Cupped floorboards - Source of moisture above or below floor?

[Deleted member 174758]

It isn't necessarily damp per se that causes it - I've seen cupping occur in Victorian houses (whose timbers would originally have been air dried to circa 16% moisture content, and which would probably get no drier than 12% MC in the days of coal fires) where there was no significant cupping - until central heating was installed. The CH can take the MC of timber down rapidly to well below 8% on the top side (leaving the bottom at 12 to 16%), resulting in cupping. Not frequent, but it does happen

 

[tel765]

Well OK - You make a good case, so does foxhole but i used the term damp to cover the issue and stay on page.
Talking about moisture content etc might lead us away from the OP's complaint.

 

[Nige F]

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[NewbieHouseGuy]

Damp causes cupping - over boarding will do nothing for damp, in fact it might increase the risk.
Presumably you have GF suspended floors?

Your problem is damp - damp from a variety of sources.
Powerful Extractors are a must in bathrooms and kitchens.
The heating system must be able to operate at its full capacity when needed.
Trickle heating with trickle venting is often successful with condensation.
Through ventilation below any suspended G/floors is needed.
Clothes dryer to vent externally.

@tel765 Thanks for this. Ventilation is definitely something I want to look into. We have three airblocks on one side of house, though I have no idea whether they have been blocked off anywhere along the cavity that they connect to (I can totally imagine a crazy DIY choice by previous owners considering all the things I am finding!). It's the upstairs that has all the issues (and there are no airlocks midway up the house). What kind of professional would I get in to check the ventilation?

 

[tel765]

Air bricks are not meant to vent cavities (but willy nilly many a/b's do open into cavities), neither are you - dont vent your cavities.
Air bricks that are low in your walls (150mm above GL) are meant to through-vent, &/or cross ventilate, the suspended floors from rear elevation to front elevation.
High level a/b's are meant to help prevent condensation & provide make-up air for appliances
A/B's must be kept clean and open. Blown CWI sometimes blocks a/b's. Shine a light thro the a/b to see if they are clear.
Regs suggest installing a/b's at approx 1.5m intervals around the house.

To basic check the ventilation post pics of interiors & exteriors on here.