DIY Doctor

1930s Semi ; Novice questions on damp / mouldy roof timber

Postby MHAD » Sat Jun 30, 2007 6:27 pm

Hi. I have some very novice queries about the roof timbers in our 1930s semi. We have just boarded out the loft and fitted proper lighting, so can now see everything clearly for the first time after buying the house last year.

Last month we had the hip and ridge tiles repointing, and the lead flashing around a chimney checked and partially replaced by a professional roofer.

Queries are in two parts:

1. There looks like there has been a long term leak around the chimney breast, which has dripped through onto the rafter underneath and spread. The rafter is drying out but when it was wet it was quite wet in places, with white surface mould on the top. When this is completely dry I want to treat it with something to retain strength and, I'm told by the roofer, prevent risk of dry rot. I've looked at Ronseal Wet Rot Wood Hardener on Screwix and wonder if this is the right type of product to use. I haven't found any other alternative consolidant yet - is this stuff any good and will it do what it says on the tin?

2. Now that I can see properly in the loft space, I've noticed numerous areas of timber with surface mould. Some of this mould is fine and dark green / black, and some is fine white. Both types come away easily when wiped. The timbers they are on seem dry in the main, although might feel a little cold to the touch in comparison to others so may have been damp in the past. I've also found some isolated stark white fluffy bits, that remind me of a chrysalis, and are about 1/4'' in length. I don't know what any of these types of mould are, how serious they might be or whether I need to treat them somehow.

I've taken photos of all of this and uploaded them to photobucket in case anyone is willing to take a look and offer any helpful advice ! I'd be very grateful for an opinion before I start spending money on timber surveys and expensive remedies that I don't know will work or if they are even necessary.

We cleared out the roof space last week before boarding it out - all the old clothes, insulation, pictures etc were very dusty but were bone dry. Ventilation seems quite good - the cobwebs move about in the draft and you can feel a draft when you're standing still. We've insulated where we haven't boarded, and have kept a gap around the edge all the way round.

I'd like to put up some kind of covering on the inside of the roof so make the loft space a bit more dust and dirt proof. I know I need to be careful about causing more problems when doing this and have read about doing anything from cotton sheets to foil backed plasterboard to foil bubble wrap thermawrap. Before I do any of this I obviously want to make sure the roof is OK.

Hope someone can help - thanks very much.

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DIY asbestos test kits

Postby Bus Godden » Mon Jul 02, 2007 4:24 pm

Hi Rich,

I’m not sure about Wood Treatment, it isn’t my area, but I do know that if you have a permanently leaking roof it should be fixed!

I also know that the timbers of a well laid roof are quite capable of lasting for many hundreds of years, without any outside help - no all singing all dancing injection of some kind of modern plastic magic potion will cure the poor, or failing handiwork, that is causing problems (better to re-direct any drips into a bucket!).

If you have a good airflow and the stuff lying about in your loft is dry, it doesn’t seem that there is much of a problem otherwise (although good ventilation should be getting rid of the threads of mould you describe! the white powdery stuff could be salt?).

Bus Godden
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