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Purlin tails rotted


BIG MAC
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Right chaps and chappesses any good 'fixes' for main purlins where the protude under the roof verges and have rotted away?

Looks as though there is still a good solid timber bearing but the protuding section has rotted to nothing  thus leaving the first chevron? vulnerable.

I thought about trying to chilsel the und as square as possible in situ then bolting a new section of timber in using 2x 12mm stainless rods fed into a dogbone type nut in the loft and with the threaded bar rebated at the end of the new section so that the nuts and washers are concealed perhaps with a wooden dowel glued in.

I thought of using an epoxy adhesive like HILTI hit or similar on the end of the new timber as it is slid in so that when the bolts are tightened there is a further connection and less opportunity for water ingress.

Is there a better / easier way?

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You seem to know more about it than most but when faced with a similar problem at our last house on four joists in line, I accrowed up the joists from inside the house on a scaffold board to spread the load on the floor joists,plus one from the ground floor as in belt and braces ,then cut a mitre about 600mm in and grippfilled joint onto new piece.cut piece of marine ply about one metre long and gripfilled and screwed this on the side showing least. I think the house is still standing.
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Mac, as you know, it's not easy to give advice without seeing the structure.  Also, you don't say how thick the wall is.

Anyway, might I suggest that, before you do anything, you make sure you have some props in place (in case anything slips!)  But, I know you'd do that as a matter of course.

Then, cut away all the rotten bits and add new beams as per Fig 213 or 214 (even better):

http://www.sawdustmaking.com/woodjoints/scarf.htm

To save time and money, I think you could also use an alternative method which is to put a new length of timber alongside and plate it in.  The new timber beam would be at a slightly different level to the old beam but, personally, I won't worry about that. 

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Hi Gastines / Sweet 17 good stuff thus far. Maybe I should explain further.

I think there is a good bearing in the 500mm thick stone wall but am loathe to cut any but the minimum from the timber inside the wall as this would reduce the bearing (I will need to cut some as the damage extends into the purlin within the wall but want to minimise this)

It seems a fairly common issue with older French houses and often the old timber gets covered in timber of clad in ply, mine is beyond this type of repair.

I toyed with the concept of cutting the purlins flush, treating them then building a 'Gable ladder' with a ply undercloak but I think this may look naff on a traditional French house and want something which I am not decorating every few years.

I would like the look and strength of a big piece of oak and am trying to come up with the best way of doing it.

My other idea was to have a box section made to measure in steel, jack the purlin up on the inside then drive the box section over the end of the purlin and bolt through then do likewise with the other (external) end. I guess in a reasonably heavy steel this may last a long time actually I wonder if theres a standard size box section wich may suffice?..hmmmm got me thinking now!

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Hi Mac, there are no easy answers to this problem, i'm sure you are aware but i think it all falls onto whether its a structure problem or not. If i am reading it correctly then its purely superficial, then you only need to put back the purlin ends for appearances only.

As these ends will be non load bearing would it be possible to cut them off squarely and drill and dowel/glue them back in situ, and then lift the tiles above and fix thru under timbers/battens with coach bolts/screws ??

If you are worried about compromising security of purlins inside by cutting away extra timber then you could bolt shoes in place inside thus providing some back up security.

Hugh.

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[quote user="Théière"]

All Purlins are structural, I like the steel socket idea Bigmack, probably what I would do (large flitches) without a picture I can only imagine. Hope you are jammy enough to find standard box section [:)]

Go on take a picture before and after  

[/quote]

 

OOO!!!!! A challenge!

Yes the bearings are structural hence reluctance to take too much out of them..If I can find standard box section which is close then I can always split it in half and re-weld or get some plate folded here in blighty and then cut and weld on site to exactly the right dimensions....dunno if my welding is up to such heavy work but I could give it a go. Real advantage to a standard box is I could get it galvanised quite easily.

