In the year 1843 Mr. Charles Cochrane, the President of the ‘Association for the promotion of Improved Street Paving, etc.,’ in a paper which he read before the Institution of Civil Engineers, on the State of the Streets of the Metropolis, said that there existed at that date 100,000 yards of wood pavement.[67] He further states that it is said to be slippery, but that he approves of it as the best material hitherto used, “both as regards its general economy and durability as well as its facility of traction, and more especially its extreme cleanliness.”

Two years previous to this date, Mr. Edward Lomas condemned wood pavement as slippery, and recommended granite pavement for horses with wood tram-tracks for the wheels of vehicles.[68]

Since these dates the question of wood paving has made giant strides, many companies and private firms having started business as wood paviors, with many various methods, which they strongly advocate as being superior to the others; amongst them I will enumerate and describe the following:

The Improved Wood Pavement Company.

—The ground being consolidated, a layer of sand is made the basis of the pavement, and assumes the shape the surface of the street is intended to take. Red-wood boards 1-inch in thickness are then laid across the roadway, from kerb to kerb, placed together so as to break joint; boards of the same material and thickness are then laid longitudinally, and breaking joint in the same manner.[69] On this foundation red-wood blocks are placed in rows, taking the same direction as the under flooring.

Between each row of blocks, a strip of wood ³/4 × ³/4 inch is nailed to the block and flooring, the blocks in all cases breaking joint; the spaces thus formed between the rows of blocks are then run with a thick composition which fills all vacant spaces there may be between the strip and the block, covering the strip about ¹/8 of an inch. Gravel, dried and sifted through ³/4-inch mesh, is then put in, solidly rammed, and composition poured in; the pavement is then covered to a depth of ¹/2 an inch with dried gravel and composition for the purpose of indurating the surface, and filling the spaces flush with the top of the block, a slight covering of sand is then spread, when the traffic may immediately pass over.

The Asphaltic Wood Pavement Company.

—After the ground is properly prepared, 6 or 9 inches of concrete is laid, on this is laid a bed of asphalte not less than ¹/2-inch in thickness; then wood blocks 3 by 8 by 5 inches or 3 by 9 by 5 inches, of good, sound, yellow Baltic timber are laid with joints ¹/2-inch in width, these joints are filled from 2 inches up with heated asphalte, the remaining 3 inches being filled with a grouting of hydraulic lime, and clean, sharp, fine river grit or sand, the whole being covered with a top dressing of fine, sharp sand, which wears in with the traffic.

Croskey’s Wood Pavement.

—Upon a bed of concrete, cross grained planks were to be placed side by side and be forced together by pressure so as to form a compact homogeneous surface of wood.[70]

Lloyd’s Patent Keyed Wood Pavement.

—The special feature of this system is that Pitch Pine blocks are used laid direct upon the concrete foundation, the blocks being grooved on each side so that the grouting (composed of Portland cement) shall run in and form a key.

Harrison’s Wood Pavement.

—This system consists of a concrete foundation, upon which strips of wood 2 inches wide by ¹/2 an inch in thickness are laid. Upon these, wood blocks 3 inches in breadth are placed, and then hot asphalte is poured into the joints, which conglomerates the whole.

Henson’s Wood Pavement.

—The main feature of this patent consists in placing common felt on the concrete bed, and between the joints of the wood blocks; thus, it is contended, giving elasticity and allowing for the expansion and contraction of the blocks. The blocks are also bevelled on the top and grooved in a particular manner.

Carey’s Wood Pavement.

—In this case the blocks are cut 4 inches wide by 9 inches long, and 5 or 6 inches deep, according to the traffic; these blocks are shaped with alternate convex and concave ends, and are laid on a bed of sand about 2 inches thick, the joints between the blocks, which have been left about ³/8 inch wide, being filled with a grouting of lime and sand.

Messrs. Mowlem and Company’s

method of laying wood paving is to form a foundation of concrete, varying in thickness according to the nature of the subsoil and the traffic; then to pave with blocks of yellow deal, 3 inches wide and 6 or 7 inches deep; the joints, which vary from ³/8 to ¹/2 inch, are filled in with sand and lias lime, and the surface is afterwards indurated by strewing it with shingle.

Patent Ligno-Mineral Paving Company.

