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Sandpaper on a flat roof - help

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Posted by jcopilot on Tuesday, April 3, 2018 10:10 PM
Trainmasterg, Yes, there is. There are so many talented, knowledgeable modelers on this forum who are willing to share what they know and have done. Jeff
If it's worth doing, it's worth doing twice.
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Posted by jcopilot on Tuesday, April 3, 2018 10:08 PM
MisterBeasley, Thanks for the warning. I've bought a can of Rustoleum Multicolor Textured spray paint in Desert Bisque. A friend found satellite views of roofs he knew to be gravel-covered and they were distinctly light brown, beige, sandy colored. The color of the stone probably varies depending on what's available locally. But I'm going with what I saw in the satellite view. So tomorrow I hope to spray some pieces of cardboard as a test and see how it comes out. Hoping for the best, Jeff
If it's worth doing, it's worth doing twice.
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Posted by trainmasterg on Tuesday, April 3, 2018 1:59 PM

That’s some really good stuff there! Thanks

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Posted by EMDSD40 on Tuesday, April 3, 2018 10:39 AM

Consider using cheap plain old cat litter sprinkled over white glue. I’ve found various sizes and texture in large containers. It seems the cheaper the better and no scented additives. Paint the glue around any roof details, sprinkle and shake off the loose for second application if you deem necessary.

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Posted by MisterBeasley on Tuesday, April 3, 2018 10:03 AM

jcopilot
Thank you doctorwayne for putting this idea in its proper perspective. And thank you ctyclsscs, cowman, and MisterBeasley for your suggestion to use Rustoleum textured paint, that's what I'm going to try.

Be aware that this paint is very thick.  When you are done spraying, invert the can and spray out the excess to keep the nozzle clear.  Sometimes, I have to take a piece of wire, remove the nozzle and manually clean it out.  If you forget to do this, the next time you use the spray can you'll have trouble getting any paint out.

It takes an iron man to play with a toy iron horse. 

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Posted by RR_Mel on Tuesday, April 3, 2018 8:16 AM

hon30critter

How do you keep a sandpaper roof free of dust? It would seem to me that the grit would hang on to the dust particles pretty good. Any sort of brushing action might push the dust further into the grit. I guess vacuuming would be an option. Compressed air might work too, but all that would accomplish is to move the dust onto another area of the layout.

Is dust on the sandpaper a problem over time or not?

Dave

 

Yes Dave, dust is a problem all over my layout and worse on rough surfaces.  I use a Mini-Vac attachment on my Shop Vacuum and it works very good.  The Mini-Vac only had a short hose and that can be a problem.  I bought a 10” extension hose (⅝”) to prevent the larger Shop Vac hose (1½”) from dinging scenery on my layout.
 
 
 
Mel
 
Modeling the early to mid 1950s SP in HO scale since 1951
  
 
My Model Railroad   
 
Bakersfield, California
 
I'm beginning to realize that aging is not for wimps.
 
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Posted by hon30critter on Tuesday, April 3, 2018 1:40 AM

How do you keep a sandpaper roof free of dust? It would seem to me that the grit would hang on to the dust particles pretty good. Any sort of brushing action might push the dust further into the grit. I guess vacuuming would be an option. Compressed air might work too, but all that would accomplish is to move the dust onto another area of the layout.

Is dust on the sandpaper a problem over time or not?

Dave

I'm just a dude with a bad back having a lot of fun with model trains, and finally building a layout!

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Posted by last mountain & eastern hogger on Monday, April 2, 2018 11:55 PM

Whistling

I have used the back side of rolled roofing or some left over shingles

not only as roofing but also for ashfalt roads or parking lots.  looks good to me after a little weathering.

Johnboy out.................

from Saskatchewan, in the Great White North.. 

We have met the enemy,  and he is us............ (Pogo)

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Posted by jcopilot on Monday, April 2, 2018 9:59 PM

To all who have taken the time to reply to my question about using sandpaper to represent a 'built-up roof':  Thank you very much.  I have learned a lot from all the replies and I very much appreciate your time and thoughts.

After reviewing all the replies, I've come to the conclusion that which grit sandpaper would be best isn't the most important issue, but rather, how the sandpaper would look when applied to the Walthers building roof with its irregularities.  The supplied roof has several 'bumps' and other 'guides' to help locate roof-top details.  Cutting and fitting the sandpaper over or around them and then getting the details to fit and look good sounds like more than I care to attempt.

Thank you doctorwayne for putting this idea in its proper perspective.  And thank you ctyclsscs, cowman, and MisterBeasley for your suggestion to use Rustoleum textured paint, that's what I'm going to try.

Again, many, many thanks to all who contributed to this question.

Jeff

If it's worth doing, it's worth doing twice.
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Posted by MisterBeasley on Monday, April 2, 2018 9:29 PM

ctyclsscs

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'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.

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Posted by ctyclsscs on Monday, April 2, 2018 6:09 PM

cowman
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.

Jim

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Posted by cowman on Monday, April 2, 2018 5:02 PM

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.

Good luck,

Richard

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Posted by dknelson on Monday, April 2, 2018 10:06 AM

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.

Dave Nelson

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Posted by mbinsewi on Monday, April 2, 2018 9:27 AM

I just noticed, when I made my post last night, Dr. Wayne must have been working on his, as when I submited my post, Wayne's wasn't there. Laugh

Great work as always, along with Ed's roof. 

Mike.

