Damp kitchen floor + raising the level

[iSelfBuild]

My kitchen floor is pretty damp, there are quarry tiles lade on a lime mortar over soil. I am planning to raise the floor 250mm so it is level all the way through the house with the dining room and lounge.

 

Would I be best taking up all the tiles? My plan was to take up the perimeter tiles allowing me to knock off about 500mm of the damp render on the inside of the kitchen. Id then probably pack the soil back in or perhaps it would be sensible to use gravel?

 

I was then thinking of laying a 30mm weak and dry mix of sand and cement to level the whole area as it is quite uneven. On top of this I was planning to lay a damp proof membrane lapped up the walls, 200mm of EPS and finish with a 18mm moisture resistant floor board.

 

Does that sound sensible? Or should I be trying to do a ventilated floor with joists - I guess the advantage of the joist option is I can build a sleeper wall slightly away from the existing damp brickwork. When the 500mm off damp render is knocked off it should allow the wall to breath if I add in some air bricks. The EPS option might just make the floor and walls sweat?

[ProDave]

I think if you raise the floor, you will need to ventilate the space underneath it, which means introducing air bricks.

 

Can you not instead lay a DPM, insulation and then concrete?

 

[Nickfromwales]

I'd avoid the ventilated option. 

Blind the quarry tiles with a smattering of sharp sand ( 5mm or so ) and get it as level as possible. Don't make the high points any higher, just fill in the 'dips'. 

Lay 25mm eps on the sand layer, and then lay your DPM. That'll protect the DPM and help absorb any sharp undulations. That's the 30mm layer sorted. 

Fill the remaining floor area with a 140mm layer of PIR.  

Fit 25mm eps around the perimeter to reduce cold bridging there. 

75-80mm of fibre impregnated screed on top as your finished floor. 

Bobs your uncle, fannys your aunt.

 

[iSelfBuild]

18 hours ago, Nickfromwales said:

I'd avoid the ventilated option. 

Blind the quarry tiles with a smattering of sharp sand ( 5mm or so ) and get it as level as possible. Don't make the high points any higher, just fill in the 'dips'. 

Lay 25mm eps on the sand layer, and then lay your DPM. That'll protect the DPM and help absorb any sharp undulations. That's the 30mm layer sorted. 

Fill the remaining floor area with a 140mm layer of PIR.  

Fit 25mm eps around the perimeter to reduce cold bridging there. 

75-80mm of fibre impregnated screed on top as your finished floor. 

Bobs your uncle, fannys your aunt.

 

Thanks Chaps,

 

Why would you avoid the ventilated option?

 

On reflection I think the ventilated option will allow the lower part of the walls to breath better? It probably will be cheaper than the concrete and EPS options...

 

I'm renovating this house for profit at the end of the day but I still want to do a proper job. The area is only about 10m2. 

[Nickfromwales]

If renovating for profit then I'd go with the simpler option, and float the floor. I thought it was one where you may be moving in, sorry. I'm a fan of a solid floor, well insulated and no cold breeze blowing under it. If you can get a good bit of wool under there then it'll be fine. 

Ive done the weyroc over eps option before and it worked really well. I doubled up the weyroc ( 2x 18mm laid at 90o to each other and glued and screwed, and that was raising a garage floor to create an utility / kitchenette with a washing machine and TD in it. Washing machine needed some shoes making to stop it moving about but it was an integrated one. 

 

[iSelfBuild]

On 28/07/2016 at 18:27, Nickfromwales said:

If renovating for profit then I'd go with the simpler option, and float the floor. I thought it was one where you may be moving in, sorry. I'm a fan of a solid floor, well insulated and no cold breeze blowing under it. If you can get a good bit of wool under there then it'll be fine. 

Ive done the weyroc over eps option before and it worked really well. I doubled up the weyroc ( 2x 18mm laid at 90o to each other and glued and screwed, and that was raising a garage floor to create an utility / kitchenette with a washing machine and TD in it. Washing machine needed some shoes making to stop it moving about but it was an integrated one. 

 

Thanks Nick, don't be saying sorry mate I am moving in but it won't be for too long. Do you think the EPS + Weyroc will be best for the damp walls? I should really do the best option for the damp. I thought a drafty ventilated timber floor would help dry things up down there? There is no insulation under the floors in the house, or in the walls (twin skin) so it's never going to be a well insulated house. I really fancy a new build next, I find renovating old properties stressful.... everything you remove uncovers about 10 more jobs.

[TerryE]

How good a condition are the quarry tiles in?  I only ask because we had a similar issue in our kitchen when we moved into our farmhouse 30-odd years ago.  Ours were ~1" thick and 8×8" so I decided to lift them and keep them.  It was trivial to do and they came in handy as getting genuine Victorian tiles like this is a real problem.  I just raked out some of the clinker bed and put down a polythene membrane and 3" of concrete with a 1" wet render immediate on top to float level.  OK, this was in the days before insulation was even considered!

 

If you have damp walls then the plaster might have gone, so  you've also probably got an issue with the integrity of the DPC.  You may need a silicon injection layer, and replaster in which case you should consider doing this before you relay the floor slab.  

[iSelfBuild]

Thanks TerryE - The kitchen walls are back to the brick on one side - I hacked all the lime plaster and lower band of modern render off as the walls were sodden. They are now pretty dry. On the other side they have tanked the wall with modern render and bridged the old slate DPC. Hopefully removing the lower band will help it dry out and I will patch it in with renovating plaster above the DPC. Really don't want to go through all the effort of smashing it off as it's a mega strong mix. The quarry tiles are not too bad - any good ones will be salvaged for a pizza oven I'm going to build in Scotland.