Roofs on Adobe Homes
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Q: We are considering purchasing an adobe-style, flat-roofed house in Steamboat Springs, Colorado, but are concerned about how the roof handles the snowfall. The exterior is dryvit stucco. Our realtor says that it just stays on the roof throughout the winter and provides extra insulation. It has drainage spouts at the flat part of the roof and looks to be very well-built, with no signs of leakage. It is 15 years old and appears to be in excellent shape. Could you advise us on what kinds of questions to ask about the roof materials/design, etc., to make sure it is built properly?

A: Hopefully the roof has some pitch to it so that water drains to the canales and does not puddle on the roof. A flat roof should not be a level roof. A minimum slope of 1/4" per foot is what is expected of flat roofs. A really good roof has crickets which are sloped sections of the roof that make sure that water runs to the canales. Crickets might be barely discernable on a low slope roof but they should be there or else water puddles long the parapet where the roof meets it. If the roof is well insulated then I would expect in the right climate that the snow would indeed persist throughout the winter and add to the insulating value.

It would be good if the canales are not on the north side of the house so that when water is discharged in transitional weather it does not refreeze when it hits the shaded ground and build up an ice dam.

As for the roof membrane itself, a well done hot mop - sometimes called a built up - roof should give about thirty years life before it needs significant attention. Brai or other torch down modified bitumen roofs might last a bit longer and a rubber or synthetic single membrane roof would be expected to last the longest at around fifty years.

It really might be worth the cost to have a local home inspector look over the house. He would have a realistic idea of the weather requirements and could see in person many details that it is hard to judge from a distance. There is the National Association of Home Inspectors and at least one other professional group of inspectors which list their certified inspectors by state.

Q: I am buying an adobe house in Velarde, NM that was constructed in the 1940's. The surface and insulation on the roof have been replaced recently with TPO membrane on top to cure a leakage problem. The vigas and the 1" boards on top of the vigas have a slight sag and the roof ponds a thin film of water in one corner. I have had the house inspected by a licensed NM inspector. He did not seem to think the sag was a major problem in an adobe house that old but he did have a problem with the ponding. The vigas span is a little over 20'. Would it be a good idea to support the vigas with a beam across the center of the span and possibly jack them up a bit, not as a cure to the roof ponding but for extra support and internal appearance?

A: I am not familiar with TPO. I do know about TC&I, Thermal Coatings and Insulation, who spray on a polyurethane insulation with a final ultraviolet protection layer. TC&I usually works hard to eliminate any puddling areas by varying the thickness of the insulation. Some membranes tolerate standing water well. In Industrial America, many flat roofed buildings are built to stand up to a thin layer of water that is sprayed on in the summer to turn the roof into a giant evaporative cooling device. Whether or not your membrane is this quality, I cannot say.

If your vigas are big enough, a 20-foot span is not a problem. But if there is indeed a noticeable sag, it might be worth thinking about. Lots of older houses had dirt roofs even as recently as the 1940's. If that were the case and the dirt has been removed that subtracts a very large load and over time the vigas might just straighten out a bit. We have seen this happen on structures in Velarde and Dixon that belonged to the Archdiocese of Santa Fe.

Q: I have built a pueblo style poured adobe home in Casas Grandes Chi MX. It has parapets and canales on the roofs. I tried Formflex 4000 on concrete roofs; it is expensive ($180 5 gal.) and has a problem adhering on one deck. Is aluminum fiber coating a viable option at $35 5 gal. and will tile stick with flex set on roof/deck?

A: I am not familiar with Formflex. Aluminum Fiber coating will adhere once the concrete is fully cured. If the concrete is at all green, it is very problematic. Tile will adhere to the roof in a thick set, cement based adhesive probably with a latex or acrylic admixture to give it extra waterproofing. I would consult a tile and/or adhesive manufacturer. I have been happiest with the C-Cure adhesives over the years for floors, walls and shower surrounds. I have no experience with tile on exterior roof systems and the added environmental intensity I would expect in Casas Grandes.

Q: I'm planning to build a small home in Mexico and would prefer to use nature-friendly techniques. As both adobe structure and palapa roofing appeal to me, I am wondering if it is practical to combine these? The plan is evolving as a "modified" A-frame with intent to use adobe exterior walls, plus as interior walls to support the loft area.

A: Perfect. That's as autochthonous (autocrono) as you can get. Just like the thatched roof Irish adobe cottages or Zapotec structures in Oaxaca.

A: (Kelly) I also live in Mexico, and have seen many adobe and palapa roofed structures, as these are completely indigenous to the area. I see no reason why you shouldn't combine these two fine examples of natural, sustainable arhcitecture. However, for an A-frame design, only vertical walls should be made with adobe, and these need a good roof.

Q: I have an adobe style house with parapets and canales to drain water off the roof. Do you know of any system that will funnel rainwater from the parapets without completely compromising the architectural integrity of the home?

A: There are some clever sheet metal folks around Santa Fe who drill a hole in the bottom of the canales just after they exit the parapet wall. They solder on a tube that connects to a standard gutter conductor pipe to the ground. If painted to match the color of the wall they are nearly invisible. In case of a heavy rain or ice, water can spill out the front of the canales as originally intended. If there are problems on the roof itself in getting the water to move to the canales, the answer is crickets. A competent roofer will know what this means.

Q: I am in the negotiating and inspection phase of a 1946 California adobe in the desert community of Apple Valley. I am noticing that some interior walls up near the ceiling appear to have water staining (only in the corners). Additionally, the coating is failing on the outside of the house. How can I tell what the coating is? How do I prepare the coating for application of a new coating without destroying the adobe. It is hard to tell but the coating that is peeling off in places is stretchy and I think it could be a latex paint. There is some failing paint up near the ceiling beams in the living room as well. The house has lovely character and it is possible that I can purchase it for the value of the land. However, I am wanting to be cautious as I will be spending cash as I go and would hate for it to turn into a money pit.

A: I have been singing the Money Pit   movie tunes lately. All homes are money pits so you just have to know when to quit. Sounds as if there may be some roof problems  if there are water stains up high. A good roofer would propose  to repair problems. Other roofers, equally good might suggest complete replacement. Always a tough decision. The outside stretchy coating may be a masonry paint or it may be an elastomeric plaster. A knowledgeable local stucco firm should be able to tell you. Standard cement based stucco does just fine on adobe walls. It should be applied directly over metal stucco netting with no paper barrier. It is the paper that introduces impermeability. Cement stucco has 5 or 6 perms which is all adobe needs to breath. If you can buy it for the value of the land, then you are most fortunate. Many times the old adobe is like an old Ford. It only needs one spark plug to get it going fine.