In a colar beam roof A. There is no horizontal tie beam B. There is a horizontal tie at the feet of rafters only C. There is a horizontal tie at almost the middle of rafters only D. There are two horizontal ties, one at the feet and other at the middle of the rafters

The correct answer is: D. There are two horizontal ties, one at the feet and other at the middle of the rafters.

A collar beam is a horizontal beam that connects the top of two rafters. It is used to support the rafters and prevent them from spreading apart. In a collar beam roof, there are two collar beams, one at the feet of the rafters and one at the middle of the rafters. The collar beam at the feet of the rafters helps to support the weight of the roof, while the collar beam at the middle of the rafters helps to prevent the rafters from sagging.

Option A is incorrect because there are two horizontal ties in a collar beam roof. Option B is incorrect because there is a horizontal tie at the middle of the rafters as well as at the feet of the rafters. Option C is incorrect because there is a horizontal tie at the feet of the rafters and at the middle of the rafters.