I’m finishing up a Walthers Champion Packing Plant which has a flat roof. I’ve seen several posts about using sandpaper to represent a particular type of roof covering. But what type? Are there roofs with small gravel/pebbles? I’ve seen recommendations for using 220-grit, 400 and 600-grit sandpaper. Am I supposed to paint the sandpaper a black/gray color? I have some 220 and 600 - the 600 grit is so fine, it seems any paint would smooth it out and ruin any similarity to gravel or pebbles. The 220-grit sandpaper I think would still show the grit through a light paint application.
Any help would be appreciated. Even referring me to a specific magazine article.
I went with 100 grit for my HO roundhouse roof. I used a print brush and a Charcoal color Crafts Acrylic paint. It turned out pretty good. Unless you’re right on top of the roundhouse it’s difficult to see the grit on the roof.
Mel
Modeling the early to mid 1950s SP in HO scale since 1951
The period that the roof for that kit represents is a flat roof called “built up roofing”, it’s a few layers of insulation, roofing/tar paper, and finished off with a coating of “hot roof” tar, and ballasted with gravel, to keep the sun, and wind off. Some types used the hot tar between layers.
Modern methods use an EPDM type covering, and not always use the ballast.
For your kit, use a sandpaper that would have grit equal to about 1" gravel size, in HO scale. Some roofs of this type used larger stone, some used pea gravel size.
If I remember right, I used small ballast (for track work) stone for the flat roofs I show.
Very nice. 100-grit and you say you can’t really see it until you’re up close? I’ll have to check my sandpaper collection. I usually thin craft paint about 50-50 with water to make it spread better and thinner. Did you thin the paint you used or did you use it full-strength.
Thanks for the information. I’ve never heard of ‘built up roofing’. Since my era is 1958, EPDM roofing would not be appropriate. 1" size? I’ll have to check my sandpapers and see how the different grits scale out.
I use 600 wet/dry for my roofs, I do not use any extra stone. The original color looks right to me. I will add a tin line of a flat black along the seams to look as tar seeping, and weather with chaulk, and/or a ink wash.
Seeing you have those grits on hand; maybe invest a little time ,and make a sample of each. See witch one you like.
One thing I noticed, if you have some thing up there; a few patches,scrap wood/metal, junk,vents ect. It looks more believable, then a picture perfet roof.
Yes, generally “pea” gravel on a hot-tarred surface. “Pea” refers to both the size and shape of the stone, about 1/4", or, in HO, about .003", which seems to agree with a quick on-line search showing a micrometre value for grit sizes, and 220 grit would be about right.
However, once painted, even lightly, the effect will be lessened. And, more importantly, are you sure that this is a worthwhile procedure, given the process needed to achieve it?
As far as I know, the packing plant has a flat roof. First, you’ll need to either trim the sandpaper to fit not only the roof, but all of the raised details on it. If it’s like most Walthers flat roofs, that may include raised shapes or ridges to aid in placement of roof details, such as skylights, vents and chimneys, water towers, etc.
Another choice would be to remove those raised forms to make application of the sandpaper simpler.
Next, you’ll need to attach the sandpaper to the roof: contact cement would be my choice. The first step is to “prep” the plastic roof with a coat of solvent-type cement or MEK: this is to prevent the plastic from absorbing the solvent from the contact cement, making it otherwise difficult to apply an even coat. While that’s working on the styrene, you can coat the back of the sandpaper with the contact cement, then apply a coat of cement to the roof. Let both surfaces sit for at least the amount of time recommended on the cement’s label.
Once it’s dried, cover the roof with waxed paper…this will allow you to line-up the sandpaper exactly as it needs to be applied: the word “contact” in the cement’s name is a very apt word, as when contact between the two prepared surfaces occurs, the bond is made. Carefull
Like I said, I’ve been on some roofs with 2" stone ballast, and I’ve been on some with pea gravel. The gravel is there to hold everyting in place, and keep the direct sun light off.
Another feature you could add, some roofs of this type had wood plank walkways to get to any roof top equipment, such has vent fans, A/C units, etc. I’ve been on some roofs that used the precast patio stone walkways for equipment access.
It wasn’t good to just walk on the gravel, and possibly damage the rubber or tar paper underneath the stone.
Another feature would be roof drains. Water needs to go some where. If it was a sloped roof, it ran through roof scuppers, and down spouts, if the roof used roof drains, like floor drains, it ran down piping under the roof, to storm drains, or to the outside.
Same here in NE Ohio. The plant where I worked had a built-up roof and pea gravel was always used. Largest “pebble” was roughly 3/8".
When I have a structure that is “up-close” and the roof will be a prominant feature I’ll sometimes print “textures” and apply those using contact cement as Wayne describes above.
I vaguely recall using Rustoleum’s textured spray paint on some models in the past. It comes in a variety of plain and speckled colors. When you first look at them, the specks look kind of big, but they can be toned down with weathering and light oversprays of other colors. I’d post some photos but I made the models for a friend and don’t have access to them anymore. I’d look into it though as an option to cutting and fitting sandpaper.
I have seen (and walked on a few) “gravel” roofs, both commercial and residential, and most people make the gravel too large IMHO (including Jeff Wilson in his excellent Kalmbach book on structure modeling).
My folks had a flat roofed porch with that kind of roof - it used pea gravel (rounded pebbles) on tar and over time due to heat and people walking on it, the gravel would sink in to the tar making it more of a textured flat surface, not visually at all like a gravel driveway or alley.
For that I would use the finest grit sandpaper - even the color is mostly right, and some modest weathering powders of a similar color worked in with an old toothbrush or mascara brush would capture the effect. You want the texture. You don’t want to see each individual grain of rock, not for the kind of roof I am thinking of and remember at least.
I have used wet/dry (black) sandpaper for rolled roofing. For that I used a 1200 grit I think. For the gravel sirface roof you are doing I think the 220 grit mentioned should be about right.
Have seen some posts with pictures of roofs done with the Rustoleum textured paint. They looked good, sorry I can’t remember which color was used.
I don’t think there is any “right” color. They have a variety so it depends on what looks best to each person’s eye, their lighting and if they want a newer looking roof or one that’s older and dirty. It could also probably vary if different shades of gravel are used in different parts of the country.
I’m a big fan of that Rustoleum textured speckled spray paint. This is a roof I did in black, my favorite of the available colors. This is from the Empire Tannning Company, a kit which was made up of Walthers modular sections. To improve the roof appearance, I cut strips of brick sheet, painted and mortared them, and then glued them to the insides of the parapet walls. This both covers over the bare plastic on the back sides of the wall parts and provides a good light-block to fill the gap where the roof sections meet the walls.
