Spoke to makers of UFH system. Staffordshire. "Document any damage for insurance purposes. - Polythene membrane (DPM) - Insulation (rigid board type) - Concrete slab min. Proposed floor is pitch pine boards secret-nailed to 2 x 2 inch battens with insulation between, onto a concrete floor not known to have a DPM under it; therefore, DPM to go under the battens. The clips only pierce the thinner layer above the insulation, which is only really there to ensure an unbonded concrete/screed above. It also looks like there could be polystyrene under the screed, this will be a barrier to damp coming from the ground. Screed & Insulation. Our quarry tiles were pretty much laid on dirt so there were some big variations in height over the whole kitchen. 28. My house has a solid screed floor throughout the downstairs, with a Damp proof membrane about 100mm down. Read more about changes to thermal elements 1 (in the 'External Walls' section)The removal leaves a surface the bonding agent can bond to, ensuring the screed does it’s job. 3k. Use 1000 gauge or thicker – ideal for this is the polyethylene use for the DPM under your concrete subfloor. Thin screed to level old concrete floor. The screed manufacturer agrees that their screed can receive an epoxy DPM. 3. For example, when installing Celotex under floor. ORDER LINE 0800 047 6775. 20 mm thickness should do it and im looking for the. 17 May 2010. Brief background: After buying a 1960s semi in south Birmingham house last year, and spending the summer managing (a) complete rewire; (b) installation of satellite and Ethernet wiring to all rooms; (c) plastering to make good chasing from (a). Jabfloor 70 has a nominal 1% compression value of 21kPa (2. One thought is to plug it at the junction under the draincover and then screed round it, and lay floor over; then it can be reinstated in future if ever needed. Moisture in the base will impede the drying of the screed. . You should use them to protect all final floor finishes. This can include timber floors, tiles, laminate flooring and carpet. How to screed by hand step-by-step with our stars Luke and Lee who are at the top of their game and Luke is only 18 years old, very impressive. Because we were laying Karndean Flooring to a new extension we needed to check the % RH(relative humidity) of the concrete with a hygrometer. Insulation is a crucial consideration for UFH. Mine is below the concrete. Brian shows how to correctly fit a Damp Proof Membrain - DPM in a new build houseLink to the T-Rex tape Website Http://bodgeitwithbri. screed finish over the insulation to match existing floor levels. I laid the conc slab badly about 6 years ago ( did the whole shed in one hit 75m2, but my workshop is athird of the shed, so 25m2 wants levelling). We have a few options: 1. This is done to maintain energy efficiency and prevent. £20 per m2. It stops around 10mm away from the internal walls in all rooms. We are in the process of having an extension built. AFAIK - PIR insulation boards need have a DPM under them to protect the board. UFH Pipwork. However I'm pretty sure there is no damp proof membrane (or course?) as our water source, a large well, is under the floor and a couple of years ago it flooded into the dining room. This can only normally be guaranteed if its an new build or extension and most houses have been sold, inherited etc. £18 - £22 per m2. I 've dug down and put 100mm of concrete down will liquid dpm to meet up with the existing dpm and 50mm screed ontop easy. 3. Flexible - easy to detail and install on site. For unbonded and floating screeds, a DPM may be specified between the base slab and the screed. 1. They are happy for the 25mm board to be laid on the screed, pipes clipped in then 9mm ply on top finally topped off with ceramics. Aug 18, 2010. For bonded screeds,4 weeks will depend on the depth - keep the screed as thin as possible - with wet UFH normally 50mm - any more will delay the drying time. There will be a damp-proof membrane under the insulation and possibly a second membrane on top, depending on the type of screed. DPM’s can be applied to either a suitable blinding layer under the slab or internally to the top of the slab. you then have a continuous damp couse not inportant if concrete above dpc level. 