HEART OF THE STONE

Lynn Mathias pur­sues a life­long pas­sion, re­pair­ing walls made of durable flint

Landscape (UK) - - Heart Of The Stone - Words: Amanda Birch Pho­tog­ra­phy: Clive Doyle

Arhyth­mic tap, tap com­petes with the cho­rus of bird­song as Lynn Mathias lightly hits pieces of flint with a metal trowel. Work­ing in the grounds of a Bed­ford­shire farm, he is re­build­ing a Vic­to­rian flint bound­ary wall. Lynn is a flint knap­per, a term which stems from the Dutch for break­ing or flak­ing. Flint is a form of quartz oc­cur­ring in chalk beds both as lay­ers and ir­reg­u­lar nod­ules. It has been used for tools and weapons since the Stone Age, and re­mains a use­ful build­ing ma­te­rial to­day. Flint walls made by the Ro­mans still stand across Eng­land, their dura­bil­ity tes­ta­ment to its tough­ness. In Bri­tain flint is found in a nar­row band stretch­ing across south-eastern Eng­land from East Anglia to Dorset, and in the South Downs. The wall Lynn is work­ing on is in the vil­lage of Kensworth, on the edge of the chalk-en­riched Dun­sta­ble Downs in the Chiltern Hills. Flint is a pop­u­lar build­ing ma­te­rial here, much of it found in the beds of a large work­ing quarry at Kensworth Chalk Pit. The ge­o­graph­i­cal lo­ca­tion of the flint dic­tates the ar­eas where Lynn works. “If you go too far east, west or north, you lose it,” he says. “I had a trainee from Sh­effield work­ing for me who had never seen flint be­fore.”

Early ca­reer

Lynn first worked with flint when he was 16. He helped his fa­ther, a brick­layer and stone fixer, to re­pair a flint sec­tion to the lower part of a me­dieval tithe barn in Edles­bor­ough in Bed­ford­shire. “My fa­ther was the only per­son I knew whose hobby was his work,” he says. “He had a real pas­sion for it and thank­fully I’ve picked that up from him. I just love my job. I like work­ing out­side in the warmer months and I also like the cre­ative as­pect of the job. It is truly re­ward­ing to re­store some­thing to its for­mer glory. I get real sat­is­fac­tion from that.”

When he was 18, Lynn went to col­lege in St Al­bans, Hert­ford­shire, where his stud­ies in­cluded his­toric flint and lime mor­tar cour­ses. He worked closely with a flint knap­per to fur­ther hone his craft. Two years later, in 1992, he founded Mathias Restora­tion with his fa­ther. To­day Lynn spe­cialises in the re­pair and restora­tion of flint and brick­work. Of the two, he prefers to work with flint. “Flint work is more cre­ative. The chal­lenge of work­ing with flint on an old build­ing is try­ing to get it as good and as close to the orig­i­nal as pos­si­ble,” he says. “The flint work can­not look like an af­ter­thought.”

A trade lit­tle changed

The tools and pro­cesses he uses are un­al­tered since me­dieval times. Lynn’s ham­mers, chis­els and trow­els would all have been fa­mil­iar to work­ers cen­turies ago. The only mod­ern ad­di­tions are a spirit level, a knee pad to rest the flint on while he splits it, gloves and gog­gles. The wall he is re­pair­ing col­lapsed dur­ing a se­vere storm. If not re­built, the re­main­ing sec­tions may also fall down. The field flint is ar­ranged in a ran­dom de­sign, although there is also a hor­i­zon­tal band of brick­work. This is known as a lac­ing course and is used to level and tie the front and back of the wall to­gether. The re­pair work will take Lynn up to two months to com­plete. He is re­build­ing the wall to its orig­i­nal height of 6ft 6in (2m), and length of ap­prox­i­mately 50ft (15m). It is 131/2in (34cm) wide and solid, filled in with flint and bits of brick. The wall does not have what would be re­garded as a mod­ern foun­da­tion with poured con­crete. In­stead, the orig­i­nal flint work­ers dug down un­til they found rea­son­ably solid ground and built on that, putting in larger pieces of flint first. With­out a solid foun­da­tion, the wall nat­u­rally bends or bows over time, for ex­am­ple when trees grow nearby, forc­ing it to move. This nat­u­ral give pre­vents it from fall­ing over.

