Buying a house with possible unknown subfloor damage

BlondBoy

Had a very similar situation when I bought last year. As others have said, worth asking the vendor via the agent if they’ll accept an invasive test. If not, a good damp and timber specialist can probably give you their best guess of the problem and cost to fix.

FWIW, in my case, the best guess was broadly right. More joist ends had decayed than guessed, so a few more to replace. But that only added around £100 to the final cost, above the specialist’s estimate. And once the cause was addressed, the elevated damp readings in the walls went away over a couple of months.

As you’re renovating anyway, sounds like it’s probably just one more (messy) job to add to the list. But a good independent damp and timber specialist will definitely be your friend here. Good luck!

7seas

youth_leader said:

When my buyer had a damp/timber survey on my victorian property, I hadn't been told to lift the floorboards.  I didn't have fitted carpets, just rugs.  I now know that it only involves getting a joiner to take up a few boards so the joists can be inspected.  Hopefully  your vendor will oblige and you will be reassured.  

I've just spent the last of my savings having all the floors in this bungalow replaced because the sub void wasn't able to be inspected.  I had wet/dry rot and woodworm, plus mushy plasterboard.  I wish I'd had an independent damp/timber survey.

Sounds like there can be a chance my seller could well be happy to lift the floorboard so I will definitely ask them at least. The house floor is just bare suspended floor board, no laminated floor, no carpet so should not be too difficult!

FreeBear

If you do buy, and you end up having to take up the floor, that will be a good opportunity to whack some insulation in - Just be careful not to compromise the under-floor ventilation. Depending on the extent of renovations, do the exterior walls (from the inside) at the same time. Cork or woodfibre boards finished off with a lime plaster would be sympathetic to the building and allow the walls to breath. With the way energy prices are going, anything you can do to improve the insulation is a good thing.

youth_leader

You can only get 'victorian' sized boards from salvage yards now I believe 7seas, so make sure your trades are careful with them if you proceed.  My plumber broke a floorboard, and I had to fix it back together with metal plates. Our nearest salvage yard is 50 miles away.

7seas

FreeBear said:

If you do buy, and you end up having to take up the floor, that will be a good opportunity to whack some insulation in - Just be careful not to compromise the under-floor ventilation. Depending on the extent of renovations, do the exterior walls (from the inside) at the same time. Cork or woodfibre boards finished off with a lime plaster would be sympathetic to the building and allow the walls to breath. With the way energy prices are going, anything you can do to improve the insulation is a good thing.

 I didn’t think about it but it seems a good additional thing if we are lifting the floor anyway. Thank you for the input!

7seas

youth_leader said:

You can only get 'victorian' sized boards from salvage yards now I believe 7seas, so make sure your trades are careful with them if you proceed.  My plumber broke a floorboard, and I had to fix it back together with metal plates. Our nearest salvage yard is 50 miles away.

Sorry I am completely novice about it, but what do you mean by ‘Victorian’ sized board? And how can they not produce ‘Victorian’ size one? Isn’t it just cutting wood in particular size?

j2009

Ramouth said:

We had a house where this had occurred due to blocked air vents and joists resting on the soil in some locations.  It was fairly disruptive to sort out as the floors needed to come up but not hideously expensive and if you don’t have to live there at the same time it won’t be nearly so bad.

In hindsight, we should have known there was an issue with the structure of the floor as it was noticeably bouncy to walk on.  Did you notice this when viewing the property?  In our case it was significant enough for plates to rattle.

Ditto, had this too, bouncy floor and big gap in one corner between floor and skirting. Our issue wasn't ventilation but poor drainage and the subfloor was filling with water (not uncommon).

The floor itself was 'cheap' to sort, and if it is drainage then there are reasonably priced options.

Sounds like the floor will need to come up and my advice is wait until Feb/March so you can see how high the water table gets as there's no point replacing the floor only to have it rot again. You will need building regs as you'll likely be lifting more than 25% of the floor and they like to see 100mm of insulation go in.

Or you could replace the whole floor (which I'm guessing is wood on honey comb sleeper walls) with a DPM and concrete. Although if it is water table you'll have problems elsewhere so better to know!

Either way not a disaster!

youth_leader

@7seas, they don't  cut the 6" boards any more.  I went to my local independent wood man, and he said I'd have to go to a reclamation/salvage yard.  

7seas

Just to update, our damp surveyor will go to the house for survey next week and he’s got permission to lift the floor board. Hopefully it will all clarify the situation, good or bad.

Thank you all for your input!

FreeBear

j2009 said: Sounds like the floor will need to come up and my advice is wait until Feb/March so you can see how high the water table gets as there's no point replacing the floor only to have it rot again. You will need building regs as you'll likely be lifting more than 25% of the floor and they like to see 100mm of insulation go in.

Depending on the room size, you may get away with 65mm of Celotex. However, there is a cop out if space is limited. The level of insulation can be less if it is not technically possible to fit enough to hit the target required for a refurbishment. With a lot of older properties, the joists on the ground floor are just 75x50mm with sleeper walls at roughly 1800mm intervals. You need to allow sufficient space above the sleeper walls for free flow of air.