Inventor's Story

History & Development of the am‑cor Ferrocement Construction System, by architect Angus W. Macdonald


The inventor and an early prototype :)

My name is An­gus Wy­man Mac­don­ald. I am an ar­chi­tect, and this doc­u­ment is an in­tro­duc­tion to my in­ven­tion, the pre­fab & pan­el­ized am‑cor Fer­ro­ce­ment Sys­tem.

I gradu­ated from Yale Uni­versity in 1964, Cum Laude, as a Say­brook rank­ing schol­ar, and from the Yale School of Ar­chi­tec­ture in 1967 with the AIA award for “ex­cel­lence in the Study of Ar­chi­tec­ture”. From Yale, I went to New York City, and worked for Har­ris­on & Ab­ramovitz Ar­chi­tects. I grav­it­ated to­wards warm­er climes, work­ing as an ar­chi­tect in Ja­maica, West In­dies, and began de­vel­op­ment of a com­pre­hens­ive, low-cost con­struc­tion sys­tem. I wished to unite my as­pir­a­tions as a de­sign­er with the world-wide need for dur­able, en­ergy ef­fi­cient, and af­ford­able shel­ter.

The Prob­lem

I had al­ways been in­ter­es­ted in mod­u­lar, mass pro­duce­able build­ing sys­tems. However, I was nev­er happy with the tradeoffs I en­countered over the years. While one par­tic­u­lar build­ing sys­tem was beau­ti­ful, it was not af­ford­able. While an­oth­er was af­ford­able, it was not dis­as­ter res­ist­ant or suit­able to be­low-ground con­struc­tion, such as earth-berm­ing/shel­ter­ing. Yet an­oth­er was en­ergy-ef­fi­cient, but quite dif­fi­cult to design and build, much less main­tain. In frus­tra­tion, I de­cided to look at the con­struc­tion pro­cess hol­ist­ic­ally, and iden­ti­fied the fol­low­ing prob­lems with stand­ard con­struc­tion:

  1. Fasten­ers are used to con­nect com­pon­ents; fasten­ers are the weak points, yet are used throughout.
  2. The usu­al meth­od of mak­ing a stronger struc­ture is to “throw more ma­ter­i­al at the prob­lem”, rather than “use the prop­er­ties of the ma­ter­i­al in­tel­li­gently”.
  3. Much ef­fort is re­peated or un­ne­ces­sary and money is wasted, be­cause of con­stant fo­cus on cheapest ma­ter­i­als rather than co­or­din­a­tion between each stage of con­struc­tion.
  4. Ba­sic­ally, stand­ard con­struc­tion is 200-300 year old tech­no­logy, patched with con­tem­por­ary “band-aid solu­tions”, giv­ing the ap­pear­ance of mod­ern­ity.

Pre­fab­ric­a­tion & Pan­el­iz­a­tion

I knew there must be a way to deal with the prob­lems of mod­ern con­struc­tion cheaply & ef­fi­ciently. My ex­per­i­en­ces with vari­ous build­ing sys­tems showed pan­el­iz­a­tion of the build­ing shell to be the most ef­fect­ive way to:

  1. Pre­fab: Util­ize the ef­fi­ciency of in­dus­tri­al mass pro­duc­tion tech­niques to con­trol cost
  2. Provide the widest and most flex­ible vocab­u­lary of forms to suit vari­ous sites and designs, and
  3. Al­low ready trans­port­a­tion to, and easy as­sembly at, re­mote sites.

While pan­el­ized con­struc­tion is com­pel­ling, nor­mally the pan­els them­selves have is­sues. Junc­tions are a prob­lem, as it is com­plic­ated to ob­tain struc­tur­al con­tinu­ity us­ing fin­ished pan­els; fur­ther­more, they are not aes­thet­ic­ally pleas­ing and have the stigma of be­ing “cheap.” Joints can ad­mit mois­ture and weath­er, and the strength of pan­el­ized build­ing nor­mally re­lies on fasten­ers. Merely fastened con­nec­tions even­tu­ally fail, as they are only as strong as the ma­ter­i­al sur­round­ing them.


I have de­signed for and per­son­ally built with vari­ous types of pan­els, and so have ex­per­i­en­ced their vari­ous char­ac­ter­ist­ics:

  • Mass pro­duced wood fram­ing
  • Pre-cast con­crete
  • Ba­gasse board (made from sug­ar can stalks after the sug­ar has been pressed out)
  • Steel frame with wooden in­fill walls, floors, and roof pan­els
  • SIPS (struc­tur­al in­su­lated pan­el sys­tem) & ICF (in­su­lated con­crete forms)
  • Mod­u­lar re­mov­able steel form­work, to cast thin shell re­in­forced con­crete build­ing shells in situ
  • Heavy tim­ber & con­crete block/ma­sonry

While each of these sys­tems has laud­able strengths, each also has dis­qual­i­fy­ing short­com­ings. In com­par­is­on, the pan­el type I in­ven­ted, in re­sponse to my hands-on ex­per­i­en­ces set­ting up pan­el as­sembly lines, is based on fer­ro­ce­ment en­gin­eer­ing. It is made of a gal­van­ized light-gage cold rolled steel frame­work, coated on site with a thin con­tinu­ous seam­less highly re­in­forced, Ferrocement skin. By pan­el­iz­ing the build­ing frame­work as a struc­tur­al mat­rix for on site place­ment of a struc­tur­al fer­ro­ce­ment coat­ing, I com­bined the com­pos­ite qual­it­ies of fer­ro­ce­ment with the op­por­tun­ity for mass pro­duc­tion of build­ing struc­tures.

