How to attach wooden floor to block basement

[repairs]

In the old days, I know that when they built a concrete block basement, the wooden floor joists were just set on top of the block walls, and they would make the top row of block with a solid topped block (no exposed core). Then after the wooden joists were set in place, they would put a thick bead of mortar on the inside, on top of the block wall.

I've lived in several homes built in this manner. I guess they figured the weight of the house would hold it in place, and that mortar bead added to this, as well as keeping air from leaking and insects and rodents from entering.

The problem with that concept is that if a tornado or hurricane hits the area, it dont take much to knock the house off the foundation.

I'm planning to build a small summer cabin. It will be set on a concrete block foundation, either as a crawl space, or possibly a usable basement depending on cost. Since the cabin will be small, that would mean is weighs less, and thus would probably make it blow off the foundation easier. This is not an area that gets hurricanes, but tornados are always a possibility.

My question is what's a better method to attach the house floor to the block walls? On:

They suggest putting an anchor bolt every 3' to 4' in the last (top) run of the blocks. I guess that would mean having an open cored block every

3rd or 4th block, and filling the block core with concrete to hold that anchor. But that brings up two questions.

1. Filling a block's core generally means all the cores below it would need to get filled, and thaT would take a lot of concrete. Unless a wad of newspaper or some insulation is crammed in the blocks in the row below the top one first.

2. Using floor joists laid on their narrow edge (such as 2x8's), this anchor would end up with no wood to attach to, unless a 2x8 was laid flat first, and then the floor joists laid on top of that, which is not something I've seen. (Or is there some sort of bracket made for this use?).

Then too, making sure these anchors dont und up directly under a joist might be tricky too, because the location of each joist would have to be measured and marked on the blocks first.

Anyone have any tips?

Please, if you want to tell me to contact a building inspector, or hire a professional, dont even reply. This is a DIY project in a rural area. There wont be any professionals involved, nor any inspections, other than getting a building permit (to keep the local officials happy and wealthy). I already inquired, they said that as long as it's not a full time home, I just need a permit to build, and they need to know the size and type of construction. (so they can raise my property taxes to suit the structure).

[dadiOH]

1. "J" bolts in the block

1. 2x8 on edge through drilled to fit over the J bolts, nut and fender washer

2. nail on hangers on the 2x8s for the horizontal sticks

[trader4]

I've never done this, but is the mortar going to fill more than just the top block? The blocks are staggered, reducing the openings. I would think the mortar would probably stick and bind up enough so that only the top block winds up getting filled.

That flat piece is how it's typically done. It's called the sill plate and it gets bolted to the foundation.

 (Or is there some sort of bracket made for this

It's amazing to me there are still places in the USA where you can build a house without any inspections at all.

[DerbyDad03]

Have you considered builing the cottage as a circular structure? They shed the wind much better than a flat walled structure and they look really cool too. However, they will challenge your DIY skills to the max.

As far as your question, attaching the joists to the block wall is just one of the many requirements to meet code for a tornado/hurricane house. I realize that you don't have to meet codes for inspection purposes, but codes weren't written just to give the authorities something to inspect. They were written to address specific safety issues. Build the place to code and you won't have to worry about it getting blown away.

BTW your statement "Since the cabin will be small, that would mean is weighs less, and thus would probably make it blow off the foundation easier" may not be entirely true.

It's not the weight as much as it's the profile presented to the wind and the strength of the envelope. Big or small, if it sheds the wind correctly, it won't get blown away. Keep the wind outside of the house and you'll be in much better shape. I saw a video of a house with a hurricane proof front door vs. a standard door. As soon as the standard door blew open and the wind got inside the house, it was done for. It collapsed backwards as the wind hit both the front of the house on the outside and the back wall of the house on the inside.

[bud--]

I believe with standard lay-up the cores align. You can fill some cores with concrete and add rebar. The top course could be offset so the cores do not align. I think something like newspaper is used to block the core.

Detail that show a sill plate and floor above:

page 24, fig 11.

This is standard construction now.

Anything that is in contact with concrete (sill plate) should be pressure treated lumber.

The joists and "band" (rim joist) are secured to the sill plate. In hurricane territory steel connectors are used to secure all connections up to the roof. Tornadoes can be stronger than hurricanes.

Oren recently posted a link to a catalog of connectors (60M)

I suggest the OP read a book on construction and maybe construction for hurricanes. (Is there a good book/website for hurricane construction?)

[krw]

When I've had it done, the concrete was done at the same time as the floor, so the holes were just filled with as much concrete as they would take (yes, the holes line up). The added strength of the filled cores was wanted but not so much so that it was specified. In one other case, filled cores were an engineering requirement so they made sure the concrete made it to the bottom of the wall.

In the '80s I was told this was a no-no, but did it anyway.

Yes, but nothing will save a wood structure from a direct hit. There is only so much "hurricane banding" will do.

Hurricanes are one thing but protecting structures against tornadoes isn't cost justified. I don't even see much emphasis on shelters.