Cutting joist for loft hatch

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Hi,

I'm after some guidance on whether i'm on the right track with what i'm planning on doing to do in our loft.

The loft has been partially converted by the previous owners by reinforcing the floor by laying lengths of 3x2" at 90 degrees to the joists and then boarding, plastering and fitting a veluxs and heating. Unfortunately they also fitted a stupid fixed ladder into the loft. The ladder is not a substitute for stairs and takes up valuable space on the landing so we're removing it and fitting a drop down ladder.

Unfortunately, i can't use the existing hole because the drop down ladder would drop onto the landing banister. I have to move the hole one joist to one side (spaced at approx 400mm centres).

However, there appears to have been 2 different configurations of loft hatch in past already (1920's built house). The joists have been cut and noggined around the old loft hatch holes but that means that there is an uncut joist running right across the line i want to fit the new hatch in with a cut joist either side.

I've already removed the noggins from the old hatches and bolted new joists in place across the gaps with approx 500mm overlap at either end and bolted into the old joists with 2 x10mm coach bolts and approx 10 no.8 screws so i believe that i've effectively reinstated the original roof construction.

I now need to cut the original uncut joist and am wondering if i need to do any reinforcement until i can support the newly cut joist to the other two reinstated joists either side with noggins.

Luckily at one end of the loft hatch, next to where i will be cutting the original joist there is a 8x3" binder running the full width of the loft so i can fix the joist i'm going to cut to that with a truss clip to make sure it has support. At the other end of the same joist there is a lathe and plaster stud wall underneath with one of the verticals butting up to the joist so i can fix the joist to that, again giving extra support until i can get the noggins in place.

So, from what i've described, am i ok to cut that uncut joist?

Any comments or advice would be appreciated. I'm pretty confident that it'll be ok, but i'd appreciate some reassurance from people more experienced than myself!
 
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You really need to take some photos..

Ceiling joists hold up the ceiling but most also act as ties to stop the roof spreading outwards.. so cutting them up willy nilly do so at your own risk.. once a roof has spread the only repair is a new roof.
Can you draw a plan with the previous hatch, new hatch and joist layout..

Sounds like the previous owner made a poor attempt at partial converting the loft and none of it would comply with current regs.
 
The previous owners has indeed half converted the loft.

But we knew it was half converted and are happy for it to be that way. In fact we are turning it even more back into an attic by removing the fixed ladder and replacing it with a drop down ladder from a hatch.

From a roof spreading perspective the roof should be stronger than it was before i started work as i have rejoined the two cut joists. However, i would be cutting a new joist which will leave a series of repaired joist, cut joist, repaired joist.

I'll look at seeing if i can get a photo or a drawing uploaded.
 
Hmm.. right so the repair you have done to the existing cut joists is to place a new piece of timber in the gap (same sized member), then another piece of timber to one side of the joist with a 500mm overlap at each end.
Then a couple of coach bolts and staggered screws. Is that correct?
 
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Hmm.. right so the repair you have done to the existing cut joists is to place a new piece of timber in the gap (same sized member), then another piece of timber to one side of the joist with a 500mm overlap at each end.
Then a couple of coach bolts and staggered screws. Is that correct?

Exactly that. 2 x 10mm coach bolts and approx 10 no.8 screws joining the bridging piece to the cut beam into the 500mm overlap at each end of the cut beam. I haven't yet put the new piece of timber into the gap. That's tonight's job.

It is a traditional cut rafter roof by the way.
 
Good just making sure you didnt just tack a piece of timber to one side. :) it has been known to happen

When you say traditional cut roof, do you mean purlins down each side? or have you any diagonal struts/king posts (central posts) etc? If you do are any near this opening.. still photos would help :)
 
I have purlins running the length of the rafters.

There are no struts, the central area of the loft has been converted to a plastered room :)

There are hangers running from rafters to joists which look original but have been used to form the walls of the converted loft area.

Basically the roof hatch hole is directly under the ridge board, so in the centre of the rafters. There is no weight bearing downwards on the area that i've repaired/propose to cut. However, there is quite a bit of support due to a load bearing wall to one side, binder on another and a stud wall (formed by 2x3" verticals spaced at 400mm) on the third.

I'll take a photo tonight, but i'll only be able to show the hole from above and below, showing the repairs i've done etc but not showing the whole roof construction.
 
Some images. Not the best i'm afraid due to lighting, space and crap camera phone.



Excuse my feet and bare legs. I was on my way out to play squash! This shot shows the repaired joist running across the last hatch hole. Next joist across is the one i need to cut. Next one across from that is the 2nd repaired joist where the oldest hatch had been.



Opposite end to my feet.



Looking back to where my feet where showing the trimmer that i plan to tie the joist i need to cut to as well as putting in a noggin.

The wood running at 90 degrees to the joists as the reinforcing beams that support the floor put in when the lost was boarded. I've had to cut them around a bit to get access to the original roof joists.
 
or have you any diagonal struts/king posts (central posts) etc? If

Dunner be daft, these will all have been removed. :rolleyes: :p
Come now im an optimist.. you never know maybe one day someone will leave them in.. one day..


Right.. thanks for the photos.. the repair you have done isnt quite as i described.. the repair should create a taught infill between the members.. the worry would be that over time that double connection would sag and the ceiling would come with it..

To be honest i think that cutting the only decent joist in the bunch would be unwise.. but lets look at a few options tho:

Firstly if you can i would reuse the original loft hatch..
If that really is impossible then you could look into propperly trimming the hatch out and taking timbers back to load bearing walls.. picking up the weaken joists and the new cut one on the way
Alternatively reinstate the cut joists with some metalwork repair which is my preference.. a quick search for joist splice gave me this and then cut and trim out the loft hatch where needed..

If you create the opening as you intend you will have 2 weakened joists supporting a cut one in an area where the most movement will occur right in the middle of the span where the most deflection occurs.. kinda like making a cake out of semtex..
 
What does a 'taught infill' mean?

I still have a piece of wood to let into the gaps between the original cut ends that would make the original joist a straight line. Is that what you mean by a taught infill?

Unfortunately, there is no other option but to cut that joist as the old hatch holes are in completely the wrong places and wouldn't allow the ladder to drop down.
 
Ok well if your only option is repair and relocate then:

Either grab a couple of splice kits and tie a new piece of timber to the existing each side.. chance are you dont have the access to do this tho but its my preference as you get a nice bond between the timbers and it wont move.

Similar to what you have started but infill the missing part of timber with another piece, and clamp that with two timber joists (one each side) that run past the missing area and well lapped into the existing, then bolt the three pieces together with staggered bolts least 2-3 each end into the existing at around 150-200mm centres.
Bit belt and braces but youll have a firm connection which wont bend of pull appart. Could be done with one joist on one side as youve shown but when you add the load from the new opening i think your asking for trouble.
Im sure you dont want to have to repaint the ceiling every time you go up the loft for a suitcase..
 
That bit i certainly can and will do.

Thank you very much for your help.

Similar to what you have started but infill the missing part of timber with another piece, and clamp that with two timber joists (one each side) that run past the missing area and well lapped into the existing, then bolt the three pieces together with staggered bolts least 2-3 each end into the existing at around 150-200mm centres.
 
Presuming you have checked that it isn’t a main supporting beam, for the time it takes I would still brace across the top of the beams just beyond the saw cut by screwfixing down two 4x2” timbers – one either side.

Once the opening is formed as you’ve suggested, I would consider buying a bespoke loft hatch to maximise the opening http://www.jupiterblue.co.uk/loft-hatches

Hope this is of assistance.
 

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