lowering cellar floor

[qr409tz8]

I have a very old house that has a dirt floor cellar and a field stone foundation. Now I have a furnace and oil tank sitting on cement pads, and a number of suport columns also sitting on cement pads. The ceiling height in the cellar is only about 6' and since im 6' this causes some walking issues down there.

What I would like to do is to dig the floor down a 1' 6" to 2' 0" and then have a 3" slab poored for a floor. The delema is what do I do about suporting the foundation, the furnace, and the suport columns while I dig out a couple feet of dirt? Thoughts ideas?? web site with pictures and instructions? thanks.

[Doug Aleshire]

qr409tz8,

This becomes a "phased project". You can only do sectional pours but please read the below on other issues before you begin to even think about this venture.

Since this is an dirt basement floor, it must be excavated to a point no deeper than the bottom of the wall footing UNLESS you incorporate underpinning. I doubt that this would be allowed. The subgrade should be prepared to provide uniform support. A new slab should be supported by expansive soils and should be designed to withstand or accommodate swelling and shrinkage of the subgrade.

A minimum of 4 inches of gravel, crushed stone, or course sand should be placed under the slab. Where possible, this granular base should cover the top of the footing by several inches so that the slab can settle somewhat without being restrained by the footing—which could lead to cracking. Moisture retarders, usually 6 mil as a vapor barrier should be placed under this.

As this is really a labor intensive project, you may want to consider hiring it out. I know the cost would be high but consider the alternatives.

The one issue is equipment and what needs to be done based upon the room you have to move around in. Beams, jacks and new support footings would have to be done as well. Digging out the basement to the degree that you describe means that "underpinning" would have to be done to avoid the home from dropping. This underpinning is an extension of the current foundation/footing and this also would be a "phased" project in itself. Based on past experiences, old stone foundations would be totally removed and replaced with block foundation.

The last issue is the need to get a permit and you would have to get a structural engineer in to give his blessing based upon approved methods. I doubt that any underpinning would be allowed with a stone foundation.

Hope this helps!

[qr409tz8]

humm... its kind of starting to sound like perhaps a 6' dirt floor bacement isnt all that bad. :wall:

[lost_ring]

I have exactly the same situation except I have 6' 6" of walking room, not including all the skull-busters (steam pipes, water pipes, sewer pipes, etc.) But I just want to have a cement basement so I can use it and not track mud up into the house. I want to do this "phased" process you speak of. I have one advantage, that my main supporting collumns have all rotted away and have been replaced by adjacent jacks. So I have room to dig footings. I was going to pour those footings and then engineer my plumbing, etc and pour the floor up to the tops of those footings. I'll still have to take a lot of dirt out of the basement to get gravel in there and leave the floor about where it is. Should I dig down to see how deep the foundation goes, or is that dangerous? Can I just walk into Town Hall and find out how big and how deep to make my footings? How does that work? Is doing this on my own without a permit crazy?

[Doug Aleshire]

lost_ring,

I would strongly recommend getting a professional to look at what you have and what you can do. The issue of existing posts that were rotten and replacement with solid steel poles is good but only if they were done on sufficient pad size for the loads they carry.

Anyone suggesting that this is all fine and good, doing this on your own and without a permit is just going to get you in trouble.

I would suggest doing this right from the start. I am sure that you don't want to chance any errors with this. I would think that such an asset, your home, is worth more than trying to save some dollars by not getting a permit.

Not getting a permit and you try and sell the home down the line, don't be surprised that a buyer has their own home inspector. They will check with city hall on all permits pulled. If there is not one for this, you may not be able to sell it at your price, if at all. Then prepare for a visit by the City Inspector. Need I say more?

I gave my thoughts in the previous post but you decide.