This is the place to post for questions on prep work. Mon, 18 May 2026 06:18:45 +0000 Mon, 18 May 2026 06:18:45 +0000 The Flooring Forum - Number 1 Floor Advise forum https://theflooringforum.com/forums/subfloor-preparation.108/ Mon, 04 May 2026 20:59:47 +0000 https://theflooringforum.com/threads/sasgo-flooring-grade-ply.152779/ https://theflooringforum.com/threads/sasgo-flooring-grade-ply.152779/ invalid@example.com (merit) merit 5 Sat, 14 Mar 2026 08:47:14 +0000 https://theflooringforum.com/threads/screeding.152768/ https://theflooringforum.com/threads/screeding.152768/ invalid@example.com (dazlight) dazlight What do you prefer ?]]> 3 Sat, 14 Feb 2026 21:55:41 +0000 https://theflooringforum.com/threads/wunda-type-ufh-to-screed-or-not-to-screed.152765/ https://theflooringforum.com/threads/wunda-type-ufh-to-screed-or-not-to-screed.152765/ invalid@example.com (Stuee1202) Stuee1202
Some suppliers are...

Wunda type UFH - to screed or not to screed?]]> 9 Mon, 09 Feb 2026 19:44:23 +0000 https://theflooringforum.com/threads/osb-overlay-over-chipboard-subfloor.152764/ https://theflooringforum.com/threads/osb-overlay-over-chipboard-subfloor.152764/ invalid@example.com (Stuee1202) Stuee1202
Need to raise the level of a floor by 12mm and have a load of 11mm OSB to hand. Subfloor is 18mm chipboard screwed to joists

What's the best way to fix? Screws, nails, staples or glue and screw? What size screws/staples etc?

Does the OSB overlayment need to run at 90 degrees to the chipboard subfloor or in line with it (avoiding joints below obviously)

Cheers]]> 1 Wed, 04 Feb 2026 07:38:52 +0000 https://theflooringforum.com/threads/subfloor-build-up.152762/ https://theflooringforum.com/threads/subfloor-build-up.152762/ invalid@example.com (Aaron flooring) Aaron flooring I’m just pricing a job for a 60sqm lounge which has a sand/cement screed down. The floor is 26mm lower than the rest of the house. The customer wants to bring the floor up level and run the flooring through.
What’s the best and most cost effective rive to get the levels up. I’ve got lvt going on top.]]> 3 Wed, 14 Jan 2026 08:09:35 +0000 https://theflooringforum.com/threads/level-zone-ultra-latex.152759/ https://theflooringforum.com/threads/level-zone-ultra-latex.152759/ invalid@example.com (davefloor) davefloor
]]> 2 Mon, 24 Nov 2025 19:46:02 +0000 https://theflooringforum.com/threads/quick-drive-system.152748/ https://theflooringforum.com/threads/quick-drive-system.152748/ invalid@example.com (Gaalar) Gaalar Many thanks]]> 1 Mon, 15 Sep 2025 17:54:42 +0000 https://theflooringforum.com/threads/kelmore-screeds.152732/ https://theflooringforum.com/threads/kelmore-screeds.152732/ invalid@example.com (Rugmunching) Rugmunching
Got a supplier offering me decent pallet rates so keen to try it unless its dog pooh then I won't ]]> 2 Mon, 07 Jul 2025 04:20:32 +0000 https://theflooringforum.com/threads/what-size-nails.20546/ https://theflooringforum.com/threads/what-size-nails.20546/ invalid@example.com (JimMos) JimMos Hi Guys

I am a DIYer about to lay a lot of LVT in my house. I have done the basic Floorskills LVT course and I’m buying a Betco CN45 Coil nailer and compressor 110v package

I will use 9mm sp101 ply over floorboards 17.5mm thick - should I use 22mm nails ?

Are these suitable ?- “Spotnails 2.0 × 22mm, Galvanised Ring Plastic Collated Flooring Coil Nails”


I have no experience of nailers for flooring and so haven’t a clue. Any advice will be appreciated.

cheers

jimbo

]]> 3 Wed, 28 May 2025 22:38:59 +0000 https://theflooringforum.com/threads/several-different-substrates-what-are-best-options-for-lvt.31865/ https://theflooringforum.com/threads/several-different-substrates-what-are-best-options-for-lvt.31865/ invalid@example.com (Matt23) Matt23

1. The existing kitchen floor is currently ceramic tiles (10mm) on an adhesive bed (5mm) on plywood (18mm) on battens over a suspended concrete slab built in the late 1980s. Overall thickness of floor build-up is about 85mm. The suspended slab has a polythene dpm.
2. The conservatory has...

Several different substrates - what are best options for lvt?]]> 2 Thu, 08 May 2025 00:19:06 +0000 https://theflooringforum.com/threads/three-floors-one-finish.28217/ https://theflooringforum.com/threads/three-floors-one-finish.28217/ invalid@example.com (Twinsignals) Twinsignals
I have a 1980's built detached, the floors are concrete and screen, and they are bloody freezing in the winter. I have just built a new extension running across the back or the house and knocked the back wall out, essentially turning the 3 rooms into one big one. I'm now at the flooring point.

• The original 2 floors are Kitchen (2.5m x 4m karndean) and Dining Room (4m x 4m) removed carpet to reveal original vinyl tiles
• I have knocked down the partition...

