Hi everyone, i have rotten joists in my back room!

Hi Sally It sounds to me that you've already sussed out the problem, the patio is higher than the damp-course.The outside ground level should be at least 150mm below the damp-course level. Maybe it's an older property with just a layer of slate for a dampcourse and hasn't had a modern damp-course injection. I would suggest getting in a Tradesman to have a look sooner rather than later, once the floor joists start to rot you could have a much bigger problem on your hands! Good luck Regards J Chappell Joiner & Builder

Hi Sally Your damp course might be visible externally! It is always 2 courses above external ground level(150mm). Or in comparison to the internal level it can be just above internal floor level depending on the external! . As for your airvents they could have debris and cobwebs blocking them from letting a better flow of air! maybe try to have a look or get a torch and shine it through. The joists if touching the external wall will take on any moisture and thus track onto the flooring and skirting(if the wall is damp under the DPC line). Joists and wall plate should be at least 25mm away from the external wall. If the vents are blocked and there is lack of ventilation then timbers will get damp and mouldy from moisture in the air off of the oversite. Lots of various things can contribute to damp,wet rot,dry rot,condensation. If timbers are damp/mouldy and sponge like then sorry it will be a case of taking out the affected timbers and replace and treat. Good luck. Scott.

The first thing to do is reduce the concrete outside to minimum 150mm below your floor level. With all suspended timber floors you need good air flow/ventilation. Make sure all vents are clear, and add more if needed, you will have to cut out any rotten timbers back to good solid wood. Treat all the timbers and if any are being built into wall, wrap the ends in dpc.