Building a new block shed where there was dry rot in the previous wooden one

[MrB]

I inherited a large (4m x3m) wooden shed with a suspended floor. It's built on two rows of concrete blocks with a DPC on top. The wooden shed frames a re mounted on the DPC. Flooring joists rest on the DPC above the blocks and the wooden floor is fixed to the joists. However, when it was constructed, no ventilation was provided underneath. To make matters worse, loads of wo od off-cuts and debris were left there and now, years later, extensive dry rot started appearing up the walls.

I've now removed the floor and the joists completely - it was quite a funga l foray! However, some of the framing timbers are also badly affected. Rath er than carry out repairs, I've decided to dismantle the wooden shed and bu ild one using concrete blocks with a solid floor.

I'd like to know if there any particular precautions that I'd need to take when building in this area. Is it safe to reuse any of the original concret e blocks that were part of the foundation as hardcore etc.?

[Fredxxx]

Some time ago I had an issue with dry rot.

In essence if the wood is dry enough, dry rot cannot establish.

I'm assuming that while you are making a concrete/block shed, the roof is going to use conventional rafters?

Ventilation of roof rafters will be the key to eliminating all kinds of rot. Any heating also helps!

Its only called dry rot as it can establish in timbers with 20% moisture content or greater, which is lower than other forms of rot.

[Andrew Mawson]

Dry Rot spores are everywhere, they just need the right conditions to propagate, so your concrete blocks should be fine as hard core, and if covered in concrete the alkaline nature of the cement will inhibit them. f you are concerned, flash over the surface with a blow lamp.

[MrB]

Thanks very much for your help guys. That's a great tip about the blowlamp.

[newshound]

Whilst I don't think you really need to worry about spores in your particular case, I am not sure that flashing with the blowlamp would get everything in those little "pockets" a few mm wide and deep. I think you would need to heat every part directly for several seconds at least. A proper dry rot sterilising solution would be better.