Tuesday, September 29, 2009

Pouring a Concrete Slab

Owning a house mean an endless slew of home improvement project. I knew this going into it, and looked for a house that was already remodeled and did not need vast improvements. I have enough projects planned that I did not want to add home projects to the list. However with my personality, the projects seem to simply appear out of the necessity to repair or to set up my home to my liking.

The first and largest project we started was to rebuild the deck which was in poor structural shape. This post is not about that project. But part of the deck job was to move my shed to its permanent location under the deck. My Keter Pent 4x6 shed has been with me through several different homes. http://www.costco.com/Browse/Product.aspxProdid=11486578&search=keter%20shed&Mo=3&cm_re=1_en-_-Top_Left_Nav-_-Top_search&lang=enUS&Nr=P_CatalogName:BC&Sp=S&N=5000043&whse=BC&Dx=mode+matchallpartial&Ntk=Text_Search&Dr=P_CatalogName:BC&Ne=4000000&D=keter%20shed&Ntt=keter%20shed&No=1&Ntx=mode+matchallpartial&Nty=1&topnav=&s=1

Since it is plastic and built from several interlocking pieces, it needs a flat base which to sit upon. If not the shed twist and flexes exposing gaps in the interlocking joints. The spot which I chose to place the shed was not level and rocky. In order to create a suitable base, I decide to pour a small concrete slab. In the past I have set the shed on driveways and even on a leveled brick paved base. The slab I intended to pour did not need to be perfect. It did not need to take much load and did not need a perfectly level smooth finish since it was going to be covered up.

The first step was to build a frame or a form for the concrete to be poured into. I decide that the frame would be a permanent leave in place one, so I used either redwood or pressure treat lumber for prolonged life. I rough fitted the pieces of the frame by digging a small trench which to lay the lumber within. The frame established the shape, size and levelness of the finished slab. It was therefor important to make the frame square and level. I was fortunate in the fact that the concrete slab was enclosed by the footing of the deck. This allowed at least one of the two free sides of the form to be locked in place. A 2x4 was used between the house and the slab, and one between the existing slab and the new one. This allowed a separation between the old and the new slab. It also allows the new slab to move independently of the old to reduce cracking. I was not sure, but decided the new concrete should not be right up against the house. In retrospect, it might have been better to do so, so that no water would seep in between the new slab and the house. However without the fourth leg of the square frame it would have been difficult to keep every thing in place.

On the morning I had planned on doing the work however, there was a power failure. So all my cuts were made using a gas powered chain saw. Good thing these were not fine finishing cuts.

Because I did not need the slab to take any substantial loads, I wanted to use as little concrete as possible. I collected rocks from around the yard and broken concrete chunks which I was about to take to the landfill. Reduce Reuse Recycle. I used these to fill in the major voids of the fill area. Each piece was carefully fitted so that it was stable and would not shift easily. I took a long 2x4 which would span the length of the frame and drew it across the entire frame to ensure that none to fill material was protruding above the level of the frame.

Next I mixed several bags of concrete extra soupy so that it would flow into all the crevices around the fill rocks. After each pour I would use my long 2x4 to scree the concrete, just like doing so with the rock filler, this made sure that I did not have any bit of concrete which would protrude above the level of my frame.

Hand mixing of the concrete was accomplished in a wheel barrow with a gardening hoe. The mixed concrete was either poured directly from the wheel barrow or shoveled into place. A concrete trowel was used to smooth out the surface.

After four 50lb bags the slab was only partially complete. I had extra bags of concrete lying around from my deck project, which is one reason why I started this little project. But I still needed to make a hardware store run for more concrete to complete the job.

At ten bags I called it quits. I could have used one or two more bags to make the surface perfectly level, but this was good enough since no one but myself would even know there was a hand poured slab of concrete under my shed.

Here is the finished product. After a day or two of curing I moved my shed in place. I do notice the slight unevenness of the slab some of the floor board flex before they come into contact with the solid floor. However I am quite pleased to have the use of my little shed again. That is one project I am glad to have checked off the list. NEXT!

1 comment:

  1. I did not see any rebar or seismic holdowns - this does not look very safe to me. haha