Ancient Roof Trusses / A Frames... Repair?

[GRW]

Storm Darragh did my elderly ole man's place somewhat of a walloping.
Went up & had a look yesterday & the woodwork is in a sorry state.
Like a lot of rural farm buildings of the time (not sure age, but I'd guess the place is 120-150yo, though the section in question is clearly a later add-on extension to the old Milking Parlour, but still stone-built (there's an RSJ in place of the old pine-end wall which was removed - I suspect its stone got re-used building the extension - so it's a wild guess at 60-70 years ago).

It all looks home-made & cobbled together on a shoestring & inventiveness (pretty typical).
There are 3 main A Frames, with horizontal interconnecting Rafters, then multiple vertically orientated 3 x 2" (I think) timbers laid on top, then the cross battens & slates atop that.
Everything above the A Frames is rotten & riddled with worm holes, so got to go.
The Timber Wall plate the 3x2's rest on its absolutely rotten through

My question is about the A Frames.
I think they are so big/thick that they would still be sound - if I could treat them & retain them, I could tackle the damaged half of the roof to get it water tight, then sort the other side at a later date.
But....
At least one of the A Frames (the others look ok) has a rotten foot on one end (on the side with the undamaged roof half as it happens).
Given this A Frame will have I think both compression and lateral loads upon it..... is it feasible to:
- acro-prop the frame to take the weight off the wall & the knackered section...
- cut the A-frame leg back to shoulder wood....
- splice in new timber & brace it (e.g. "splint" it either side of the cut, and drill/bolt with threaded bar to effect a sound repair.
It seems feasible to me.... but then I'm not a structural engineer or a Roofer!

 

[Porkypine]

I've bodged similar old farm type buildings very successfully like that. If the main sections are oak for instance ( like some of the stuff I've messed with) they'll be likely quite solid enogh even if there's a fair bit of rot present.
I'd press on with your idea myself, obviously the 'pros' would suck air thru teeth and say 'ooh it all needs replacing from new' type thing !

 

[GRW]

I've bodged similar old farm type buildings very successfully like that. If the main sections are oak for instance ( like some of the stuff I've messed with) they'll be likely quite solid enogh even if there's a fair bit of rot present.
I'd press on with your idea myself, obviously the 'pros' would suck air thru teeth and say 'ooh it all needs replacing from new' type thing !

Brilliant, thanks! Given the original build snd somewhat..... rustic nature of the whole building with very "creative" let's say construction techniques... an all new roof would not be affordable & in any case would be polishing a turd.
(If going that far it'd really warrant doing out the entire building ground up, with new doorway lintels, windows, electrics, plumbing......

 

[Beanwood]

Sounds very like the A frames my chippy had to fix many years ago. Treated them for woodworm and very solid apart from the end couple or three feet. He scarfed in new ends with a sort of stretched z cut- glued and dowelled- perfectly fine for years after.

 

[Beanwood]

Like this one? Wedged stop scarf joint

 

[Mark 5]

Storm Darragh did my elderly ole man's place somewhat of a walloping.

Everything above the A Frames is rotten & riddled with worm holes, so got to go.
The Timber Wall plate the 3x2's rest on its absolutely rotten through

My question is about the A Frames.
But....
At least one of the A Frames (the others look ok) has a rotten foot on one end (on the side with the undamaged roof half as it happens).
Given this A Frame will have I think both compression and lateral loads upon it..... is it feasible to:
- acro-prop the frame to take the weight off the wall & the knackered section...
- cut the A-frame leg back to shoulder wood....
- splice in new timber & brace it (e.g. "splint" it either side of the cut, and drill/bolt with threaded bar to effect a sound repair.
It seems feasible to me.... but then I'm not a structural engineer or a Roofer!

I'm not a roofer but yes I think it is.

The first concern would be to insure you are supporting and not lifting the section of the roof, then splint either side of the cut.

I personally wouldn't use threaded bar but some long coach bolts, square plate washers and dog tooth where you can to help prevent twisting in the splice.

And start treating the timbers.

 

[GRW]

I'm not a roofer but yes I think it is.

The first concern would be to insure you are supporting and not lifting the section of the roof, then splint either side of the cut.

