• LOFT CONVERSION FORUM UK

  How best to reinforce loft conversion floor?

  Posted by Rob Charles on March 22, 2025 at 2:05 pm

  Hi All,

  I am most of the way through a complete renovation of a 1950s bungalow that previously had a loft conversion. The previous occupant put chipboard straight onto the ceiling which has since come down and I’ve had the downstairs ceilings plastered (the plasterer screwed new boards through the old ceiling into the joists to pull everything back up together). I paid for a structural engineer visit who confirmed the floor was too weak and wouldn’t meet current regs. The advice was to reinforce the floor by building a proper separate structure to support the floor based on thicker joists running parallel to the existing ceiling joists and supported by the walls.

  Unfortunately I can’t afford ££££s for the engineering drawings to be produced and to bring a builder for this. I am a relatively competent DIY’er and it seems like there are websites that sell posi-joists etc. where you can enter the span and it’ll recommend the right thickness joist. Or I can just put in a thicker joist next to every existing ceiling joist then put the new floor on that. My logic is, without paying for calculations and drawings, surely duplicating all the existing joists with thicker timbers running in parallel then putting a new floor down on that has to be significantly stronger.

  Does anyone have any advice on how best to do this? How would I stop the new timbers twisting for example and what is the best method of attaching them to the wall plate?

  As for access I have stripped the old room out so will try and pass new joists in through the dormer window rather than make a hole in the roof. The old room had no insulation so decided to take it all out anyway so I can add PIR board between the rafters (with a ventilation gap) and having taken out an old water tank and a chimney I can expand the room out as far as the roof purlins.

  Any advice much appreciated! As mentioned I’m nearly there now but due to a few unforeseen issues completely out of money on this project now as much as I would love to be able to pay someone to do it for me. Fortunately all the things like first & second fix electrics, updating the central heating system, moving gas pipes, replacing windows, plastering etc. has all been done now.

  • This discussion was modified 1 month, 2 weeks ago by  Rob Charles.

  Rob Charles replied 1 month, 2 weeks ago 1 Member · 0 Replies
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