Form­stone. Perma-Stone. Ros­tone. By what­ever trade name, the mere men­tion of sim­u­lated masonry can cause a wide range of reactions—from the rolling eyes of home­own­ers who want des­per­ately to be rid of it, to pas­sion­ate defense by preser­va­tion­ists of 20th-century build­ing materials.

Perma-Stone is such a com­mon trade name that it’s almost become generic for any of the cement-like mate­ri­als applied to exte­rior walls and manip­u­lated to look like stone. If you hail from Bal­ti­more and envi­rons, though, the name you prob­a­bly know is Form­stone, which native son and avant-garde film direc­tor John Waters called “the poly­ester of brick.”

Patented by Bal­ti­morean Albert Knight in 1937 for his Last­ing Prod­ucts Com­pany, its use was so wide­spread that in 1997 Waters made it the sub­ject of a 30-minute doc­u­men­tary film Lit­tle Cas­tles: A Form­stone Phe­nom­e­non, told by the peo­ple who made it, sold it, bought it, and installed it.

Copro­ducer Lil­lian Bow­ers (with Skizz Cyzyk) says she got the idea for the doc­u­men­tary when she dreamed that her father’s grave­stone was being cov­ered with Formstone.

Other brands included Ros­tone, Tru-Stone, Field­stone, Bermuda Stone, Mod­ern Stone, Roman­stone, Mag­no­lia Stone, Dixie Stone, and Sil­ver­stone. It was applied in a man­ner sim­i­lar to stucco, usu­ally in mul­ti­ple lay­ers, to wire net or lath attached to exist­ing exte­rior walls, then scored with sim­u­lated mor­tar joints to sug­gest indi­vid­ual stones. Adding to the illu­sion were often art­ful col­oration and some­times mica chips that would sparkle on a sunny day.

Perma-Stone was reg­is­tered as a trade­mark in 1929 by a Colum­bus, Ohio, com­pany of the same name, which trained and autho­rized local deal­ers and pro­vided them with the molds and mate­ri­als they needed to install it. Its imme­di­ate suc­cess spurred com­peti­tors to fill the desire for a maintenance-free cov­er­ing for poorly con­structed exte­rior walls.

At the 1933–34 Cen­tury of Progress Expo­si­tion in Chicago, the Ros­tone Com­pany of Lafayette, Indi­ana, was among exhibitors using model houses to dis­play what show spon­sors billed as “a futur­is­tic view of what archi­tects pre­dicted would some­day be the norm.”

The Wieboldt-Rostone House was a steel-frame struc­ture clad in Rostone’s pre­fab­ri­cated pan­els of shale and lime. Later relo­cated to serve as a res­i­dence in Bev­erly Shores, Illi­nois, the house served more than any­thing to demon­strate just how wrong they were. The orig­i­nal Ros­tone failed and was cov­ered in the 1950s with Perma-Stone, which has also now fallen apart.

The orig­i­nal use of Form­stone, patented in 1937, was to apply a uni­form exte­rior cov­er­ing to sub­ur­ban houses that had under­gone addi­tions with unmatched sid­ing. How­ever, it quickly became more pop­u­lar for cov­er­ing the exte­ri­ors of old row houses in Bal­ti­more, built by the tens of thou­sands using porous brick that left them plagued by pen­e­trat­ing mois­ture. Form­stone sales­men touted seal­ing qual­i­ties and a 20-year guar­anty that, for the cost of three paint jobs, would vir­tu­ally assure a life­time free of leak­ing walls and peel­ing paint.

Eter­nal sal­va­tion from main­te­nance wasn’t a lure that appealed only to home­own­ers. Many reli­gious insti­tu­tions chose sim­u­lated stone for new build­ings, to side older rec­to­ries, and to match addi­tions to real stone churches. Edu­ca­tional build­ings also got the treat­ment. Father T. Byron Collins of George­town Uni­ver­sity in Wash­ing­ton, D.C., wrote on July 14, 1955, that “In my opin­ion, this process called Tru-Stone makes a much supe­rior job as far as appear­ance and dura­bil­ity as com­pared to shingling.”

