Q: What is the highest R-value I can expect in the walls of a building, if I build the walls of concrete block?

A: R-values as high as 17 can be achieved using a lightweight 12x8x16 Hi-R insulated block wall with foil backed gypsum board on furring strips on the inside surface of the wall. If the wall is exposed block on both sides, an R-value of approximately 13.7 is attainable with a lightweight 12x8x16 Hi-R block wall.

Q: What is the difference between normal weight, medium weight and lightweight block?

A: Normal weight is the industry vernacular for what the mason refers to as a “heavyweight” block. Normal weight refers to a block made of concrete that has a density of 125 lbs per cubic foot or greater.

A lightweight block is made of concrete that has a density of less than 105 lbs. per cubic foot. In between lightweight and normal weight block is the classification of “medium weight”. The concrete used in manufacturing medium weight block has a density from 105 lbs up to 125 lbs per cubic foot.

Q: What can I do to increase the fire resistance of a masonry wall?

A: Fire resistance can be increased by filling the empty cores. Materials that may be used include; grout, perlite, sand or other non-combustible materials.