I personally wouldn't use threaded bar but some long coach bolts, square plate washers and dog tooth where you can to help prevent twisting in the splice.

And start treating the timbers.

By dog tooth I assume you mean cut and fold the plate washers to bite into the timber?

 

[gaz1]

im going to say this

no one on this forum can advise you if it can be done just by what your saying

its an unseen beam with no pics and no sizes to play with

 

[Mark 5]

By dog tooth I assume you mean cut and fold the plate washers to bite into the timber?

Just like me, have I used the wrong term? I mean these.

 

[addjunkie]

I looked at doing exactly what your talking about……but on deeper inspection, and adding up the costs including time, materials etc. But I had to make sure a proper structural bloke would put his name to it being ok, as part of my planning/ building inspector etc.

It worked out far cheaper to rip the lot off and buy brand new raised leg trusses for a complete new roof.

 

[Mark 5]

I looked at doing exactly what your talking about……but on deeper inspection, and adding up the costs including time, materials etc. But I had to make sure a proper structural bloke would put his name to it being ok, as part of my planning/ building inspector etc.

It worked out far cheaper to rip the lot off and buy brand new raised leg trusses for a complete new roof.
View attachment 494831View attachment 494832

Some times it's just better and more cost affective to start anew.

 

[GRW]

im going to say this

no one on this forum can advise you if it can be done just by what your saying

its an unseen beam with no pics and no sizes to play with

I understand that yes. It was more the idea/principle. I might have got a logical, structural aspect that I hadn't considered or known about, so I sought input from others with more knowledge than I.

 

[sako243]

Depending on your use case internally you could also put some legs down the inside of the wall. We couldn't scarf a new piece into one of the slightly dodgy A frames on the office due to access. It was timber plated either side with some threaded bar through it (couldn't find big enough coach bolts at the time locally). The new bits of timber were planted thoroughly and bolted down to some new concrete on top of the stone walls.

Since we also had the wall plate for the floor below some 4x4 posts were then also used between the A frame and the wall plate. You've seen has a silly number of anchor points concreted into the wall.

 

[GRW]

Depending on your use case internally you could also put some legs down the inside of the wall. We couldn't scarf a new piece into one of the slightly dodgy A frames on the office due to access. It was timber plated either side with some threaded bar through it (couldn't find big enough coach bolts at the time locally). The new bits of timber were planted thoroughly and bolted down to some new concrete on top of the stone walls.

Since we also had the wall plate for the floor below some 4x4 posts were then also used between the A frame and the wall plate. You've seen has a silly number of anchor points concreted into the wall.

This one can be got at I think OK to cut etc.... and it's only single storey.
Yes, it could be propped but its not a wide space so that'd be last resort I think

 

[gaz1]

now the longest roofs are cathedrals and churches the oldest are wood frame jointed wood pegged and scarf joint galore on there builds

but to give you a good idea of size they play with

scarf joints are best used at supported areas whilst the long scarf joint is one of the strongest

yes you can sister joint them

 

[gaz1]

what is the size of building that you have

now you can use a scissor truss like this

 

[GRW]

what is the size of building that you have

Its single story & without being there to put a tape over it, I'd say inside dimensions about 10 metres L x 5m across.

It's an old cowshed parlour that was converted into loose boxes for horses by my old Mum 20-odd years ago.

The damaged part is an added-on extension to the original building, with its roof going into and tying into the original roof (which is in the opposite orientation - so a "Hip" roof maybe??) & not even at 90-degrees to the pre-existing - more like 80-degrees to allow for a gateway & access between it & the Dutch barn I think. Usual rural oddness.

I think a can of worms might be opened when I get into it, with loose mess atop the walls, short wood pads under the A frame feet, and a rotten wooden wall plate for the batten carrier timbers (apologies for any/all failures to apply correct terminology!).
I might need to do some stonework repairs and maybe shutter a concrete beam on top for the roof to rest on - not sure at this point tbh.

It's a case I think of just how far do you go with an old weird outbuilding. We of course want it sound and retaining its character, but don't have a bottomless pit of money to throw at it - esp. with the essential work needed on the house (if we get the house pine end dry, there's all the inside rendering & plastering to sort out after that).

 

[gaz1]

if you want to see scissor trusses best place is cathedrals and notre dam is one of them