-of-Wetness" framework. Indoor air vol. 30,5 (2020): 978-992. doi:10.1111/ina.12686