Advice on timber rot/woodworm infestation and sub floor ventilation

cherrytree123

Hi all, we're looking to buy a house built 1935 and just had a structural survey done. The report came back with a number of 'Defects that are serious and/or need to be repaired, replaced or investigated urgently' and some of them we aren't really concerned about. But there's these points below that we aren't too sure about and wondering if someone who is an expert in this area would be able to advise please

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1) Suspended timber floors in properties of this age can sometimes be found to be affected by rot/woodworm infestation once carpets/floor coverings are lifted due to reduced levels of ventilation and elevated levels of dampness. Therefore, provision should be made for replacing any affected timber as and where necessary
2) The sub-floor ventilation is not up to modern standards. Vents should be fitted at 1.5m intervals. Restricted ventilation can result in noxious gases and/or condensation that can cause woodworm and wet/dry rot to affect the floor timbers and other components of the building. Therefore, the timber floors should be inspected by a timber treatment contractor. This will require removal of floor coverings and floorboards to allow a thorough inspection. The ventilation should then be increased as much as possible to modern standards by a reputable building contractor. It is unlikely cross ventilation will be able to be achieved therefore mechanical ventilation should be considered.
3) As is usual for buildings of this period, the render extends down to ground level. This is now considered poor practice as it may result in bridging of the damp proof course and ideally render should be terminated in a bell drip above the damp-proof course

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To us the house is beautiful and in excellent condition. From the report, there's no evidence of any dampness (we assume they had used a moisture meter as it's a full building survey). Also no evidence of rot or infestation (but then again floors are all floored and carpeted so couldn't be inspected).

Are the 3 points above just general recommendations or is it really something urgent we should look into? Any thoughts or advice on this would be appreciated, thank you

FreeBear

cherrytree123 said:

Hi all, we're looking to buy a house built 1935 and just had a structural survey done.

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To us the house is beautiful and in excellent condition. From the report, there's no evidence of any dampness (we assume they had used a moisture meter as it's a full building survey). Also no evidence of rot or infestation (but then again floors are all floored and carpeted so couldn't be inspected).

It is fairly certain that there will be signs of woodworm in some of the floorboards. Most likely in the bathroom & kitchen. As long as the timber is dry, it won't be a problem, and I certainly wouldn't waste money on getting a damp & timber survey done - If you go that route, the company will want to sell you some expensive treatments involving toxic chemicals being sprayed around. In all probability, the chemicals wouldn't get to where the woodworm had been.. Instead, spend a few quid on a cheap moisture meter and check the floors yourself. Anything under 20-25% will be good. Woodworm & rot doesn't infest in timber that dry. As to the comment about air bricks, it would be wise to check that the air bricks are not blocked, and you have one every 6 to 8 feet. Again, I wouldn't bother with mechanical ventilation - It is something else that will need regular maintenance and replacing once in a while.

Should you find any floorboards that do need to be replaced, pay a visit to a local building reclamation yard for some old boards. If the floors are anything like mine, the boards will be ~22mm thick. Off the shelf boards from the likes of B&Q will be 19mm, so you either need to use packing shims or get a timber merchant to plane them to size if reclaimed boards are not available. The joys of an older property...

knightstyle

We bought a similar house a few years ago and found rot and active woodworm under the ground floor. We ripped up and burned the worst boards and treated the rest and the beams, replacing two of them as the ends were very bad. All fairly simple DIY jobs and we did a room at a time whilst living there working full time on our regular jobs.  We then took floor boards from upstairs to use down stairs and used chipboard upstairs, we rewired at the same time.  
Lots of disruption for us and our children but well worth it.  All this took just under a year and the house still looks great.

cherrytree123

Hi both, thank you so much. We appreciate your time and advise. We will start with getting a moisture meter and check the floors, and yes will also check the air bricks. Relieved to hear we shouldn't bother with mechanical ventilation (did google earlier and it seemed complicated and expensive). Hopefully we won't have find any dampness and won't have to replace any floorboards. You did say it's fairly simple but we aren't good at DIY..  Will get a moisture meter and take it from there. Thank you so much!

FreeBear

A 1935 build will probably have tongue & groove floorboards on the ground floor - These can be a right royal pain to lift without causing damage. An oscillating multi tool with a suitable blade run along the length of the board sidesteps that little problem.

As for woodworm - If you see some small holes (1-2mm dia), this is where the worm has exited the wood as a fully grown beetle. The holes will remain in perpetuity and can not be relied on as an indicator of an active infestation. The grubs (if there are any) will be hidden inside damp timber munching away for two or three years.

cherrytree123

With the moisture meter, do we just stick the metal needles through the floors to check? We only need to lift the floorboards if the reading is over 25%, is that correct? Have ordered a moisture meter now so will be checking the floors soon. Fingers crossed no damp. Will update you how we get on, thank you FreeBear :-)

FreeBear

Just poke the pointy prongs in to the wood firmly, but not buried up to the hilt. Be warned - These things do not give valid readings on plaster, brick, or any other material except (untreated) wood. If you find readings of 25% and above, you need to investigate the source of the problem before replacing. No point in replacing damp or rotting wood as the new stuff will go the same way if the root problem isn't fixed.

Even if you do find timber with readings of 25% and above, they may not need replacing - If you get to them before rot/woodworm sets in, after drying out, they'll be fine.

cherrytree123

Noted and thank you so much. The moisture meter is meant to arrive tomorrow, hopefully we can go to the house sometimes this week and check the floors. We're keeping our fingers crossed everything crossed! 

cherrytree123

Just an update, we checked the floors and there was no damp :-) Also it turned out the surveyor missed a vent at the rear extension (garden storage was blocking his view) so he thought the property didn't have enough ventilation hence all those recommendations. We're now happy to proceed with the purchase. Thank you again for your advice!