—This company lays claim to the speciality of using hard woods as well as pine, and that the pine blocks they employ are preserved or mineralised so as to be more durable than the wood in its natural state.[71]

Nicholson’s Wood Pavement.

—This is principally in use in the United States, and consists of rectangular blocks of pine laid upon a close flooring of pine boards, 1 inch thick, laid lengthwise with the line of street, their ends resting on similar boards laid transversely from kerb to kerb, the boards being thoroughly tarred and laid upon a bed of sand. The joints of the wood blocks are run with an asphaltic mixture, and the whole surface is finally covered with hot coal tar and sprinkled with fine sand and gravel.

Stowe’s Wood Pavement.

—This is also American, the blocks resting directly upon sand or gravel about 6 inches in thickness.[72] “The blocks are set in courses transversely across the street, so as to break joint lengthwise of the street, the courses being separated from each other 1 inch by a continuous course of wooden wedges placed close together edge to edge, and extending from kerb to kerb. These wedges are set in the first instance with their tops flush with the top surface of the blocks. After the whole pavement shall have been well rammed, so as to give each block a firm bed, the wedges are driven down about 3 inches, and the open joints thus formed above them between the courses are filled in with a concrete composed of hot coal tar and fine roofing sand and gravel. The surface of the pavement may then be coated with coal tar prepared by boiling with pitch, and finished off with a thin layer of sand.”

Wood Paving in Norwich.

—Mr. P. Marshall, the City Surveyor of Norwich, states[73] that the wood pavement in that city is “simply laid on the road formation levelled up with shingle. The blocks are grouted in with blue lias lime and well rammed down. This makes a splendid road, and is superior to any portion of the road that has been laid with concrete. This wood paving, 5 inches deep, laid as described, costs 7s. per yard super. We have had some down here now for 2 years, and have had no settlement whatever. It is a very important matter, for it makes wood paving possible for country towns.”

Shiel’s Composite Block Paving.

—This pavement consists of composite blocks 12 inches by 15 inches, cast in iron moulds with two rows of wood placed at an equal distance from either side and each other, the vacant spaces being filled with granite broken as for macadam; over all is poured a boiling composition of pitch, chalk, and sand. The blocks are thus treated at the works, and are, when cool, taken to the street, laid on a concrete foundation, and grouted with cement grouting.

Prosser’s Wood Pavement.

—This is composed of blocks sawn at an angle of 60°, the grain of the wood running in the same direction. Each end of the block rests on the other, transversely to line of street. Between the rows of blocks a plank, the same depth as the blocks, but with the grain of the wood horizontal, is placed. The blocks, which on one side of the plank lean in an opposite direction to those on the other, are secured or dowelled together by wooden pins running through the plank and piercing the blocks about an inch.

In Chicago, U.S.A., cedar blocks 6 inches square, set on a composition of tar and gravel, are used, and are said to make a very durable pavement.

The following sanitary objections to wood as a material for pavements are made in the Report on the Application of Science and Art to Street Paving and Street Cleansing of the Metropolis (1872) page 17.

“The General Board of Health set aside wood as an ineligible material for this amongst other reasons, that street surfaces ought to be impermeable; and for roads of light traffic and cheap construction, they looked to modifications of macadam, with bituminous binders of mineral tar. Since then wood has been reproduced for the purpose, and strongly pressed in improved forms for trial. It certainly offers the advantage of a great gain in noiselessness over granite, more especially from the horses’ feet, though with some disadvantage from a dead rumble and vibration; and further it has the advantage of being more available than smooth pavements for inclines. But hygienists object to its use on grounds which, in the absence of sanitary science, are overlooked, but which it is important to particularise as showing the dangerous state of ignorance and incompetency of the authorities by whom they are not entertained or are disregarded.”

The sum total of these charges against wood as a pavement consists in the following: “Wood is porous, it is composed of bundles of fibres, it absorbs and retains wet, foul wet especially.” Why foul wet should be absorbed more than ordinary wet does not transpire.

There is no doubt that wood in its natural state does absorb a large quantity of water,[74] but this can be avoided in wood paving by preserving the wood of which it is composed by one of the following processes.

