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How to increase basement ceiling height?

RaceStreet's picture

The basement under the original house is 6' 7".   Not impossible but I have been in a house where they dug the basement floor down to get nearly 8' ceilings and it changed the quality of the space enough that I would bear the cost to try and get a little more height.   I have popped the house to 2 story 10 years ago and did a 16' addition on the back that included a basement addition that has near 8' ceilings.  You have to walk through the short part to get to it.  I have a father-in-law and 5 brother-in-laws that are all 6' 5"


The house is a brick 1923 bungalow in Denver.  The basement walls are 14" poured concrete on a roughly 14" spread footer.  I know that sounds wierd but I have confirmed that the walls are poured on a seperate footer that is roughly the same with as the foundation walls. 


The concrete foundation walls are about 4' above the floor and then they change to triple wythe brick laid with a weak lime and sand mortar that was popular in that era.  The above grade walls go to double wythe above the joist pockets.  The floor is 2 1/2" to 4" thick and the bottom of the footer is is roughly between 2 1/2" and 4" below the bottom of the floor slab.   


I have a room that is 27' x 12' wide that I would like to get down at least 10" making the ceiling height 7' 5"


I have checked the options and I can underpin the exising foundation which I will have to have someone else do and is very expensive.


The other option from an architect friend is digging down flush with the outside walls below the foundation and pouring a 4" reinforced wall next to the foundation and below it.  Sort of a retaining wall.  And pouring the floor up against it to hold the retaining wall and earth below the foundation.  Since it's 4" I can frame the wall right on top.  I can do this which is less expensive that undepinning.


I understand that I can go down at a 1:1 but I don't want to lose the 10" in an already narrow room.


Those are the two ideas I have so far. Has anypone got any great ideas or comments on my two?

(post #81163, reply #1 of 5)

I'd say that's a great deal of trouble and expense for a basement.  Put your money into improving the house instead (energy-efficiency upgrade, for instance).


 

Riversong HouseWright

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Riversong HouseWright
Design *  * Build *  * Renovate *  * Consult
Solar & Super-Insulated Healthy Homes

(post #81163, reply #3 of 5)

I live in a neighborhood near Washington Park in Denver.  Most of the houses are +/- 1,000 SF brick Bungalows.  My house is 2,000 SF and I was lucky to get that.  The lots are 37 1/2' x 120'   The houses have alleys and alley fed detached garages.   There is a restrictive bulk plane and lot coverage requirements.  Basements are a big part of the living space in these houses. 

(post #81163, reply #2 of 5)

I don't believe a 4" wall would retain much of anything, better check that out.


 What about lifting the house, and infill the foundation, would that work in relation to the site?


Edited 2/6/2008 6:42 pm ET by rlrefalo

(post #81163, reply #4 of 5)

What are the foundation soils?  This will determine how steep you can cut down beside them without caving/sloughing.  The soils also determine other methods that might work.


If you went the concrete stub wall route, you'd have to build the wall in short panels, not one wall in a single go, to avoid undermining the foundation.  4" seems way too thin... 4" would work for a stubby retaining wall at surface (like a planter bed).  Add the load of a concrete wall and two stories right beside it, and the 4" likely won't hold--even if it's braced by a new floor slab.

(post #81163, reply #5 of 5)

Thanks for the reply Peter.


I did a boring when I did the addition and the soil is nonexpansive sandy clay.  It's bearing was 2,000 lbs/SF + and my spread footer for the two story brick veneer addition is 2' wide and 10" thick. 


I see what your saying but if you look at the distribution of the load at a 1:1,  technically I could just move over 10" and go 10" down and not disturb the bearing.  The floor slab would almost totally support this little retaining wall.  I dont think the retaining wall would have a lot of pressure against it.  Draw it on paper and you'll see what I mean. 


I worked for a big commercial GC as an estimator and one of my projects was turning an old warehouse into lofts.  Part of the scope was underpinning the foundation 2' +.  The company that did it, marked off 4' sections and dug every other one out.  They formed and poured this 4' section the width of hte footer and about an inch short of the bottom of the foundation.  Then they dry packed the inch void with non-shrink grout. 


Then they did the the other 4' sections.   This was a heavy 4 story brick and timber early 1900s warehouse and the footers were 24" + by memory.  The soil conditions were similar to mine.  The reason for the story is that when they had it excavated they basically supported the building on half the foundation without harm.  I don't think I would have trouble excavating next to the footer.


I have thought about just underpinning the foundation but I don't know if I want to do it.  I'm 55 and not the man I used to be nor are the friends that would help me.