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Question DetailsAsked on 3/2/2015

Old home w/rock wall basement. Looks like dungeon w/low ceilings but doesn't leak. Can the floor be lowered? Cost?

I have a 100 year old home on rock wall basement foundation. It has low ceilings and concrete floors. It doesn't leak. Is there a way to lower the floor or re-do the foundation altogether? How much might it cost?

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4 Answers

0
Votes

Fieldstone or stacked/mortared rock foundations are tempermental - they do not self-support well if you undermine them, and commonly require interior lateral support at the base to be stable - so you cannot just take out the slab and lower it with immunity because tht leaves the stone wall without lateral support at the base. Commonly, for this type foundation, you have to rebuild or extend the foundation down in very narrow segments of only a foot or two each. Actually safer is usually taking out the slab near the wall in small segments and casting a concrete step block foundation to support the wall at current height, anchored into the ground. Then with this perimeter footing all around completed (typically about 1 foot or two wide), you can then take out the interior slab, dig down to the desired depth (which would be the level the new footings were installed to) and put in the new slab.


Note this method loses you a foot or two around the base of the room, for a height equal to about the amount you are lowering the slab plus about 6 inches or so - so like a low shelf of concrete, so you typically lose some floor area, though room remains same width at body level.


Of course, jacking the house up and building a new foundation under it is also possible - but again, pricey and commonly in the 410-20,000 range.

NOT cheap - certainly several thousands, and likely more like $5-10,000 range for a normal sized basement.


I would start with a Structural Engineer to look at what can be done (and will likely require taking a few cores to determine slab thickness and maybe wall thickness too), for probably $500 minus, who can then come up with a design for the work. He will most likely want to do inspaction of the work as it progresses - at least in the earlier stages, so engineering alone may run closer to $1000 than lower. Then, depending on the condition and construction method used in your wall, can determine your options.


Answered 5 years ago by LCD

0
Votes

Answering two similar qeustions in one here - and the answer is it depends a LOT on the foundation type, soil type and groundwater level, size of house, type of foundation construction, etc.


Generally speaking - usually a house can be lifted up and the foundation raised to the new level - means disconnecting utilities for a few days and not being able to live in the house for that time, and of course raising ground level around it or building new raised entry porches or decks.


A foundation can also be deepened - very old brick and stone foundations do not take so well to this, concrete and concrete block more amenable to it. Taking the perimeter wall down a foot or two can be done one of two common ways - 1) excavating and removing the inner stickout of the footear so the wall contionues basically straight down (at least the finished wall) to the new footer, or 2) excavating to the footer and then putting a new foundation and footer below it - either with the new wall basically flush with the inside edge of the old footer, or sometimes "taked" onto the inside face of it. In that case, you end up with the old footer acting as a ledge or shelf in the finished room, with a typically 6-12 inch setback at that level - like is common at the top of the foundation in daylight basements, where the wood framing sits on top of the foundation wall but leaves a shelf on the inside. The latter is generally cheaper, but you also lose about 1-3 feet of floor space in each direction in the basement because the deeper addition is "inside" the original wall line.


Hard to give a ballpark cost or say which is "better" - lifting the house and raising the foundation, assuming the existing foundsation is structurally suitable, is generally a lot quicker, but is pretty much guaranteed to cause at least minor drywall cracking, and if not professionally done correctly can cause more serious structural cracking and warping of door and window openings and such. Lifting the house is generally much harder on brick and stone wall houses, which tend to crack a lot more - and if old (unreinforced) can be seriously damaged by this.


Of course, deepening the foundation also has substantial risk, especially if the contractor hits poor bearing capacity material or water at the old foundation level or below or gets too aggressive about how much of the foundation he excavates and undermines at one time - to put the new foundation section under it - commonly done in 3-6 foot stretches where the existing foundation is unsupported while the new deeper section is put in.


Generally speaking - if you have poor soil conditions or wetness in the basement slab level soil and below, or old deteriorated foundation raising the house (with foundation repair/replacement for deteriorated sections) is probably usually the better choice. Ditto with solid brick (as opposed to brick facing) and mortared stone foundations. Ditto with houses that sit on a lot of posts or piers - deepending each of them can be a real high cost so just lifting the house up in one unit to raise the foundation walls, then put in new longer posts can be cheaper in some cases - but it can be a real tossup in houses with short joists and a lot of support posts or columns without main supproting lead transfer beams to allow you to pick the house up in one unit.


