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How to form and flash concrete steps

geoffhazel's picture

I am going to replace a wooden ramp with concrete steps, and the steps will be directly against the house on one side. What's the best way to build the form for the front of the steps since I have no side boards?

Also, I'm a bit leery of pouring concrete right up to the building, should I be cutting back the siding and putting in building paper or some flashing?

Edited 7/16/2009 1:01 pm ET by geoffhazel

(post #108622, reply #1 of 10)

If this were mine, I'd be removing the siding and installing galvanized flashing as a minimum. Felt paper between the flashing and wood. A minimum of 1/2" air gap between the siding and the new concrete slab. Slope the concrete "AWAY" from the house. The conduit/extension cord needs to be corrected too.

(post #108622, reply #3 of 10)

Harry, thanks for the plan, that sounds good. Yes, the extension cord. It was a quick-n-dirty fix that will get an upgrade at the time I do the steps. I knew the steps were coming and had a fountain to install in the front yard for the missus, and had limited time and materials at that end. It'll get revised to include full conduit and a photocell. It powers a fountain in the front yard.

Now I just have to figure out how to hold the forms in place while pouring the concrete.

removing the siding? (post #108622, reply #7 of 10)

I'm a little confused by the comment "removing the siding".  In my case, the siding is T-1-11 and it is right up next to the studs, so if I remove the siding where it would be 'behind' the concrete, I'll have concrete right up next to (or with an air gap) open studs.  Of course I could put a piece of flashing or building paper over the hole. Is that what is recommended?  Or would I be OK just to put the foam with zip strip next to the siding, right over it, and then pour up to that, zip the top off and fill with butyl caulk?  I'll be overlapping the exising siding by about 8" or so.


The other issue I have is that when I get to the end of the top step, there's a door straight ahead, one just to the right, and then the exisitng deck to the left. (we've removed the deck right up to the steps, so the concrete will go all the way to the front door).  So I have to meet the level of three sides of a square, and each of those is in the same plane.   How am I going to put any slope on the concrete so wind-blown rain is encouraged to drain off?

walkway.jpg133.15 KB

I presume there's no other (post #108622, reply #8 of 10)

I presume there's no other sheathing behind the T-1-11.

If it were my project I'd remove the T-1-11 up to about 2" above the finished slab, replacing it with foundation grade plywood or cement board.  If cement board, place rubber membrane behind it over the studs, if plywood put rubber over the plywood.  Use a Z flashing between the T-1-11 and the new board.

Use a foam or tar/fiber expansion strip where the concrete abuts the house.

I'll let you figure out the slope yourself.  It will involve compromises (as does the entire project).

Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

(post #108622, reply #2 of 10)

What harry said.

They can't get your Goat if you don't tell them where it is hidden.

Life is Good

(post #108622, reply #4 of 10)

Might want to add a foam expansion w/zip strip between the new concrete and the existing foundation/wall. When set, pull the zip strip and apply a flexible caulk/self leveling such as SL-2 by Sonneborne.

To keep your forms in place on the existing concrete make some wooden "shelf brackets" out of 2 1x4's nailed/screwed at 90 degrees on their ends and then add a triangle of wood to keep them from folding. Add a couple of tapcons or "texas anchors" to keep the forms where you wish.

When remove there will be two small holes per support, which will fade out and fill with dust.

............Iron Helix

.......Iron Helix

(post #108622, reply #5 of 10)

Watchout for cat tracks..LOL

Spheramid Enterprises Architectural Woodworks

Repairs, Remodeling, Restorations

"If Brains was lard, you couldn't grease much of a pan"
Jed Clampitt  

(post #108622, reply #6 of 10)

You might consider installing a few short rebar dowels to connect the old slab to the new to eliminate any possibility of the top slab shifting/sliding. Sledghammering a hole in the old slab would do the same thing. Just provide a pocket for the new concrete to sink into. The zip-strip & Sikoflex is an excellent idea also.

To tie the new slab to the (post #108622, reply #9 of 10)

To tie the new slab to the old, just drive Tapcons into the old slab at intervals, leaving about 1.5" exposed.

Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

Looks like your top step will (post #108622, reply #10 of 10)

Looks like your top step will be flush with the floor of the house. You have to do something to keep water from running between the concrete and the wall of the house or it will rot out both the T 1-11 and the framing. The easiest solution would be to keep a 6 inch, or more,  space between the house and step. That eliminates any need for removing siding or trying to flash the unflashable.

Florida Licensed Building Contractor, 50 years experience in commercial remodeling, new homes, home remodeling and repairs and all types building maintenance.