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Nail Popping in Two Housing Projects in Toronto, 1965

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Publisher’s version / Version de l'éditeur:

Technical Note (National Research Council of Canada. Division of Building Research), 1965-06-01

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Nail Popping in Two Housing Projects in Toronto, 1965

Platts, R. E.

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NATIONAL RESEARCH COUNCIL OF CANADA

divisioセ OF BUILDING RESEARCH

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II

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NOTIE

No.

442

RESTRICTED CIRCULATION

PREPARED BY R. E. Platts

CHECKED BY A.T.H. APPROVED BY N.B.H.

June 1965

PREPARED FOR Mr. J. A. Graham, Domtar Construction

Materials Limited

SUBJECT Nail Popping in Two Housing Projects in Toronto, 1965

The Rubin Corporation in Toronto has experienced unusually severe "J;lail-popping" in the drywall interior in recent row-housing projects. The developer and the builders had not satisfied themselves as to the cause, except that their general change to electric heating coincided with their worst "attacks" of nail popping damage. Ontario Hydro personnel in the 'area pointed out that similar scattered houses with electric heating have not suffered abnormal popping, but they had no previous history with such project developments. They asked the advice of Mr. J. A. Graham, chief engineer, gypsum products, Domtar Construction Materials Ltd. He in turn asked DBR/NRC to discuss the question. On a visit to Toronto on 1 June 1965, the author of this Note met with those concerned and inspected one row':'housing project where nail popping had occurred.

Mr. Trenholm and

Mr.

Christie of Central Hydro and North York Hydro were able to show the author where the most troublesome nail popping had occurred and provided pertinent

background information. Mr. Alexander, the construction inspector of the Rubin Corporation, was very helpful with his knowledge of construction aspects and times for the several relevant projects. Construction histories are always a bit

nebulous but a pattern began to emerge. No relationship between the nail popping and the type or stages of heating or insulation -was apparent.

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-The significant details are as follows. All projects involved are row housing of solid masonry construction. with party walls and exterior walls strapped with 2 x 2's. Internal partitions and c.eilings are of normal wood-frame construction. The exterior wall strapping space is filled with mineral wool insulation. The units visited, in Yorkwood Village Phase I and Phase II. showed normal drywall workmanship, except perhaps in the taping and filling aspects which are not relevant here. Excessive "waviness" of studs or joists. was not evident from the appearance of the surface. Nails had not broken the paper surface. The double nailing practice was used. The popping pattern was random over all walls, ceilings and partitions, and the same was reported in the other projects where nail poppinghad occurred. In sum, workmanship does not appear to be a prime factor. nor does insulation springiness, strapping methods etc.

Yorkwood Village Phase I: Started in spring 1963. with progressive completions through all seasons to early spring 1964. Where units were drywalled in winter, propane "salamander" heatmg was used for short, indeterminate periods before drywalling, then full heating on (electric, baseboard). Annular ring nails. double-nailed, were used on all walls and ceiling. Nearly all units showed

severe nail popping soon after occupancy, and squeaking floors - a related problem. No correlation with construction season was evident, and this alone suggests that the type of heating or rate of heating or drying was not a factor. (In this regard, summer drying of spring completions is quite ァャGセ、オ。ャL yet no reductions in popping were noted. Further, the rate of drying and final "dryness" with electric heating is inherently less than with combustion heating. due to the greater air change with the latter. )

Although most of the nail popping had been repaired in these occupied units before this visit, a few were awaiting repairs or needed further repairs. Inspections of these showed extensive popping, and potential popping everywhere: the board was no longer tight against the studs or strapping. Some "pops" were slight, others protruded up to 1/8 in. (Variations are expected due to the different shrinkage in radial vs tangential-grained studs.) Such nails were not loose. Pops of 1/8 in., occurring in such a short time (ruling out any question of cumulative popping due to seasonal cycling) can be explained on the basis of wood shrinkage from the green, saturated-fiber state to a normal winter dry state. It was stated that one lumber supplier served Phase I, with deliveries timed as needed.

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Village Phase II: Completed in December 1964. Same construction details as in Phase I except drywall screws used in ceilings. Substantial popping occurred in walls and partitions, but little in ceilings. Cracking is common and often severe (up to 1/2 in.) at junction of walls and ceiling. This was not common in Phase I, and the builder attributed it to the use of screws close to this joint. The cracks and pops seen here again point to wood shrinkage from the relatively green state.

Braeburn Woods Phase I (not visited). Essentially similar and contemporaneous with Yorkwood Phase I, except that gas-hot water heating is used. Mr. Alexander stated that nail popping problems and repairs have been extensive, but he did not think they were generally as severe as in Yorkwood.

Braeburn Woods Phase III (not visited). Here the builders exercised unusual caution to avoid the popping problems which have hurt them quite seriously. It was stated that they shopped for dry lumber, turned the heat on in early February (electric) and delayed drywalling until late February. Using three different electrical moisture meters, they measured the moisture content of the wood before drywalling,at

12 to 14 per cent. (The shrinkage of such wood to the normal winter dry condition in a heated building would be only one-third that of green lumber.) Screws were used throughout. Following rough drywalling, there was a waiting period for further checking before taping and filling, and again before painting. Normal electric heating continued from

February through this spring. No significant nail popping has been reported.

Again, the only factor that could be suggested by the author as causing unusual nail popping would be the suspected use of green lumber in all but Braeburn Woods Phas.e III, with Yorkwood Phase I being particularly suspect. No relationship between nail popping and the type of heating is apparent.

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