Thursday, September 24, 2015

Wood Rot

Yes that is my house

Wood rot is sometimes called “dry rot,” but that is simply a misnomer. Decayed wood is often dry in the final stages when the wood has blossomed with the bodies of wood-rotting fungus giving rias the illusion of dry rot, but moisture is required for the rot to spread. While the decay is taking place the wood must be moist. Wood rot or decay is caused by fungi, microscopic plants that form threads almost invisible to the naked eye unless clumped together. Some fungi merely discolor wood, but decay fungi destroy the fibers that give the wood strength. Spores or “seeds” of decay fungi are always present in the air; they can’t be kept away from wood. But fungi can only grow in wood only when it contains more than 20 % moisture.

There are also two species of fungi that spread from moist soil into dry wood by conducting water to the wood through vine-like structures, but most fungi cannot conduct moisture. Decay happen most frequently when two conditions are present, the wood is regularly soaked and remains wet and a section of the wood is exposed or in contact with soil.

Fungi and termites may sometimes occur in the same wood because the moisture attracts pests. Decay fungi soften the wood and, in the final stages, make it spongy or cause it to shrink, crack and crumble, but do not produce the continuous, clear-cut tunnels or galleries characteristic of termite infestation. Often wood decay occurs without termites.To prevent wood decay you need to keep decay fungi from entering the bottom of the structure and keep the wood elements dry.

To prevent moisture, your home site should be well drained. The soil surface should slope away from the house, and downspouts should discharge into drains or masonry gutters or splash blocks that lead the water several feet away from the house. I was careful to choose a house with a natural slope from northwest corner to southeast corner. I added French drains to the west side and south side of the house to move water away from the home and I was careful about maintenance, and yet my home developed a wood rot problem.

Serious decay damage is most often due to one or more of the following errors in construction or maintenance:
  1. Poorly drained soil and insufficient ventilation under houses without basements.
  2. Wood such as grade stakes, concrete forms, or stumps left on or in soil under houses.
  3. Wood parts of the house in direct contact with the soil. 
  4. Wood parts embedded in masonry near the ground.
  5. Use of unseasoned and infected lumber.
  6. Sheathing paper that is not sufficiently permeable to moisture vapor.
  7. Inadequate flashing at windows, doors, and roof edges.
  8. Poor joinery around windows and doors and at corners, and inadequate paint maintenance.
  9. Lack of rain gutters and roofs without overhang.
  10. Unventilated attics.
  11. Roof leaks; leaks around shower-bathtub combinations, kitchen fixtures, and laundry rooms.
  12. Failure to use pressure treated lumber or naturally durable wood where moisture cannot be controlled.
When we ripped apart the front of the house and jack hammered the edge of the concrete step we found that the side wall of the house had not been properly flashed and that there seem to be water infiltration below the palladium window and possibly from above the palladium window. In general, architectural frills or decorative elements of construction often provide entry points for water or pockets were moisture can remain long enough to let decay get started. Lumber absorbs water most readily through exposed ends, and in joints.

As the contractor took the front of the house apart, he did not find a “leak” what he found were several of the construction errors above. So, it was decided to rebuild central section of the front wall of the house that was covered in decorative imitation stone. I had to have the imitation stone removed because the decayed wood extended under it. By removing the stone we were able to see the extent of the damage and rebuild.
the old front of the house
Since I was spending a lot of money to repair the damage I spent even more to improve the construction of the house so that hopefully wood rot will not re-occur in the future. After removing the stone facing from the front of the house, they removed the Tyvek house wrap, the oriented strand board subsiding and insulation. Some of the insulation was damp and an entire side of the sub-structure was rotted as well as the cantilevered floor that formed the entry way.

All the damaged structural wood beams were removed and replaced with pressure treated lumber. Once repairs were made, new r-15 insulation was installed on the main part of the house and the garage (which was being rebuilt because the fake stone had to be removed from that wall, too so the decorative stone would match). After that the house was re-sheathed using pressure treated plywood to replace subsiding and all exposed siding was wrapped with DuPont Tyvek.
same corner as on top rebuilt

After rebuilding the base of the wall the new flashing was installed at the base that extends a foot above the steps. The palladium window and door were replaced with a Marvin window and the front door, transom and sidelights with a Pella door. All were very carefully flashed. Finally, the contractor installed a Driwall Rainscreen system by Keene products on top of the Tyvek wrap to move moisture that might build up under the stone away from the house and then installed the new real stone facing.

Decorative elements of the front were reworked to prevent water infiltration. Between the palladium window and the top of the front door is a single sheet of plastic material with trim applied on top, rather than the separate elements that were there before. The new window has a pronounced sill that was lacking in the old window. New gutters were installed with gutter returns. Beefier trim was installed around the window and above the stone. A French drain moves water away from the front steps and ultimately away from the house. Every change made was intended to prevent water infiltration with the pressure treated lumber was my last defense against future damage. Now I am hoping that this all works.
A lot of money was spent and it does look a little prettier

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