Cost varies by location and your specific situation, but generally tends to run similar for either option - but if I had to say one is more likely to be cheaper or be less likely to overrun on cost, I would have to say jacking the house up and raising the foundation would be the better of the two for that. Cost commonly $10,000 minimum, and $10,000-20,000 is a pretty common range for smallish (say under 800 of so SF footprint) rectangular footprint houses, getting into the $20,000-40,000 range for larger houses and ones with a non-rectangular footprint, and of course can go up from there in special cases or large houses.


One other thing to look at if you have the land available - sometimes just building an adjacent addition with or without new basement (especially in areas where foundations do not have to be deep to get below frost line) can be as economic as deepening an existing basement or raising the house. - using the old basement mostly for storage or uses where the low headroom is not a problem, the new addition for living space.


I would talk to an Architect (with Structural Engineer evalluation) about your situation and for some conceptual costs for alternatives

Answered 3 years ago by LCD

0
Votes

Answering two similar qeustions in one here - and the answer is it depends a LOT on the foundation type, soil type and groundwater level, size of house, type of foundation construction, etc.

Generally speaking - usually a house can be lifted up and the foundation raised to the new level - means disconnecting utilities for a few days and not being able to live in the house for that time, and of course raising ground level around it or building new raised entry porches or decks.

A foundation can also be deepened - very old brick and stone foundations do not take so well to this, concrete and concrete block more amenable to it. Taking the perimeter wall down a foot or two can be done one of two common ways - 1) excavating and removing the inner stickout of the footear so the wall contionues basically straight down (at least the finished wall) to the new footer, or 2) excavating to the footer and then putting a new foundation and footer below it - either with the new wall basically flush with the inside edge of the old footer, or sometimes "taked" onto the inside face of it. In that case, you end up with the old footer acting as a ledge or shelf in the finished room, with a typically 6-12 inch setback at that level - like is common at the top of the foundation in daylight basements, where the wood framing sits on top of the foundation wall but leaves a shelf on the inside. The latter is generally cheaper, but you also lose about 1-3 feet of floor space in each direction in the basement because the deeper addition is "inside" the original wall line.

Hard to give a ballpark cost or say which is "better" - lifting the house and raising the foundation, assuming the existing foundsation is structurally suitable, is generally a lot quicker, but is pretty much guaranteed to cause at least minor drywall cracking, and if not professionally done correctly can cause more serious structural cracking and warping of door and window openings and such. Lifting the house is generally much harder on brick and stone wall houses, which tend to crack a lot more - and if old (unreinforced) can be seriously damaged by this.

Of course, deepening the foundation also has substantial risk, especially if the contractor hits poor bearing capacity material or water at the old foundation level or below or gets too aggressive about how much of the foundation he excavates and undermines at one time - to put the new foundation section under it - commonly done in 3-6 foot stretches where the existing foundation is unsupported while the new deeper section is put in.

Generally speaking - if you have poor soil conditions or wetness in the basement slab level soil and below, or old deteriorated foundation raising the house (with foundation repair/replacement for deteriorated sections) is probably usually the better choice. Ditto with solid brick (as opposed to brick facing) and mortared stone foundations. Ditto with houses that sit on a lot of posts or piers - deepending each of them can be a real high cost so just lifting the house up in one unit to raise the foundation walls, then put in new longer posts can be cheaper in some cases - but it can be a real tossup in houses with short joists and a lot of support posts or columns without main supproting lead transfer beams to allow you to pick the house up in one unit.

Cost varies by location and your specific situation, but generally tends to run similar for either option - but if I had to say one is more likely to be cheaper or be less likely to overrun on cost, I would have to say jacking the house up and raising the foundation would be the better of the two for that. Cost commonly $10,000 minimum, and $10,000-20,000 is a pretty common range for smallish (say under 800 of so SF footprint) rectangular footprint houses, getting into the $20,000-40,000 range for larger houses and ones with a non-rectangular footprint, and of course can go up from there in special cases or large houses.

One other thing to look at if you have the land available - sometimes just building an adjacent addition with or without new basement (especially in areas where foundations do not have to be deep to get below frost line) can be as economic as deepening an existing basement or raising the house. - using the old basement mostly for storage or uses where the low headroom is not a problem, the new addition for living space.

I would talk to an Architect (with Structural Engineer evalluation) about your situation and for some conceptual costs for alternatives

Answered 3 years ago by LCD

0
Votes

OK - that was odd - this popped up as a new question today, and no answers showed when I went to it - but after answering (and somehow got a duplication in there on that too, which the AL system does on occasion), I see I answered it before - oh well, bit more detail in this answer.


I also noticed in the original answer it says 410-20,000 near the top - should have read $10-20,000.

Answered 3 years ago by LCD




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