Expert: Terrace Construction Will Be a Fifth Cheaper This Year Than Last Year
According to Mari-Liis Mihkelson, the manager of the Tartu branch of Puumarket, the largest timber retailer in the Baltic states, building a terrace this year is a fifth cheaper than last year and 30-40% cheaper compared to two years ago due to falling timber prices. However, over the years, both materials and construction methods have changed, and the so-called pencil rule of old-school builders is no longer recommended.
According to Mari-Liis Mihkelson, timber for terraces is being purchased a lot nowadays, and although the price is cheaper, the construction is being planned more carefully than before, and rather than taking a 20-percent safety margin. "Attempts are also being made to economize elsewhere – instead of expensive reinforced concrete foundations, foundation blocks or paving stones are increasingly being used for base construction, which actually work just as well," said Mihkelson.
"Whatever foundation is used, it is important to build a bed of sand or lightweight gravel under it so that the stones do not rest directly against uneven grass or soil. Between the base and the foundation stone, geotextile could also be added so that moisture and plants don't seep between the soil and the terrace. The textile layer itself could be lightly covered with sand so that rodents don't damage it," advised Mihkelson.
"Moisture insulation and ventilation are extremely important for a long terrace lifespan, which is why each layer should be isolated from another. For example, there should be waterproofing between the foundation and the wood, which can also be classic roofing felt. There should also be insulation between two wooden parts, such as between the beam and the board – special beam tape that keeps moisture away from the material. Boards laid lengthwise should also have a couple of millimeters of ventilation gap between them. Also, following the wood material, all cut ends of the terrace should be soaked with terrace oil so that wood protection is uniform," advised Mihkelson.
The terrace should have a slight slope
"For building a truss on the foundation, you should definitely use deeply impregnated material, which helps keep the wood strong for 15-20 years. For the terrace base joists, you should use at least 50x100mm thick beams, and consider that the sparser the foundation spacing and board gap, the thicker the frame timber needed and vice versa. The beam could be ordinary and not excessively planed sawn material, as it absorbs impregnation better. The gap between base joists should not be wider than 40 centimeters – if the base joist is dense and thick material, then the terrace will remain sturdy underfoot later and won't creak," said the manager of Puumarket's Tartu branch.
"Many people who build their own terrace try to make it perfectly level with a spirit level, but in fact you could create a small slope away from the house wall so that moisture and rain flow in the right direction and water puddles don't form," said Mihkelson.
The gap between boards could be minimal
According to Mari-Liis Mihkelson, the pencil rule was very popular before, meaning the gap between two terrace boards was essentially measured by the thickness of a pencil. "Board installation depends on the board's moisture content, but I recommend making the gaps narrower than a pencil. If built in spring and the board is freshly impregnated or not completely dry, it will shrink later and the gaps will become wider. This can result in being able to put your toe essentially through the board gaps by the end of summer. Therefore, when building with fresher wood, the gap between boards could be only a millimeter. If the wood is completely dry, the gap can be somewhat wider. Certainly, you should not put the boards right together, but leave them room for expansion in winter with moisture," said Mihkelson.
"Terrace boards can be fastened classically by screwing in from the top, but clips are also used, where the fastening is not visible. Certainly, you should not use random drywall screws for terrace construction, as they cannot withstand moisture. Screws have environmental classes from one to five based on moisture resistance, with 3-5 suitable for outdoor use. If the terrace is located in a more salty and acidic seaside environment, it would be worth using stainless steel screws with the highest environmental class," advised Mihkelson.
"When installing wooden boards, their placement is also important – you should make sure the heartwood side faces up. Since a board dries from the heartwood outward, so to speak, when installed correctly, water runs off the surface and cracks don't form. When buying grooved boards, the manufacturer has taken this into account, and therefore you should turn the groove side upside down," added Mihkelson.
