As a follow on from my previous “what LED spotlights” question, taking the ceiling down has opened up a new can of worms.

The joists are not big enough. 6″ x 2″ used for a 4.85m span, on joist hangars rather than butted into the masonry. I’ve got no problem with the task of replacing these with suitable size (195mm x 97mm going by a load/span calculator) but they would result in lowering the ceiling by 2″, and it’s low enough as it is. Is there another option available that means we can keep the ceiling at its current height?

I should add that we’re having loads of work done by insurers as a result of a water leak, but during the work they’ve uncovered this little conundrum and of course it isn’t covered. We’ve got to sort it out pronto so they can get back to what they’re here for.

It’s less than 2 inches, can’t you make the floor above 45mm higher, or split the difference, ie, lower the ceiling by an inch and raise the floor by an inch?

can it be beefed up with steel in between? Probably expensive though.

looking at £100 a length from what i can see.

Preferably not, as that would mean our bedroom has a nice 2″ toe-stubber as you enter from the hallway. Ceiling downstairs is already very low – think old cottage low – so very little room for movement there.

Would it be possible, if maybe slightly expensive, to just use big fat 6″ x 6″ joists or similar?

Would it be possible, if maybe slightly expensive, to just use big fat 6″ x 6″ joists or similar?

that was my first thought. Adding width is a lot less effective than depth though, but an easy calc to work out in a stiffness sense.

What’s the steel option? RSJ type thing half way along?

If so, would it matter that one end of the RSJ would be totally central above French doors, so not much wall/masonry to support it.

If you want to go fat then how about bolting another joist to the existing joists?

EDIT : Solid blocking would help if there isn’t any already – spreads the load and reduces flexing.

The guys who uncovered it said to just bolster up what’s already there, but how will that help with strength? We’d just be bolting more weight onto already under-specced joists. Or am I missing something…?

no idea if its allowed, i guess a structral engineers would be best to advise. Saw you can get a 152 x 89 16kg/m RSJ for about £20/m

Doubling up joists increases their strength.

EDIT : Obviously correct support either end of the extra joists helps.

Ah, yes. Makes sense now. Will look into structural engineer advice too. Cheers.

I’ll see what the insurance contractors say tomorrow, as I’m getting all this drama second-hand via the current Mrs Flying Ox. Either way, it’s going to be a busy weekend.

The guys who uncovered it said to just bolster up what’s already there, but how will that help with strength? We’d just be bolting more weight onto already under-specced joists. Or am I missing something…?

by bolting up to the sides you are effectively just using a wider beam.

brains not with it at the moment but using h^3 * w I get an extra 4″ each side to make 250mm! (that is stiffness calc ignoring the weight of the beam).

If you are going down the road of bolting extra joists make sure it’s done properly with preferably dog tooth washers between the 2 joists and the correct heavy duty square plate washers on the outside.

Hang on. RSJ would go perpendicular to joists, wouldn’t it? Effectively halving the span, and so 6″ x 2″ joists would be fine. That’s the way to do it I reckon.

I was thinking parallel to joists, clearly illustrating why I’m not a structural engineer.

Are the other two walls capable of taking the weight?

One of them is gable end built of sandstone with bricks lining the inside, the other is internal brick. 3.85m span that way, roughly 60kg for that length of RSJ plus dead weight from rest of the floor. Obviously I’ll be taking yo a specialist for advice on how much the walls can support, but I’m hopeful.

You could look into using what are called ‘Fitch Plates’. Whereby you sandwich a 150x10mm steel plate between your existing joists and a new 6×2 (150×50) softwood joist, through bolted at regular intervals, approx every 400mm. Worth seeing if the structural engineers and calcs would work on that.

RSJ perpendicular to the wooden joists might be the way to go, it might also need brick piers to support its ends. Lets hope not
You might be able to halve the distance between joists with additional parallel 6×2 joists spaced evenly, as opposed to bolting through to the existing
Very much expert advice time

Steel plates bolted either side of each joist is the usual way, similar to Ernie’s method but using steel. Costly and time consuming but leaves you with the original ceiling height through out.

a cable of flitch beams and wood joists between the smaller span

My approach would be to do nothing. They’ve lasted OK this long, what’s changed? Use 9mm plasterboard and a light skim to save weight when you redo the ceiling.

I’m with Big John

how old is the house/floor… ?

If it’s been there for x number of years doing it’s job quiet happily… before you found out… what’s to say it will not keep doing it …?

Just keep the bedroom gymnantics towards the more sensual side … 😆

Unfortunately, doing nothing is not an option. Bedroom floor was lifted/living room ceiling taken down by insurance people to check for rot in the joists. Instead they’ve uncovered under-specced joists. They won’t put the floor/ceiling back because it’s not to building regs. We have to fix it before they’ll do any more work.