001 Ardex Australia 2015 Bulding regs would require 100mm insulation and 70mm reinforced screed for this. Mastic Asphalt – this is the earliest form of liquid DPM and is usually laid on the top of another membrane or a fibreglass surface. All other sheet membranes can be used with unbonded toppings. Some houses in early 70s don't have a DPM as I've found out over the years. Would that require two layers of DPM? For example: Level layer of hardcore; Layer of sand blinding; DPM; Concrete slab at a thickness of 3" inches; DPM (?) Jablite 70 floor insulation (75/100mm thickness) Vapour control layer ; Screed (1. Is it possibly to lay a new insulated floor without a concrete slab, using only floor screed? For example: Level layer of hardcore; Layer of sand blinding; Damp proof membrane. For traditional screed, the usual total will fall within the range £18. View complete answer on allthingsflooring. Any advance on laying 75mm kingspan directly on existing screed with DPM beneath, then laying 18mm T&G moisture resistant chipboard. It's a complete lack of knowledge on your floorlayers part or possibly just a carpet fitter trying his luck. To avoid damage to the insulation layer and the dpm it is necessary to take care in tipping, spreading and compacting wet concrete or screed. Below are a few photos of the extension so far which show the dpm that’s under the slab coming up next to the opening. Resin and cementitious floor finishes combining performance and design. Can be used under a surface DPM Excellent flow characteristics Protein-free and low odour USES Bostik Screedmaster Flow is a two-part, protein and casein free, cementitious underlayment with improved flow for smoothing uneven floors prior to. For this, a metal mesh standing with plastic pillars ( (feet) will be laid before the concrete is. Lay and level the concrete slab, allowing sufficient time to dry out, as per BS 8203. £51. When this is down I will then lay more sand or light concrete mix up to the level of the old screed or just below, then let this dry and then apply about 3 coats of bitumin floor paint. The floor make up is compaced hard core, 125mm concrete, dpm, 100mm insulation, 75mm concrete screed ( polished and heated). A water based is more likely the screed itself will blow as it cant take moisture at all, so it would be the 1st thing to blow. The surface should be of sufficient quality and. DPM is usually below the concrete, then the insulation, then a polythene sheet to stop the insulation floating as the screed is poured. Is this okay? Or does this present a real risk of corrosion of the frame in the future?that's rising damp mate, need to dig up subfloor new concrete base, dpm leave 30 days then screed and surface membrane that should help fix the problem. Information ARDEX DPM 1 C. DPM sheets should be overlapped by at least 300mm. The mat will get glued down to the screeded UFH, and then the. 1 tonnes per m²), which is suitable under a 75mm screed in normal domestic situations. Use polyethylene sheeting to create a waterproof membrane to ensure that there is no leakage of the screed when it is pumped in wet. Give it a good wipe with a damp cloth and let it dry before you start. Floor board overlaps new screed by 50mm so is supported by new screed on inside edge. Preparation is key with these coatings and the substrate must be sufficiently clean and dry. DPM sheets should be overlapped by at least 300mm. I am assuming its asphalt with a bitumen top layer, 10-15mm thick. Flowable liquid floor screed suitable for applying up to a depth of. USES For priming, consolidating and sealing of: Absorbent and non-absorbent sub-floors, consolidat-ing weak cement screed and isolation of old adhesive residues. If you are getting up to the 50mm, you would question whether you want to use a smoothing product really just from an economic point of view,. For under screed use: Must have from ground up: dpm (under subfloor in this case), insulation, plastic vapour check, sand-cement screed or fibre-concrete. Reinforcing concrete. Top. (DPM) with joints well lapped and folded. Start of next year i will be putting in my finished floor in our new extension, as it stand we got it water tight late last night with the glazing. i'n not farmiliar with wickes dpm and the primer used for professional (if you like) screeds is neoprene. Or have you asked them can you install Surface DPM on a Wet subfloor that does still have a DPM under it? Don't confuse the TWO. Small domestic areas that are going to have carpet, wood or synthetic floors as the final surface are ideal to use in conjunction with. Like x 2; Agree x 2; List (You. Option 1 is clearly cheaper but as long as it takes a screed floor (says it does) and gets signed off by. Do your slab as intended, single course of brickwork around the perimeter, then build your frame. With the number of planning applications for basement extensions rising by 183% according to research by Halifax, tilers need to be aware. Yup so the plan is: Existing garage is concrete which is a 75mm lower than the current house level. I always put the Celotex under the slab to ensure that it doesn't deteriorate between laying it down and screeding. blocking/nogging for support of plasterboard 43mm x 38mm. . What should normally happen is the inner course should be removed to concrete slab level. Developer has quoted £3744 for approx. Visqueen 2000 gauge Polythene - 12. It will - I believe - deteriorate with UV light, but that won't apply to anything cover by the soil itself. 