Aug 7, 2011, 12:49 PM
Post #1 of 4
I have a design/construction question that I haven't seen addressed here previously. Sparks' “The rain and my new roof” thread prompted me to write this. Any input on these issues would be really appreciated.
I've got a great floor plan for a small house to be built with regular Mexican techniques. It will be masonry block construction with regular infill posts of reinforced concrete (castillos) and horizontal tie members (dalas, vigas). The planta baja will be liveable but without too much extra space, so the plan is to allow for an ultimate second story for guest bedrooms, etc, but that will follow at a later date. We'll make sure the building is designed to support another level, and will extend the castillo rebar, etc)
The questions I have deal with putting on the ground floor ceiling/roof, also reinforced concrete, which will ultimately be the floor of the upper level. What's the best technique for waterproofing that surface and allowing for rain runoff in the interim years before the structure grows taller? Seems like the options are:
1) Construct the roof flat and seal the bejeezus out of it, and hope we remain dry inside until the next phase of construction starts.
2) Construct a flat roof surface, but apply an additional cap of concrete (perhaps using lightweight aggregate) slightly thicker along a “ridgeline” – creating a slight slope so the rain runs off quickly. Sealing would be easier, since there never would be standing water puddles, due to the slope.
3) Construct a flat roof surface and instead of multicoat sealing, erect a short sloped framework structure on top of the slab, and attach a corrugated sheet metal temporary roof, which could later be sold or recycled. Oh, and pray every time the wind blows hard.
Are there any other ideas? Which is the least cost or “best” option? A few more related questions...
Is lightweight aggregate concrete an option that would work for the additional cap coat?
Does the sealer make it difficult to adhere new concrete when you go to the next construction phase?
Any techniques for removing the sealer if that's what has to happen?
Seems like it would be easier to float in additional fill to level all the primer piso floors, rather than to chop out & remove the sloping cap, assuming there's a technique for adhering the additional mud.
Oh, and we can't just throw a tarp over the structure for a few wet weeks, as rain is frequent in the area where we're thinking of building.