I thought building regs were not retrospective, ie. it’s there and met the requirements at the time of installation.
Certainly the case in the electrical world.

Are the company that are doing the rest of the work hoping for the additional maybe?

Could be, but they’re asking us to do the work rather than suggesting they do it.

I’m just looking at flitch plates. Seems to be a bit less work than getting a RSJ in. Any thoughts on these?

If you are going down the road of bolting extra joists make sure it’s done properly with preferably dog tooth washers between the 2 joists and the correct heavy duty square plate washers on the outside.

My workshop joists were signed off by BC with just coach bolts with nuts and washers.

I thought building regs were not retrospective, ie. it’s there and met the requirements at the time of installation.

They are, there is no obligation to do anything retrospectively unless you’re doing new structural work which requires a change.

I’m guessing that the contractors will not be allowed to carry out work for the insurance company that doesn’t meet current building regs.

If it weren’t for the insurance company I’d be just replacing the joists like for like.

RSJ perpendicular to the existing joists sounds like a plan but the sandstone wall may have little in the way of structural strength (which is why it’s been helped by the brick wall inside it) and the brick internal wall at the other end may not be strong enough either.

What’s the current ceiling height?

7′ 6″

It’s low.

On the plus side, it’s always been a doddle to change the spotlight bulbs that keep popping.

I think I would go with an RSJ (or 2, 3 breaking up the span further?) across the floor rather than bolting stuff to the sides of the existing joists.

All depends on the side walls as you’ve pointed out.

They won’t put the floor/ceiling back because it’s not to building regs

Have the joists been removed? Are you actually replacing the joists?

If not, and your insurance job is now “simply” replacing existing floorboards, my understanding (and IANA builder/structural engineer/legal beagle), was that you therefore didn’t have to do anything. As mentioned above, its there and it was ok at time of installation.

Because if that wasn’t the case, they could just rock up at your front door, point to your entire house, and say “needs replacing mate, not building regs”.

Maybe time for legal advice?

Whether you’re happy with slightly undersized joists is another matter.

Where abouts in the country are you ?
You may have a friendly steel fabricator close to you

Rsj’s is not an option surely unless the room is 2m wide. The depth of the beam will encroach badly into the room and also look shit!
9mm board on ceilings is bodge!
Plates either side is standard practice and one I’ve done many times.

Flitch plates could be your answer, 10×120 flat steel cut to the width of the opening with an angle welded to each end.Angles are bolted to the vertical walls and the wide flat Flitch is screwed/bolted to floor joist.Fitted loads when installing composite windows in a screen elevation.

because it’s not to building regs

By the sounds of it, your ceiling height is too low to meet buidling regs. Are they suggesting you increase the height of your house?

But Flitch joists sound the best plan if you feel you really, really must make the change.

7′ 6″

It’s low.

It is low but could you really not live with 7′ 4 1/4″ ? Get a thinner carpet/walk barefooted 🙂

Based on your joist length of 4.85M, if you put a 120×10 flat (primer painted) either side with an angle at the end to bolt into the wall then you should be looking at paying a ball park figure of around £140 + VAT a joist
Factor in some M12 bolts and some resin masonary anchors at each end then you are up to around £150 per joist (would you need to every one ?)
That would be an Ex Works price.
(you certainly wouldn’t want to be paying more than that 😉

The Building Regs themselves are very general. In effect, they say the structure must be strong enough. The Approved Documents (ADs) have a lot of detail; if you comply with the approved docs, that is automatically “deemed to satisfy” the Regs. If you don’t meet the ADs, and you can prove to the Local Authority that the floor is adequate, you would still meet the Regs – the difficulty is convincing the Authority. If you get a structural engineer to do actual load and deflection calculations for the maximum load you could reasonably put on the floor, that should work.

But, as above, you only need to meet the Regs at new build or major refurbishment – the insurance company are probably regarding the work as refurbishment to reduce their risk. But if refurbishment is a consequence of the insured damage, they should pay!

If you do decide to strengthen / stiffen the floor, rather than use steel, I’d put extra joists in, centrally between the present ones. Something else that would help (a post above mentioned solid blocking) is to fit short sections of joist sized wood between the joists, near the ends, at right angles, to stop them twisting on the joist hangers. If the joists can’t twist, either by being blocked or built in, their nominal load capacity would be higher.

They’re called Noggins 😀

Good idea too.

Nog out the joists at 1/3rd & 2/3rd span & if you can remove the floorboards, glue & screw 18mm ply on top of the joists, which effectively turns each joist into a “T” beam, which is inherently much stiffer. I have seen this done several times on old floors which have a bit of ” bounce” & it works a treat.