The Solu­tion

I pat­en­ted this pan­el type in 1996 and called it the am‑cor Sys­tem™. In this sys­tem, fasten­ers are used to hold the frame to­geth­er dur­ing ap­plic­a­tion of the Fer­ro­ce­ment skin. However, they are ac­tu­ally re­dund­ant: on harden­ing, the Fer­roce­ment skin it­self be­comes the ul­ti­mate “fasten­er”, join­ing all frame parts to­geth­er to form a com­pos­ite unibody monoqocue shell, sim­il­ar to a boat hull, auto­mo­bile chassis, or air­plane fu­sel­age. By har­ness­ing the in­her­ent phys­ic­al & chem­ic­al prop­er­ties of steel and ce­ment, I have been able to cre­ate a com­pos­ite as­sembly that is com­pletely mod­ern and ef­fi­cient in its use of ma­ter­i­als.

Over time, I have im­proved the per­form­ance of the am-cor System through col­lab­or­a­tion with build­ers, en­gin­eers, and ce­mento­lo­gists, and by con­struct­ing many build­ings for cli­ents. Today, we are at a point where the qual­it­ies of this in­ven­tion sat­is­fy my build­ing sys­tem wish-list:

  1. Con­forms to in­ter­na­tion­al build­ing codes for im­me­di­ate ap­plic­a­tion world-wide
  2. Mass pro­duce­able by re­gion­al fab­ric­at­ors (and so read­ily avail­able world-wide at ex­tremely low cost)
  3. Raw ma­ter­i­als read­ily avail­able world-wide
  4. En­ergy & labor ef­fi­cient, es­pe­cially dur­ing con­struc­tion, and over the life­time of the build­ing
  5. Mod­ern, re­new­able en­ergy and ser­vice sys­tems are eas­ily in­teg­rated in­to the pan­el­ized struc­ture
  6. Eas­ily ex­pan­ded, ex­ten­ded, and ad­ded onto
  7. Safe & se­cure, for af­ford­able “for­ti­fied and bal­list­ic res­ist­ant con­struc­tion”
  8. Truly sus­tain­able & re­si­li­ent: Min­im­al use of re­cycled ma­ter­i­als that last
  9. Ex­tremely strong (high strength-to-weight ra­tio)
  10. Dur­able and res­ist­ant to all types of de­teri­or­a­tion in­clud­ing rot , delamin­a­tion, and rust
  11. Dis­as­ter res­ist­ant: flood, fire, hur­ricane, tor­nado, flood, earth­quake
  12. Res­ist­ant to ver­min, in­sects, ter­mites
  13. Eas­ily made hy­gi­en­ic, res­ist­ant to mold, mil­dew, fungus, bac­ter­ia
  14. In­ex­pens­ive & af­ford­able
  15. Com­pletely scal­able: equally good for large and small pro­jects
  16. Trans­port­able (nestable & flat-pack­ing)
  17. Eas­ily as­sembled and en­closed by own­ers and loc­al build­er crews (fast learn­ing-curve)
  18. Sim­pli­city of con­struc­tion & ma­ter­i­als elim­in­ates com­plic­ated de­tails and re­dund­ant build­ing prac­tices
  19. Beau­ti­ful: with in­teri­ors and ex­ter­i­ors com­pli­ment­ary to re­gion­al tra­di­tion­al ar­chi­tec­tur­al styles
  20. And above all: work­able in a way to ful­fill the con­cepts and as­pir­a­tions of the de­sign­er; truly uni­ver­sal, without design con­straints of size, shape, tex­ture, sur­face or ap­pear­ance.

The Fu­ture

The am‑cor Uni­fied Steel & Ce­ment™ Sys­tem has been used to make many build­ing types, in­clud­ing res­id­en­ces, be­low-ground earth-sheletered/earth-bermed struc­tures, com­mu­nity build­ings, of­fices, res­taur­ants & food ser­vice, ag­ri­cul­tur­al in­dus­tri­al, schools and day care cen­ters, ho­tels and casi­nos. In each case our Fer­ro­ce­ment en­gin­eer­ing & for­mu­las has proven to provide the op­tim­um bal­ance of con­struc­tion speed, low cost, and build­ing qual­ity.

The suc­cess of the am-cor System in the USA and abroad is lead­ing to a new struc­tur­al paradigm. New ideas and meth­ods will open up the po­ten­tial for even great­er strength and weath­er res­ist­ance, us­ing even less ma­ter­i­al, at even lower cost.

It is my goal to fol­low this path: to make sus­tain­able, resil­li­ent, en­ergy-ef­fi­cient, and per­man­ent shel­ter af­ford­able to all people.

To learn more about An­gus W. Mac­don­ald: