Rotted rafters

[adamr7747]

Hi All,

I went to see a property the other day which we're considering buying at auction. It's a couple of hundred years old & grade 2* listed. My main concern is the roof. There seems to be a mix of very old & newer timber. Lots of the rafters have the same problem: the lower third of the rafter is totally decayed & comes away easily into powder. The exterior of the decayed portion has a honeycombe texture & the whole rafter is a slightly odd dark brown colour.

My general understanding is that any decay needs moisture, but the strange thing is I can't see any indication of any moisture in the roof space and it looks sound from the outside - no missing slates or sagging areas. So what would have caused the lower portion of the joists to decay? And can I assume that because everything's dry now it'll be fine for the foreseeable future?

Thanks,
Adam

 

[mrrusty]

honeycomb sounds more like woodworm than rot.

 

[adamr7747]

Sorry, I was using "rot" to refer to any decay - I'll edit to make clearer.

 

[adamr7747]

Any thoughts? I guess one potential source of moisture would be condensation resulting from the heavy sarking restricting ventilation & blanket insulation on the floor making the void cold - but wouldn't the decay work down from where the timbers touch the sarking in that case?

 

[gonch69]

That's not rot it's wood worm/Beatle you can tell by the dryness and bore holes and powder left behind

 

[Old Salt]

Looks like it may be woodworm. The second picture, top left if you blow it up you can see what appears to be exit holes.

 

[Nige F]

It's woodworm + Grade 2 * = How deep are your pockets ?

 

[gonch69]

Yep gonna need to be very deep

 

[adamr7747]

Well, the guide price for the house is quite very low, so hopefully if we have to spend a fortune on the roof we'll get the money back in increased value. I don't know what "very deep" means though - are we looking at £20k or £200k? It's a large, 3-bed C18 stone house in Cornwall.

I'm still wondering how the decay happened, but perhaps it's a bit academic...

Adam

 

[mikeey84]

From what I understand, they usually want roof structures repaired, not replaced, which is obviously more labour intensive.

Costs is a difficult one, as its not a usual rip out and replace job, so ideally you'd need to speak to someone who knows how to handle old roof timberd

 

[adamr7747]

they usually want roof structures repaired

Something possibly in my favour is that the decay seems to be in relatively new timber - so perhaps I'd get away with replacing that

ideally you'd need to speak to someone who knows how to handle old roof timbers

I'm intending to try and get a builder (ideally experienced in "heritage" properties!) to look round with me, but because it's an auction property the timing is so tight so it just might not happen :/