Replacing floorboards with mdf in Victorian flat

[iwilson16]

Hi,

I have an old Victorian Edinburgh tenement flat. The floorboards in the hall and living room have been sanded and varnished, but are in a bad state after a rewire and re-plumb.

To make matters worse, in some places the joists have been notched such that it will be impossible to re-lay the flooboards.

So I'm thinking of replacing the floorboard with 2400x600x22mm MDF T&G floor panels. The current floorboards are 25mm thick, and 150mm wide in hall and 75mm wide in living room. I plan to pack the joists with 4mm stripwood so that the boards clear the old iron conduit belonging to the flat below (its a conversion ... and the conduit sits slightly higher than the joists).

Does this sound like a reasonable plan? And is it something a fairly competent with DIY'er could do?

The biggest issue I think I'd face would be the edges of the room. Should I remove the skirting first? If I did that, then there's a chance the plaster would come off as well. I was kind of hoping I could slide the MDF under the skirting.

Thanks
Ian

 

[TheVictorian]

Could we have a photo please? I personally would try to get 25mm ply with a 4mm channel cut out where the conduit sits, I don't like packing as it might allow movement/squeaks in the future, I also don't like MDF!

 

[JohnD]

As it's a tenement, I would use the opportunity of the floor being up to pack between the joists with dense mineral wool batts to reduce sound transmission. They are heavier than loft insulation, and found in builders merchants and larger DIY sheds.

Yes, ply is much better than MDF. Screw it down, rather than nails, and re-tighten after a couple of weeks. Nog all short edges..

 

[iwilson16]

Between the joists is filled with 'deafening', so no space (or need) to add any mineral wool. Sound insulation is very good in these old Edinburgh flats.

Good idea re. the 25mm plywood, plus the notching. I guess a router would be the best tool to take a few mm of the underside where the conduit it. Its really only the old conduit junction boxes that the the problem.

The joists are at 460mm centres. I'd aim to get the short wedges half way over the joists, so where would nogging be required?

Thanks
Ian

 

[JohnD]

noggins under any short ends that are not over a joist.

 

[ree]

Have you removed the cover to the conduit J/B, or used a cable tester, and tested for live - i doubt it but is it possible that the conduit is carrying redundant cables?

Has the floor had a history of creaking or squeaking?

No need to lift all the floor - use chipboard nearest to the wall T&G floorboards. Square off to fit chipboard. In fact, removing the T&G too close to the wall and under it will open up another rats nest. So leave the T&G near the wall alone.

Replacement would require carefully marking out the chipboard or T&G for points that can be screwed down into the joists. You would have to face screw the boards.

There's a whole bunch of other stuff but most of it will be obvious to you.

FWIW: nexttime you havea rad pe-positioned, paint behind it before re-hanging.

 

[JohnD]

chipboard, vom vom

 

[Burnerman]

Slip tubing! Right on.....
Be sooooo careful when you screw your new boards down - lots of good targets there!
John

 

[iwilson16]

Thanks ... all good advice. The living room floor is actually in not too bad a state, apart from the ripped up boards. Plus I plan to carpet the LR anyway. So I might get away with patching up the LR floor with the 150mm boards lifted from the hall (i.e. replace two 75mm boards with one 150mm one), then screw 6mm plywood over the lot to give a good draught-free level floor for the carpet fitters.

For the hall I really want a smooth level floor as I plan to put down laminate or LVT. Good idea about leaving the edge board alone. That will save a lot of work and mess!

I've already repaired all three bedrooms and upstairs landing floorboards after the rewire. That was a job and a half! Didnt help that the boards had been resting on the old lead water pipes, so had to pack up the joists etc. before fitting the floorboards back down. So I'm very careful to measure twice before screwing down the boards so that I avoid the wires and pipes.

The electrician did check all the old conduit wiring using an induction type tester (I things thats what its called ... I was so impressed I bought one myself). Its a conversion from a Victorian town house into lower and double-upper flats, so the lights for the flat below are underneath my floorboards. Not ideal, I know.

Re. the radiator, I'll probably take it off when I get round to decorating.

My local timber merchant only has one type of plywood in 25mm thickness - Exterior Far Eastern plywood 25x2440x1220 at £49 per sheet (£39 for 6+).

Thanks,
Ian

 

[JohnD]

I used 18mm from Wickes, it was cheaper than from the woodyard.

If you are not going to tile it, 18mm should be fine.

 

[iwilson16]

I kind off have to use 25mm sheets if I am to leave the edge floorboards in place. They will be difficult to handle and cut though.

Ian

 

[JohnD]

Does the wall stand on the floorboards?

 

[iwilson16]

No, I'm pretty sure the walls dont stand on the floorboards. The skirting does though, and thats pretty tall and thick compared to modern skirting. I keep changing my mind about taking the skirting off. It would be much easier to replace the floorboards if I did, however it would be hard to replace. In a previous Victorian flat I had to get a one-off tooling thing made in order for the timer merchant to make new skirting. And its very likely large chunks of the old plaster would come off as well.

Ian

 

[iwilson16]

Some question on fitting the plywood ....

Should I butt the edges together as close as possible? Or leave a small gap then fill that with
floor mastic (to avoid boards rubbing together)

Are 3.5 x 50mm screws the best choice for screwing 25mm plywood to floor joists?

Or should I use a larger screw, and pre-drill a pilot hole? Or a longer screw?

Thanks
Ian

 

[joe-90]

You want to replace original Victorian boards with ply and laminate? Are you mad? You'll devalue your flat.