16 Steps to Self-build: Plas­ter­ing

Step 9: fin­ish­ing first fix and plas­ter­ing

Homebuilding & Renovating - - CONTENTS -

Self-build ex­pert David Snell talks us through what needs to be done be­fore and dur­ing plas­ter­ing, and the dif­fer­ent op­tions avail­able at this stage in the build

Our step-by-step guide to build­ing your own home reaches the next stage: plas­ter­ing. David Snell ex­plains what needs to be done be­fore and dur­ing plas­ter­ing, and the op­tions avail­able

W hile work has been go­ing on out­side to put in the drains and the drainage system, work should also have been go­ing on in­side, gear­ing up for the ar­rival of the dry­lin­ers and plas­ter­ers. To a large ex­tent, many of the trades nat­u­rally work along­side each other but the ex­cep­tion is, per­haps, th­ese two. Once dry­lin­ers, tack­ers and plas­ter­ers are in an area, ev­ery­body else has to clear out. How­ever, in our build there are a few re­main­ing first fix tasks that still have to be car­ried out be­fore the plas­ter­ing trades ar­rive. If the stair­cases haven’t al­ready been fit­ted then this ide­ally needs to be done and, once in place, pro­tec­tive mea­sures have to be taken to cover up all treads to pre­vent im­pact dam­age and stain­ing from plas­ter­ing and, later, dec­o­rat­ing ma­te­ri­als. Stringers against the walls can some­times be left off and many choose not to fit newels, balustrad­ing and handrails un­til a later date. The car­pen­ters will also fit the loft trap at this point but may leave the ar­chi­trave sur­round un­til later. If you have cho­sen to leave the screed­ing of any floors un­til this stage then now is the time to get that done. Many feel that it is bet­ter to carry out this task at a much ear­lier time, es­pe­cially as un­der­floor heat­ing should not be run un­til most screeds have had at least three months to cure. Brick­lay­ers need to build the fire­places and hearths in ei­ther brick or stone and th­ese then need to be cov­ered and pro­tected. Sur­face-mounted fire sur­rounds can, how­ever, be fit­ted af­ter plas­ter­ing. In­su­la­tion also should be fixed be­tween in­ter­me­di­ate floor­ing joists and be­tween the studs of all studwork par­ti­tion­ing. This is typ­i­cally in­stalled for the pur­poses of sound­proof­ing rather than in­su­la­tion, although some ther­mal in­su­la­tion be­tween floors, and be­tween some rooms, can be ben­e­fi­cial.

Tack­ers and Dry­lin­ers

To start with, any soil vent pipes or ser­vice box­ings should be boxed in with ei­ther plas­ter­board or ply­wood and the cav­ity packed with in­su­la­tion to deaden any sound. The tack­ers can now com­mence fix­ing the plas­ter­board to the ceil­ing. Some tack­ers pre­fer to work from a full board scaf­fold, set at a height that en­ables them to reach the ceil­ing at any point. Oth­ers pre­fer a sin­gle board ar­range­ment, and oth­ers are hap­pier work­ing from the floor with hop-ups and floor-to-ceil­ing props, also known as a ‘dead man’. Joints should be stag­gered and all boards should be tacked to each joist they cross and fixed to a nog­gin at both ends. The joints in all ceil­ing boards should be taped and filled. This can be done in one of sev­eral ways: a pro­pri­etary pa­per scrim tape fixed up with a fin­ish plas­ter mix; a pro­pri­etary self-ad­he­sive tape; or a mesh scrim tape (of­ten re­ferred to as ‘silk scrim’), which is fixed to the joints us­ing a mix of top­coat plas­ter. The lat­ter is of­ten con­sid­ered to be the best. Next, all of the ex­ter­nal win­dows and join­ery should be sealed from the in­side us­ing a foam gun, and you should en­sure that all cav­ity closers are firmly fixed back and sealed.

The dry­lin­ers can then come in and fix the plas­ter­board to all of the in­ter­nal and ex­ter­nal walls to be plas­tered. Studwork walls will be tacked in much the same way as the ceil­ings and their joints taped and sealed, while block­work walls that are to be dry­lined will have plas­ter­board af­fixed to them us­ing ‘dots and dabs’ of a fix­ing mix­ture. This is tech­ni­cally a mis­nomer as, strictly speak­ing, the fix­ing ma­te­rial should be con­tin­u­ous at the top and bot­tom of the board. Oc­ca­sion­ally the board­ing is fixed to the walling us­ing ver­ti­cal bat­ten­ing. All ex­ter­nal an­gles, joints and junc­tions should be scrim taped. If cov­ing is not pro­posed, care needs to be taken to en­sure that the joint be­tween the wall board­ing and the ceil­ing board­ing is taped and filled, oth­er­wise crack­ing is cer­tain to oc­cur at this point in the fu­ture. skim All coat boards or fin­ish should plas­ter, now re­ceive start­ing a with coat the of ceil­ing boards. This should be smooth and not show any trowel marks or un­du­la­tions as it is, es­sen­tially, the fin­ished sur­face of the walls and ceil­ings of your new home. Th­ese days, most ex­ter­nal walls are dry­lined, re­gard­less of whether the main con­struc­tion is tim­ber frame or ma­sonry. How­ever, there are sit­u­a­tions where wet plas­ter is still used.

Wet Plas­ter

At any point where there is a change of walling medium from, for ex­am­ple, block­work to brick­work, or block­work to tim­ber or ply, or where there is a straight joint, ex­panded me­tal mesh should be firmly at­tached to bridge the change. An­gle beading should be fixed to all ex­ter­nal cor­ners and an­gles too, while gaps around the win­dows and ex­ter­nal join­ery should be filled with pro­pri­etary foam and all cav­ity closers should be firmly fixed and sealed. It is usual for the ceil­ings to be set with plas­ter, as above, be­fore work com­mences on the walls. All block­work walls to be plas- tered should re­ceive one coat of sand and ce­ment ren­der, known as a ‘scratch coat’. This is left to set and then scratched, us­ing a float with nails in it, in swirling fash­ion to pro­vide a sta­ble key for the next coat, which is ap­plied when the first scratch coat is still green but be­fore it has dried out com­pletely. Th­ese two coats can be used to ‘dub’ out and fill any in­den­ta­tions or un­du­la­tions in the wall. (Both of th­ese un­der­coats of sand and ce­ment ren­der can be sub­sti­tuted for pro­pri­etary brands of plas­ter un­der­coat­ings.) At a point where the plas­terer judges that the ren­der has set suf­fi­ciently, the top­coat plas­ter skim fin­ish is ap­plied in much the same way as for the dry­lined house, save that a longer time will need to be left for it to dry out suf­fi­ciently for dec­o­ra­tion. Once the plas­ter­ers have fin­ished, the sec­ond fix trades can be geared up to come in and com­mence their fin­ish­ing work. But be­fore that there are a cou­ple of lit­tle jobs that need do­ing. The dec­o­ra­tors should take ad­van­tage of empty rooms to set up their tres­tles and paint the back of all skirt­ing boards and ar­chi­traves with un­der­coat or preser­va­tive. The loft trap, its sur­round and the loft lad­der, should be fit­ted. And any min­eral wool in­su­la­tion des­tined for the roof void can be taken up into the loft and laid out. The home now awaits the ar­rival of the sec­ond fix and fin­ish­ing trades.

Tack­ing and Drylin­ing The plas­terer shown here is work­ing alone, us­ing floor-to-ceil­ing props to hold the boards in place be­fore se­cur­ing with a nail gun and then tap­ing the joints.

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