Next time I am over I will get photos and dims

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I have no knowledge of english building terms but assume that a purlin is a "solive".

I have two adjacent solives in my lounge which were hanging in the wind;

I did not want to be delayed at the time in my renovation work, so I removed all the rotten wood leaving three horizontal steps on each side

Then installed a splice with marine ply all held together with epoxy resin; left propped and clamped for a week.

Been there over 10 years and never touched it again.

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[quote user="BIG MAC"]

I think Solives are engineered Lattice beams but may be wrong. Purlins run at right angles to the rafters/chevrons and beneath carrying  the weight into gable walls and A Trusses / Crux  frame.

 

[/quote]

Called a ferme maybe but could be a truss, basically not the faintest as to lattice beam; solives are across shortest span, normally wall to wall; length wise roof support called a panne, faitière, moyenne or sable depending on position; pignon to pignon unusual but found in narrow houses with large distance between facades; old houses in St Loup sur Thouet are typical and are called poutres. But heavy section beams are called poutres.  Historically length of heavy beams was restricted to building ships, etc by the state; so rare to find long ones in normal dwellings.

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http://www.poutres-i-bois.fr/media/panne.jpg

I am going to guess a Panne .....Poutre is just a beam as far as I gather. The link shows a engineered 'Panne' mine however are about 250 x 100mm timber possibly fir, I don't think they are oak but then my knowledge on wood identification not great.

The area of concern however is the section outwith the facade/gable......Funny I thought Gable may be a French word....it looks French!

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Hi Guys, in most uk houses they do not use purlins that protrude, only a timber 'ladder' that takes the weight of the tiles and timber battens that overhang the gable that is where my query about whether structural or not cane from.

The ' ladder' i mention is partially supported by the block/brick skin on the outer wall but primarily by the battens and the structure of the ladder. So it is feasible to have the purlin ends as purely decoration although in this case they are part of the roof structure but not to the extent that if they were not there the roof would fall down or collapse. There would be sagging of the outer most timbers but this could be offset by using false/renovated ends and fixing/supporting by the battens and of course the method used for connecting to the old purlin ends to the new. There are also the bolts that are used to bolt together stair stringers to the posts, one end is a heavy screw and the other is a machined thread to take a nut/washer combination that sits in a pocket routered into the new/false ends and tightened by a spanner ( not you Mac ) a real spanner lol

I'm sure there are several easy fix methods but if there is any anxiety at all then you will have to support the purlins and strip back the old wood and perhaps use a slip joint. This method would mean stripping out the tiles above and digging into the wall a bit, this usually means the slip joint cut is about three times the depth of your timber, 750 mm in your case.

Either way you do it, good luck,

Hugh.

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The purlins in our English property are not tied into the walls but merely sit on brick pillars. They are of course supporting the rafters and the weight of the roof.

The purlins in our French house on the other hand are supported centrally by the A frame and at each end are set into the walls. Completely different roof design.

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Solives are joists, faitieres are the ridge, sabliere (dunno in english) runs along the top of the wall and the chevrons or rafters rest on them , pannes are purlins, voliges are sarking. Without pictures it sounds like it could be a job for resin and rods?

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Your house appears to be 20th century, if it has parpaings that would make it post second world war.

The curvy bits sticking out are largely decorative but do serve to ventilate the timber.

The house probably has three fermes/trusses at each inside gable end and in the middle.

The fermes are normally located on chainage pillars tied into the foundation slab.

The suggestion above to rod or dowel a suitably shaped extension looks the simplest.

Trim the timber back until good wood is encountered before treating and attachin extension piece.

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When in Rome and all that.

What the professional tradesman in our region would do is to present a devi for cutting back and scarf jointing in a new section of purlin and then protecting this with a trimmed piece of zingue to prevent further problems.

On acceptance of the devi  they will send an apprentice or SMIC employee up a rickety ladder with a bucket of pug, a trowel and the piece of zingue know locally as une cache misere

Job done [:D]

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