(1)	Burnetising	Chloride of zinc is used in this process.
(2)	Kyanising	Corrosive sublimate is used.
(3)	Renwickising	Boiling in coal tar.
(4)	Boucherising	Sulphate of copper is used.
(5)	Bethelising	Creosote heated to 200° F. is used.
(6)	Seelyising	Creosote is also used, the wood being first boiled.
(7)	Hayfordising	Creosote is also used, wood being unseasoned.

The fibres of the wood are also compressed, and no open joints between the blocks are permitted, by paving the blocks transversely, with butt joints closely packed together, and by filling the cross joints with an asphaltic or other impervious grouting.

Wood paving should, however, be laid in streets with moderate traffic, and plenty of sun and air. In confined spaces such as courts, it soon rots and becomes a source of much unhealthiness.[75]

Many reports have been from time to time made on the advantages and disadvantages of wood paving, and much has been said and written upon the subject, so that I will only touch upon some of the principal questions at issue.

The first of importance is that of durability, and although the life of a hard wood constantly exposed to attrition is amazing, as may be seen on the stairs of the Metropolitan Railway Stations, and in many cog wheels of old machinery, still some diversity of opinion exists as to what may be fairly put down as the wear per annum of the surface of a street paved with wood blocks.

It must be remembered that to arrive at any fixed ratio of wear, a standard of traffic should be fixed; but this unfortunately has not hitherto been done, so that the results of observations are bound to differ considerably. It must also not be lost sight of that the reason of excessive wear in a wood pavement generally arises from wide joints being the means of causing the edges of the blocks to abrade and become worn.

Mr. D. T. Hope, in a paper he laid before the Scottish Society of Arts, upon some most careful investigations he had made on this subject, gives the wear as ¹/8 of an inch in 18 months on blocks laid with vertical fibre, which he proved was the best manner of laying them to ensure the longest life.

Mr. Deacon estimated the wear at from 1³/8 inch to 25/16 inches per annum.[76]

Mr. Copland estimated the wear at ³/16 of an inch per annum.[77]

Mr. Howorth estimates the life of wood paving at 25 years per inch of wood, if an absolutely uniform quality of wood fibre could be assumed.[78]

Mr. Haywood says,[79] “Wood pavements with repairs have in this City (London) had a life varying from 6 to 19 years, and that with repairs, an average life of about 10 years may be obtained.”

The life of wood is no doubt extended by being preserved by one of the processes I have enumerated, but as its life may be taken as an average of 8 to 10 years, and as the blocks are bound to wear unevenly, they should be made as shallow as is consistent with stability; as it is an undisputed fact that the foundation of a roadway is the important carrier of the traffic, the surface material, of whatever it may be constructed, only acting as a skin to preserve it. If the blocks are too thick, unnecessary capital is locked up.

Wood pavement was laid in Sunderland[80] in 1859 with strips of creosoted red pine, creosoted beech wood, and unpreserved oak, the bulk of the paving being unpreserved red deal, and this was replaced in 1867.

In 1877, on renewing the pavement, it was found that the creosoted wood suffered less from wear and tear than the unpreserved, so the whole was done with creosoted red pine, the original strip of creosoted red pine was left untouched, the strip of oak was turned, and the beech was merely raised; and there is no doubt that the best wood pavement is that which can be constructed in the simplest manner, as for instance deal blocks 4 or 5 inches deep, laid with a close joint upon a Portland cement concrete bed, the blocks being well grouted in with Portland cement grouting, their surface being afterwards sprinkled or strewn with sand or sharp gravel.

The woods employed for paving are beech and oak, both of which are said to be too slippery, elm, which is not durable, pitch pine and Baltic fir. Memel and Dantzic timber is better than Riga, the best wood for the purpose being said to be Wyborg or St. Petersburgh red deals.

All sappy wood must be at once rejected as unsuitable. This is a great objection to creosoting or other preserving processes, as it hides defects in the wood.

The advantages of wood paving may be summed up as follows:—

(1.) It is the quietest of all known pavements, wheels make scarcely any noise upon it and there is no clatter of horses’ hoofs.

(2.) It is much safer than either asphalte or granite pavements for horses travelling upon it and if a horse falls he can rise more easily.

(3.) The traction necessary upon it, though slightly greater than upon asphalte, is compensated for by the better foothold given to horses.

