foundation pad

[Hobby_Man22]

I've been meaning to ask the neighbor how much it flooded a few years back before I bought my property. Code calls for foundations to be 12" above the road. I want make my shop a good 24" above the ground. I think that's a good height for any good floods, but still be able to back trailers and such into the shop. As far as building a taller foundation pad by bringing in more dirt. I'm going to assume this isn't going to add much to the price in the way of labor other than the cost of the dirt? They just built a house across the street from me and I swear the road is higher than it is. I just don't understand people. I mean if you buy a house and it's already at ground level than it is what it is, but to purposefully build a house that's going to flood in a hurricane or any big rainstorm is ridiculous.

 

[The Cobbler]

trucking costs need to be included , where are you getting the fill? is it free?
what about compacting ? are you using stone for fill?

 

[472scout]

It costs whatever your dirt guy charges you.

 

[wssix99]

I've been meaning to ask the neighbor how much it flooded a few years back before I bought my property.

If something bad happens, then you could both end up standing together and talikng about how you "didn't know..."

This is a much better resource to use for your your risk assessment: https://www.fema.gov/flood-maps

^ You should be able to locate your property and see where you stand. If your area has been surveyed for flooding, these maps should give you an idea of how deep the typical flood would be, vs. what it may have been recently. (And then, it can always be deeper. I believe these maps are only for 30 year floods. There was just a 1000 year floood in TN and planning for things like that is a whole other ball game.)

 

[Hobby_Man22]

I just think 2ft is a good height. We had a 1000 year flood about 4 years ago.

 

[welder4956]

You could lay a block foundation 3 courses high and fill with compacted dirt or 3/4" stone.

 

[Docbentley]

If something bad happens, then you could both end up standing together and talikng about how you "didn't know..."

This is a much better resource to use for your your risk assessment: https://www.fema.gov/flood-maps

^ You should be able to locate your property and see where you stand. If your area has been surveyed for flooding, these maps should give you an idea of how deep the typical flood would be, vs. what it may have been recently. (And then, it can always be deeper. I believe these maps are only for 30 year floods. There was just a 1000 year floood in TN and planning for things like that is a whole other ball game.)

Fema maps are notoriously outdated in most areas. They show my entire neighborhood in the 100 year flood plain and it sits on a hill up high and dry. Fema does not do surveys to establish their maps, but use some kind of hocus pocus while looking at maybe a road map and just draw lines. To keep from having to buy flood insurance each property owner has to get a LOMA from fema. They will not even update their maps with this surveyed information.

 

[NUTTSGT]

If I remember correctly, you live on a private gravel roadway. I doubt it will get raised very much over the years. I live on a state route and every time they pave, it changes the way the water flows during a heavy rain storm.

I'd do the 24" in a heartbeat for a floor height. Then after that was done, I'd try to make sure you have proper drainage, tile, french drain swales or whatever to move the water away from your place.

 

[ConCretin]

I agree. Now is the time to minimize the risk to your new structure from floods as well as ensure normal drainage away from the building. The cost will be several times the cost of the material from the labor and equipment required to place, grade and compact it but this is a small cost relative to the cost of the structure and the benefit of protecting it.

A couple additional thoughts; Make sure they remove all topsoil and organics under the new fill. The final size of the pad should be a minimum of a foot larger than the foundation. The first lift of fill needs to be larger still to allow each successive lift to step back a min of 45 degrees and permit proper compaction. For example, a 24" deep fill for 24x24 structure should have a 30x30 footprint on the ground as a bare minimum. You can use non-structural fill to taper the slopes more gradually if it's cheaper but don't scrimp on the structural fill described above.

Take a look at my Guide to Floor Slabs in the link below for some additional thoughts on floor slab construction. Congrats your new garage.

 

[Hobby_Man22]

So since I want to be able to drive into the building without there being a steep ramp so to speak, do they just bring in more npm structural dirt around the perimiter of the building so there is a gradual slope?

 

[ConCretin]

I w

So since I want to be able to drive into the building without there being a steep ramp so to speak, do they just bring in more npm structural dirt around the perimiter of the building so there is a gradual slope?

Extend the structural fill to the driveway area and build it the same way as the building pad. The 45 degree slopes for the structural fill are the bare minimum and could be extended as far as you want. The other option is to come back and use a less expensive material to build out the slopes. It's really a question of cost that can only be determined by site conditions and your contractor.

 

[Hobby_Man22]

If something bad happens, then you could both end up standing together and talikng about how you "didn't know..."

This is a much better resource to use for your your risk assessment: https://www.fema.gov/flood-maps

^ You should be able to locate your property and see where you stand. If your area has been surveyed for flooding, these maps should give you an idea of how deep the typical flood would be, vs. what it may have been recently. (And then, it can always be deeper. I believe these maps are only for 30 year floods. There was just a 1000 year floood in TN and planning for things like that is a whole other ball game.)

Fema flood maps don't mean anything. I'm in flood zone C or X whatever the least risk area is and I assure you while I don't believe my street had an issue many other properties that were in the same flood zone got flooded out. If it rains for a week straight like it tends to do in the summer eventually an open plot of land will look like a swimming pool. I saw property with probalby 2ft of water with plenty of $800,000 heavy wrecker trucks and a couple pump trucks just sitting there. Wide open land probably 80 acres worth with one two lane highway down the middle. Not really any reason to flood, but the soil can only absorb so much. Pay for some dirt now extra $10K? so what? better than losing your shirt down the road.