Get­ting started

The first step is to as­sess what is there al­ready to en­sure it is repli­cated as much as pos­si­ble. Lynn stud­ies how the wall was built, what flints were used, their size, colour and tex­ture. He also looks at whether the flints are coursed – laid in a straight row – or not, and what mor­tar has been used. This in­for­ma­tion forms a blue­print that he then copies. Once that has been done, he sorts the pieces of field flint left by the da­m­aged wall. “I look for pieces that have good faces – they are the ones that will be on show,” he says. “The mis­shapen ones I put aside to use in the mid­dle of the wall to con­sol­i­date it. Noth­ing is wasted.” Any soil on the flint is brushed off and un­sta­ble pieces are re­moved. The base area is swept clean with a coarse paint brush. This en­sures there is as much con­tact as pos­si­ble be­tween the ex­ist­ing flint and the re­place­ment stone. The flint that has been re­moved for later use is cov­ered with plas­tic sheet­ing to keep it dry in case it rains. Flint is not por­ous, so does not ab­sorb water well. When it rains the water stays on the flint, in­stead of soak­ing in or drip­ping off. Dry stones bond bet­ter with moist mor­tar and are more se­cure, act­ing to sta­bilise the wall. If the flint is wet, it moves, and the wall buck­les. Lime mor­tar is used to hold the flint in place. Lynn uses a soft hy­draulic lime mor­tar due to its in­her­ent flex­i­bil­ity and breatha­bil­ity. “The com­mon mis­take is to use ce­ment, which won’t al­low any move­ment and will frac­ture and crack over time,” he says. The lime mor­tar mix com­prises two parts coarse sand to one part hy­draulic lime from Suf­folk, and ap­prox­i­mately 1 gal­lon (5 litres) of water. It is mixed the day be­fore he needs it in a con­ven­tional drum mixer. This al­lows time for the mix to ‘fat­ten’. Lime is ex­tremely por­ous. It needs as much time as pos­si­ble to ab­sorb the water and cre­ate a bet­ter qual­ity mix that is eas­ier to work with. If mixed and used straight away, the mix tends to be

stiff and dry, and can shrink. “Some­times peo­ple add more water the fol­low­ing day if the mix is stiff,” says Lynn. “This makes the mor­tar too runny and it will not set well. The se­cret is to sim­ply remix it and the lime mor­tar will grad­u­ally re­sume its orig­i­nal tex­ture.” Us­ing a spirit level helps en­sure the flint in the wall is straight. A string line is fixed to a wooden post at one end and to the ex­ist­ing wall at the other. The string is po­si­tioned ap­prox­i­mately 4in (10cm) above the flint line that is be­ing laid. This is used as a guide through­out the build­ing process. Two brass plates, called tin­gles, are placed over the string to stop it sag­ging and to keep it in place.