(4.) It is clean. If well constructed there should be no mud made upon it; all that appears upon its surface should arise either from its being imported upon it, or from the gravel with which it is sometimes necessary to dress the surface.

(5.) It presents a uniform and slight elasticity, which is of great benefit to vehicles passing over it.

(6.) It may be laid on a gradient of 1 in 20 with safety to the traffic.

The principal objections to wood as a paving are:—

(1.) It is said to absorb moisture and to smell offensively, but this has often been refuted.[81]

(2.) It is said to be difficult to cleanse without the aid of water, as dirt adheres to the wood, and lingers in the joints.

(3.) It is not easy to open it or repair it, for the purposes of gas and water pipes, etc., and rather a large surface has to be removed for this purpose, and it has to be left a little time after repairs before traffic is again allowed on it.

(4.) The wood swells if wet, and cases are on record of the side kerbs of streets being raised, and lamp posts thrown down, by the pressure of the wood thus swelling.[82]

With regard to the cost of wood paving. This must vary in different localities, according to the value of labour, of materials, and in the manner in which the work is done.

The practice of most of the companies engaged in this class of work is to make a fixed charge per square yard for the pavement, including the concrete but excluding the excavation, and they also guarantee to keep the pavement in repair free of charge for one or two years, and then for so many years after, at so much per yard per annum.

About 14s. per square yard is generally the first charge for constructing, and 1s. per square yard is the annual charge for maintenance.

Upon the subject of cost the following tables[83] may be useful.

Table showing the Actual Duration and Cost
of certain Wood Pavements in the City of London.

Situation.				Date when laid New.	Life.		First Cost per Square Yard.				Total Cost of Repairs per Square Yard during Life.				Average Cost per Square Yard per Annum.
					Yrs.	Mths.	£	s.	d.		£	s.	d.		£	s.	d.
Cornhill	-			May, 1855	10	2	0	12	2		0	17	4	¹/2	0	2	11
				July, 1865	6	8	0	11	6		0	8	9	³/4	0	3	0	¹/2
Gracechurch Street	-			Nov. 1853	11	7	0	12	8		0	17	1	¹/2	0	2	6	³/4
				June, 1865	6	0	0	11	6		0	6	11		0	3	0	³/4
Lombard Street	-			May, 1851	9	4	0	9	6		0	6	0		0	1	7	³/4
				Sept. 1860	10	7	0	9	2		1	0	2		0	2	9
Lothbury	-			May, 1854	12	3	0	12	6		1	8	4	³/4	0	3	4
				Aug. 1866	6	1	0	12	6		0	3	5	³/4	0	2	7	¹/2
Mincing Lane	-			July, 1841	19	1	0	14	4		0	13	4		0	1	5	¹/4
				Aug. 1860	13	0	0	9	2		1	2	6	³/4	0	2	5	¹/4
Bartholomew Lane	-			May, 1854	12	3	0	12	6		0	17	5	³/4	0	2	5	¹/4
				Aug. 1866	5	5	0	12	6		0	3	11	¹/4	0	3	0	¹/4
Foundations are included, but no excavation.

Table showing First Cost, and Tendered Cost per Annum
for Maintaining Certain Wood Carriageway Pavements in the City of London.

Situation.	Date when Laid.	Name of Contractor.	Years to be main- tained by Con- tractor.	First Cost per Square Yard.			Agreed Cost of maintenance per Square Yard for the Contract Term.	Total Cost of Pavements during Contract Term, per Square Yard.			Average Cost per Square Yard per Annum.
				£	s.	d.		£	s.	d.	£	s.	d.
King William Street	Feb. 1873	Improved Wood Paving Co.	16	0	18	0	1 year free	2	0	6	0	2	6	¹/4
							15 years at 1s. 6d. = 1l. 2s. 6d.
Ludgate Hill	Nov. 1873	Ditto	16	0	18	0	1 year free	2	0	6	0	2	6	¹/4
							15 years at 1s. 6d. = 1l. 2s. 6d.
Portions of Great Tower Street and Seething Lane	Sept. 1873	Ditto	16	0	16	0	1 year free	1	14	9	0	2	2
							15 years at 1s. 3d. = 18s. 9d.
Bartholomew Lane	Jan. 1872	Carey	No agree- ment	0	12	6	——	——			——
Ditto	Dec. 1871	Improved Wood Paving Co.	3	0	16	0	3 years free	0	16	0	——
Duke Street	May, 1873	Mowlem and Co.	[84]5	0	15	0	2 years free	These pavements will no doubt last some years longer than the contract term of maintenance.
							3 years at 1s. = 3s.
Houndsditch	Not yet laid	Ditto	[84]7	0	17	0	2 years free
							5 years at 9d. = 3s. 9d.
Ditto	Ditto	Carey	[84]7	0	13	6	2 years free
							5 years at 1s. = 5s.
In the wood pavements the cost of the foundation is included, but no excavation.
The pavements at the end of each financial year are to be in a good sound condition.

