Slab / flooring system

[Mark P]

1st time I’ve seen this system. The house has a slab foundation, but the floors are elevated about 4 - 6 inches. The subflooring rests on 2x4 that lay flat on top of metal frames on top of the slab. Or just look at the picture and you can figure it out. The duct work is under the floors. The termites had done so much damage I just kicked a hole through the ½ plywood subfloor to see what was below. HUD forclosure. The termites were even in the attic.

Does anyone know a name for this system or know anything about it?

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[Ben H]

New one on me. Why in the world would you do that?

[Scottpat]

I have never seen that either in a home and I'm from an area that a good number of the homes are on slab foundations.

It kind of looks like something you would see in a commercial building so that electrical, phone, computer and air ducts can be run without tearing things up.

Very strange.....

[Rocon]

I have never seen this system before however In the mid 90’s there were several attempts in residential construction to insulate and isolate the basement floors (almost like a rain screen wall) the interstitial space is a drainage area. You could use a system like this in homes where they would expect possible high water table and light flooding of the slab. The slabs would have localized depressions and drains located throughout the basement allowing incidental moisture to drain. One system I saw in Fine Homebuilding magazine had layers of XPS foam laid on the slab for insulation. The OSB was then fastened through the foam to the slab. You could supposedly even lay hardwood flooring over the OSB successfully.

There are several products still on the market one with the textured plastic material you would find on Miradrain instead of having the geo fabric they would laminate it to 2’ by 2’ tongue and groove OSB of all things. They have obvious problems with getting too much water into the system and trapping water between the OSB and the plastic liner.

All of these systems have the basic flaw of dealing with symptoms instead of preventing the water in the first place. This one also has a rat problem.

[Neal Lewis]

Looks like it makes a good pathway for the rats to run around under the floor.

[barlyhop]

Being in the proximity of the Mississippi River, this is some sort of raised floor system due to flood plain location.

It seems that after a past flood the homeowner had to rebuild/repair. The city probably required a higher floor level before approving repairs, etc. This system looks very "cheesy". A low cost alternative to raising the whole house as should have been done. After the heavy flooding over the last 2 summers, FEMA made some requirements to building elevations in some flood plain locations.

Also, flood insurance is much cheaper if these new floor heights meet certain criteria.

I may be off base here, but that seems to be the logical conclusion here. I have never seen this system, A preferred system would have elevated the entire house and not built a system inside the walls to meet these height requirements. Roughly $150,000 repair if done correctly. Some Goverment programs picked up 75% of these repair costs.

[Rocon]

Being in the proximity of the Mississippi River, this is some sort of raised floor system due to flood plain location.

It seems that after a past flood the homeowner had to rebuild/repair. The city probably required a higher floor level before approving repairs, etc. This system looks very "cheesy". A low cost alternative to raising the whole house as should have been done. After the heavy flooding over the last 2 summers, FEMA made some requirements to building elevations in some flood plain locations.

Also, flood insurance is much cheaper if these new floor heights meet certain criteria.

I may be off base here, but that seems to be the logical conclusion here. I have never seen this system, A preferred system would have elevated the entire house and not built a system inside the walls to meet these height requirements. Roughly $150,000 repair if done correctly. Some Goverment programs picked up 75% of these repair costs.

This is too minor (5") to be a FEMA or jurisdictional usually FEMA in any of the AO flood zones requires 2 feet above the 100 year flood, and jurisdictions usually require one foot freeboard above the FEMA requirement. Zone B requires minimum 1 foot from FEMA and 1 foot freeboard, or floodproof the structure, I have had to deal with FEMA on these issues before and they are not forgiving. I will include some pictures of a flood proofed building I did that complies with FEMA 488 Appendix D. The slab had to be thickened and reinforced to control the buildings bouancy.

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[Tim Maxwell]

I've seen it once, or should say I've felt it once. Slab home but you could tell when you walked on the main level hardwood floors that it was not sitting on the slab.

The builder was at the house and said that he framed the floor up off the slab to be able to use real hardwoods. Adding rosin paper over the slab surface first to help hold down any moisture.

Other than the one time I have heard of it being done in a basement for the same reason, to add real hardwood flooring.

It is odd and not something I would consider.

[Mark P]

While we are not to far from the Mississippi, this house is above the bluffs and well out of the flood plane. I have seen house in the flood zone that have flow through basements / crawlspaces, but these are often 6+ feet high. There are opening for water to flow through / under the house and when the flood is over they can just go down and hose the area out and collect the dead fish. This house is nothing like that.

I'll ask they guy who is going to flip it to call me when he starts ripping up the rotted floors and try to get some more pics with the subfloor removed.

I was just wondering if there is a name to the system. Interesting for sure. If the floors had not been so termite eaten that I could just rip it apart I would have told him there was a crawlspace with no access and no vents.

[Chad Fabry]

Being in the proximity of the Mississippi River, this is some sort of raised floor system due to flood plain location.

It seems that after a past flood the homeowner had to rebuild/repair. The city probably required a higher floor level before approving repairs, etc. This system looks very "cheesy". A low cost alternative to raising the whole house as should have been done. After the heavy flooding over the last 2 summers, FEMA made some requirements to building elevations in some flood plain locations.

Also, flood insurance is much cheaper if these new floor heights meet certain criteria.

Randy, when you're posturing a wild assed guess you should start off by saying " this is a WAG" rather than making a statement that looks like a declaration of fact. Lot's of good comes from throwing WAG's into the mix but no good comes from offering them as though they're fact.

[barlyhop]

Maybe you missed the " I may be way off base here" portion of my reply.

I will be more careful in the future, thanks for your advisement!

[Chad Fabry]

Maybe you missed the " I may be way off base here" portion of my reply.

I will be more careful in the future, thanks for your advisement!

I didn't miss it, it was in the next paragraph. I just didn't get it.

I re-read my post and I could have been (as usual) a tad more diplomatic.

A lot of people rely on the information posted here; we have a responsibility to be accurate.