14) Screed. This generally takes 1-2 days, depending on the thickness of the floor screed. Our costs are ballpark averages – get a local tradesperson to quote now. Will prim t be okay as primer on top of turbo? Thanks PeteUnless designed otherwise, the minimum specification for all partitions should be: sill and head plates 63mm x 38mm. The plan was to lay American Black Walnut but the hallway floor was not level. In terms of where the insulation should be placed, it can either be placed under the slab or between the. 1200g DPM will be fine. 1 left. Norfolk. heated levelling screeds. The liquid membrane forms a strong seal and makes a permeable layer to enable moisture to evaporate off. Hull. Uses/Subfloors:If you have under floor heating, you can use it to dry the screed 7 days after installation and the additional depth, (up to 65mm), becomes less important, But you’re still wasting money on screed you don’t need. screed. There will be a DPM under the slab and up the edges already. I'd like to change our tiled dining room room floor to a carpeted floor with underfloor heating. For rafts, DPM and screed must be on top of raft and screed must be at least 65 mm thick. You can usually achieve this with at least 100mm of good quality foam insulation or 150mm of mineral wool insulation, but this figure will vary depending on the make-up and size of your. What is DPM under screed? Damp-proof membrane (often called DPM) is used in construction to prevent moisture from entering the building, usually through capillary action. Reinforcement is required when you’re concreting areas that will be subjected to heavy loads, such as garages and car parks. Lay the dp membrane over the concrete slab and lapped over the brickwork. rip some 18mm ply. The old adhesive should of been removed. Request a callback. Renovation property: £60 to £85 per square metre. We need to raise one level by 6mm then screed then laying 2. Pro-Screed Gold is moisture tolerant and can be used under and over DPM’s. screed thickness. 1. Under ambient conditions, PALACE 1-COAT DPM is ready to receive a smoothing compound as soon as 4 - 5 hours after application. Apply sand-blind base (this base should be level to within 5mm along any 3m straight edge). Ideal for use where there is no functioning structural DPM (common in older properties). Country. Damp proof membranes (DPMs) can be used to help resolve damp issues which already exist or to avoid damp or moisture problems in the future. #1. 4m x 50m x 500g (200sqm) Black Polythene Vapour Control layer 4m x 25m (100sqm) TPS. The rest of the floor will be as follows (top down); flooring. Trustpilot. This is why first choice is always strip footings. Consideration should be given to applying the DPM to the top of the slab, as the installation and moisture sensitive internal finishes are then protected from any residual moisture in the concrete. The idea is that you are to prevent any screed material from falling down any joints and coming into contact with the cold slab. #3. Get it level then when it is dry and can screw through floor board into blocks. For a self-levelling screed a system such as Flowcrete UK’s Hydraseal would be used. Wet underfloor heating installation cost. Am hoping for UFH in screed (supplied won't do 50mm, only 65mm). 10) Timber block between U channel and Cavity Weep Holes 11) Galzing unit (window/glass) 12) Tiles glued 13) Polypropylene 14) Screed 15) DPM under screed 16) Concrete slab 300mm 17) DPM under. 24 Jul 2009. Perfect for new builds and refurbishment projects, our range of floor insulation products include optimum peformance OPTIM-R Vacuum Insulation Panels (VIPs) with an insulating performance up to five times better than commonly used insulation materials, and. . If in the screed then no problem with this. (This is assuming its a slab insulation. If the DPM is still wet you should have not tiled over. On the other hand, a dpm on top of the new concrete will push all the moisture towards the walls, so you would have to incorporate the dpm into. Property is mid 1960s, solid ground floor. I've read that you shouldn't install DPM under SPC flooring as it can affect how it clicks together 3. If a screed such as A38 or Topcem was used, this can reduce the drying time, and with A38 this can be just one day. Developed to suppress residual construction moisture in cementitious subfloors including power floated concrete and sand/cement screeds. DPMs on top of the slab, i. Normally you would put a compacted bed of about 50mm sand under the DPM. When sand-blinded, BAL DPM allows tiling onto difficult substrates such as steel. I see some under the wood bearers, so hopefully this will keep the base dry. Damp proof membranes can be used to help resolve damp issues. You can lay a fast track DPM (damp proof membrane) if your new concrete has had 2/3 weeks drying time. Laying new floor - needs DPM? dunroving Posts: 1,881 Forumite. The water got under the DPM and wet the slab and blinding layer. Will prim t be okay as primer on top of turbo? Thanks Pete Unless designed otherwise, the minimum specification for all partitions should be: sill and head plates 63mm x 38mm. BS8203 