Com­plet­ing the puz­zle

The flint for this wall is laid flat in a ran­dom de­sign as op­posed to a coursed one. For Lynn, the process is sim­i­lar to a jig­saw puz­zle. “It’s in­stinc­tive and you get an eye for it,” he says. “You see a gap in the wall and you find the ap­pro­pri­ate-sized piece of flint and knit it to­gether. Gen­er­ally you try to get each piece to touch the one below. If the joint is made too big your eye is in­stantly drawn to that joint and not the over­all look of the wall.” Us­ing a metal trowel, he la­dles mor­tar onto the spot, then fits an ap­pro­pri­ately shaped piece of flint onto it. The stone is given a gen­tle tap with ei­ther a metal trowel or ham­mer. This ac­tion squeezes out any ex­cess mor­tar and cre­ates a tighter fit­ting joint. Some­times old Vic­to­rian glass bot­tles, found in fields, are built into a wall to pro­vide dec­o­ra­tion. In two days the mor­tar will have stiff­ened, but it takes at least eight weeks in dry weather to cure, or dry, com­pletely. As this hap­pens it turns a lighter colour. “The process can be deeply ab­sorb­ing and I get into a rhythm,” says Lynn. “What is sat­is­fy­ing is when I see a sil­hou­ette of a gap and a shape that’s cre­ated. Then I find a flint and lay it down and it fits per­fectly. I think, ‘Wow! That piece was made for it’.” Dry, cloudy days with no wind pro­vide the per­fect weather con­di­tions for work­ing with flint. Too windy or too much sun means the mor­tar is at risk of dry­ing out and shrink­ing. If this is al­lowed to hap­pen, cracks form in it and it will not hold the stones. If this oc­curs, Lynn gen­tly sprays a fine mist of water over the lime mor­tar with a fine noz­zled water pump spray. He cov­ers the wall with hes­sian and poly­thene overnight to en­sure the mor­tar is kept damp and the lime cures. Once he has fin­ished the re­pair, the wall should stand for an­other 150 years. “With ev­ery job I do, I feel as if I’ve left a le­gacy for the next gen­er­a­tion,” says Lynn. “It is deeply sat­is­fy­ing to see that, by us­ing the same ma­te­ri­als and the same de­sign, I have done a sym­pa­thetic re­pair. At the same time I have re­spected the work done by the orig­i­nal flint knap­pers.”

When the chalky white cor­tex of a flint stone is bro­ken, the in­ner face re­veals var­i­ous colours that range from grey, as pic­tured here, to or­ange. › This flint in this wall is in a ran­dom de­sign, rather than coursed – that is laid in straight lines – like the brick layer. flint use in bri­tAin Flint is thought to be the re­mains of sponges that grew on the floor of chalk seas. When the sponge died, the ooze left be­hind would get trapped in the chalk, slowly hard­en­ing into flint. The first ex­ten­sive use of it for build­ing in this coun­try dates back to the Ro­mans who used it mainly for the cores of com­pos­ite walls. Coarse, quar­ried flint was also used in the con­struc­tion of Saxon and Nor­man churches, a prac­tice that con­tin­ued dur­ing the Mid­dle Ages. A more ar­chi­tec­turally so­phis­ti­cated use of the ma­te­rial be­gan in earnest at the be­gin­ning of the 14th cen­tury, when the com­bi­na­tion of flint with an­other ma­te­rial to pro­duce flush work emerged. Flint fell out of favour dur­ing the 17th and 18th cen­turies, but was re­vived in the late 18th cen­tury when flint gar­den grot­tos be­came fash­ion­able. The Vic­to­ri­ans pro­duced a whole range of flint build­ings, in­clud­ing cot­tages, church restora­tions and grand coun­try houses, where the flint was cou­pled with lime­stone or brick.

A course of brick­work runs the struc­ture’s length. It pro­vides both dec­o­ra­tion and prac­ti­cal pur­pose, help­ing to con­sol­i­date the front and the back of the wall. Lynn’s ham­mer would be recog­nis­able to flint knap­pers from the Mid­dle Ages.

A string erected with the help of a spirit level en­sures the wall runs straight and true. Lime mor­tar is used in flint walls as it is flex­i­ble, al­low­ing the wall to move with­out cracks form­ing.

Find­ing the ideal stone to fit a spe­cific gap gives Lynn im­mense sat­is­fac­tion. An old glass bot­tle built into the wall adds fur­ther in­ter­est. Dec­o­ra­tive fea­tures are cre­ated us­ing pud­ding stone. This is a nat­u­rally formed con­crete, con­tain­ing small stones. The quartz and sed­i­ment have bonded to­gether over time to form one big rock. Pud­ding stone is found in flint-rich fields but is rare.

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