Replacing a floor

[richard.selwyn]

I've got to replace a floor that's been eaten by woodworm. It is in the local lawyer's office and the secretary's chair just made a hole in the floor. I've just got back from patching it.
The current floor is pine t+g nailed to joists which are sitting on the ground. If I replace the joists, what should I use for the joists and should I put a dampproof membrane under each joist? There does not seem to be any ventilation and the client does not want to add any. The current joists seem about 100mm tall. I had planned on 22mm t+g damproof chipboard panels screwed to the existing joists, but they may be eaten through as well.

Any advice greatfully received.

(Please note I am in France. The client has said that if my solution does not meet local building regulations he is happy to sign a release)

 

[Dibs-h]

I've got to replace a floor that's been eaten by woodworm. It is in the local lawyer's office and the secretary's chair just made a hole in the floor. I've just got back from patching it.
The current floor is pine t+g nailed to joists which are sitting on the ground. If I replace the joists, what should I use for the joists and should I put a dampproof membrane under each joist? There does not seem to be any ventilation and the client does not want to add any. The current joists seem about 100mm tall. I had planned on 22mm t+g damproof chipboard panels screwed to the existing joists, but they may be eaten through as well.

Any advice greatfully received.

(Please note I am in France. The client has said that if my solution does not meet local building regulations he is happy to sign a release)

I wouldn't be suprised if the release is actually meaningless.

I suspect the lack of airflow is the reason for rot. As for sizes - it depends on whether you will put the new ones on the ground or lift them off.

 

[richard.selwyn]

Thanks for the first reply. The floor is not rotten - just woodworm eaten. I don't think I have any choice but to put the new ones on the ground for height reasons.
Any more help please?

 

[BigShot]

Can't offer any advice, but I've been known to walk away from jobs where the clients actually wanted work doing the cowboy way. I do the design side of things but have never been short on work enough to need to take up something like that.

I'd be wary about doing things not to code and relying on a disclaimer for protection unless you can get a solid backing to it.

I forget the term but in France isn't there a profession that can draw up binding contracts between people? Maybe a noteur or something like that?

Might be worth using one.

 

[richard.selwyn]

Thanks for the reply - the client IS one of those people who draw up legally binding contracts - a notary.

Since I can't establish clearly what the code requires for such a job here, what would I have to do in the UK for the job to be approved?

 

[trousers]

Approved by who?
If you mean Building Control, then I'm not sure he'd be that interested in a replacement timber floor.
If he did say you need building regs, one of the first things he would look for would be adequate ventilation, and the second would be min 75mm clear space to the bottom of any wall plate supporting a timber joist.
I reckon your shagged on both those counts :roll:

 

[grainoftruth]

I'm a surveyor before I'm a woodworker so this is an interesting one for me. I'm not familiar with French law and this sounds like odd construction detailing even by their standards.

If I understand you correctly, there is only 100mm between a solid sub-floor (earth?) and the flooring. If this is the case then ventilation would be problematic even if you could install it as there is no opportunity for circulation between the voids. Also, are you sure it's woodworm, termites are a common problem in France too?

If I were you I would only do the job if you need the work and I would definitely confirm his instructions that he wants the floor put back as is rather than the detailing improved, and get his 'release' from liability.

From what you say damp is not a major problem otherwise there would be rot too. I would definitely roll out a DPM under each joist but I don't think I'd membrane the whole floor, this could lead to other problems. Then use quality treated joists and flooring - as well as buying it pretreated I would put extra preservative on everything and doubly on the cut edges. This should withstand quite a bit of attack from rot, woodworm or termites. For belt and braces it might also be worth treating the sub-floor surface with preservative. Boron based compounds are extremely effective and there are products for brickwork or earth as well -boracol is a water based product, quite expensive, but you can rinse the sub-floor surface with it. I have used it successfully on dry rot before.

Finally, as an alternative you could consider repacing the floor with solid construction. From the sound of it 50mm polystyrene topped with a reinforced 75mm screed could do the job.

Hope this helps and good luck

Steve

 

[BigShot]

Richard - thought i was something like that but couldn't think of the english word for it. I lived in France for a while and can speak the language to a semi-alright level but can't read or write it so saying things on forums is always a bit difficult for me.

If he is a notary, I expect you'd be using a different notary to draw up the release, seems like what one might call a conflict of interest for him to be drawing up one that he was also party to. Haha.

 

[MIGNAL]

Woodworm love damp wood. Dry it out below a certain moisture content and they flee to better pastures. If you don't cure the air flow problem they'll be back. Chemicals might stop them but rather you than me.

 

[Cowboy _Builder]

What area are you in ,I've done quite a bit of restoration work in France and i'm in the prosess of renovating a house near Brive la Galliard in central France .
I always use treated timber and treat it again on site with Xylophene triple action .
If you find that it's Termites and not wood worm i'd get a company in to treat all the surrounding brickwork as termites will nest in the walls so just removing affected timber doesn't eradicate the problem .

 

[richard.selwyn]

Thank you everyone for the helpful replies.

It is definitely woodworm - they call them capricornes here - as the holes are tiny and the dust very fine. I've worked with termites in the US - they are impressive tunnelers!

One of the issues that will compound the problem is that the floor is covered in foam backed carpet which probably forms some kind of a vapour barrier. I would love to tell the lawyer to get someone else in but he is a) the local notary for the surrounding area, b)my notary and c) a friend. I don't think he wants a cheap botch doing, it's just knowing how to do the job right. The problem with pouring concrete will be access and the delay while it dries before he can move back in.

I've just been on a site where they glued a solid oak engineered floor to a concrete slab before the slab was dry. I think that they've got about £10,000 worth (its a hotel) of scrap flooring - but I don't think the owner has really understood the problem. I saw the company that fitted it come back last week, cut out planks that had raised and glue down new ones. How on earth they think that that will work is anyones guess. To make matters worse there are no expansion gaps anywhere.


I am in Normandy near Rouen, by the way.