by Dwight Barnett
Scripps Howard News Service
Q: The coils in our central air unit inside are freezing up. We cleaned them. And the filter is clean. What can we do?
A: The unit could be low on refrigerant, the coil might still be dirty in areas you cannot reach, the fan may be unable to move enough air across the coil, the outside coils may be dirty, etc. You really need an HVAC professional to check the unit.
Q: I read your discussion about the "sagging roof." I have approximately the same pitch on a "stick built" HUD house. Can I remove the ceiling rafters by supporting the roof with a beam down the center of the roof (at the peak) under the two-by-four that joins the two sides of the roof?
The beam would be supported approximately every 15 to 20 feet along the span. The total roof length is 40 feet.
My other concern was lateral stress that I thought could be relieved with horizontal supports near (about 6 inches below) the peak of the roof from a rafter on one side of the peak across to the rafter on the other side of the peak. Is this feasible, and what other concerns are there?
A: As long as the ridge (the center board at the peak) is supported properly, you can remove the ceiling joists. The ceiling joists not only hold the ceiling covering, they also prevent the walls from spreading out due to the downward push of the roof rafters.
The ceiling joists act as collar ties. A collar tie can be moved up on the rafter to prevent spreading; however, the higher you move the collar tie the more strain is applied to the rafter at the mid-span.
When you get close to the ridge, then the collar-tie support becomes a gusset, a triangle-shaped support that is fastened to the top portion of each rafter. Gussets will not prevent the lateral movement by themselves, and the roof will need the ridge support.
The larger the gusset the lower the support beam will be because the bottom of the gusset will rest on the top of the beam.
(C. Dwight Barnett is a master inspector certified by the American Society of Home Inspectors. Questions may be addressed to him at P.O. Box 14091, Evansville, IN 47728, or e-mail dbarnett@evansville.net.)
