Shed foundation - dek block question

[964haus]

I've searched and searched, but being new to construction, wanted some confirmation from the wise folks here before starting...

I'm constructing a 10x16 shed and I'll be using dek-block as foundation. Great material, but I don't like seeing the blocks sticking out at the edges of the shed.

So my question is:
Can I inset the block a bit 'inside' the floor framing so that all you'd see from the perimeter is the edge boards? Does it impact the load bearing of the walls? I was thinking moving them 12" or just enough that the outside falls inside the outside frame (maybe 8"?)....am I making sense? I imagine i'd need to shore up the connection between the outside and the supported joist...

Any advice from the seasoned carpenters here would make a novice feel much better.

Thanks in advance everyone.

Matthew.

 

[ajhester]

Im not sure of the dek product. If you are asking can you set block inside so the material on the outside of your building covers the block then yes. If dek block are like concrete blocks there would be no issue with that.

 

[p_mori7]

I had originally thought of using deck-blocks to support my 12x16 patio...but when I saw the price of each piece I decided to pour two 12" wide by 7" tall by 16' long concrete piers. Made the piers level, then framed my 12' patio joists crosswise right on top of the piers. I think this made for a much more stable patio than if I'd have used deck blocks.

 

[rocklobster]

Yes it will make a difference for the same reason that outriggers on boom trucks stick out and to the side. If you don't want to see the block sticking out then bury it and raise the floor joist of the shed with a cinder block resting on the dek block.

 

[sirsloop]

^ not a bad idea but you could have your shed fall off the dekblock that way!

I think realistically you COULD move them inside the outside edge of the wall, but do not rely on your flooring to hold the weight of the structure. You could set down the block,level them off, build your inside-the-block frame, then frame in a box all the way around the ouside diameter of the dekblock. I would cap the top of that with like a 2x12 (or two!), then set down your wall on top of the 2x12. Just realize that you are relying on that 2x12 to distribute the load to the inside ring, and you are relying on the shear strength of the framing to hold up the structure. If that fails the shed will basically fall to the ground. That 2x12 needs to be like lag bolted in there SOLIDDDD.

Just curious... how are you preparing the ground under the dekblock?

Another option? hide it... build a planter, garden, or something along side your shed.

 

[964haus]

http://www.finehomebuilding.com/CMS...s/Homebuilding/Book_Excerpts/tr031-02_med.jpg

I guess in my mind I had something like this - the block have been moved inward. My worry is whether this would make the walls unsupported and therefore weaken the overall structure. The shed will be for a motorcycle so there will be some weight on the floor.

I remember a few months ago on another shed build where there was some concern on the framing, but I think that was where the wall framing didn't come in direct alignment with any flooring structure.

Just want to make sure i'm doing this right....

Thanks and keep the ideas coming (i'm also thinking about skirting something around the perimeter when done - plants, gravel, etc - to hide the raised look of the shed)

M.

 

[p_mori7]

You can also pour a 10x16 concrete pad...3" thick would be plenty...and something solid to anchor your walls into...and be just the right height to get the bike in/out...2 yards of concrete at best.

 

[964haus]

^ not a bad idea but you could have your shed fall off the dekblock that way!

I think realistically you COULD move them inside the outside edge of the wall, but do not rely on your flooring to hold the weight of the structure. You could set down the block,level them off, build your inside-the-block frame, then frame in a box all the way around the ouside diameter of the dekblock. I would cap the top of that with like a 2x12 (or two!), then set down your wall on top of the 2x12. Just realize that you are relying on that 2x12 to distribute the load to the inside ring, and you are relying on the shear strength of the framing to hold up the structure. If that fails the shed will basically fall to the ground. That 2x12 needs to be like lag bolted in there SOLIDDDD.

Just curious... how are you preparing the ground under the dekblock?

Another option? hide it... build a planter, garden, or something along side your shed.

I'm planning on digging out the areas under each block and fill with drainage gravel. Underneath the shed I'm planning on throwing down some landscape fabric to keep weeds down. I'm also going to dig in some chicken wire on the inside of the frame to disuade critters from underneath...

My concern is exactly as you've described above - that there will be weight coming down the walls and redirected (hopefully) to the blocks. I'm leaning towards keeping it more conventional and then think of creative ideas to hide the gap.

Thanks,
M.

 

[964haus]

You can also pour a 10x16 concrete pad...3" thick would be plenty...and something solid to anchor your walls into...and be just the right height to get the bike in/out...2 yards of concrete at best.

My preference, but it can't be a permanent structure....

 

[Justanoldguy]

If you had a couple of 4 x 4 bearers running under the joists at 90 degrees and set in 6 inches or so, you could then put your blocks under them and set them in a bit from the ends. Cantilevered style, it will hold up a house.

 

[Sureshot]

If you built the base out of the better treated lumber you could just let it sit on the ground. It will last many years in my experience.

