In my home, our basement for the most part has a concrete floor. The house is very old (around 1896 from what we can determine) and we have no idea how old the floor is. For the most part it is in good condition, with few cracks, but is horribly unlevel and has one area with moderate effloressance. The slab is also thin, less than 2″ in some places and very thick in others. It is used just for storage and mechanicals now, but we would like to use it much more. I have a lifelong background in remodeling and construction, but don’t work in this field currently. Budget and work time are limited, so here is the question. Is it advisable to pour over a new floor? It would not be possible to demo the old floor except by hand which I physically cannot do. headroom is not a constraint, and there is good access through an exterior bulkhead and basement windows. We are high and dry on a hill and have had no moisture problems in the 15 years we have been here. I sincerely appreciate any input I can get.
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bow, about 25 years ago we did what you propose in a large 1500 sf basement. We applied a blue liquid we called concrete glue at the time. It is a bonding agent. We poured an inch and a half to 2'' over the old slab. It has stood the test of time. If the base is sound, I would think you are on the right track if done right. The area of efflorescence concerns me. Usually indicates a moisture source working it's way up through the slab. Could you cut out that area and see what the problem is. The efflo. could un-adhere the concrete glue. You could pour a full thickness slab there to patch it in.
A great place for Information, Comraderie, and a sucker punch.
Remodeling Contractor just outside the Glass City.
Quittin' Time
Thanks for the reply. Not sure about the spot that is bad, its in the middle of the room and moisture below should not be an issue. I'll try cutting out a sample and check it out. Curious though, could a person lay down a foam board layer and pour a new floor right above rather than bond to what's there?
I don't think I'd ever pour a 1-1/2 to 2'' isolated slab.A great place for Information, Comraderie, and a sucker punch.
Remodeling Contractor just outside the Glass City.
Quittin' Time
Understood, I have plenty of room for a 3-4+ inch slab
I should say that I learned concrete 30 yrs ago and times were simpler then. With a good base and maybe smaller agregate, one could I suppose thin it up with the proper reinforcement.A great place for Information, Comraderie, and a sucker punch.
Remodeling Contractor just outside the Glass City.
Quittin' Time
The foam needs to be solidly supported, IE layed on a flay surface. Otherwise the foam will bridge over the low places and then crack or break up.Something like ponytail did or pour one lay enough to level it and then the foam and top layer.
I did the same as you suggested using the blue bonding agent. This over a large garage floor. The slab was cracking slightly in the center. We used the bonder at the perimeter 2' and layed 30# felt over the center field, over the cracks. This was to alow for movement and reduce some of the chance it might telegraph the cracks. I also had fibreglass added to the mix. I poured from about 1" to 3" to get it all level. This lasted for about 8 years before showing any major issues.
You might consider the tar paper over the eflouressence if it won't stick it might as well not pass it on through.
if you can give up 4-5 inches... this is what i did in my wine celler
sand portland dry packed over 4 mil plastic then screeded to level most was less than 1.5" .... then 3/4" foam board over that w/taped seams, laid in #10 flat 6x6 wire and used a 5000lb pea gravel mix 2" thick... then scored & stained to look like stone
was only a 16x 16ft room but cost was less than $600 total materials
p
Since the concrete floor is so thin why don't you pay a couple of high school kids to break it up, install a vapor barrier, then pour a new floor. Just a thought!
Hey, wanted to say thanks for the feedback. All good info, will kick this around some and decide which way to go, and post how it turns out sometime in the future.