About to replace a floor

'68 Fastback

Hi,

I'm rennovating my new(1873!) home. I've gutted the downstairs, damp proofed, replaced rotten sud walls etc, etc. The next job on the list is to replace the rotten floor in the sitting room.

There are three tassle walls to support the joists, one of which ive had to re build. I've got 3x4's for the tassle walls and 2x5's for the joists.

I'd be very greatful for any hints, tips or advice in relation to laying it all down and getting it all level. I'm pretty handy when it comes to this stuff but i need a bit of direction on this one.

Cheers.

RKQ

Check out the Homebond Manual, for notes and drawings about best practice.

Lay 100mm wide (4') pvc damp-proof-course along top of tassel walls.
Use galvanised straps at 1200mm centre, to fix treated wallplate to tassel wall.
Fit treated joists at 16' or 450mm centres.
Fit plastic mesh or chicken wire between joists to support Rockwool insulation.
Install Rockwool, tightly between joist.
Staple 500 guage vapour barrier to top of joists, over whole room.
Lap any joints by at least 150mm (6')
Fit t&g final solid floorboards.

'68 Fastback

Nice one!

would never have thought about the chicken wire for the rock wool.

Thanks a mil.

builditwell

If you fit dampproof on the tassel walls there is no need for 500 gauge membrane. You could use Tyvek which is a breathable roof covering comes on a 1 mtr wide roll and is like a very fine canvas which would be more suitable for holding rockwool in place as chicken wire would be like leaving a load of nail heads sticking up from joists and cause you hastle when you try to lay the t & g floor. Obviosly you could cut these peices of wire to size and tack to side of joists but why go thru all the hastle the roll will take seconds and is a continuous surface. One thing to bear in mind is the floor timbers must have adequate ventilation so as to prevent dry rot. Check that the breather vents at front of house are not blocked or obstructed or even plastered over. If they are not there they must be installed otherwise you will be redoing floor again in a couple of years. As RKQ said the Homebond manual is an excellent source for best practice.

Regards
Builditwell

RKQ

This drawing may help:-
http://www.woodspec.ie/iopen24/pub/detail_b_5.3.1.jpg

The vapour barrier is to prevent interstit condensation in the insulation. On a practical note it stops draughts.

Tyvek would work, but its expensive at €200 per roll ( 50m x 1.5m wide)
Its a breathable membrane so its not air tight, so expect draughts...
(500 guage costs afew euro!)

Staple Chicken wire or netting, which would be fitted between joists only!
Forming a "u" shaped support to the insulation. Cheap, effective & practical.

Ventilation is extremely important. Clean existings vents and install extra vents if required.

'68 Fastback

Thanks lads.

I've been told to use slate to level the wall plates. Is this true or is there a more modern alternative? Slate sounds a little messy.

RKQ

Slate was used in the past as a damp-proof-course and cavity closer.

Modern man made slate could perform this function, if you cut the slate accurately.( Water-proof fibre material)

IMO its easier to level the top of a wall with mortar - even if you have to use a small shutter!
Then un-roll 100mm plastic d.p.c and lay the wallplates on top, to hold in position.

Lots of people have lots of valid ideas... its up to you which works best for you. (Depends on how handy you are, time and money)

Good luck!

'68 Fastback

Cheers RKO, I think the walls are pretty level so i should be ok.

Jnealon

I did this a couple of years ago on my old cottage and if I was doing it again I would fill it with concrete instead.
Remove all the rubble under these floors as the insects love it under there. I also sprayed everywhere with this stuff I got from the damp store for insects etc. I used pressure treated timberand treating the ends with protim . put down a layer of 1000 gauge plastic to help keep out the moisture. Also check the vents are not blocked up and that under the floor is properly ventilated.
If I remember anything else I'll post it

'68 Fastback

Thanks for the response Jnealon.
Yep, rubble's gone, ground's sprayed and the vents have been cleared.
I was going to treat the whole timber as i've seen alot of woodworm evidence including one or two of the little ba$tard$. Do you think this is overkill?

builditwell

Hey Fastback

Its not overkill at all you are doing the right thing. It is better to treat the timber to the full extent that you can before it is covered again for another 100 years (You hope) Fingers crossed though. Like Jnealon said treating for damp is good practice on timber ends but people often overlook the insect problem, they hack out old wood and replace but often not enough and infect new timber installed. Jnealon mentioned where to get this stuff and is a good place for getting this product although there are plenty of suppliers.

Regards
Builditwell