Rafter deposits

[cjfmgowan]

Hi All,

I've just bought a period property (circa 1840) and been in the attic, the condition looks okay but noticed a deposit on the rafters (it's not on them all).

I've attached a picture of the worst effected rafters. I *think* it's perhaps the rafter has got wet in the past and the salts / minerals have comes to the top? (that's a laymans guess)

I've attached the picture.

 

[JanJonWestWales]

hard to tell from the picture, as it is quite small.
But it could be remnants of lime left on the rafters after the laths have been removed?
or it could be mold. Is it damp , or are there signs of damp in the past??

 

[cjfmgowan]

Yes I couldn't upload a larger photo unfortunately, I might upload and try again.

I don't think there has been previous lath and plaster in the attic, so I don't think it can be that.

I'm not sure if it's mold as it's dry and crumbly, it breaks away very easily when I touch it.

I'll check again for signs of damp, it's not wet now but anything could have happened in the last 150 years!

 

[Abi Cott]

I'd vote for salts

 

[Kearn]

I'd vote for salts

Certainly looks like that from as much as I can zoom in on the pic...!

 

[Anonymous]

Salts in wood ?? am thinkin it's lime from the scorching

 

[stuart45]

By scorching do you mean the lime mortar used on the base of the tiles? I know the method by the name of torching. I have seen white marks in roof spaces where there has been a leak. Possibly salts washed through from the tiles.

 

[philpjuk100]

Could it have been sprayed with some type of insecticide/preservative?.We were warned that the timber in our south facing hipped roof had been treated in the 70s and could it could contain arsenic.

 

[CliffordPope]

I've seen this on perfectly sound and apparently dry timber.
This is what Property Expert Jeff in the Daily Telegraph said in 2004:
" It is common to find white powdery deposits on the rafters of old houses, and on the undersides of the clay tiles that they support. This is the result of salts being leeched through the tiles by the slow penetration of rainwater over the years, and, as long as the rafters are dry, is no cause for concern. The powder is usually magnesium sulphate".

 

[cjfmgowan]

Thanks everyone , very useful information.

CliffordPope , thanks for digging out that quote, definitely sounds like the case here!