DC5 Posted August 29, 2020 Share Posted August 29, 2020 Hi folks (mods feel free to move this wasn't sure on best section), Our new extension is strip footings, 3 row of block and an insulated concrete raft. The main room will be tiled however there is a narrow wrapround part of the extension which will have a carpeted room and the rest wooden flooring. How would concrete raft normally be finished can 18 / 22mm floorboard be laid directly on top with a membrane? I'm managing this extension closely myself and I've been reading a few horror stories of builders not getting old and new floor levels to line up so I want to make sure that doesn't happen. The original house is very old so I would be surprised if both transitions into the extension from different ends of the same room line up! Any input appreciated! Link to comment Share on other sites More sharing options...
PeterW Posted August 30, 2020 Share Posted August 30, 2020 Wooden Flooring is either laid as a floating floor or bonded to the concrete slab with flexible adhesive. The usual method to get floors level is use a water level to set the datum lines off another floor and then they should all join up Link to comment Share on other sites More sharing options...
Russell griffiths Posted August 30, 2020 Share Posted August 30, 2020 You will probably end up with a bit of discrepancy in floor level as the areas you knock through into the extension won’t be level so you will be trying to level three or more points into one, I would decide on a finish floor height and work down from there to get your concrete height. Then allow 3-5mm down to allow for cock up factor and before you finish use a self leveling compound to ease out any height differences. Get a laser level set set up and go around and set up some marks on all relevant points, measure down and work out what needs to be added to what areas to come up to FFH. Link to comment Share on other sites More sharing options...
Pete Posted August 30, 2020 Share Posted August 30, 2020 Mate of mine built an extension and decided to make a small hole at joists level to find the level of the old house joists so he could match the new ones. He did not want to open up to the old house until as late in the build as possible to avoid all the mess/dust in the old bit. He asked his Mrs to make a mark on the other side of the wall to fix his joists to, only trouble was he was working to the bottom of the level and she was working to the top so when he knocked through the new joist was approx 50mm higher than the old joists! 1 Link to comment Share on other sites More sharing options...
DC5 Posted August 30, 2020 Author Share Posted August 30, 2020 Thank you for the input thus far!!! Pete - that is a cracker and absolutely what I want to avoid. Although other people will be marking it out I want to have an exact idea of where I think it should be and if they don’t match I’ll want to know why! im very lucky as we are knocking through an existing window which means we can easily do as you mention with a spirit level! The wood flooring to concrete is interesting I didn’t know you could do that, what’s the situation with carpet? Link to comment Share on other sites More sharing options...
MJNewton Posted August 30, 2020 Share Posted August 30, 2020 13 hours ago, Pete said: He asked his Mrs to make a mark on the other side of the wall to fix his joists to, only trouble was he was working to the bottom of the level and she was working to the top so when he knocked through the new joist was approx 50mm higher than the old joists! Oh how they laughed... ? Link to comment Share on other sites More sharing options...
DC5 Posted August 30, 2020 Author Share Posted August 30, 2020 I bet they still laugh today every time they trip! Link to comment Share on other sites More sharing options...
Conor Posted August 31, 2020 Share Posted August 31, 2020 17 hours ago, DC5 said: Thank you for the input thus far!!! Pete - that is a cracker and absolutely what I want to avoid. Although other people will be marking it out I want to have an exact idea of where I think it should be and if they don’t match I’ll want to know why! im very lucky as we are knocking through an existing window which means we can easily do as you mention with a spirit level! The wood flooring to concrete is interesting I didn’t know you could do that, what’s the situation with carpet? When we knocked though the back of our house to the extension, it turned out that the existing floor of the house had a fall of 30mm or so from one side the the other. The builder refused to last his screed match the existing floor. So solution was to lay the screed to the same height as the highest point of the existing floor and pour sled leveller on the lower parts to match the screed. Worked ok but a year to so later we got some cracked tiles around the transition from screen to self leveller... I think there was some differential movement. Link to comment Share on other sites More sharing options...
Onoff Posted August 31, 2020 Share Posted August 31, 2020 When we decided to gut the bathroom SWMBO decided she wanted the door in another wall. As luck would have it I uncovered a blocked up doorway near enough where she wanted it...or so I thought she said. Turns out I was wrong and had to move it by about a foot. But with the new opening I discovered the the bathroom concrete floor was about 60mm higher than the rest of the house. I'd never really picked up on before. The walls are a foot thick and there was just a bit of a slope at the doorway. It was finding this that prompted me to dig the floor up completely. Link to comment Share on other sites More sharing options...
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