So, done a lot of internet searching which has revealed lots of “get a structural engineer answers”…..

I have a 90’s bungalow with a very steep pitched roof (massive attic space). I’d like to convert it to put a couple of extra rooms in. At the moment the roof is a Finks Truss (‘W’ style) construction. I’m not 100% on sizes but at the apex it must be close to 3m high – so plenty of space. I’ve seen the tele-beam things and heard the whole you need to take the roof off and replace it….but, I’m an engineer (mechanical) by trade and can’t understand why it wouldn’t be possible to convert / reinforce the existing structure to add cross ties and make it look like an attic truss style of roof. Surely beefing everything up from 2×4 to 2×6 and adding the cross ties etc is sufficient? Or am I missing something really obvious? If I think about it in terms of metal work the solution seems really simple…..I have a friend who is a structural engineer who could work me up some drawings – but I just want to know if it possible / advisable (if not, why not) before I do that.

The new roof, tele-beam and move house options are too expensive. I would intend on doing the work myself and would stagger the purchase of materials over a few months to make it remotely affordable!

Most of the answers I’ve seen so far consist of:
– buy a new house
– get a structural engineer
– put on a new roof

No body really discusses sistering beams to reinforce them or why it might not be a good idea…..

So, does anybody have any experience?

You could get plans from a Structural Engineer for £200-£300 which will get you through Building Regs. Whilst he’s round you can chat through the options etc.

Have you asked your friend, the structural engineer? Or will he just do what we/STW tell him to do?

So in theory you’re thinking of cutting out all the timbers bar rafters and ceiling joists?

I’m in a situation similar to you and have made similar enquiries and come up with zip. Apparently it’s just not feasible or cost effective to slide full length steels through holes in the roof along with other structural modifications that would be needed as the house is simply not designed to take the weight of the beams plus the floor and everything else associated with the room. The telescopic beam solutions are made from aluminum so are lighter and seem to be the only possible solution without re-roofing. I’ve put the idea on ice for now.

My mate lives approximately 5 hours away on the West Coast and has just had a new born baby. I’ll try and call him at some point but TBH if the only options are a new roof or these tele-beams, then I can’t afford it and don’t see there being any virtue in wasting his time.

Not planning on cutting out any timbers – yet. Merely adding extra (bigger) timbers spanning the width of the house and alongside the rafters (? – angled bits) and then adding cross ties above head height to form a new ceiling. Once this is in the roof (hopefully – this is the bit I’m trying to get clarification on) be supported to allow the existing trusses to be removed.

My question isn’t so much how should I go about doing it….it’s more, in theory (in my head) reinforcing everything should be possible without removing the roof. No body seems to do this though and I’m curious why / what I don’t know. If it’s down to time and effort I can work around that as I would do it myself. But if it somehow causes roofs to fail early then there’s no point in pursuing it. I’ve got architects plans (not detailed – just outline) that came with the house and the accompanying letter suggests that no foundation work is required so I don’t think it should be a weight issue other than replacing the ceiling framework with something more substantial.

My same friend mentioned something about stressed floors (glued and screwed plywood I gather) too allowing for use of lighter 2×4 floor joists.

I think (have been told) that timbers are not allowed under current building regs. I didn’t think the aluminium telescopic things were that expensive, and DIY-able and effectively work in the way you describe I.e. Slide in next to the existing non-structural beams and allow the trusses to be removed, but I think there are weight limits in the resulting rooms, so no home gym or workshop with heavy machines, strictly just bedrooms. It’s about 18 months since I went round it, so I might be inaccurate in my recollection.

Tele-beams are £450 per beam…..unfortunately a bit out of my price range! Now I can probably afford a couple £k’s in timber.

Not being in the building regulations would make sense – ie. in theory it’s ok but you’re not allowed hence why nobody mentions it as an option.

Thanks,
Oli.

Did ours 8 years ago, modern detached house. Steelwork was in 3 sections per side of house and builders took them in through main door and up stairs, about 3 m long sections. These sit on gable walls and take load of roof and upper floor. New roof trusses are bigger than originals and all hidden. We sacrificed a box room for a full size stair and put in one big room and some walk in cupboards. 2 velux windows on rear. I think we were about 30k all in. I had a mate do the drawings and I did the building warrant stuff myself. Had to replace all the downstairs doors with fire doors which was costly to meet regs for 3 storeys.

Luckily we wouldn’t go over the 4.5m thing so hopefully no fire doors required. Strangely, it hadn’t even occurred to me to look at using steel work and joining it in situ.

Generally wouldn’t need fire doors for that.

If there chance is you are going to ultimately take the roof trusses out, why not just have attic trusses designed by a truss manufacturer.

Being 90’s, i assume they are modern trusses with gangnail plates as opposed to created in-situ with separate members and bolted with toothed plated connectors. Modifying of the former is likely to be costly the latter maybe not so.

The likelihood is an engineer would want a ridge beam spanning between the gables and purlins. Collars tend to pull the roof down wanting to force the roof apart at the eaves, where as a ridge beam fixes the “apex”.

Look at the trada span tables which will give you an idea of the member sizes likely to be required.

It’s a gangnail style one that you describe.

Is it possible to have a truss manufacturer design you attic trusses and then assemble them in place – without taking the roof off? Essentially that’s what I was planning on doing.

It might be, but i haven’t come across it before.

The manufacturers usually design to such tight tolerances that they are only guaranteed if the trusses are manufactured off site and have their quality control. Some might though so could be worth asking.

Usually though trusses have cross bracing diagonal timbers, often on the underside of the rafters to stop racking (collapsing like dominoes), not sure the practicality or sequencing of how it would work, installing type one then removing the other.

Ultimately it is an engineer either the truss manufacturer or your friend. Buidling control are going to want to see calculations to prove the design will work and sign it off.

Okay – I’ll get my mate on it. Sounds like something must be possible without having to totally rebuild the house so at least it’s not a waster of his time.

Thanks,
Oli.

You have to consider time v cost. It may sound “cheaper” to you to do it the “easy” way, ie not replacing the roof. But in reality most of the time its far quicker and cost effective to strip out and start from fresh.

Replacing pre made truss rafters 1 by 1 in situ with out disturbing your roof. Good luck finding someone that would go ahead with that job.
Sounds like your creating work for yourself there.

The time factor is definitely worth a mention as above. Far far quicker to strip and re do with a new truss. Main problem I see is getting the bearing required for new floor joists at the wall plate.

Looked a little “lean” didn’t it!

Sounds like something must be possible without having to totally rebuild the house so at least it’s not a waster of his time.

This………however as above mentioned the shear time and buggeration factor would be immense for someone to actually do it.

Hence my initial point

If there chance is you are going to ultimately take the roof trusses out, why not just have attic trusses designed by a truss manufacturer.

wrightyson – Member
…………….. Main problem I see is getting the bearing required for new floor joists at the wall plate

Not to mention any trimming of the ceiling (to be floor) joists to take the head of your new stair – these would likely cut through the bottom chords of the existing trusses so might need lots of strengthening whist in-situ.

Do it right first off (if economically viable) short term pain versus long protracted death.