Enormous masonry in ground swimming pools fall victim to HYDROSTATIC PRESSURE each year. The same forces act on your foundation and try to lift but can not because the weight from your home sitting upon the sill plates. In extreme cases wall failure or bowed, buckled walls occur.
Prior to construction, your property was sitting on top of thick layers of soils and hard pan clay. The layers were deposited through the millennia and lay in horizontal rows. The clay layers will meander side to side and weave there way towards a natural water source, a stream, brook, pond or lake. Chances are there is a natural water source close to your home.
Water from rain or melting snow will percolate into the ground as gravity pulls water through the top soils. Water builds up and collects in between the layers of earth and when acted upon by gravity, hydra flow moves through the arteries, capillaries and veins. Once it reaches a water source it flows to the discharge area and joins the body of water. A large percentage of this rain, snow melt will be pulled into the ground on a journey to recharge the unconfined aquifer at typical flow rate of ten feet per year. The process of water filling all the loose voids and gaps within the soil is called super saturation.
The air and gas deposits that are now filled with water will compress any remaining air and witch greatly increases water pressures below the surface sending water through the veins ultimately reaching the surface as Artesian water.
When the building lot is picked out and surveyed the pins are set and staked marking the outer edges of the homes foundation.
A team will now excavate the foundation. The layers of soil and clay are cut and sheered altering the flow of normal subterranean water.
After the floor of the pit is cleaned and leveled, Mason contractors will set wood forms in place for the footing of the foundation. The footing is one piece of concrete, it must balance the weight of the block walls and home, its purpose is to keep the home from significant settlement.
The footing sets after curing for 30 days, Once cleaned off the surface is ready for mortar. Block walls are constructed one block at a time until the entire foundation is standing.
Prior to being filled in or "back filled" the walls are free standing and weak, much like a card board box with no top or bottom.
The floor must be poured of solid concrete aprox. 4 inches thick, this floor acts as a bottom beam , a support structure that touches all walls acting as a brace when the walls are subject to pressure from the weight of the soils, pressures etc.
Carpenters now install the sill and floor joists completing the top beam and the foundation. The structure is much like a rigid box. The top is constructed of wood joists and bottom is a 4 " floor slab.
The home is built from wood and sided as well as roofed. The peak determines the location of basement lolly columns made from US steel.
Hydrostatic pressure is caused by water building up around the foundation. For many thousands of years water would flow under the ground in the veins on the way to a water source. When your foundation was installed, that natural flow was cut off as the excavator dug, now the water builds up temporarily in the loose backfill next to your walls. Loose fill around the foundation walls are very attractive to the hydra flow and so the water builds up next to the wall in the back fill area. As the precipitation increases water will start to gain height in the pit. The higher it rises the more pressure increases on the foundation. Due to pascals law, the pressure climbs to levels that exceed the rated strength of the block. The rated strength is tested on dry cured concrete block. As the foundation ages this cycle creates a "false water table".
The original contractors waterproofing is black bituminous tar, and 5/8"cement parging. Water has acidic levels when running through clay, this acidity combined with pressure spider crack the parge, allowing water to push through the slightest gap, filling the block pockets, soaking the wall. In most cases the walls are water logged and exceptionally weak!!
Home owners may notice "water seepage", cove leaks perhaps a stream of pee piddling out of cracks or mortar joints. In many cases the walls are so degraded, an actual "acid load" will rot the first coarse of cement block away, a mushy consistency. "Soft Block Syndrome" found in the corners, pier supports in the block walls.A good way for homeowners to gage is to look for white powder on the walls. A lyme salt pushed out of the block from acidic water collecting inside. The chemical reaction is called efflorescence.
A simple algebraic formula regarding Pascals law (pressure = Area at base cove x Height and Weight) + Depth of Grade. What Pascal missed was the creation of "the false water table" that also states Hydraulic water pressure increases 10 fold with every inch of precipitation, creating obscene amounts of hydrostatic pressure, Now the Pascals formula results will send the most conservative mathematician scampering off to find his hard hat and pocket protector. 15k lbs per inch on a wall that was rated DRY at 6,000 psi . Factor aging, acidity, cracking, water logged, wet walls!! The reality is that foundation repair is huge business in the USA due to archaic building codes.
Any service on a block foundation in clay bound areas must take into consideration the outside water pressure when designing a waterproofing coating service or waterproofing system.
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