recommends a maximum of 75% RH prior to the installation of sensitive finishes. weberfloor flex is a self-smoothing floor levelling compound — often incorrectly referred to as a self levelling screed or self levelling floor compound — which can be tiled onto and is an easy screed for applying onto floor substrates subject to some movement, such as wood or underfloor heating. The tiler can then latex or screed over the DPM. An important benefit of Jablite Thermal Floor Systems are the speed of installation. com Do I need a DPM under laminate flooring? Simply put yes. Insulation Below A Floor Screed. Watch on. 1955 house, recently moved in and presuming no DPM under concrete slab. Spoke to makers of UFH system. Location. What’s the difference between a DPC and DPM? The DPM dries to form a permeable membrane that allows moisture to evaporate off in a controlled way. We provide a range of solutions including DPM screed, flooring primers and more! We are also radon barrier suppliers, making us perfect for all your needs! Call: 0330 223 2364 ; Email: estimating@cscscreeding. 45sqm to supply and fit. But too much water will extend the drying time and. The outcoming drain will have the dpm taped to it all the way around. B. DPM sheets should be overlapped by at least 300mm. I will post up a pic of the failed LVT in a minute for you! Screed seems to be getting damper. Concrete & Sand/Cement Screeds Concrete and sand/cement screeds must be dry and any laitance or surface treatments removed. Mot1 Sand/hardcore sub base. As you would expect, you need as much heat as possible to flow upwards and into the room. The optimum thickness of a sand. DPM's must be carefully protected where folded up the perimeter walls, and lapped under the DPC particularly at door openings. rev 2023. Use screed on top of a concrete base to give your floor a level and smooth finish. A DPM should be impermeable to water in liquid or vapour form and should be tough enough to withstand possible damage during laying of screeds, concretes or floor finishes. 19 Mar 2011. Damp proof membranes (DPM) A DPM should be a minimum thickness of 1200g polythene and linked to the DPC with a minimum 100mm overlap. Tramex reading at the time of vinyl removal was 3-4+. Also checking, the dpm is meant to be underneath the insulation? Two options: - Jablite Jabfloor 70 100mm (or jabfloor 100 or 150 grade but not sure what the difference is, building merchant sells the 70) - Xthratherm/Kingspan 100mm. 10 Feb 2020. uk ;. To avoid damage to the insulation layer and the dpm it is necessary to take care in tipping, spreading and compacting wet concrete or screed. DPM, Celotex, 1000 gauge poly, 100-150mm concrete with or without reinforcement, 50-80mm screed. The reasoning behind the 'sub-base:bedding' school of thought is that the membrane prevents the bedding from trickling down or being washed into any voids within the sub-base material, while the 'sub-grade:sub-base' orthodoxy, in which I include myself, maintains that keeping the sub-base material from mixing with the sub-grade, and reducing or. 11. . 2. Ask yourself where the gallons and gallons of water in the slab are going to go - apart from potentially lifting the DPM it will come through any defects in the DPM and cause problems. It is essential that this. hot bitumen, or cold bitumen in solution. USES For priming, consolidating and sealing of: Absorbent and non-absorbent sub-floors, consolidat-ing weak cement screed and isolation of old adhesive residues. Only one coat though. weberfloor DPM can be applied on to concrete or cement based screed surfaces with a. The Concrete slab will have been placed in January so it's had about 8 months to dry out. DPM is normally used in floors. DPM, Celotex, 1000 gauge poly, 100-150mm concrete with or without reinforcement, 50-80mm screed. To remove the screed in order to relay a DPM is, in most cases, completely unrealistic and actually completely unnecessary. If you are installing where existing floors have been removed, check that there are no traces of previous adhesive residue. If DPM ok then. You also mentioned that there are vinyl tiles over the floor. It is good practice to either fit another DPM or tape the insulation joints, when adding a screed on top of inso'. If under the screed this is normally a polythene dpm so the screed is then an. would it beneficial to change the floor structure to incorporate circa 250mm of eps insulation under the concrete slab, instead of the 150mm pir above. below this liquid screed I am adding 50mm EPS100 to build up the depth (which reduces the thickness of the screed) and also to fix the UFH pipes to. 2m3). It is advisable to incorporate a light mesh within the raft for reinforcement. Covering it in denso tape and maybe putting some dpm over the top before screeding? Yes copper is best and lasts forever, but in this situation what would you do? So far I'm leaving towards plastic which makes like easier, less stress thinking that there are all those copper joints under the screed and underfloor heating. It’s primarily designed for brushing onto concrete floors and fine concrete screeds. Apply ARDEX DPM 1 C to protect the floorcovering installation from residual construction moisture and ground bearing moisture. of the screed should be checked by the Main Contractor. The heating must be switched off at least 48 hours before and after application Bostik Screedmaster One Coat DPM and Bostik Screedmaster One Coat Accelerator are both solvent free products and are suitable for use in all project workHow-to video with step-by-step instruction on how to apply liquid damp proofing, priming and then self leveling. 