The following table[85] is also given as showing the comparative cost of wood paving with macadam and bituminous concrete paving in Liverpool.

Description of Pavement.	Original Cost per Square Yard at present prices.			Deductions from First Cost to determine Cost of Renewal.					Interest on Original Cost at 4¹/2 per cent. per Square Yard per Annum.		Sinking Fund in- vested at 3 per cent. Com- pound Interest.		Mainte- nance per Square Yard per Annum.			Scav- enging per Square Yard per Annum.		Gravel- ling per Square Yard per Annum.		Total Annual Cost per Square Yard.
				Cost of Foun- dation not requiring renewal.			Allowances for old Materials at date of renewal.
	s.	d.		s.	d.		s.	d.	d.		d.		s.	d.		d.		d.		s.	d.
No. 6.
Bituminous Concrete Pavement	3	9		Nil			Nil		2	·0	Nil		0	9		2	·4	..		1	1	·4
No. 7.
Wood Pavement	15	1	·5	2	0		Nil		7	·5	4	·3	0	1	·0	2	·7	5	·0	1	8	·5
No. 8.
Macadam Pavement	6	9		Nil			Nil		3	·4	Nil		1	0		8	·0	Nil		1	11	·4

In concluding this chapter upon wood paving, I will give a specimen specification for work of this description.

Excavation.

—Excavate the ground to a depth of — inches below the level of the proposed finished surface of the roadway.[86] The formation surface thus excavated must be well watered and rolled or punned if found necessary, and any soft or made earth removed to such a depth as may be found to be sufficient.[87]

Foundation.

—Upon the excavated formation surface a bed — inches thick of concrete is to be laid, composed of one part of good approved Portland cement to two of fine, sharp river sand, and three of clean river ballast or broken stone. The concrete to be finished off with an even and smooth top surface conforming with the contour line of proposed finished roadway.

Wood Blocks.

—Upon the concrete thus laid, and after it has sufficiently set, wood blocks are to be laid.[88] These blocks must be of the best description of Baltic red timber[89] (or such other timber as shall be specified), sound and thoroughly well seasoned, free from all sap, shakes, large and loose knots or other defects, and any that may be rejected by the surveyor as unfitted for the work shall be at once removed from the works or broken up. The blocks must not be less than 6 inches or more than 12 inches in length by 3 inches in width and 6 inches in depth, they are to be carefully laid with the fibre of the wood placed vertically, their ends must butt with close joints to each other, and each course must be kept ³/8 of an inch apart by means of wooden laths, which are afterwards removed.

Joints.

—The joints are then to be carefully run with a grouting composed of one part of best approved Portland cement to two parts of fine, sharp, clean river sand. (In some cases a hot bituminous mixture or asphalte is run between the joints as a grouting.)

Top Dressing.

—The whole surface of the pavement is then to be spread with a coating, at least ¹/2-inch in thickness, of fine sharp gravel or chippings.

The following heads of general conditions under such a contract may also be useful.

Alteration of gullies, sewer man-holes etc., will be done at the expense of the sanitary authority.

Contractor must make good at once any damage caused to gas or water mains or services—time penalty for delay.

Maintenance of work after completion for a specified time.

Power must be reserved to surveyor to suspend work during bad weather or from other causes.

Heavy time penalties for non-completion of contract by a certain date.

Payments to be made to contractor on surveyor’s certificate, up to 80 per cent. of whole contract, remaining 20 per cent. to be paid at end of (say) 2 years after completion.

With the above specimen specification I conclude the chapter on Wood Paving.

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