Correspondence.

Progress, Volume VI, Issue 5, 1 March 1911, Page 589

Correspondence.

Rough Cast. (To the Editor.) Christchurch, Feb. 18, 1911. —Being somewhat, exercised in mind regarding the merits mid demerits of rough casting, I am taking the liberty of seeking your advice, which I feel sure you will readily impart. .1. Half the people I have spoken to about the matter say that rough casting on wood lathes is quite satisfactory if done properly, and the other half—many of whom are practical men say: "Don't have it on any account." One technical paper f read condemns the use of metal, lathing, for the reason that in course of time is rusts through, with the result that pieces of plaster drop off. The same paper advocates metal, lathing made of "ingot, iron." and then coated with a. mineral paint, What is your opinion of this? 2. I have" just read a booklet dealing with "Keylock" interlocking steel lathing, and the inventor claims that 90 per cent, of the lathing

is embedded in the covering matter, and that if the remaining 10 per cent, should corrode, the stability of the wall will not be affected. That is a point on which I should like independent advice. A chain is no stronger than the weakest link, and if the 10 per cent, of uncovered lathing corrodes at the vital place, i.e., where it is fastened with nails to the studs—seems to me very probable— the whole thing would certainly be affected, and very seriously at that. Judging from the information I have collected, I have concluded that rough casting on brick work or concrete blocks is the ideal method, although considerably dearer than lathing. 3. Another point on which I seek information is regarding the best method of waterproofing. In a recent issue of your journal I read an article re "Hydrated Lime in Cement Work," which seemed to me to be a solution of the waterproofing question. Can "Hydrated Lime" be procured, or is it merely a process than can be adopted by the plasterer? 4. T. contemplate having a house erected with walls merely Sin. thick and 10 feet high, of concrete blocks rough cast on the outside. Reinforcing would be done by means of crimped wire running horizontally. Would that be strong enough or would you advise 4in. blocks for the outside walls? 0. I am not a builder, and in raising these questions I have no "axe to grind," but simply desire to find out the best method of building a satisfactory home. Thanking you in advance,— Yours faithfully, BUNGALOW. 1. Metal laths make a much stronger job than wood. Wood laths are durable only if the wood is a really good one, such as oak or jarrah. Painted metal laths are unreliable, as the paint often peels off before the piaster is applied. 2. It is essential that metal laths should be as completely embedded in the plaster as possible to prevent corrosion. Good metal laths must be of thick metal, say IS or 20 gauge, with a mesh say V-in. x l!/>in. A smaller mesh is not so good, because the plaster cannot be applied to

a large _ mesh without embedding the metal, while with a small mesh the plaster can be applied with only just enough key to hold it on and nearly all the metal can be seen from the back. • ■■■ 3. Waterproofing precautions of special nature are not necessary with rough cast on wood framing, as the construction is practically that of a hollow wall. Hydrated lime can be procured from Francis Holmes, Wellington. (See our advt.) . 4. A concrete block wall Sin. thick would not be satisfactory. If suitable shingle is available, blocks with sides 2%in. or 3in. thick, and with a cavity, say 4in. wide, would make a good job. The blocks would be like long boxes without top or bottom, and with sides and ends 2V»in. or Sin. thick, the whole wall being 9in. to lOin. rough. Where special strength was required, the cavities could be filled solid as the blocks were built up, and left hollow elsewhere. 5. Good rough cast is better than indifferent wood, and is more draught proof and waterproof. Good brick or concrete is the best, and lasts literally ten times as long. The cost of a cottage such as recently illustrated in our columns would be less than 10 per cent, dearer than wood. The cost of upkeep would soon reduce this, and in 20 or 30 years the wood building would be practically valueless. —Editor.