 

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Posted by RR_Mel on Monday, April 2, 2018 9:26 AM

jcopilot

Mel,

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.

Jeff

 

Jeff
 
Yes I did thin the Acrylic Crafters paint, It’s been a long time but I think about 2 water to 1 paint.
 
A lot of work went into that roof ED, looks very realistic!
 
 
 
Mel
 
Modeling the early to mid 1950s SP in HO scale since 1951
  
 
My Model Railroad   
 
Bakersfield, California
 
I'm beginning to realize that aging is not for wimps.
 
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Posted by ctyclsscs on Monday, April 2, 2018 9:13 AM

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.

Jim

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Posted by doctorwayne on Monday, April 2, 2018 9:12 AM

Ed, that is one good-looking roof!  Thumbs UpThumbs Up

Wayne

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Posted by SouthPenn on Monday, April 2, 2018 6:50 AM

Most of the roofs I have been on here in central Pa used stone chips. The same as the tar and chip road repair.

South Penn
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Posted by SeeYou190 on Monday, April 2, 2018 6:29 AM

I have used "Pavement" material from Arizona Rock & Mineral for roof coverings and held in place with diluted white glue.

.

I have never been good at cutting sandpaper to fit or gluing it in place well.

.

-Kevin

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Living the dream.

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Posted by gmpullman on Monday, April 2, 2018 12:38 AM

7j43k
In my area (SF Bay Area), these roofs were covered with pea gravel, maybe 1/4" in diameter.  It is a very light color--not dark at all.

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.

 PO_annex1 by Edmund, on Flickr

 

 PO_annex3 by Edmund, on Flickr

 PO_annex2 by Edmund, on Flickr

Note the tar around the vent stacks.

 IMG_4630_fix by Edmund, on Flickr

On this one I rolled the roofing up the inside of the parapet as is done on a re-roof job and new flashing is not installed.

I download "textures" from this site:

https://www.textures.com/

Then use photoshop and CorelDraw to manipulate the images to my liking.

There are scores of roofing types, new, old, rolled, tin asphalt etc.

https://www.textures.com/category/roofing/108

Some of these textures are "seamless" and they can be tiled into a single image and printed to your liking. I use basic matte photo paper then give it a light coat of flat clear fixative (Dullcoat or similar).

By registering at textures.com you can download several higher-resolution images a day. There are scores of useful photos and I like to use them for walls, flooring and interiors. Make a folder and place these images there for future use.

 

Years ago I used "sandpaper" to cover a flat roof on a structure and every time I looked at it it would scream "Sandpaper"! Then a visitor mentioned once, "I like the way you used the sandpaper to make that almost look like a real roof".

Never again...

Good Luck, Ed

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Posted by 7j43k on Sunday, April 1, 2018 11:07 PM

In my area (SF Bay Area), these roofs were covered with pea gravel, maybe 1/4" in diameter.  It is a very light color--not dark at all.

 

Ed

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Posted by mbinsewi on Sunday, April 1, 2018 10:45 PM

jcopilot
1" size? I'll have to check my sandpapers and see how the different grits scale out.

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.

Too much info for an HO scale bulding, hey?  Laugh

Mike

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Posted by doctorwayne on Sunday, April 1, 2018 10:35 PM

jcopilot
...Are there roofs with small gravel/pebbles?...

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.  Carefully begin to slide the waxed paper from beneath the sandpaper, smoothing the latter in place as you follow along with your free hand.

Once the sandpaper is in place, I suppose that it can be painted or, perhaps, the roof details need to be added first...I'm not familiar with that kit or your preferred order of assembly. 
You'll need to decided what to use to affix those details.  If the cast-on forms are still present, solvent-type cement should work, while I'm uncertain what would work to attach styrene details to the rough surface of the sandpaper, without looking too messy.  Contact cement is difficult to apply precisely, ca will immediately leach out into the sandpaper's grit, and white glue isn't very good at sticking to styrene, although it should stick well to the sandpaper.

In my opinion, I think that you will be disappointed by the results or simply become frustrated by the process.  Most Walthers kits, neatly assembled and painted, can look sufficiently detailed and well-finished using the parts included, and, of course, you can also add your own embellishments.
I don't mean to discourage you:  if you really think that it is worth the effort, by all means try it.  For me, I wouldn't bother, even though I do like to add touches "beyond what was in the box".  I see it as too much effort for almost negligible return.
This is a complex constructed from DPM modular walls, with roofs and simple details scratchbuilt from styrene...

Wayne

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Posted by UNCLEBUTCH on Sunday, April 1, 2018 10:33 PM

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.

just my thoughts

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Posted by jcopilot on Sunday, April 1, 2018 10:21 PM

Mike,

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.

Thanks,

Jeff

If it's worth doing, it's worth doing twice.
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Posted by jcopilot on Sunday, April 1, 2018 10:19 PM

Mel,

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.

Jeff

If it's worth doing, it's worth doing twice.
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Posted by mbinsewi on Sunday, April 1, 2018 10:12 PM

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.

Mike.

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Posted by RR_Mel on Sunday, April 1, 2018 10:03 PM

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
  
 
My Model Railroad   
 
Bakersfield, California
 
I'm beginning to realize that aging is not for wimps.
 
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Sandpaper on a flat roof - help
Posted by jcopilot on Sunday, April 1, 2018 9:36 PM

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.

Thanks,

Jeff

If it's worth doing, it's worth doing twice.

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