Foundations in New York have to be built to withstand the most extreme environment of any other area in the world. We have frost down as far as 5' during the winters, every soil type imaginable, high water tables, humid summers, and I've seen 70 degree temperature changes in one week. From these harsh environmental conditions; mold, water damage, ice heaving, and other potentially catistrofic problems may occur.
What foundations are best in NY?
Answer- NOT CRAWL SPACES! Crawl spaces have none of the major features you want in a foundation. A full foundation down 6' below grade with pored walls and that 's properly waterproofed and vented is the best type for NY. Crawl spaces lack the depth needed to avoid ice damage. Their walls can be waterproofed but the floor cannot. Radon is difficult to remediate. Pest issues are imminent. Moisture problems are generally present. Lastly, the access is terrible; and this makes repairs and inspection from pests like termites super expensive. I highly advise avoiding crawlspaces, even for small additions. After 15 years in business, the number of customer crawl spaces that would have not needed repair is startling!
A full foundation built perfectly should have the following qualities:
-Pored Walls. Pored walls are stronger, and in New York's cold winters you need that horizontal strength to resist frost cracks in walls. Done correctly, they are also better at distributing weight and help take the load off the wall footings as your only defense from step cracks caused by settling.
-Waterproofing Exterior walls.I recommend exterior waterproofing of walls with a Marflex waterproofer. It lasts 10 times longer then tar and just about guarantees you a dry foundation. This also extends life of foundation for hundreds of years. If kept dry concrete is forever. Only field stone foundations used to be able to say that but those cannot be fully waterproofed.
-Exterior Waterproofing Footings.A full perimeter French drain using #2 stone and perforated pipe ran to a solid exit line to daylight. If daylight isn't possible then this needs to be ran to sump pit to relieve pressure. Footings should not be sitting in water.
-Backfilling. Backfilling with sand up to the last top 6" of soil is important for relieving ice pressure and allowing water to fall to footing drains. Clay can expand and cause cracks.
-Interior waterproofing. Although walls are now sealed on the outside, you still need a system for water under the slab to relieve hydraulic pressure and other rising water nuisances. For this French drain system products such as Grate Products Grate Drain is great! French drain refers to a full perimeter drain pipe with holes surrounded in #2 drainage stone, and in sand conditions weed matting is used over the stone. In a ideal foundation site, the French drain would connect to a pitched solid pipe going to day light. In event this isn't possible, then a quality sump pump should be installed with an above grade frost free discharge line. To help both the radon and water system work well, 6'' or more of drainage stone under entire slab but not under the footings is recommended.
-Passive radon system. There is naturally occurring radon almost everywhere, and if considered during new foundation construction, a passive system can alleviate the dangers. Passive meaning no mechanical fan. Generally, accomplishing this is easy by connecting the water system to a vertical pvc line that extends above the roof line, a natural vent will allow gasses bellow the slab a easy point of discharge. To enhance the systems function sealing off all other points of access is important. It is also important to use 16ml plastic under the floor before poring the concrete. The plastic is sealed to the walls with silicon. Also, seal any drilled holes or points of access below the slab, like sump pit covers, etc. A properly sealed foundation will vent up the pipe. Later, if radon is still detected, the simple addition of a fan to the exit pipe should be all that is needed.
-Egress Exit. Adding egress exits later is very costly, not having them is dangerous, and usually it is a poor use of space in a foundation. Costs during construction are very inexpensive and it's well worth it. I recommend using traditional Man Doors rather then Bilco style exits. Bilco style doors are constant maintenance, inconvenient, unattractive, and expensive. They were originally designed for areas where other doors could not be used, and now are way over-used. My favorite foundations are walk out. Walk out basements don't have a need for egresses at all, but this is rare and not possible on most site plans. A full staircase to a real door is the way to go.
-Dehumidification. With a properly waterproofed foundation, the humidity is mostly affected by the humidity in the rest of the home from heating and AC, or, more so, by the weather outside. I recommend that basement doors be closed in order to dehumidify the foundation without the need for dehumidifying outside air coming in. If windows in the structure are always closed, then this isn't necessary. For dehumidification, a good quality dehumidifier such as Santa'fe brand is recommended. They work at greater temperature ranges efficiently and are meant to last years. Small store bought units cost far more to run, break, and are likely not to get the job done.
-Painted. After the foundation is waterproofed, the interior should be painted. Simply wait until the concrete has cured for 30 days and proceed with heavy paint like Bear Porch and Floor. This application looks great and reduces dust in the air. Cleaner air makes for a healthier structure. Without dehumidification in NY paint will peel. The temperature must be kept below 50 percent humidity for the paint job to last and to keep mold away.
-Proper Grading and Gutters. Installation of gutters is necessary anywhere a roof doesn't provide 6' of water shed. Gutters should have down spouts connected to solid lines below grade that run as far from structure as possible and to daylight. Gutters without discharge lines make problems; not correct them. The property should have grading that pitches away from home and does not puddle. This is extra important as you get closer to the home.