Cracks Around Ceiling Edges After Boarding Loft .

[DaveSimmo]

Last August I boarded out the loft in my 1930s bungalow. An area of 6m x 3m or so. The original ceiling joists are 4x2 at around 14” centres (ish) and I crossed them with some 3 x 2 equivalent CLS timbers at 600mm centres. Every intersection was packed so as not to pull on the existing joists and then they were screwed at every intersection. Then I installed Kingspan equivalent in between the gaps and left a 20mm gap between the ‘Kingspan’ and the boards for airflow. The boards were 18mm moisture resistant boards which were all screwed with staggered joints.
As the cold weather arrived, I noticed that there were cracks between the ceiling and the walls in the two bedrooms. No cracks in the inner ceiling areas, just around the edges. I’m wondering if this could be a temperature issue as the loft has vents which allow cold air in and make the loft very cold but now that I’ve insulated it, there’s a big temp difference between the 2 sides of the ceiling.

There’s a solid brick supporting wall from one end to the other where you see the original joists overlapping just right of centre in the pic below.

Happy to just leave it for now in case it’s just movement from the new timbers or something and then just fill the cracks.

 

[freddiemercurystwin]

Whilst these timbers are commonly called ceiling joists they're not joists, a joist is a structural member and these are not structural. Anyway cracks have appeared probably because the 'joists' are undersized anyway and you've added some weight and presumably are storing some stuff up there adding further to the weight. Don't go storing any dead bodies up there, and stick to lightweight stuff - Xmas decs, empty suitcases and you'll probably be OK, just monitor things, I bet the ceilings have bowed a little in the centre of the rooms. Don't know why you bothered with a gap anyway that's a red herring here.

 

[big-all]

the place to put the heavy stuff [but still light ]is from the plug socket to the right hand side for 800mm and in a line 400mm either side off the wall underneath

 

[freddiemercurystwin]

I'd be placing the stuff on top of the existing walls, despite them not being 'load-bearing' they will inevitably taking some loading.

 

[cdbe]

I've read this so many times on here. KEEP THE NEW FLOOR AWAY FROM THE OLD CEILING. Fill the gap with some nice insulation