12 Sep 2015. I really need to get the living room useable for my family and am hoping that a dpm under the engineered wood is possible. It is much easier to work on sections of the floor than try to achieve an even finish across the whole floor in one go. #1. hallbeck New Member. 17) DPM under slab. insulation 60mm. Greater thickness of screed may lead to a colder floor. Dig the oversite ground to whatever height allows your hardcore, insulation, blinding, slab,screed. Nice. Kingspan GreenGuard is available in a range of compressive strengths starting at 300 kPa 10% compression. 5m) It will have 50mm insulation boards on top of it, followed by 18mm/22mm. He has sealed the joints as well so hopefully they won't squeak. Once set, you can then apply your screed flooring to the DPM base. Description. 001 Ardex Australia 201550mm insulation would be better than nothing be it under screed or timber. 5-10mm thick. Temporary protection should. 13) Polypropylene. Looking for a FLAT membrane as I am told the creases you get when you unfold 4m wide DPM / polythene from a 1m roll can cause cracks (plus its a real pain to lay). The work falls under building regs part L and you need minimum 70mm PIR insulation. jeds. Effectively a thick plastic sheet, a damp proof membrane (DPM) is used to create a barrier between a concrete (or screed) subfloor and a wood floor. Side extension refurb: old concrete slab is uneven with a line of about 10mm difference in heights down middle, and dpm under screed is visibly not 100%, with a few gaps. Overlap it and tape it with duct tape or 100mm pvc tape. e. ), then 500 gauge plastic (or just use the leftover 1200 gauge DPM) then 100mm concrete slab. But what I dont understand is what to do to. Ideally with a screed pump. 034 W/mK, and is used to insulate inverted roofs, basements, car park decks, and heavy-duty commercial, industrial and cold store flooring. I was then able to put in a dpm and a hefty layer of cellotex and then screed to the level of the house. 19)Cement. So, as money's too tight to mention round here, I replaced the leaking door with a cheap UPVc one. CSC screeding was very efficient that they screeded our floor in under 4 hours (around 91sqm) with the help of the Mixamate. The basic screed construction for under floor heating systems generally follows the ‘floating’ screed construction, where a Damp Proof Membrane (DPM) and tacker insulation panels are laid over the concrete substrate before laying the heating elements of the under floor heating system. Your builder or yourself should have laid dpm under the dpc course on top of the hardcore Base laid on soft building sand . I could put the dpm under the concrete which would be as effective. 8 Oct 2015 #4 So you have a concrete slab laid on a DPM, and later a 65mm sand & cement screed laid on the Extn. e. At the junction of wall and floor the membrane overlaps the damp-proof course in the wall. DPC and DPM are lapped together at this stage. Find. 9. As for the rest of the bungalow, I noted that there is DPM under most the sole plates of the original stud walls around the bathroom, but it's. Thanks, Gastines3, FreeBear, and gwynlas! Well, I called a damp proofing guy in, he had a look said if it was him he would put in a screed at least 2 inches high and concrete outside. Ground-bearing concrete floor slabs should be protected against ground moisture by providing a continuous damp proof membrane (DPM). This reduces the risk of harmful interstitial condensation by ensuring that any moisture within the. Should I lap DPM under or over Dpc then celotex, then another DPM lapped up the wall with. I think this is too expensive, so got a quote of another supplier of £2565 plus any potential floor preparation, with latex screen costing £13 /sqm or a feather finish at £2. As a rough guide, laying a conventional sand/cement screed costs around £15/m2, increasing by around £5/m2 when delivered ready-mixed. If there was no dpm I would suggest a uniformal distribution across the whole floor. com. 9% screeds been down since February. 30 Jun 2023. It has excellent adhesion to. Replacing over half of your floor will mean you’ll have to insulate to at least 0. 