Pine boards, probably original to the 1910s house, in the sitting room. Every winter once the heating goes on the gaps open up to maybe 5mm in places and I can see down between them. In summer they close back to almost nothing. First winter here so I don't know if this is a house problem or just what old wood does. Should I be filling them?
Second the no-rigid-filler advice. If you want to close them visually, the slivers method is the only one I've seen still look right after five years. It's slow work — figure a full weekend for a decent sized room — but it's permanent.
Whatever you do, don't lift and re-lay them tight in January. People do this and then in July the boards have nowhere to expand and they cup or lift at the edges. If you ever do re-lay, do it in a damp month.
Check your humidity too. 5mm is normal but if your house swings from 65% in August to 30% in January that's a bigger cycle than most, and it's hard on furniture and doors as well as floors. Cheap hygrometer will tell you in a day.
Agreed. Radiators cranked high in a house with poor ventilation dry timber out far more than the outdoor climate does.
A big rug helps more than you'd think, and costs an afternoon rather than a weekend. Not a purist answer but a real one for a first winter.
@rueben_alsop · 2mo ago · 3 replies
Completely normal and it's a moisture cycle, not a fault. Timber gives up water when the heating is on and takes it back in the humid months, and it moves across the grain far more than along it. On a 150mm board a 5mm swing is unremarkable.
Do not fill them with anything rigid. Filler, resin or wood glue in a gap that moves seasonally will either crack out or, worse, hold the boards apart so they can't close in summer and then split them somewhere else. The traditional answers are slivers of matching timber tapped in and glued to one side only, or a rope-and-caulk method, or accepting the gaps and dealing with the draught underneath instead.
Honestly, in a room you want warm, insulating between the joists from below and draught-proofing the perimeter does far more than filling gaps ever will.
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@rueben_alsop · 2mo ago
Very much so, and having cellar access makes you lucky. Mineral wool batts held up with netting stapled to the joists is the standard approach — leave an air gap and don't block any subfloor vents, because those keep the timber dry.
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@levain_lorna · 2mo ago
There's a cellar under this room so I could get at the underside. Is that a DIY job?
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