At that point, though, faux stone was reach­ing its zenith, about to be over­taken by much cheaper alu­minum and vinyl siding.

Two types of sim­u­lated stone were avail­able to home­own­ers, whether for remod­el­ing or new-home con­struc­tion: sid­ing man­u­fac­tured off-site in molds and applied some­what like real stone and cement-based mate­ri­als applied in lay­ers on-site.

Ros­tone was prob­a­bly the best known of the for­mer group, shipped in inch-thick pan­els mea­sur­ing 16″ x 24″ in a vari­ety of nat­ural col­ors and fin­ishes, from matte to pol­ished. Finely ground shale mixed with lime and water was poured into stone-shaped molds, and then heated to cre­ate a stone­like wafer that could be applied much like con­tem­po­rary faux inte­rior “bricks.”

Perma-Stone and Form­stone, among oth­ers, were cre­ated on the job site, much like inte­rior plas­ter. Nor­mally the first step was to nail up a lath to anchor the ini­tial 1/4″ to 3/4″ rough, or brown, coat. The lath was usu­ally metal but some­times wood; chicken wire was com­monly used with Form­stone. Some prod­ucts were sold as not need­ing lath, so work­ers applied the cement-like mix directly to the exte­rior walls—a cause of great pain to any­one try­ing to remove it decades later.

When the brown coat was dry, the installers applied a sec­ond coat of equal thick­ness and, while it was still wet, some artistry could come into play. Like ambi­tious chil­dren build­ing a sand cas­tle, crafts­men could press the sur­face with molds, score it, or run an alu­minum roller across it to cre­ate a crin­kled sur­face. Faux mor­tar lines could be left or filled. A fin­ish coat then pro­vided sub­tle col­oration; a final mem­brane coat­ing helped water­proof the layers.

This on-site instal­la­tion, plus the vari­a­tion in skill lev­els and per­sonal flour­ishes from con­trac­tors or home­own­ers, explains the wide vari­a­tion often seen among even adja­cent buildings.

If you’re con­sid­er­ing removal of Form­stone, of greater inter­est is what you don’t see. The installer could apply the coat­ings any­where that chicken wire could be nailed—around curves, up and over cor­nices, over sills and dec­o­ra­tive brick­work. Thus the struc­ture could be given large faux key­stones, quoins, or other dec­o­ra­tive touches—sometimes far off-center or out of scale.

Worse, orig­i­nal archi­tec­tural fea­tures were often entirely removed—chiseled off and not merely cov­ered up. Mor­tar around dam­aged brick may be mis­matched or the bricks filled in with an entirely dif­fer­ent mate­r­ial. Work­ers remov­ing Form­stone on an upper storey in Fell’s Point found a layer of cement up to 6″ thick that had been used to level out a brick wall that had bowed in. When home­own­ers were “mod­ern­iz­ing,” they often installed new win­dows and doors—no mat­ter that they were smaller. The sur­round­ing areas were just filled in with non­match­ing brick or cin­der block before being cov­ered with Formstone.

Lost archi­tec­tural fea­tures weren’t just dec­o­ra­tive. Cor­nices, belt courses, lin­tels, and sills that once did their job to divert water away from exte­rior sur­faces were chipped away. Add to this the dete­ri­o­ra­tion of the Form­stone itself—which after time can crack or pull away from the wall—and a pocket is cre­ated where water can seep unde­tected behind the faux masonry, lead­ing to destruc­tive freeze-thaw cycles. This is espe­cially trou­ble­some on wood-frame struc­tures where the dec­o­ra­tive cor­nice was removed, caus­ing water dam­age around ceil­ings and windows.

