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Technical Note (National Research Council of Canada. Division of Building Research), 1963-03-01
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Inside Conditions in House Under Construction in Halifax
Tibbetts, D. C.; Robson, D. R.
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DIVISION OF BUILDING RESEARCH
NATIONAL RESEARCH COUNCIL OF CANADA
'fE
C
1HIN ][ CAlL
NOTlE
No.
390 PREPARED BY D.C. Tibbetts and D.R. Robson CHECKED BY A PPROVED By NBH March 1963 PREPARED FOR SUBJECT General DistributionINSIDE CONDITIONS IN HOUSE UNDER CONSTRUCTION IN HALIFAX
On 23 January 1962, at the request of a local architect, a house under construction on the east shore of the North West Arm in Halifax was visited. The primary purpose of this visit was to measure the moisture content in a 2- by 4-in. mill deck floor in which expansion had occurred. The builder estimated the total
over-all expansion in the 16-ft wide floor to be 3/4 in. The architect was concerned about what effect shrinkage of the wood in returning to its original moisture content (M.C.) (thought to be about 10 per cent) would have on partitioning materials fastened to it. Of particular interest was the M.O. of the wood following the plastering stage when door jambs and other interior trim would be installed.
The architect attributed some of the moisture expansion to concrete slab placing operations on the level below this floor. Before another slab was placed immediately below the mill deck floor, he had had the underside of the floor system covered with a polyethylene sheet. At the time of the authors' visit this second slab was being placed. It was also thought that the equilibrium moisture content of the wood would be increased over the original M.C. because of the humidity condition of the outside air. Some
temporary heat from wood-burning stoves was being supplied at the time of the authors' initial visit when the following readings were taken.
2
-Wood Moisture Contents Living room area framing
Kitchen area framing Upstairs ceiling joists
Top surface 3/4-in. subfloor (a) edge (b) centre - 14 - 16 - 17 - 19 - 25 - 22 - 28 - 24
Top side mill deck (a) edge - 19 - 21 (b) centre - 16 - 18 Uhderside 3/4-in. subfloor - 16
Uhderside mill deck (through
polyethylene) - 14
Psychrometer readings were taken the first day in the upper level bedroom area (mill deck floor) where it was thought that future hygrothermograph records would be taken.
Time Dry Bulb Relative Humidity Absolute Humidity
11.00 a.m. 52°F 75% 42.6 gr/lb
3030 p.m. 48°F 68% 32.4 gr/lb
The outside weather records for that day show:
8.00 a.m. 42°F 95% 35.0 gr/lb
2.00 p.m. 36°F 66% 20.0 gr/lb
Because of normal construction activity and the lack of overnight security, it was decided to take daily psychrometer readings for a period and to install a hygrothermograph following completion of the plastering stage. Daily observations were
•
e
e
INSIDE (1) OUTSIDE
2.00 p.m. Date Time M.O. % R.R. % Temp of Abs. H. gr/lb
R.R.
%
Temp of24 Jan. 10.00 a.m. 60 46 26.5) ) 42 21 24 3.30 p.m. 54 61 42.6) 25 11.00 a.m. 62 58 44.3 (2) 86 42 . 26 1.00 p.m. 14 - 16 55 55 35.1 45 26 29 2.00 p.m. 12 50 43 20.1 55 11 30 2.30 p.m. 58 45 25.4 92 23 31 2.00 p.m. 12 - 13 50 52 28.7 59 12 1 Feb. 2.00 p.m. 63 43 25.4 72 11 \>l 2 2.00 p.m. 12 56 43 24.2 63 8 5 2.00 p.m. 53 54 32.4 92 35 6 2.00 p.m. 64 62 53.6 100 45 8 1.00 p.m. 50 50 26.5 59 20 9 3.00
p.m.
56 59 42.6 100 33 13 2.00 p.m. 42 68 44.3 (3) 69 29 16 4.00 p.m. 31 64 27.6 51 29 19 3.00 p.m. 8 34 64 29.9 55 23 23 11.00 a.m. 44 60 33.7 81 33 27 2.00 p.m. 64 62 49.7 57 30 2 Mar. 2.00 p.m. 70 56 46.0 57 14 (1) Outside records obtained ｾｲｯｭ the local meteorological ｯｾｾｩ｣･Ｎ(2) Psychrometer reading at 11.00 a.m.
4
-*
E.M.C.=
equilibrium moisture content.No detailed attempt was made to relate R.Ho, dry bulb
*
temperature, and depression of wet bulb temperature to the E.M.C. of the wood (Eastern Spruce). An approximation of the E.M.Co was made using this data which indicates that the E.M.Co decreased over the 4-week instrumentation period; when the instrument was removed, it was apprOXimately 10 per cent.The conditions noted are thought to be typical of those existing in houses constructed during the winter months in the Halifax area. Nevertheless, limited value must be attached to the findings as only one house was involved and the data recorded was for only one winter.
35.5 41.5 40.0 43.0 15 14 13 15 Temp Abs. Ho of gr!lb (GM) House No.2 28 33 33 32 R.H.
_%-33.0 39.5 3905 39.5 10 11 11 11 Temp Abs. H. of gr/lb (DCT) House No.1 R.H.-L
30 35 35 35 31.5 35.5 39.0 31.1 55 55 58 59 Temp Abs. H. of gr/lb R.H._%
58 55 52 49 3 4 1 2 Week no.House Under Construction
The covering of the mill deck floor with plywood before the plastering was done made the M.C. readings taken immediately before and after the plastering operation impracticable. The plastering began on 26 February and is reflected in the readings taken on 21 February as shown in the preceding table.
Application of the finishing plaster was completed on 13 March and a hygrothermograph was installed in the upper level
(bedroom area) on 20 March. This instrument was removed after
4 weeks' operation due to activity associated with inside finishing work. Results from the records obtained were averaged on a weekly basis and are compared below with those from two plastered houses that have been occupied for 2 years. The occupied houses are referred to as House No. 1 and House No.2.
All measurements were obtained after the house had been enclosed and the exterior cladding applied. The initial M.O. of the lumber used is not known with the exception of the 2 by 4 in. used in the mill deck which was selected at a M.O. of 10 per cent.
The findings do suggest, however, that designers should consider the initial wood M.O. and the expected E.M.C. for parti-cular climatic conditions where large quantities of wood are
involved in structural systems. Considerable expansion and shrinkage can occur and design provision should be made to
accommodate resulting movements especially when the edge may be restrained. Laminated 2- by 4-in. decks are frequently used in roof construction and movements of the size -noted in this study could have a damaging effect on roofing materials applied over them.
The Division of Building Research welcomes inquiries of this nature and is especially interested in conducting field studies, whenever possible, and in the instrumentation of bUildings with a view to adding to eXisting knowledge and assisting with the development of new and improved techniques.
