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Hi folks,
Apologies for yet another variation on the question "Can I cut this joist to fit a loft hatch?", but I've not been able to find any examples similar to our situation.
The kitchen in our 30s semi is in part of a single-story side extension that replaced a lean-to garage, and its loft inspection hatch is a rather narrow (i.e. between adjacent 400mm centred joists) of 650mm x 360mm, which I'd like to extend - if not too big a job.
The roof over this loft is finished in plain clay tiles, pitched at about 37º, and extends 4m from a gable-end abutment at the original outside wall of the house, to a hipped far end. Its ridge is about 1.75m long, supported by six simple triangular trusses at ≤400mm centres, each formed from a pair of 6x2 common rafters tied with a 7x2 ceiling joist, with a 4.25m clear span. There are no other timbers, such as collars or purlins, and unfortunately, whilst the wood appears to have been treated, no ends are visible and no other obvious markings signify whether C24 or C16 has been used.
The photo below shows (most of!) one side of the loft roof - the house side-wall just visible on the right, alongside the six common rafters involved with the trusses mentioned above. The current inspection hatch lies between the 2nd and 3rd joists from the right - to the right of the highlighted rafter, which is the one that would need to be cut to allow a larger loft hatch.
Perhaps the roof has been over-engineered and the five remaining trusses would more than cope with the loads involved. On the other hand, it may be just enough as-is and shouldn't be messed with, and we'll have to live with the small access panel.
If something could be done, the small access panel and limited loft headroom mean that, whilst trimming a hatch outer frame would be fairly straightforward, it wouldn't be feasible to add sister joists - at least not without opening up the roof at the eaves to pass in timber. It may be possible to brace a hatch frame with some steel angle to effectively keep the two parts of the cut joist connected, but I'm out of my depth here.
I'd welcome any insights - is this an everyday situation with a proven work-around, a job for a structural engineer or do I save my money and live with things as-is?
Apologies for yet another variation on the question "Can I cut this joist to fit a loft hatch?", but I've not been able to find any examples similar to our situation.
The kitchen in our 30s semi is in part of a single-story side extension that replaced a lean-to garage, and its loft inspection hatch is a rather narrow (i.e. between adjacent 400mm centred joists) of 650mm x 360mm, which I'd like to extend - if not too big a job.
The roof over this loft is finished in plain clay tiles, pitched at about 37º, and extends 4m from a gable-end abutment at the original outside wall of the house, to a hipped far end. Its ridge is about 1.75m long, supported by six simple triangular trusses at ≤400mm centres, each formed from a pair of 6x2 common rafters tied with a 7x2 ceiling joist, with a 4.25m clear span. There are no other timbers, such as collars or purlins, and unfortunately, whilst the wood appears to have been treated, no ends are visible and no other obvious markings signify whether C24 or C16 has been used.
The photo below shows (most of!) one side of the loft roof - the house side-wall just visible on the right, alongside the six common rafters involved with the trusses mentioned above. The current inspection hatch lies between the 2nd and 3rd joists from the right - to the right of the highlighted rafter, which is the one that would need to be cut to allow a larger loft hatch.
Perhaps the roof has been over-engineered and the five remaining trusses would more than cope with the loads involved. On the other hand, it may be just enough as-is and shouldn't be messed with, and we'll have to live with the small access panel.
If something could be done, the small access panel and limited loft headroom mean that, whilst trimming a hatch outer frame would be fairly straightforward, it wouldn't be feasible to add sister joists - at least not without opening up the roof at the eaves to pass in timber. It may be possible to brace a hatch frame with some steel angle to effectively keep the two parts of the cut joist connected, but I'm out of my depth here.
I'd welcome any insights - is this an everyday situation with a proven work-around, a job for a structural engineer or do I save my money and live with things as-is?