In short, dam­age is inher­ent to the sur­face under­ly­ing sim­u­lated masonry. The ques­tion is how much?

Steve Call­cott, preser­va­tion plan­ner for Wash­ing­ton, D.C., says the issue of whether to remove Form­stone has arisen on only three occa­sions in that time. “My expe­ri­ence has been mixed. We would never dis­cour­age peo­ple from uncov­er­ing his­tor­i­cal fea­tures,” he says, “although Form­stone had its own period of sig­nif­i­cance and, next year, some peo­ple may con­sider us heretics.”

Prob­lems arise, he says, when peo­ple anx­ious to be rid of the stuff begin rip­ping, ham­mer­ing, and chiseling—especially if theirs is faux stone applied directly to the under­ly­ing siding.

Rip­ping down Form­stone can be a fast and inex­pen­sive process—it can be taken off a two– or three-storey row house in a weekend—but restora­tion of what lies beneath can take weeks, in the case of wood sur­faces that need nail holes filled and a new paint job, to months for masonry sur­faces that have been severely defaced.

Once you have assured your­self of a suf­fi­cient amount of match­ing brick or other mate­r­ial to replace dam­aged areas, you may want to tackle the removal of Form­stone yourself.

The only tools that are needed are a pry bar or two, ham­mer, wire cut­ters, cold chisel, hard hat, gog­gles, and heavy work gloves. You’d be wise, though, to com­mit to scaf­fold­ing rather than a lad­der, since cement lay­ers up to 1 1/2″ thick can be humon­gously heavy.

Work from the top down, since loos­ened sec­tions will fall off the face of the build­ing. For that rea­son you should also think about pro­tect­ing win­dows with ply­wood. Rope off the area to keep away chil­dren, pets, and side­walk superintendents.

Start­ing at a win­dow edge or door frame, chisel away enough faux stone to let you wedge a crow­bar behind it. Once you get started, you should be able to ham­mer in your crow­bar and remove the stone and lath in fairly large sheets. Don’t try to peel away big­ger sec­tions than you can han­dle, and use a nar­row piece of ply­wood under your crow­bar to avoid chip­ping into the brick or wood. On brick sur­faces focus on nail points in the lath, usu­ally placed in the mor­tar joints. In most cases the weight of the sim­u­lated masonry will break the lath or chicken wire; if not, you may need the wire cutters.

Once the Form­stone is off, and you are spared night­mar­ish sur­prises like shrunken win­dows and doors, the pro­ce­dure is like a typ­i­cal façade repair.

If the Form­stone was applied with nails, you can antic­i­pate replac­ing face bricks, espe­cially around win­dows and doors. Even if the installers were care­ful to put nails into the joints, you may find that removal has bro­ken them off or pulled them out, and you’ll have to rake out the joints and repoint. You’ll prob­a­bly want to strip and clean pre­vi­ously painted brick—or you may find that you need to paint it to mask dam­aged and non­match­ing masonry.

As with most restora­tion projects, you won’t know for sure what lurks beneath Form­stone until it’s fully removed.

For some time now, the idea that sim­u­lated masonry may be wor­thy of preser­va­tion has been creep­ing into some his­toric guide­lines. Although the city of St. Louis pro­hibits its use on land­marks, the posi­tion of the Ham­den Vil­lage Main Street Pro­gram in Bal­ti­more is that “while Form­stone removal may also be included as a façade improve­ment, appli­cants are encour­aged to keep Form­stone that is in good con­di­tion as it is a dis­tinc­tive part of Baltimore’s unique heritage.”

And many real estate agents, as they did more than a half cen­tury ago, read­ily adver­tise a faux stone exte­rior as value-added feature.

The debate is likely to become even more heated as 20th-century build­ing mate­ri­als leave their mark—in this case often all too literally—on Amer­i­can architecture.

Related posts:

• Under the Dome
• Encoun­ter­ing the Poe Toaster
• The Gwynns Falls Trail
• Good Sports