When it comes to a loft conversions, most consider it a rather simple task. Simply build up and out on what’s already there. And while this is a rather simple way of looking at it, with loft conversions being notoriously easier to build than normal single or double storey extensions, there’s a little more to them than merely ‘going up’.

Floor Joist - Clapham Construction

Most roofs, certainly here in the UK, are constructed with something called internal support struts within the loft space. These prop up the rafters and the purlins – the horizontal roof beams. This is certainly the case for traditional cut and pitch roofs. In modern truss rafter roofs, they make up a web of braces almost.

While loft conversions do indeed make the most of the space you already have, they do require you removing these beams and rafters in order to make way for the new room. This will mean constructing new supports, not only above the loft conversion for the new roof, but also below… why? Because ceiling joists will almost certainly be considered inadequate when it comes to turning them into floor joists.

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Can Ceiling Joists Be Turned Into Floor Joists?

In short, no. While we could never make a sweeping statement, applying this to every home, it is worth noting that it’s almost certainly the case that the vast majority of ceiling joists would be inadequate as floor joists. To understand why, it’s worth considering just what these floor joists need to do.

The ceiling joists which were in place were supporting a roof. While this is indeed a substantial part of the home, asking them to suddenly support a room that’s lived in on a daily basis would be impossible, especially when you consider additional weight from a new bedroom, a new office or even a new ensuite bathroom. In doing so, you can rather clearly see that all that extra weight will need additional help. 

While this may sound like a lot of work, it’s something that can be taken care of with the help of a structural engineer. Structural engineers will be brought in to assess the separation distance required between joists in order to support the new anticipated weight. Here at Clapham Construction Service, this is something we’re fortunate enough to keep in house, ensuring our structural engineers work alongside our construction workers for clear communications at all times.

These new joists will run alongside the existing ones and span from one load bearing wall to another. The additional joists will usually be required to be anywhere from 200mm to 225mm in depth and will rise above the ceiling joists in order to form that new floor structure. Should the current load bearing walls not be strong enough for this, additional steels or timber beams can be utilised to ensure adequate support for the new floor joists.

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Ask The Experts

While it will of course change for each building, it’s worth noting that a structural engineer will be needed to ensure your ceiling joists and new floor joists are of the right size and strength to support the weight of a new room. Here at Clapham Construction Service, we can provide you with these services in house and what’s more, we can provide you with a free consultation where we’ll be happy to take a look at current construction and advise you of what you’re likely to need. For more information or to book the free consultation, call us today on 0203 9507957.

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