Installing joists in stone wallls

[Wibblywobbly]

I need to install a ceiling in a converted outbuilding with bedroom space above, which will require the installation of joists. Can anyone explain the secrets of getting the joists in and achieving a level floor? I could get the pro's in but as the place has cost me an arm and a leg already, I would happily tackle this myself if I could.

Hoping someone can help!

Rob G

[Gluestick]

You have a choice of two methods.

First and more work is to cut out the walls at the ends of each joist - or "Bastaing" as they called in France - into "Joist Sized Holes" and sit the joist on a bed of  cement. Or, depending on the height of the wall and where the roof beams sit, perhaps on the top of the walls, bedded on a pad of cement to level the joist and then "Tosh" nailed to locate. (Tosh nailing is an effective chippie's method, where a large nail is driven through the joist at the side, at a significant angle into the masonry).

Second (and probably easier for the amateur) is to use what the French call "Sabot": these are galvanised mild steel U-shaped brackets which are fixed into the wall - and sometimes on top, too - by Rawbolts or similar. The joist then simply slots in and wood screws locate the joist and prevent it from moving.

Be careful to calculate your total expected load!

Joists deflect with load and it is critical to ensure the total deflection, in the middle (the point of greatest deflection), when the maximum planned weight is on the floor, does not exceed the norm.

What's the norm? The floor, above, should not detectably bend when someone is standing on it!

To ensure a good level line, treat yourself to a reasonable laser level: not one of the cheap Mickey Mouse ones ( you won't be able to see the line!) but a more expensive item which with luck, you'll have for years.

Before you start, carefully work out how you are going to install the floor: will you finish the lower ceiling with plaque de platre? With insulation already on? And then what will the floor sit on?

A bit of thought up front, will ensure a far better job.

Far too many loft conversions, in France I've seen - and experienced! -  simply bang flooring chipboard onto the beams: and when anyone walks around upstairs, uses the loo whatever, everyone downstairs can hear their every movement and listen to the floor creaking and groaning!

Perrhaps the best was  a Dutch "Renovation" of a small cottage, where the "upstairs" was half of the cotttage, joists in the French equivalent of  2 X 2 circa 4 meters wide and the "Floor" was hardboard!

I exited rather quickly, before the chunky and heavy-looking double-tier bunkbed came crashing down onto our heads! Apparently two kids slept up there..................[Www]

Best of luck.

 

[Iceni]

We used wooden upright posts with beams sitting on top then sabots to hang the joists. This avoided any need to chop holes in the stone walls. An English architect friend advised on timber dimensions.

If this approach might be of interest please pm me and I will provide more info.

John

not

[Gluestick]

Rob:

This might assist!

http://www.johnbridge.com/vbulletin/deflecto.pl

 

[La Guerriere]

Assuming your stone walls are fairly uneven and extremely hard, I think I would:

a) Try and mark out levels as best you can (see previous posts, much common sense).

b) Fix a big end beam to the wall each side, stuff comes in standard sizes cannot remember of the top of the head, I think it would be something like 175mm x 65mm or 75mm. This would entail propping it up with acrows or similar and then drilling fixing holes through into the stone. I would go for big expandy type bolts 20mm dimater or better, and drill into the stone where you can,, but nominally at about 500mm centres and get in deep, at least 200mm. You will need a very big and ugly SDS drill to do this.

c) Get it as square and level to the as you can, tighten all the bolts as best you can, stuff morter mix in behind the beam and when set, retighten everything.

d) Then use ordinary galvanised hangers on your two big beams and put joist across probably 150mm x 65mm or so.

Not rocket science but it should work.

 

[La Guerriere]

..... joists at 500mm centres as well.

[Gastines]

One add on. Make sure you install your joists to suit your flooring panels as they do like making things in odd sizes here. Worth thinking about is the cable/tubing/pipe runs for any downstairs ceiling lights and upstairs services before you nail/screw the whole lot down.

Regards.

[powerdesal]

[quote user="La Guerriere"]

I would go for big expandy type bolts 20mm dimater or better, and drill into the stone where you can,,

[/quote]

Or use chemical anchors if you can get them, I'm a great fan of chem anchors over "expandy type bolts".

[La Guerriere]

Steve,

Agreed. The nice thing about chemical anchors (and they are widely available in France) is that they are very forgiving in dodgy stonework. Expending bolts sometimes just don't work if the stone splits. Whichever you use the hole must be exactly as specified and clean the grot and dust out or the anchor / bolt whatever doesn't work. Don't drill oversize.

[powerdesal]

Vacuum cleaner to suck the hole clean.

[shimble]

what size are the joists? ive found it reasonably easy to cut the stone out and bed the joists into the wall the only hard bit was lifting them in but extra hands turned it into 20 minutes work giving me the time to adjust the level of each beam. if youve tried drilling into crumbling stone  wall at precise points to hang joist hangers your braver than me ide personally prefer to have the joists held by 30cms of solid stone rather than a few screws in a not so solid wall each to their own

[Gluestick]

Agreed, Shimble.