Three floors, one finish.]]> 7 Wed, 07 May 2025 22:16:26 +0000 https://theflooringforum.com/threads/wundatherm-ufh-ultra-floor-level-it-two-cracking.21682/ https://theflooringforum.com/threads/wundatherm-ufh-ultra-floor-level-it-two-cracking.21682/ invalid@example.com (James Elliott) James Elliott
My flooring guy adhered to all the advice from the Wundatherm folk about using the right primer and products to prep and latex over the Wundatherm XPS boards, but still we're getting a lot of cracks along where the edges of the boards were.

Unsure if this is a total disaster, or if recoverable. Floor was laid 2 weeks ago and flooring guy said to ensure UFH is fully working for 2 weeks so he can inspect if anything has changed. I'm super worried now that this will cost a lot of money to...

Wundatherm UFH Ultra Floor Level It Two cracking]]> 18 Sun, 04 May 2025 12:22:35 +0000 https://theflooringforum.com/threads/crunching-popping-sound-from-plywood-overboarding.27801/ https://theflooringforum.com/threads/crunching-popping-sound-from-plywood-overboarding.27801/ invalid@example.com (deanhill1) deanhill1
I recently overboarded my living room in preparation for some LVT.
The room itself has been extended so half the room is original house and half is the extension.
Unfortunately the ply in the extended area crunches/pops when you walk on it of a morning. Small poppy. crunchy sounds. It then stops. However you can intermittently hear them afterwards when no one is stood on them.

The floorboards were all in good condition, nothing loose anywhere and were all cleaned prior to...

Crunching/popping sound from Plywood overboarding]]> 13 Thu, 01 May 2025 07:17:05 +0000 https://theflooringforum.com/threads/subfloor-prep-for-ufh.26199/ https://theflooringforum.com/threads/subfloor-prep-for-ufh.26199/ invalid@example.com (Stratos102) Stratos102 I am hoping for some pointers , do's and don't for a wet UFH install covering appox 50Sqm. Final floor covering will need stone tiles and laminate. Tilting towards Wunda Rapid Response system but open to suggestions.
Current sub Floor: 1950s vinyl tiles 25%, 1990s concrete 75%. The latter has been liquid DPM'd, and levelled using Mapei renovation screed. The former has been left as is.

I have spoken to some UFH installers who have said it is OK to lay the UFH boards on vinyl tiles....

subfloor prep for UFH]]> 3 Sun, 27 Apr 2025 15:43:59 +0000 https://theflooringforum.com/threads/flooring-build-up-advice-and-products.21738/ https://theflooringforum.com/threads/flooring-build-up-advice-and-products.21738/ invalid@example.com (Pip) Pip
I'm redoing my kitchen and hoping to lay down some gluedown LVT and wanted to make sure what I was doing is correct.

As it stands the area covers 2 different types of flooring in total of 27sqm. On the kitchen side we have a suspended timber flooring which is made up of 21mm(?) T&G planks (1970's) and the other 22mm moisture resistant T&G chipboard on PIR boards rested on a concrete slab....

Flooring build up advice and products]]> 9 Wed, 23 Apr 2025 08:56:57 +0000 https://theflooringforum.com/threads/how-do-i-level-my-old-joists-before-subfloor-fibre-board-tiles-go-on.26252/ https://theflooringforum.com/threads/how-do-i-level-my-old-joists-before-subfloor-fibre-board-tiles-go-on.26252/ invalid@example.com (Dudefinch) Dudefinch
I've removed and replaced (with 95x45mm C24) all the joists on the smaller section of the suspended floor as they had woodworm, and checked and treated the other side. I think the woods ok, but trying to work out how to level both sides has got me scratching my head a bit. I've bought some u shims I was going to use on...

How do I level my old joists before subfloor, fibre board & tiles go on?]]> Sun, 20 Apr 2025 10:38:57 +0000 https://theflooringforum.com/threads/subfloor-high-moisture-ufh-installed.23489/ https://theflooringforum.com/threads/subfloor-high-moisture-ufh-installed.23489/ invalid@example.com (Drakey) Drakey
Subfloor high moisture UFH installed]]> 9 Thu, 17 Apr 2025 21:16:04 +0000 https://theflooringforum.com/threads/lvt-onto-egger-protect-boards.20325/ https://theflooringforum.com/threads/lvt-onto-egger-protect-boards.20325/ invalid@example.com (teaandbiscuits) teaandbiscuits
I'm want to lay Karndean Van Goch planks on my bathroom floor (1.5m x 1.7m area excluding tub and fitted cabinets) as a DIY job and I understand that the standard instruction is to overboard chipboard with ply, then use featherfinish etc. etc.

However - in my case I've relaid the bathroom floor using Egger Protect boards, glued and screwed to the joists, rock solid. If you're not familiar with these boards, it's T&G 18mm chipboard but with a bonded textured membrane on the surface...

LVT onto egger protect boards]]> 13 Fri, 04 Apr 2025 21:09:53 +0000 https://theflooringforum.com/threads/water.22132/ https://theflooringforum.com/threads/water.22132/ invalid@example.com (Gibbo) Gibbo There were a couple of areas not finished great due to levelling issues between screed and original, so flooring company returned to...

Water]]> 6 Sun, 30 Mar 2025 08:42:06 +0000 https://theflooringforum.com/threads/diamond-segments.22091/ https://theflooringforum.com/threads/diamond-segments.22091/ invalid@example.com (Rugmunching) Rugmunching
My usual source doesn't have any coming in soon enough so looking to buy another 5 blocks for a spare plate I have for the general anhydrite grind out.]]> 1