Advise on beefing up a loft floor

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Hi all, long story short previous owner of the house boarded out the loft. Some time in the 90s judging by the decoration. The beams are only 3x2 and flex when walked on. Ceilings below have cracked. I'm just wanting to beef it up so it can be used for light storage and not crack the ceilings.

There are three 3x2's that run the length of the loft. One up the middle and one either side about 1.8m away. These rest on brick. You can see one of them below. As you can see the other timbers which are also 3x2 run underneath these. This is what the previous owner has laid the boards on. Leaving the other 3 3x2's protruding above.

Iwmh9FL.jpg

Now I'm thinking of putting 4x2's on top of the three lengths that run the length of the room. I came across this method while searching along with this diagram.

SEwJ6O6.jpg

Now three joists would not be enough so rest new loft boards on top. I presume I can just add 4x2's perpendicular to these and board on top? Any ideas welcome. This will not be a habitable room, it just needs to be a reasonably strong floor for a bit of storage.
 
Soldato
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Now I'm thinking of putting 4x2's on top of the three lengths that run the length of the room. I came across this method while searching along with this diagram.

SEwJ6O6.jpg

Now three joists would not be enough so rest new loft boards on top. I presume I can just add 4x2's perpendicular to these and board on top? Any ideas welcome. This will not be a habitable room, it just needs to be a reasonably strong floor for a bit of storage.
Really you need to make the ones at the bottom stronger as those are the ones flexing and holding the ceiling up. Im no expert but Im fairly sure you would need to sandwich the joist together side by side to make them stronger rather than placing one on top.
 
Soldato
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Ideally you should consult a builder or loft specialist.

This looks very sketchy as it is, flexing joists and cracking ceilings. If you add more weight to the existing timbers you could compromise the roof itself, as the timbers all interconnect, I'm assuming the truss rafter supports are behind the plasterboard at the sides and haven't been cut away or modified by the previous person? When you build a loft extension you install dedicated beams to rest on the block work of the house and set out the floor from that.

The arrangement of insulation is pretty poor also, have you looked behind the plasterboard on the roof to see if there's any there?
 
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Hi @norm yes it is a little sketchy and a bit of a bodge by the previous owner. Behind the plasterboard is a large purlin either side. I am going to remove the plasterboard and coverings so I can have a good look what is going on. The insulation is indeed poor. It does run under the plasterboard and to the edge of the roof but is very patchy in places so I think this needs replacing.
 
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I am doing something similar in a loft this summer.

It depends entirely on the construction as to how much weight it will take. Some roofs are designed for additional weight, some are not.

The best idea has already been mentioned. It's best to double up width ways rather than height ways so the strength is added without placing any further load on the existing beams. You need C24 treated timber. It's expensive, but it's very strong. You can join shorter pieces with lap connections. I find a good lap connection can be made using PU glue with a few nails. Be careful to never nail or strike anything in a down direction or you will loosen the plasterboard in the ceiling below.
 
Soldato
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The shear strength of the 2 by 3's should be quite good but it is worth checking for the additional load. Probably about 900 psi, depends what the load is, but it's hard to imagine it is greater than that.
 
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