Any suggestions for pouring a slab over a storm shelter?

mebke33September 27, 2012

This storm shelter is under the front porch. We are considering making a 2x6 frame that fits over the opening and then placing 3/4inch subfloor on the frame and placing 2" foam board over the subfloor. A membrane would then be placed over the foam board and the concrete on top of that. Any suggestions or recommendations would be appreciated.


Thank you for reporting this comment. Undo

Wet concrete is VERY heavy.

Make sure you can support the weight until it develops enough strength to support itself.

    Bookmark   September 27, 2012 at 4:00PM
Thank you for reporting this comment. Undo

Your description is unclear to me, but if it were me I'd handle the design and construction using a 4-inch reinforced floor PIP concrete slab over a waterproof membrane over insulation over 8-inches of compacted fill material. Around the perimeter I'd use a reinforced continuous stem footing to support the perimeter walls. For the walls I'd use 8-inch reinforced PIP concrete walls with a reinforced top concrete slab designed for the span that you will have. I'd also waterproof the outside face of the perimeter walls and backfill such that all surface water will drain positively away from the concrete walls. How will you enter the shelter--from inside your house or outside?

    Bookmark   September 27, 2012 at 4:28PM
Thank you for reporting this comment. Undo

Please READ this! We just had this issue and the first pour of concrete had to be ripped out! We are having many issues with our builder and how he builds things and this was one of the worse. He constructed the framing incorrectly. Didn't follow engineered plans. So he had to use foam to avoid having 10" of concrete poured. The rebar ended up on the bottom of the poured concrete and not in the middle of the concrete. The foam only permitted the rebar to be pushed down into it. They had concrete chairs...but once they walked on just pushed it into the foam. So you have to majorly have support underneath. If you use foam allow for a solid board to go on top then cover in plastic if you don't want anything to stick to concrete. But we had to have rebar 6" apart with wire mesh. We used water stop and flashing around edges first time (we he homeowners supplied it)...second time around we didn't thinking the builder would do it NOT...and it leaks!! So Yes get waterstop or atleast flash it!

    Bookmark   September 29, 2012 at 5:58AM
Thank you for reporting this comment. Undo

This is a structure that must be designed by an engineer. An engineer would first need to know the dimensions between the foundation walls. He/she would then decide if the slab would be structural or if the slab would be supported by a substructure like metal decking or Pressure Treated wood framing.

Your solution would probably work if you held the wood framing back at the edges so only concrete was exposed to the outside. Anchor the turned down slab to the foundation wall as you would any other structure. Welded wire fabric might reduce slab cracking. Use a durable mix (air-entrainment, etc.)

For the waterproofing membrane I recommend Grace Ice & Water Shield (without substitution) self-adhered directly to the plywood with the overlapping joints rolled with a steel hand-roller (very important). Grace makes a water-based primer (WB Primer) that greatly increases the bond to porous materials (it is sold in 5 gal containers but a foundation contractor might have some). The insulation should be high-density extruded polystyrene mechanically fastened in place with concrete poured directly on it.

The size and spacing of the joists depends on the span, the weight of the concrete and the regional outdoor deck loading.

Provide adequate flashing at the wall of the house and any penetrations for posts and railings. The walls of the shelter should be waterproofed, drained and insulated as needed for your climate and site conditions.

    Bookmark   September 29, 2012 at 9:08AM
Sign Up to comment
More Discussions
Door heights and sliding door
We are remodeling a small apartment in a modern high...
Foundation parging for new house construction
We are getting a new house built for October. The builder...
Kenny LY
Need help with rigid foam and wall insulation
I am designing a house in Northern Arkansas and am...
Small things that get forgotten
I keep hearing that most people find that there are...
Master Bedroom Floorplan Review
Hello, I am currently working on building a new house...
Sponsored Products
St. Paul Bathroom 25 in. x 22 in. Stone Effects Vanity Top with Basin in
Home Depot
Emerson Leather Sofa - Brighton Soul White White
Joybird Furniture
Madison Rug 8' x 10' - DARK GRAY
$2,499.00 | Horchow
Accent Rug: Candice Olson Cream White 2' x 3'
Home Depot
Drum Shaped Wooden Shade Pendant Light Small
Corona Chair & Ottoman Reproduction-Black - 100% Italian Leather
IFN Modern
Cream Textured Silk Ava 5-Light Bronze Ceiling Light
Lamps Plus
Exaco 66 Gallon Roman Rain Barrel with Planter - 211601
$432.14 | Hayneedle
People viewed this after searching for:
© 2015 Houzz Inc. Houzz® The new way to design your home™