Hi group,
Advice / experience / "I've done that and this worked" suggestions much appreciated!
I want to board my loft for storage, and insulate under (not between) the rafters so that things don't get too cold or got up there.
Currently it has a few boards thrown down (old wardrobe fronts!), with
5cm vintage glass-fibre insulation between the rafters, and 20cm 2006 glass fibre insulation on top of, and across, that.I'm concerned about loads, and ventilation after insulation. Here's the details...
=== description ===
1973 terrace house. Loft.Ridge parallel with front of house (i.e. running left/right full length of house). No hip in roof.
Party wall to right, old external wall to left.
=== current woodwork ===
- joists running front to back (sitting on inner cavity walls) are 11cm x 5cm. spacing (centres) = 41cm. Span = 714cm, covered by two 397cm long joists overlapped by 80cm and nailed together.
- Then there are three cross-beams 10cm x 5cm, running left to right sitting immediately above these joists, nailed to each and every one of them. Span = 572cm plus ends sitting in party + old external wall.
- collar ties running front/back (15cm x 5cm)
4.
2 very chunky beams running left/right (30cm x 5cm) supporting rafters mid-way up5.
1 flimsey wind-brace6.
7.5cm x 5cm rafters (41cm spacing).7.
15cm x 2cm ridge=== "problems" ===
== 1. support
The joists aren't supported from below (apart from the cavity walls at each end, 714cm apart!). All first floor walls are stud partitions and don't offer any support. The joists aren't that beefy.
So I worry that boards + lots of things stored on top will be too much for the existing joists.
It looks like the 3 cross-beams are supposed to be helping the 11x5cm joists to stay up, though some of the nails joining cross-beams to joists have simply split the wood.
Would screwing these existing joints, and adding another couple of similar cross-beams (have to be formed of two bits of timber overlapped and joined in the middle, since there's no way to get 5m of wood into the loft!), help matters?
If I do this, shall I run floor boards on the joists, or the cross beams, or add extra wood over, or in parallel to, the joists but attached to the cross beams, to carry the floor boards?
== 2. ventilation.
50cm Celotex under the rafters looks like the way to go. It seems there's a little ventilation at the eaves, but absolutely no ventilation at the ridge. How can I rectify this (cheaply, simply)? As long as I have good ventilation at eaves + ridge, leaving a well- ventilated "cold roof" above the celotex, I should be OK? Or should I have some ventilation directly into the warm loft space too?Any advice greatly appreciated. While this space is "just" for storage, we don't have a garage, so it's the likely place that all kinds of things will end up - tools, toys+books+clothes (when one kids outgrows them and the other isn't ready for them yet) etc etc so it needs to be strong, dry, not too cold/warm, and fairly easily and comfortably accessible (so I have a decent loft ladder in mind, and all glass-fibre insulation will be banished, except below whatever floorboards I fit).
TIA.
Cheers, David.