changing a wood deck to composite

Changing a Wood Deck to Composite


Should we change this wood deck to composite?

We are thinking of changing this old wood deck to composite, how much will it cost?  Ok, slow down there. We hear this question more and more these days. Since the EPA banned a few chemicals from exterior stain, none of the stains work very well. That means you may have to stain your deck every year or hire someone to do it. With an average of $3k to re-stain an old deck that option is unappealing to most.

Let’s just start fresh and change this old wood deck to composite or PVC. How hard can it be?  All you are doing is ripping off the wood decking and sticking on PVC or Composite boards right? Thinking that changing the type of decking is easy? You should read this entire article because it isn’t. Even a small rectangular deck is more work to reclad with composite than you might expect.

Are you doing this to save money?

As you read on you will realize how much work is involved in converting a deck to PVC or composite. Are you are expecting to save 50% on the budget of a new deck? Turn back now to avoid disappointment. If you are doing it yourself you may save 20% on the budget and hopefully, you won’t have to dig footings. Planning to hire a professional to do the conversion? Expect to save about 10% off the budget of a new low maintenance deck. Keep reading to understand why.

How Old is the Deck?

Decks less than 10 years old are the best candidates for this type of retrofit. When a deck is more than 10 years old, rot is setting in and putting high-end decking down on a rotten frame will only get you another 10 years before having to rebuild. These days code requirements are onerous and deck builders are building heavier decks. Decks currently clad in the old composite are often better suited to the conversion to PVC or capped composite.

Was the Deck Well Built?

Get down low and look across the surface of the deck. Is it level and flat? Look at the leading edge. Is the deck straight across the front? Give the deck the jump test…is there any movement? Jump side to side. Is the deck made of pressure treated wood? Check the beam for rot. Use a scratch awl (pointed screwdriver), and try to push it into the wood in the middle of the beam on the underside. You could also drill a small hole through the beam above a post. Look at what comes off the drill bit. Is it paste or is it sawdust?  If it is a paste, the beam is rotten.

The best indicator that a subframe is worth saving is whether the decking and skirting were spaced or not. If everything was as tight as a drum for 10 years, water was going in and not able to escape. Tightly clads deck often are not worth salvaging.

composite, cedar or PVC decks
Decks with frameless glass guardrails–We decided on Red Cedar for this re-deck.

Wood Deck Framing VS a Frame for Composite:

Wood decks are framed differently than a frame for composite or PVC. These materials need a very different spacing of joists to feel right and last. Here is a handy list of the differences and things you may have to change to retrofit with composite:

  • Wood deck joists are usually 16″ apart–Composite is usually 8-12″ apart (depending on the brand). You may have to add extra joists–possibly one per space.
  • Wooden decks are normally built with 2×8 joists to last 25 years. Composite Decks are usually built with 2×10 and include joist flashings to extend the life of the frame to the 40-year mark.
  • Wood deck beams are typically smaller vs a larger composite deck beam. It is always a good idea to add another flashed layer to the beam to extend the life of your retrofit deck!
  • Wood decks normally have wood posts installed which become part of the railing. Composite decks typically use aftermarket bolt-on railings. You should likely remove the existing posts and add blocking to attach the aluminum (low maintenance railings). Why use low maintenance decking with wooden rails?
  • Wood decks rarely have borders and breaker boards to limit the length of decking. Composite decks need breakers and borders to hide the end grains and make expansion less obvious. You will have to add in plenty of blocking to support these borders and breakers, in fact, by the time you finish installing the blocking and extra joists, a frame for composite or PVC may have 100% more lumber in it.
  • Some big box deck builders not worried about permits are building floating decks on deck blocks or patio stones. Often using a 2×6 frame, most will not be suitable for a decking swap. Why put a new Mustang body on an old rusty Pinto chassis. In some cases, you are just better off to rebuild entirely.
  • If any rot is obvious, it’s time to reframe the deck. A composite or PVC deck should last 40 years. If your deck is starting to rot already, even if we install flashings you may only get 10 or 15 years from your deck, and it’s not worth reusing composite decking.
framing for composite
A  homeowner asked for a composite re-deck but soon decided that the old deck was too far gone to work with.

Making a Final Call… with the Decking Off.

So, your deck is not perfect, but what deck is? You and your builder will need to make a decision. Often the best time to make a final call is after the decking is off. You can see much more now. Does the deck have a ledger flashing, and if not, is the house rotting where the deck is connected?  Are the support posts rotting?  Would the deck meet code today? If everything looks ok, let’s make it happen! You saved a few bucks! Congratulations. You are about 1 in 10. Most grades will fail our inspections along the way and we end up replacing the entire structure.

Another option for the challenged budget;  If the deck frame is borderline, and you are happy with the layout of the deck, why not save a bit of money and use red cedar for now. Imported stain and flashing on joists will help get another 10 or 15 years from a deck or let it grey and get 10 years. This may be a good option if you had a little bit of sticker shock when you saw the budget from your builder to convert it to PVC.

Preserving the deck frame you have.

Beams flashed with rubber tape–Beams rotting prematurely is a problem of late. We flash all built up beams to prevent it. We often use flashing tape to extend durability.

Installing a wall flashing and joist flashing tape on the joists, (rubber tape–similar to that we use around window openings), helps an old deck last much longer. It can extend life for decades. Keep in mind, it is not a cure for rot. A rotten frame is not something you should invest in.  Better to bite the bullet now, than to plow your hard earned money into a deck that may fail in a few years.

Complete Replacement?

No need to get upset about it. You are going to end up with a much better structure in the end and it will last longer! It is an opportunity to improve the design and make it look much better than you may imagine!  Let’s redesign this deck so that it makes sense, functions and actually makes your home look better! Check out some of our 3D Deck Designs here! A modern deck can have helical footings, expected to last a hundred years, heavier frames and we can waterproof them to make them last many decades. This is your chance to build a spectacular composite deck that will outlast many homes! Make this new deck your last new deck!


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