Exterior \ PT Wood


    ▸ Fences
    ▸ Decks.
    ▷ Treated Wood.

MicroPro Sienna:

  1. Information
  2. Treatment
  3. Maintenance
  4. Wood Choice


Once your pressure treated wood deck is dry, it is recommend to treat your deck with a protective finish.

A weatherproofing finish will provide resistance to weathering and UV exposure. The wood will still shrink and crack, but, slower than if not treated.

Reapply the weatherproofing finish every year or two to keep your deck nice.

New and Old.

Pressure Treated Wood

Most decks and fences are made with pressure treated wood.

The new wood is sooo nice.

Aging Fading Wood

Within weeks pressure treated wood will shrink. Fence board width will go from 5.5" to 5.25", thus boards that are installed butted against each other, will end up having 1/4 to 1/2" spacing overtime.

Untreated, the initial brown colour will lighten in one season to golden colour, then slowly turn grey. The "New and Old" picture shows a year-old fence that abuts a twenty year old fence.

Untreated Deck

5 Years Old

Cracks and twist develop as the wood dries.

The "5 Years Old" picture shows a deck and handrail. Many of the boards and posts have developed cracks.

For many people this is OK, given that they wanted a no-maintenance option (and could not afford composite materials).

MicroPro Sienna


MicroPro Sienna is a trademark of Koppers Performance Chemicals Inc. See their site for product information.

Most PT wood from Home Depot, Rona and Leathertown Lumber is the MicroPro Sienna type.

Finishing Treatments


How fast wood fades and cracks will depend on exposure to weather and sunlight.

Wood aging can be slowed by the application of a semi-transparent stain, water repellent or weatherproofing finish; these provide resistance to weathering and UV exposure.

There are many products out there, and new ones every year. Consult the experts at Heer's, Dulux or Home Depot, etc., describe the condition of the wood and listen to their recommendations.

Weather-Resistant Finish

To protect your wood, exposed wood should be treated with an a water-replelent exterior stain or finish.

When to Finish?

Generally, a finish can be applied as soon as the wood is dry to the touch... so says the MicroPro Sienna site.

We used to wait a month and a couple rain storms to ensure that the wood was dry enough and excess surface chemicals had been washed away. This change reflects the move to water-based wood treatment chemicals versus older woolmanizing processes.


Lots of products out there:

Clear products can be applied every year or two very quickly, and so are recommended for people not interested in deck maintenance.

Golden-brown semi-transparent products are available to return a fading deck closer to the Pro-Sienna original look... but prep work is likely required.

Opaque stain finishes give the wood a uniform painted look, good for decks that have had extensive repairs.


Yearly Treatment

Recommend that every year you apply a weatherproofing finish; these provide resistance to weathering and UV exposure. The wood will still shrink and crack, but, slower than if not treated.

Talk with your paint and finish experts. Clear products can be brushed on quickly and easily, and if you don't know what you want, look for these.

Sand and Treatment

If you a apply a clear or semi-transparent product on your deck, the differences in wood colours will remain... so a weathered deck will likely still look weathered.

Deck Wash products are available to prep surfaces by cleaning dirt and opening pores, thus allowing stains deeper penetration. Cleaners also prolong deck life by removing molds, mildew and algae.

If the deck is weathered and wood is rough to touch, you may want to sand it before applying a weatherproofing product.

Extensive Repair and Refinish

Example of Deck in need of repairs and refinish:

  1. Presure-washed deck to remove loose, peeling finish.
  2. Replaced rotted boards.
  3. Sanded boards.
  4. Applied opaque stain.
Bench Details
Deck Details

Solid vs Transparent Stains

Transparent stain is thinner than solid stain and soaks into the wood. It is easy to apply and shows natural grain (and flaws). Solid stains are thicker and sit on wood surfaces more like paint to produce a thin film for protection.

Transparent stains come in limited colours.

Solid Stains are not recommended for low-to-the-ground decks where boards might swell alot due to humidity and cause solid stain to crack and peel.

You can go from transparent to solid... but usually not the other way.


Dulux Exterior Stains have a 3 year horizontal, or, 5 year vertical guarantee. Mostly just mentioning this because of the novelty of a warrantee varying with surface orientation.

Deck Wood Selection

Deck Board Thickness

Generally people go with 5/4" thick boards if joist are spaced 16" apart, and to 1.5" thick boards if joists are 24" apart.

A 2x6 board will resist warping and cracking slightly better than the 5/4" board, so something to consider even with 16" spans.

Square vs Beveled.

1 1/4 x 6 (5/4" x 6) deck boards typically have a rounded edge, making them nice for walking surfaces.

1 1/2 x 6 (2x6) PT lumber from Leathertown Lumber is also rounded, making it a good choice for decks and steps.

Leathertown Lumber are in Acton but have free delivery for orders over $500. Leathertown site.

Getting the Best Price

Prepare a list of materials and request quotations from the Pro-Desk or Service Departments at Home Depot, RONA, Leathertown, etc., and include delivery charges.

Most places will allow you to pick your boards, which can be very important with expensive wood like large 2x12 lumber for stringers. With volume pieces, like fence boards it is better to order more than you need and return the lesser quality boards after the project is completed.

Installation of Deck Boards
Top Screwed or Hidden


Deck board are screwed down into the deck joists, either through the top or through the edge of the deck board.

top screwed:

  • Most common installation because it's cheaper.
  • Screws are drilled down and heads of screws remain visible.
  • Faster installation.
  • Cheaper screws.
  • Board gap approx 1/4" after PT wood dries.

side screwed:

  • The hidden method takes longer but looks nicer.
  • Screws are hidden on edge of board.
  • Guelph Reno uses the Camo gig and related screws .
  • Slower installation.
  • Screws more expensive.
  • Board gap approx 3/8" after PT wood dries.

Board spacing.

PT boards are installed while still wet with weather resistant chemicals. The boards will shrink as they dry out, revealing a 1/4" gap or board spacing. The Camo gig, by it's design, adds 1/8" space between the boards when installed... so when the boards dry out, you will have a wider spacing.

PT boards are installed while still wet because if you let the boards dry before installation, they warp, making even installation difficult. There are double kiln dried PT products available in the USA but I've never seen them in Guelph Ontario... and they would likely be expensive.

So... if you are a DIY person, have your fence or deck boards delivered just before you are ready to install.

Deck and Stairs

Hidden Screws

2x6 Deck Boards on 24" centers.

Installed with Camo hidden side-screws.


©Guelph Reno, updated: 2020 02 21.