9. Lay the damp proof membrane (DPM) (normally 1200g polythene sheet/300g micron or a radon barrier if specified), over the sand-blind base. Ground-bearing concrete floor slabs should be protected against ground moisture by providing a continuous damp proof membrane (DPM). 6 March 2017 at 8:04PM edited 6 March 2017 at 8:59PM. Our team of highly experienced technical experts are always on hand to provide the highest level of support and advice to our customers. The guidelines state that a damp proof membrane that is placed under the flooring should be around 1200 gauge and constructed of polyethene. Easy Handling & Installation. 10 Sep 2021. These tiles have failed as some are missing/ some broken/ the bitumen broken down, meaning the DPM has failed, hence allowing the water through. It is important to ensure that a proper seal is achieved around all services. it could easily be up and down by up to 15mm. When applied on top of screed, it needs to have a further coating to protect it from damage such as laminate, tiles, vinyl, wood and carpets. This will allow the screed to bond to the dpm. – the UK’s leading manufacturer of flooring adhesives and floor preparation products for the contract flooring industry. I would guess, that a standard mix was used, as that would be cheapest, so could assume 1mm per day, but that`s why a test would be needed. This told us tha. #2. As you are always relying on the subfloor surface strength you are always at risk if there is no sheet DPM under the floor as it will be under pressure. It's a small garden room with a 2 course brink plinth, DPC, and then timber sole. The OPTIM-R VIPs should then be fitted from the corner following the installation instructions. I'm not saying this is the best thing to use. Ultraplan Renovation Screed 3240 is suitable where good resistance to loads is required, also for castor wheel traffic and underfloor and undertile heating systems. • To provide a wearing surface. Pricing. A section of the old screed layer has broken up around the edge of the patio door threshold. . I am happy to employ gs guy to do pipe and install boiler but don't want to be calling the guy several times months appart, hence the attempt to make. Use a thick bed adhesive unless your competent to use screed, it takes skill and practice to create a flat floor. 1200 Gauge DPMs should be used when a floor is direct to the ground. We converted our garage and building control are insisting I install a DPM over the screed (even though the DPM runs under the concrete raft foundation of the house). The maximum depth you would use a smoothing compound would generally be around out 10mm, you can add aggregates, to bulk up the screed going up to 30, 40, 50+mm. flooringman, Apr 7,. It is better to put the insulation under the concrete (which wants to be 100. However the chance that the floor tiles or adhesive can release fibres and become respirable when disturbed is very low. Buy Now. 21. BONDED VERSUS UNBONDED SCREEDS Bonded topping screed installations are the most common as this allows the minimum thickness (15mm) to be applied thus limiting the weight load on the structure. The floor make up is compaced hard core, 125mm concrete, dpm, 100mm insulation, 75mm concrete screed ( polished and heated). The lower sand ratio means a higher ratio of cement, which gives a stronger mix. Do you need DPM under garage floor? Solid floor The existing concrete floor can be used as a base, however a new damp proof membrane (DPM). If the DPM is still wet you should have not tiled over. For unbonded and floating screeds, a DPM may be specified between the base slab and the screed. so FBall seems the way to go). Try it free. BBA certified - third party accreditation. Find. This allows for the full 5kg or just half to be mixed at once depending on the area to be covered. The advantages are the relatively low price of about £12 per square metre in combination with also relatively low installation costs of £8 – £12 per sqm as well as the high load- bearing capacity of cement screed. This was due to a neighbour redirecting the water from his gutters. 4 Screed. Hi guys. royaloakcarpentry Senior Member. It's joining onto the garage I'm converting so the whole floor is getting built up with polythene DPM,. This means of course I can't get a DPM under the slab; is it ok to put the DPM over the concrete slab, and then put down 50mm insulation and then 100mm screed? Ed209 , May 1, 2020 #1Assuming that the damp proof membrane (dpm) under the concrete has failed in areas then yes you possibly would get the odd patch of dampness showing in the floor. The option of 50mm insulation between battens is appealing. The Epoxy DPM 5kg is supplied in two 2. What you don't want to do, with a DPM under the screed, is create a moisture trap - which a second DPM would do. I want to level my workshop floor. Step 3: Lay the watertight membrane. Brian shows how to correctly fit a Damp Proof Membrain - DPM in a new build houseLink to the T-Rex tape Website Http://bodgeitwithbri. However to get BC off your back you can use a epoxy DPM and sand scatter it before it sets.