Slab foundation on a 4 ft. footing

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Posted by: from Ajax
3/3/2012 at 8:07:19 AM


I might be purchasing a home in Bowmanville, it's an 8yr old raised bungalow, it sits on a six inch poured salb with a 4 ft deep footing underneath. The house is on a bit of a hill and it slopes nicely to the street.

My question is are these foundations suitable or good, and what about water leaks from the water pipes. I hear they can be embedded in the concrete pour. I have asked the towns building dept for a copy of the house plans or drawings i'm hoping they will show where the pipes are located.

Let me know what you think, its very important the deal depends on the info i get.



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Date/Time3/3/2012 at 11:44:26 AM

While there is nothing wrong structuraly with this type of foundation. My personal opinion is they have no place is Canada in a 4 season house. Your heating bills will be huge and the floor will always feel cold. Ask the seller for the heating bills from last year, to get an idea of your costs.

When you have concrete on top of earth, it is the same temperature as the ground. Garages are build with the same construction, so think how cold there floors are in the winter. If they insulated the foundation wall and underneath the concrete floor it will help a lot, but is still not great.

The plans will proabley not show the pipes, and if they do, I wouldn't trust them to be exact. You can always have the floor x-rayed and that will show the location and depth of the pipes in the concrete. Hope this helps.

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Date/Time3/3/2012 at 11:59:38 AM

Hi Ricky,

Your existing slab on grade with a 4' frost wall is completely fine and meets code requirements (in principal).

Typically the frost walls are sitting atop poured footings and the interior or exterior or both are insulated with some type of insulation material. If the house is only eight years old it should be closed cell rigid Extruded Polystyrene (XPS) insulation (usually pink or blue), however with your four foot frost wall (foundation) it was actually not required.

Your concerns about water leakage from existing plumbing would be the same as those with a full basement. The plumbing should not be leaking under the slab. If it is, the repair would be the same as a full basement, you would have to break up the floor.

A bigger concern is always water leakage from ground sources.

You mention that your potential home is located on a hill that slopes nicely to the street. The last half is a fantastic scenario. If your rear or side yards are further up the hill and slope to the street with your house in the middle then your house can have a daming effect and cause water pressure (in this case hydrostatic pressure) to build which will force its way into the building envelope over time if the proper steps were not taken during construction to deal with it.

Having said that, a slab on grade foundation is about the best possible foundation you can have to mitigate water penetration (next to building on raised piers or "stilts").

If you have a specific concern regarding the possibility of plumbing leaks, that is another story and will a slab on grade foundation that is usually more intrusive to repair as your "basement" slab is in fact your finished floor and would need to be damaged and replaced to repair as opposed to a bare concrete floor in some basements.

I am attaching a quick diagram of what should be under your possible new home.

I hope this helps. Best of luck.


Jason Irving

The Cedarbrook Group

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Date/Time3/6/2012 at 6:08:33 PM

Hi Ricky,

I know you have this resolved from our telephone conversation, but you mentioned the diagram did not come through.

Here it is for good measure.

Take care

Jason Irving

The Cedarbrook Group

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