Dry rot masonry specification

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Hi Folks

My Victorian (3-floor) terraced house has solid (no cavity) brickwork walls, and a cellar under the front half of the property which opens directly onto the street.

Inside, the front elevation in the cellar has a 1m high 'bench' of brick that is about 1m wide, and two parallel walls, one beneath the hallway/lounge wall, and another whose purpose I believe is to support overlapping lengthwise (street parallel) joists directly under the middle of the front lounge, as well as (possibly) to provide some stiffness to the front wall.

There are also two mostly blocked up coal holes located adjacent to the ends of two newer intermediate beams that have been added between these original walls to prevent floor sag. The front gutter I had replaced recently seems to be dripping water directly opposite one of these vents/intermediate beams.

Dry rot has afflicted the ends of these beams, as well as the original floor joists, underside of floor boards at about 1 m centres and evidence for it trying to get up the staircase.

I therefore plan to:
1) Remove and replace all the wood (the house is fairly gutted, so no decorations to care for), which I imagine? would be best to treat/dip in preservative additional to the wood treatment as supplied.

2) New joists under the hall would continue to run street-parallel across the 1m span, bricking up gaps to party wall as potential new rot/fire-spread risk, instead using joist hangers. At the other end, these joists would rest in slots cut in the wall beneath the hall.

3) Create an opening in the hall wall adjacent to the front elevation with a lintel above to improve ventilation and spaciousness, doubling thickness of remaining 1 m length to increase stiffness.

4) Remove other parallel wall also to increase space, but also to increase ventilation. Improve front elevation stiffness by building 0.4m short lengths of wall (colonnades) at 0.4 m centres off starter bars, resting on front brick 'bench'.

5) Remove pathetic airbricks and open back to original 0.5 x 0.2m ‘coal hole’ vents with new cast iron grills, also similar grills to replace risers on door steps, opening on to cellar.

6) Large central area to now have joists running front to back of 3.4m span at 0.4m centres of 5-7" timber (depending on grade), hanging off front colonnades to avoid cavities cut into front elevation. Other end supported on wall with cellar steps other side, except near top steps where would be in contact with soil on step side, instead use joist hangers here.

7) Scrubbing of brickwork with steel brush and raking out to help remove fungal material.

8) Replacement of slate dpc, as somewhat broken up/damaged, with new overlapping along front elevation.

9) Buy new stairs sub-structure in kit to avoid worrying about new attack.

10) Get front gutter fixed asap!

Please could you tell me:
A) Is the above so far okay?
B) What product to use to re-point brickwork. If I replace with lime mortar, this will be good for ventilation, but worried may be vulnerable to attack as it has a more open structure. Is there kind of paste/sealant I could use instead, or additive I could add to lime mortar to dissuade dry rot?
C) What is this 'wrapping ends of timber in dpc'? Do I just cut from roll of material, or some special product? Please name!
D) To spray brickwork, what anti-fungal should I use, together with what spray system? Would prefer something paint-on as would go where needed/less inhale?
E) Front elevation is 225-450 mm thick, so what product of borate rods should I drill in at what spacing where. Over all brickwork, just front wall, what height/spacing etc?
F) Want to finish walls so easier to light. Cellar is on dry sandstone bedrock on side of hill, so any water spills rapidly seep away. What paint to use? Or, could I attach plasterboard on battens as long as leave small gap at base/top for ventilation? Does not need to look like a perfect room, but would look a lot better/more usable space, even for diy!
G) Floor is bricks on bedrock. Is there a simple spec I could use to improve, possibly concrete with some drains around the walls or something?
H) What height to hack off plaster from walls in hall/lounge above? Rather nice plaster, so would prefer not to lose too much. Believe new plaster needs to contain ZOC and new skirting to have gel paste on back.
I) How high up can dry rot get? Could it affect the floor above? Have had bad roof leaks in past (new roof now), but presume any problem up there would be wet rot.

Please if folks can answer the numbered points -thankses!!
 
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B) What product to use to re-point brickwork.

Lime mortar.

C) What is this 'wrapping ends of timber in dpc'?

Just fold and wrap with poly and staple - there are preformed wraps but they're not that common and probably only viable for large jobsites where you could order loads at a time.

D) To spray brickwork, what anti-fungal should I use, together with what spray system?

zinc oxychloride is the standard treatment but this is only secondary protection. You must remove the source of moisture and you must ventilate. After that you must monitor. My concern over chemical treatments is they are never 100%, they don't last forever and can lead to a false sense of security.

E) Front elevation is 225-450 mm thick, so what product of borate rods should I drill in at what spacing where. Over all brickwork, just front wall, what height/spacing etc?

Well, follow suppliers spec is probably the best advice, Again though, this is secondary to removing mousture source and ventilation and you can't think job done that's the end of that.

F) Want to finish walls so easier to light. Cellar is on dry sandstone bedrock on side of hill, so any water spills rapidly seep away. What paint to use? Or, could I attach plasterboard on battens as long as leave small gap at base/top for ventilation? Does not need to look like a perfect room, but would look a lot better/more usable space, even for diy!

I would avoid plasterboard with a gap behind. Even with ventilation this sounds like a mould/rot nursery to me. Try Halocell paint or similar - from www.mgcltd.co.uk

G) Floor is bricks on bedrock. Is there a simple spec I could use to improve, possibly concrete with some drains around the walls or something?

Plenty of options - Difficult to say without being completely familiar with the situation.

H) What height to hack off plaster from walls in hall/lounge above? Rather nice plaster, so would prefer not to lose too much. Believe new plaster needs to contain ZOC and new skirting to have gel paste on back.

If the plaster is sound and dry I would leave alone.

I) How high up can dry rot get? Could it affect the floor above? Have had bad roof leaks in past (new roof now), but presume any problem up there would be wet rot.

I'm not aware of a limit to its travel distance. It will keep going as long as the moisture source remains and it has food - i.e. wood.
Please if folks can answer the numbered points -thankses!!
 

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