I also can't clearly see the rationale of first installing side wall plates - which are bolted to the stone walls and putting the anchor bolts under extreme sheer loading: and then using sabots??

If one is going to use sabots, fix 'em straight into the wall!

That said, like you, with the minimal effort required to cut out the relatively small square holes - Super SDS drill on Rotostop - and the inbuilt opportunity of bedding the joists on cement pads to level, to me, it's a no brainer.

No problems about fixing into friable old mortar and crumbling stone and a positive load take-out all the way along.

If the walls can't take the load, then the whole concept is poiuntless anyway.

Next suggestion, no doubt, will be to also fix uprights under the longtitudional beams..........................

 

[sharkhunter]

I don't like using joist hangers on old properties or on any if push comes to shove. I would much rather use acrow props and a good true edged beam to level and stabilise the joists before setting them in the walls on a pad stone or concrete footing. After that its a simple matter of settling in the joists with some natural stone that has been removed to create the pockets for the joists in the first instance. At least this way you can achieve a level throughout, afterwards, depending on what finish you are after, you can lay plasterboards direct onto the joists before laying your top floor covering of parquet etc and then all you have to do is the odd joint in the placo and seal around joints between placo/joists. If you wish to insulate then depending on floor to ceiling heights in the newly created room you can batten out on top of the placo to accomodate the depth of insulation before laying your parquet etc. Good luck whatever you choose to do, most important is to take your time, measure twice and cut once.

[powerdesal]

[quote user="Gluestick"]

Next suggestion, no doubt, will be to also fix uprights under the longtitudional beams..........................

 

[/quote]

Now theres a thought.................[:D]

[Gluestick]

Well, Steve, no doubt we could always suggest Cross-RSJs for load bearing, supported on steel pillars: and then knock down the old stone walls and replace with blockwork!

 

[Www]

 

[powerdesal]

A lot of people like the "industrial retro" look       [Www]

[Just Katie]

And wouldnt it be necessary to damp proof the end grain prior to fixing it into the stone?

[Pierre ZFP]

Wow!  You really have a damp problem if it gets up that high!

[Just Katie]

[quote user="Pierre ZFP"]Wow!  You really have a damp problem if it gets up that high![/quote]

Errrm ...... Penetrating Damp Sir?   Especially if the elevation is South Westerly and more open to the elements.  But of course, this would be more prevalent in UK.

 

[Gyn_Paul]

The only thing I would add to this excellent array of advice is to say that an amateur will tend to make a mimsy little hole just big

enough for the end of the beam. A professional builder will wack an

enormous, over-sized hole which will make you heart stop when you see

it ! However, the advantage the builder has is space to work and

manipulate the heavy beam to the perfect level final position whilst

retaining the skin on his knuckles. And the pleasure of using a

betoniere of mortar rather than a bucketful.

The latter route is only a problem if you intend to have a wall with

exposed stonework, not something I'm keen on personally. My feeling is

that if God had intended us to have internal exposed stone walls, he'd

never have given us plasterboard.

p

[Dave&Olive]

hi ok

 must be something wrong with me then .. I just knocked holes in the wall for the ends of the wall plates then just  fitted a couple of quoins for extra support ,and then dropped the joists in on hanger brackets at 400 centres ... 500 centers no use nor ornament not for plaster boarding after

          Dave 

[Just Katie]

[quote user="Gyn_Paul"]
The latter route is only a problem if you intend to have a wall with exposed stonework, not something I'm keen on personally. My feeling is that if God had intended us to have internal exposed stone walls, he'd never have given us plasterboard.

p





[/quote]

Plasterboad over exposed stone? Will somebody please escort that man to the guillotine! God GAVE us stone.  MAN gave us plasterboard.  But there you go, it would be a boring place if we were all the same.[;-)]

Hey Dave, nice to see you posting! 

[Chris Head]

Just glossed over the thread. Have a look at what the artisans did a century or two ago and do the same...by the time any problems develop you 'aint going to worry much about problems developing.

Green Oak....Joist hangers....screws...nails? Mmmmm.... 

Buildings and timbers they put up a few centuries ago are still standing quite happily.

I just saw some lovely internal stonework that had been plasterboarded over too...what's that all about? It's a wonder several generations managed to survive in the house before the advent of plasterboard!

Anyone familiar with the KISS principle?

[paw862]

What are chemical anchors called in France?

[Gyn_Paul]

'Kit scellement chimique' (sorry paw862, can't quote earlier postings for some reason)

... and nobody who has had to live with my naked stone walls which

CONSTANTLY drop particles on the floor (in the quiet of the evening,

you can actually hear the pitter-patter of bits falling on the floor!)

would ever consider living with this for ever.

I conceed that there are some walls which were intended to be left

revealed, but my lumpy, mis-shapen granite is not amongst their number.

It was always intended to be plastered over. Had that not been the

case, the builder would have used (at least I hope he would have used)

better quality, dressed-face stone.

It's not unlike the UK obsession in the 80's for stripping pine

interior doors in old houses. You've only to look at the quality of

the wood - full of knots and shakes - to see that they were always

intended to be covered with paint.

I'm happy to be a Luddite on this particular point.

p