The material should be treated with a penetrating sealer on all 4 sides.
Dark Red Meranti, (commonly referred to as Mahogany) is kiln dried but can still absorb moisture, so it is important that the material is sealed thus minimizing the dimensional change. Lengthwise, there is virtually no expansion; therefore neatly trimmed ends can be butted tightly together.
Nailing success has been achieved with 7d or 8d finish nails. Stainless steel will provide the least amount of staining, although galvanized nails also work well. Blind nail through the tongue at about 45%. The nail must penetrate the joists when face nailing within ¾” of the edge or end of the board. Pilot holes are recommended to prevent splitting.
Ventilation is important. Do not box in the deck underneath as the moisture underneath a boxed deck will be absorbed by the bottom side of the board. The sun and wind will dry the top side of the board which will cause cupping.
- Slope the soil underneath the porch away from the center.
- Install a moisture barrier on the ground underneath the porch.
- Leave 2 feet of exposed soil around the perimeter under the deck.
- Allow a ½” gap at the wall of the house and use trim board to cover.
- Slope the deck ¼” per foot away from the house.
- “Vent” (leave space around) columns/posts allowing for movement of flooring. If the flooring expands, it could move the posts.