How about using the Edible Sugar Mold process?

Broghan ~ Gingerbread house recipes might work well for your project. There are some tried-and-true recipes that have previously been posted here on The Recipe Link.

Another idea would be to make your haunted house out of "sugar mold." Sugar mold is most commonly used to make sugar easter eggs.

I used the process a while back to make a three-dimentional edible chain saw cake. I made the blade of the chain saw out of sugar mold. The blade stood upright nicely on the cake board. (The body of the chain saw was cake.) I formed the shape I wanted on a cookie sheet (dusted with corn starch) and baked it at 200 degrees until is was solid. You could also use parchment paper, or non-stick cooking paper between the sugar mold and the cookie sheet.

I used the egg white sugar mold recipe when I made my chain saw cake. I have posted that recipe below. I am also positing a recipe for sugar mold using just sugar and water.

You can decorate your house using royal icing. (recipes for that also here on TRL).

Sugar mold and royal icing are quite hard when they dry, but they are both edible.

I hope this helps. Let us know. It is always fun to hear back -- especially regarding such a creative project.

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Egg White Sugar Mold

5 pounds white sugar
2 egg whites

(cornstarch as needed according to the size of your mold, or parchment paper, or non-stick foil)

Preheat oven to 200 degrees F (93 degrees C).

Place sugar in a large bowl, stir to get rid of lumps.

Make a well in the center and pour in egg whites. Mix and knead with hands 5 minutes, until well blended.

If you are using molds, dust them with cornstarch. Press sugar and egg white mixture firmly into mold with the heel of your hand.

Scrape off excess sugar with the straight edge of a knife.

Unmold at once and place on baking sheets.

Bake in preheated oven 20 minutes, until hard.
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Sugar Mold Recipe

4 1/2 cups granulated sugar
3 tablespoons water

Place sugar in large mixing bowl. Mix sugar so there are no lumps in it.

Make a well in sugar, then add water.

Rub mixture between your hands and knead for about 1 minute or until well-blended and mixture packs like wet sand.

Be sure there are no lumps in mixture.
NOTE: Keep sugar mixture covered with a damp cloth when not in use. Bake as directed above.