 

[964haus]

This view of the underside from my Sketchup model is what I'm thinking. Anyone see any issues or as others have said, should I just put the blocks under the exterior joist and do something creative to hide them?

Thanks again everyone,
Matthew.

 

[rocklobster]

Thanks for the sketchup! that clarifies things much better. I was thinking the block product would have a larger footprint (more like a patio stone) in the advice I was giving above. My misunderstanding.

To further clarify your plans can you tell us more about the site such as: what soil conditions you have, what is your frost penetration depth (if any), and is the shed going to reside on level ground?

 

[964haus]

Thanks RockLobster,
The soil is pretty typical (I think) topsoil, not too much clay, not too much rock. I'm in Vancouver so we don't have a frost issue to consider and the ground as it sits now is fairly level.
My plan is to dig down 3-4", put gravel down, then sit the blocks on the gravel. Cover the entire area underneath with landscape fabric. Using 2x8 PT wood for floor/frame.

Thanks again,
M.

 

[Sureshot]

I would just double the load bearing sill(I think that is the right name, someone will if it is not) and use half the blocks. A lot easier and cheaper. You could also set it on the larger flat patio blocks for a bigger footprint.

 

[Dustball]

A search of Google brought this-

 

[paullie]

if you build it like your pic, that SOB will be fine. Hell that's more than alot of houses have under them. build it, it will be fine

 

[964haus]

Just had a friend stop by who suggested using PT skids instead of blocks just to remain sane while trying to level everything. There's a slope running in 2 directions and while it's not huge, I think it will be far easier to level skids than 24 individual blocks...

Now I'm thinking of using 3 skids (2 sides and one down the middle). I'm hoping this will make it sturdy enough to hold the motorbike.

I'm guessing laying out skids is simple too - dig trench, fill with gravel, lay skids on gravel, build up from there....

Any tips from the experts?

M.

 

[akdiesel]

First off just how much weight do you plan on having in the structure?
I for one only like to use 4 of these blocks on each corner. Unless you have fully compacted the soil with equipment you will get un-level conditions over time. By having each corner supported you have the ability to level the structure better at start and later in life.
You need to have another joist in the back to support the wall in that area.
Another thing to worry about is the wood directly in contact with the dirt. I have see pressure treated wood decay (overtime due to continuous moisture and the elements). Planter boxes are fine but for structures I would not suggest it.

 

[Sureshot]

Put two skids a quarter the width in. You are way overthinking it. A motorcycle is light and ontop of the decking and flloor joists you will be able to park a car. I have 24" centers on my storage area covered with 3/4'" ply and park my 1800cc bike and lots of other heavy stuff for 6 months at a time. Use 3/4 t&g for the floor.

 

[964haus]

^^
sureshot - you're absolutely right, I am over thinking it....

Enough talk, time to start digging. Will update as I proceed

Thanks for all the input. I'm sure I'll be bugging you all along the way!

Matthew.

 

[Hootbro]

I used dek blocks also when I did my 8'x12" shed. Below is some pics showing what I did in the corners to help with the floor loading.

Once it is built and framed, quite a bit of rigidity will be there and any concerns of not having enough strength in the floor and side walls will be gone.

 

[Wingnut65]

Matthew, To answer your original question, yes they can be offset from the edge of the wall. Like Hootbro and others have posted samples, it can and has been done and will provide a nice result.

But, something to consider, the walls are loadbearing for the roof and all weather-related loads (wind, snow, etc.) With the Dek-Block not directly under the walls, then the joists will now have cantilever loads imposed on them. I don't think I saw what you are planning on using for the joists - 2x6, 2x8...? depending on the size (height, etc) and design of your shed, bigger would have more safety in the load carrying ability.

Also, are you tying the shed down to the ground in any way? I could see a screw tie-down anchor in each corner with a strap to the joists, would be better than nothing.

Just my 2 Cents worth...

 

[ALLTYPEPM]

the term is cantilevered, overhanging joist...rule of thumb is the distance from the outside edge can not be more than the depth of the floor joist, so...a 2x8 joist can not overhang by more than 8 inches, a 2x10 can not overhang more than 10 inches, etc...

 

[ALLTYPEPM]

great looking work

 

[964haus]

Need to do some more updating, but see here for progress...

http://garagejournal.com/forum/showthread.php?t=163328

M.

 

[NewShockerGuy]

I'm in the same boat, I don't know how many blocks to use... Now looking at pictures I'd like to not see the blocks when looking out at the shed... any way around this?

Note that these blocks are going to be use right on the shed floor framing right? I have attached a picture of where I think the blocks are going to go on my 10' wide by 7.5' depth...

The manufacture recommended just using 4x4 10' long posts only two one on each side of the floor.. running the 10' length. But states that it should be wood that is able to contact the ground... I figured deck blocks would be better but honestly now I don't know. It almost seems like people are building a floor for the actuall shed floor to sit on top of which is confusing me..

Thanks,
-Nigel