Barrage

[evdama]

How do you join damproof membrane when concreting an oversize room?-abig overlap and lots of bitchumen is one way Ive been told..

Whats an appropriate mortar recipie for rpairing stone (sandstone in this case.The old mortat is wite and crumbly (lime?)

Whats the minimum size timber that you would use for light domestic floor joists?

 

[DAZB]

Your local Builder's Merchants should stock a product called Visqueen Joint Tape. After overlapping by a minimum 6-8 inches apply the tape and smooth down ensuring it all seals to both surfaces.Not so sure of the result you want with the Sandstone repair but a strong mix of 3 parts sand to 1 part cement and the use of an appropriate colour Mortar Dye ( again, ask at the Builder's Merchants ) should do the job. And finally for the floor joists it will all depend on the span of the floor and how close the joists are to each other. A minimum of 6 X 2 is common if you are not exceeding 3.5 metres but the longer the span the deeper and wider the joist will be . If you can let me know the span I can post back with a recommendation for you.

 

[evdama]

Thanks DAZB
The stone repair is not on display-I have to bond some engineering- brick piers to the original walls where the previous owners efforts to merge two semi's had gone wrong.
I think Ill do a separate posting in DIY Disasters!
I wanted to know a good mix of ingredients for the mortar as Ive tried to join stone before and modern mortar just doesnt stick.Ive been told to use lime mortar but what ratio?
The floor is supprted by three beams holding up four sets of joists.The longest span is 7' and the shortest is 6'.

 

[ChrisR]

Put some PVA in the mortar, - man it will stick!!

 

[evdama]

Chrisr -Im a great fan of pva (I'd put it on me cornflakes if I could)but it didnt work for long.
lime is the only thing I havent tried yet ....

 

[masona]

Lime acts as a plasticiser which make it more flexible

Have a look at this website. Very useful information

 

[DAZB]

A joist size of 6 X 2 will be more than adequate for a 7' run. Happy building.