I know this question has been asked before, but none of the answers seem definitive.
I want to insulate my loft and still be able to use it for storage.
The current joists are 100mm high X 50mm and I want to increase their height so as to fit in 270mm of insulation and board on top of it.
I am thinking of fitting these 175mm X 50mm wooden planks (http://www.diy.com/diy/jsp/bq/nav/nav.jsp?action=detail&fh_secondid=9276000) at 90 degrees to existing joists.
Fixing these with angle brackets at regular intervals (http://www.screwfix.com/prods/61576...Angle-Bracket-Heavy-Duty-50-x-50mm-Pack-of-10).
Then I am going to put 1 layer of 100mm insulation between existing joists, and another 170mm on the raised joists, leaving about 5mm gap for ventilation/wiring.
On top of all this, I will be fitting standard chipboard (http://www.diy.com/diy/jsp/bq/nav/nav.jsp?action=detail&fh_secondid=9276437) with screws.
The span of the roof is 4.8m (W) X 9.5m (L) and the joist run lengthwise, i.e. 8 joists at ~60cm gaps covering the 4.8m width.
I will try and attach pictures of the roof truss and joists for clarity.
My questions are
- is the recommendation to raise the joist at 90 degrees or along existing joists?
- does raising the height by 175mm seem excessive considering I am going to board on top? can I get away with raising by 100mm only?
I want to insulate my loft and still be able to use it for storage.
The current joists are 100mm high X 50mm and I want to increase their height so as to fit in 270mm of insulation and board on top of it.
I am thinking of fitting these 175mm X 50mm wooden planks (http://www.diy.com/diy/jsp/bq/nav/nav.jsp?action=detail&fh_secondid=9276000) at 90 degrees to existing joists.
Fixing these with angle brackets at regular intervals (http://www.screwfix.com/prods/61576...Angle-Bracket-Heavy-Duty-50-x-50mm-Pack-of-10).
Then I am going to put 1 layer of 100mm insulation between existing joists, and another 170mm on the raised joists, leaving about 5mm gap for ventilation/wiring.
On top of all this, I will be fitting standard chipboard (http://www.diy.com/diy/jsp/bq/nav/nav.jsp?action=detail&fh_secondid=9276437) with screws.
The span of the roof is 4.8m (W) X 9.5m (L) and the joist run lengthwise, i.e. 8 joists at ~60cm gaps covering the 4.8m width.
I will try and attach pictures of the roof truss and joists for clarity.
My questions are
- is the recommendation to raise the joist at 90 degrees or along existing joists?
- does raising the height by 175mm seem excessive considering I am going to board on top? can I get away with raising by 100mm only?