Collapsing roof trusses
by Rene Pollak
I have a tiled roof over the small building circa 4 meters square, that houses my oil tanks. The roof is conventionally pitched with a dozen wooden trusses forming the skeleton of the roof structure. The problem is that one concrete block wall is no the move. Its now about three degrees off the vertical, at the top now leaving a five cm gap between it and the adjacent wall to which its supposed to be abutted. Not surprisingly the roof trusses are drifting apart too. I am trying to find a way of coupling the opposite pairs through a screw and strapping mechanism that will allow me to pull their bases back towards each other, sufficient for me to rebuild the wall and have them sit on it. As it stands, a rebuild would leave the timber ring beam to which the feet of the trusses are nailed, hanging over the edge of the new wall. Does such a tensioning mechanism exist, if so where does one get them and more importantly are they expensive - this is after all only a shed to keep the oil tanks in.
Any help would be appreciated.
Sorry for the delayed response to your question.
A photo would help a great deal in trying to figure a solution because this type of situation does not affect everyone in a regular basis to demand products that directly address it. You mentioned the wood roof structure pulls away from concrete block wall. I think that’s the point to start.
You can try threaded rod with epoxy. At the wood plates adjacent to the 5 cm gap Drill 2 or 3 holes about 15cm (6 inches) apart through the wood into
the concrete wall. Make sure you have 6 or 7 cm (3 or 4 inches) into the concrete block. Next blow out any dust from the holes and pump the epoxy into the holes in at the concrete block. Next stick the threaded rods into the epoxy through the holes in the wood and let it dry for a day or two.
Threaded rod is a steel rod with threads, use 1 cm or 1.5 cm (3/8” or ?” inches) diameter and should be cut to about 20 cm (8 inches) long. This job requires special drill and bit that can drill thru concrete, diameter of drill bit should be slightly bigger the threaded rod.
After the epoxy is dried insert washers and nuts into the all thread rod and tighten them. If done correctly this should bring the two structures together nicely. You can make judgment if you need more than the 3 mentioned. The threaded rod will be left in place permanently which will guarantee that the two structures will remain together which should had done at the beginning at construction stage.
This may not work if the concrete block wall is hollow meaning it was not grouted solid when the wall was constructed.
If the wood structure is as small as described, the 3 or so concrete cell wall should be enough to get the job done but you probably need 6 or more threaded rods.
As far as cost, you might be able to rent equipment from rental stores or home improvement stores. The epoxy here in the US is about $40 for a tube and extra $20 for the all thread rod. Rental is probably another $40 a day.
Hope this helps