Replacing RSJ in loft

Discussion in 'Builders' Talk' started by Dun Dun, Apr 27, 2019.


What Need to Be Done?

  1. Remove the roof?

    0 vote(s)
  2. Support from floor below

    2 vote(s)
Multiple votes are allowed.
  1. Dun Dun

    Dun Dun New Member


    We recently had a loft conversion done, but due to poor design the space is not suitable as an extra bedroom. It currently has 2 small dormers; and we now (finally) have planning to create a large dormer. The new plans require us to change over the old steel (2 for the floor and 1 ridge).

    Now that the purlins have already been removed and steel in place, when we swap over steel work will the roof be stable during the works. We've had one builder who told us the whole roof has to come down. They quoted us £60K. Another told us that it wasn't a problem and acro prop support from the floor below would suffice without having to take the roof tiles off.

    Is this really the case? Please advise. Thanks in advance.
  2. gas monkey

    gas monkey Well-Known Member

    Already had work done so 60 k for 1/2 a job think about it
  3. Jord86

    Jord86 Screwfix Select

    Post some pictures up. If your existing joists need to be upgraded to deeper ones then its game over I'm afraid.

    Without seeing it it's impossible to give a degree of certainty but hypothetically I would look to change the ridge beam first by acrow propping off the floor structure, and possibly the floor structure under that, remove the support around the first beam and somehow lower it down, then slide it out of the roof via eaves or knocking a hole through the brickwork and onto the scaffolding. Some tiles will have to come off, very probably the ridges and first couple of courses to detach the tops of the rafters from the beam if needs be, may be lucky and they may just be resting on top without fixings. Fit the new ridge beam and build and secure everything back tightly and wait for any cement to go off. The floor structure is the next step, again remove the floor, prop the roof from below, detach the joists from the RSJ's, remove and insert your new ones and secure everything back.

    I make it sound so easy...... I've only very briefly summarised it. It will be an absolute nightmare to undertake all of this work, it will cost you thousands, thousands and more thousands, your house will be ripped apart with a huge amount of work needing redone, at least one side of your roof will have to come off in order to build the new dormer, internal stud walls removed, stairs ripped out and new ones needed, floors ripped up, ceilings down, new joists, electrics and plumbing need reconfiguring, reboarding,replastering, redecoration, basically all you've had done will need redoing.

    Builder 1 saying £60K sounds a bit overkill though it depends on the level of finish to put back and where you are in the country, if he's VAT registered etc, Builder 2 saying it's no problem sounds very much underkill, or at least it's no problem as long as you've a large chequebook.

    I would look to do anything other than what you've described you wish to do. Try moving house.
  4. stevie22

    stevie22 Screwfix Select

    60 grand would be pretty dear for a conversion from scratch and you should have stairs, fire doors, wiring etc done. BUT how much has to be undone to do what you need to do now? We don't know. Neither can we second guess your builders. Maybe cowboy, good guy ultra cautious
  5. sospan

    sospan Screwfix Select

    More than likely the whole roof will need to come off. If you are fitting a dormer, to one side then there isn't going to be much of that side left. If the ridge needs replacing to fix part of the dormer to, then supporting the other side of the roof without a ridge will be quite interesting.

    I would tout your problem around a few architects and ask them if a SIP solution would be appropriate. With a SIP solution the rafters. insulation and interior boarding come in one piece. If you go down this route. You may be able to get a crane to lift the new ridge and fit the SIP panels as part of the same visit.

    I would be even more cautious when selecting a builder for this type of work as you don't want someone whom will take to long and leave the house open to the elements but the worse case would be some cowboy that starts the demolition and then walks off the job because it is too difficult
  6. Jord86

    Jord86 Screwfix Select

    I was on a job end of last year on a new housing estate, trussed roof had to come off a finished house for many various reasons and me and another bloke had to cut part of it back on by hand and utilise the existing best we could. I'd never worked in the environment before but once a full scaffold was erected around the entire house a company from Scotland that specialised in it constructed a fireproof, waterproof heat shrunk wrap around the entire house, selling it in against the elements. Quite brilliant really, though the downside was that and the scaffolding cost in excess of £14,000.
  7. sospan

    sospan Screwfix Select

    I am surprised with the nightmare that is the party wall act that it isn't insisted on more often. If not just for weather protection but also dirt/dust and all round health and safety
  8. Jord86

    Jord86 Screwfix Select

    You know how people are tighter than a nuns chuff though when it comes to money, the mere mention of an item that's not absolutely essential, that costs a few hundred let alone a few thousand has the Scrooges choking on their Earl Grey. And the more unscrupulous builders knocking other competitors down "ah, you don't need that nonsense, we don't use that, it'll cost you a fortune" sort of stuff sadly leaves it scarcely used, except seemingly in London, or some of the more "affluent" locations.
  9. Dun Dun

    Dun Dun New Member

    Thanks for your replies.

    Our house is in London, in our area its hard to find a property for less than £800K so we're not keen on moving out. If the job really is £60K then we'll go ahead but just needed some clarity on this. The builders we're going for are really top notch, a large fraction will be spent on the finishing team. The bathroom alone will cost £7.5K - that excludes the tiles/showers etc. We are going for the best.

    We know that everything will be demolished again, but thats because we've got a completely new layout. It hurts to have to go a second time but it is what it is :/.

    Do you think; that the whole roof along with trusses will have to be taken out? Or will they be able to work around this. Again, I'm just trying to have a better understanding of the process so as not to end up with a company who'll either do less work than needed or quote for far more.

    We'll also be moving out as we're having a GF extension done and full refurb. So disruptions not an issue. They were talking about umbrella scaffolding. I assume this combats the elements?

    Thanks again.
  10. stevie22

    stevie22 Screwfix Select

    What gets kept and what gets ripped out is largely due to you designer
  11. Jord86

    Jord86 Screwfix Select

    As you're in London, then the job will definitely be £60k then. You have your terminology mixed up slightly, trusses are the entire relatively modern roof timber structure which if taken out, you won't have any framing left for the felt and tiles to sit on. You probably have a cut roof made up of individual components,rafter, purlins, struts etc. These can be removed singularly, but as you're having ridge beams swapped, dormer constructed and probably umbrella scaffolding erected it's probably safe to say they're planning on taking at least one side of your roof off, possibly in one go.
  12. sospan

    sospan Screwfix Select

    The problem is that the roof has been altered once for two dormers and the purlins have already been removed. Who knows what is going to happen when the loading changes as the roof is altered for the second time.

    I would suggest employing an independent project manager to deal with the builder and check with your house insurance company about the work you propose.
    Jimbo likes this.
  13. Jimbo

    Jimbo Screwfix Select

    Second the above, check the insurance, make sure you absolutely trust your building company, get stage dates in the contract with penalties, and leave yourself budget to move out for a few months should things go wrong.

Share This Page

  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.
    Dismiss Notice